Edexcel Triple Science: Biology — Recall & Retrieval

1.1 Explain how the sub-cellular structures of eukaryotic and prokaryotic cells are related to their functions, including animal cells, plant cells and bacteria

1.

What is the function of the nucleus in a eukaryotic cell?

Controls the activities of the cell and contains genetic material.

2.

What is the function of mitochondria in animal and plant cells?

Site of aerobic respiration, releasing energy for cell processes.

3.

What is the function of ribosomes in animal, plant and bacterial cells?

Site of protein synthesis.

4.

What are the functions of chloroplasts and the permanent vacuole in plant cells?

Chloroplasts absorb light energy for photosynthesis; the permanent vacuole contains cell sap and helps maintain turgor.

5.

What is the function of the cell wall in plant cells?

Supports the cell and helps maintain its shape.

6.

What are the functions of chromosomal DNA, plasmid DNA, the cell membrane and flagella in bacterial cells?

Chromosomal DNA contains genetic information; plasmid DNA carries additional genes; the cell membrane controls movement of substances in and out; flagella allow movement.

1.2 Describe how specialised cells are adapted to their function, including sperm cells, egg cells and ciliated epithelial cells

1.

How is the acrosome of a sperm cell adapted for fertilisation?

The acrosome contains enzymes that help the sperm penetrate the egg cell.

2.

How are the mitochondria of a sperm cell adapted for its function?

Many mitochondria provide energy for movement of the sperm tail.

3.

Why is the nucleus of a sperm cell haploid?

It contains one set of chromosomes so that the diploid chromosome number is restored at fertilisation.

4.

How are the nutrients in the cytoplasm of an egg cell adapted for its function?

The cytoplasm contains nutrients that support the early development of the embryo.

5.

What happens to the egg cell membrane after fertilisation, and why?

It changes so that no more sperm can enter the egg.

6.

How are ciliated epithelial cells adapted to move mucus and trapped particles?

Cilia beat to move mucus and trapped particles towards the throat.

1.3 Explain how changes in microscope technology, including electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures

1.

Why did improvements in microscope technology allow scientists to observe more detailed cell structures?

Improved technology increased magnification and resolution.

2.

Why can electron microscopes show smaller structures than light microscopes?

Electron microscopes have much greater resolving power.

3.

What is meant by the resolution of a microscope?

Resolution is the ability to distinguish between two close objects as separate.

4.

How does increased resolution improve the ability to distinguish between two closely positioned structures?

Greater resolution makes closely spaced structures easier to distinguish.

5.

Why would an electron microscope be more suitable than a light microscope for studying the ultrastructure of mitochondria?

Electron microscopes have higher resolution, so they can show the internal structure of mitochondria in greater detail.

6.

How have advances in microscopy increased understanding of the functions of sub-cellular structures?

Seeing structures in greater detail helped scientists relate their structures to their functions.

1.4 Demonstrate an understanding of number, size and scale, including the use of estimations and explain when they should be used

1.

What is meant by an estimate?

An approximate value rather than an exact measurement.

2.

Why are estimates useful when an exact measurement is difficult or unnecessary?

They provide a useful value when exact measurement is difficult or unnecessary.

3.

What is meant by the order of magnitude of a measurement?

The power of ten that represents the approximate size of a measurement.

4.

How can an object's known size be used to estimate the size of another object?

Compare the unknown object with the known object and use the scale to estimate its size.

5.

Why is it important to consider scale when studying structures such as cells and organelles?

It allows the relative sizes of structures to be understood correctly.

6.

When would an estimate be more appropriate than an exact measurement in biology?

When an exact measurement is difficult, unavailable or unnecessary.

1.5 Demonstrate an understanding of the relationship between quantitative units in relation to cells, including milli, micro, nano, pico and calculations with numbers written in standard form

1.

What multiplier does the prefix milli represent?

10⁻³.

2.

What multiplier does the prefix micro represent?

10⁻⁶.

3.

What multiplier does the prefix nano represent?

10⁻⁹.

4.

What multiplier does the prefix pico represent?

10⁻¹².

5.

How many micrometres are there in 0.000004 metres?

4 μm.

6.

What is the result of calculating (3 × 10⁻⁶) × (2 × 10³), expressed in standard form?

6 × 10⁻³.

1.6 Core Practical: Investigate biological specimens using microscopes, including magnification calculations and labelled scientific drawings from observations

1.

What equation is used to calculate microscope magnification?

Magnification = image size ÷ actual size.

2.

What is the magnification of a specimen with an actual size of 50 μm and an image size of 10 mm?

10 mm = 10,000 μm; magnification = 10,000 ÷ 50 = ×200.

3.

What is the actual size of a cell with an image size of 8 mm viewed at ×400 magnification?

Actual size = 8 mm ÷ 400 = 0.02 mm = 20 μm.

4.

What features should be included in a labelled scientific drawing of a biological specimen?

Clear single lines, accurate proportions, labels with straight ruled lines and relevant structures.

5.

Why should biological drawings use clear, single lines rather than shading?

It makes the drawing clear and avoids obscuring structures.

6.

Why must measurements be converted into the same units before calculating microscope magnification?

The units must be the same so the calculation gives the correct magnification.

1.7 Explain the mechanism of enzyme action including the active site and enzyme specificity

1.

What is an enzyme?

A biological catalyst that speeds up a reaction without being used up.

2.

What is the active site of an enzyme?

The region of an enzyme where the substrate binds.

3.

What is meant by the specificity of an enzyme?

An enzyme only works with a particular substrate or small range of substrates.

4.

Why can a substrate bind to the active site of one enzyme but not another enzyme?

The substrate has a complementary shape to the enzyme's active site.

5.

What happens when a substrate binds to the active site of an enzyme?

An enzyme-substrate complex forms and the reaction occurs.

6.

How does the shape of an enzyme's active site determine which substrate it can bind to?

Its complementary shape determines which substrate can bind.

1.8 Explain how enzymes can be denatured due to changes in the shape of the active site

1.

What does it mean when an enzyme is denatured?

Its active site has changed shape so the substrate can no longer bind effectively.

2.

How can a high temperature change the shape of an enzyme's active site?

Excessive heat can change the bonds maintaining the enzyme's shape.

3.

Why does changing the shape of an enzyme's active site reduce enzyme activity?

The substrate no longer fits the active site correctly.

4.

Why can a denatured enzyme no longer bind effectively to its substrate?

The active site has changed shape.

5.

How can an extreme pH change the shape of an enzyme's active site?

Extreme pH can disrupt bonds in the enzyme and change the active site shape.

6.

Why is enzyme denaturation usually permanent?

The enzyme's structure has been permanently altered.

1.9 Explain the effects of temperature, substrate concentration and pH on enzyme activity

1.

Why does increasing temperature initially increase the rate of an enzyme-controlled reaction?

Particles have more kinetic energy, so there are more successful collisions.

2.

Why does enzyme activity decrease rapidly above the optimum temperature?

High temperature denatures the enzyme and changes the shape of its active site.

3.

How does increasing substrate concentration affect enzyme activity when enzyme concentration remains constant?

The rate increases until the enzymes become saturated.

4.

Why does enzyme activity eventually stop increasing when substrate concentration continues to increase?

All available active sites are occupied, so enzyme concentration becomes limiting.

5.

Why does each enzyme have an optimum pH?

Changes in pH can affect the bonds maintaining the enzyme's shape.

6.

What happens to enzyme activity when the pH moves substantially away from its optimum?

Activity decreases because the active site is altered and the enzyme may become denatured.

1.10 Core Practical: Investigate the effect of pH on enzyme activity

1.

What is the independent variable when investigating the effect of pH on enzyme activity?

pH.

2.

What measurement can be used to determine the rate of an enzyme-controlled reaction?

The amount of product formed or substrate broken down per unit time.

3.

Why should temperature be kept constant when investigating the effect of pH on enzyme activity?

Temperature affects enzyme activity, so it must not become a confounding variable.

4.

Why should the concentration of enzyme be kept constant when investigating the effect of pH on enzyme activity?

To make sure differences in rate are due to pH.

5.

Why should the concentration of substrate be kept constant when investigating the effect of pH on enzyme activity?

To make sure the amount of substrate available is the same.

6.

How can experimental results be used to determine the optimum pH of an enzyme?

The pH giving the highest reaction rate is the optimum pH.

1.11 Demonstrate an understanding of rate calculations for enzyme activity

1.

What equation is used to calculate the rate of an enzyme-controlled reaction?

Rate = change in amount ÷ time.

2.

What is the rate of an enzyme reaction that produces 24 cm³ of product in 6 minutes?

24 ÷ 6 = 4 cm³/min.

3.

What is the rate of an enzyme reaction that breaks down 40 mg of substrate in 8 minutes?

40 ÷ 8 = 5 mg/min.

4.

How long does an enzyme reaction take to produce 15 cm³ of product at a rate of 3 cm³/min?

15 ÷ 3 = 5 min.

5.

What is the rate of an enzyme reaction that produces 10 cm³ of product in 20 seconds?

10 ÷ 20 = 0.5 cm³/s.

6.

Why is reaction rate useful when comparing enzyme activity under different conditions?

It allows enzyme activity to be compared under different conditions.

1.12 Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates, proteins and lipids and their breakdown into sugars, amino acids and fatty acids and glycerol

1.

What is the role of enzymes as biological catalysts?

They speed up reactions needed to build and break down biological molecules.

2.

What smaller molecules are produced when carbohydrates are broken down by enzymes?

Sugars.

3.

What smaller molecules are produced when proteins are broken down by enzymes?

Amino acids.

4.

What smaller molecules are produced when lipids are broken down by enzymes?

Fatty acids and glycerol.

5.

Why are enzymes needed to synthesise larger biological molecules from smaller molecules?

They make the reactions occur rapidly enough at suitable biological temperatures.

6.

Why are enzymes important for the breakdown of large biological molecules during digestion?

They speed up digestion so large molecules can be broken down into smaller molecules that can be absorbed.

1.13B Core Practical: Investigate the use of chemical reagents to identify starch, reducing sugars, proteins and fats

1.

Which chemical reagent is used to test for starch?

Iodine solution.

2.

What colour change indicates a positive test for starch using iodine solution?

Brown/orange to blue-black.

3.

Which chemical reagent is used to test for reducing sugars?

Benedict's solution.

4.

What colour change indicates a positive Benedict's test for reducing sugars after heating?

Blue to green, yellow, orange or brick-red, depending on the amount of reducing sugar.

5.

Which chemical reagent is used to test for proteins, and what positive result does it produce?

Biuret solution; blue to lilac/purple.

6.

Which chemical reagent is used to test for fats, and what positive result does it produce?

Ethanol followed by water; a cloudy white emulsion forms.

1.14B Explain how the energy contained in food can be measured using calorimetry

1.

What is calorimetry used to measure in a food investigation?

The energy transferred from food to the surroundings, usually measured through the temperature rise of water.

2.

How does burning food transfer energy to water during calorimetry?

Burning food releases chemical energy as thermal energy, which heats the water.

3.

What measurements are needed to calculate the energy transferred to water during calorimetry?

Mass of water, specific heat capacity of water and temperature change.

4.

What equation is used to calculate the energy transferred to water during calorimetry?

ΔE = mcΔT.

5.

How can the energy transferred per gram of food be calculated in a calorimetry experiment?

Energy per gram = energy transferred ÷ mass of food burned.

6.

Why does heat loss to the surroundings reduce the accuracy of food calorimetry results?

Some energy is transferred to the surroundings instead of the water.

1.15 Explain how substances are transported into and out of cells, including by diffusion, osmosis and active transport

1.

What is diffusion?

The net movement of particles from a higher concentration to a lower concentration.

2.

In which direction does a substance move during diffusion?

Down the concentration gradient, from higher concentration to lower concentration.

3.

What is osmosis?

The net movement of water through a partially permeable membrane from higher water potential to lower water potential.

4.

In which direction does water move during osmosis?

Water moves from a more dilute solution to a more concentrated solution through a partially permeable membrane.

5.

What is active transport?

The movement of substances against a concentration gradient using energy from respiration.

6.

Why does active transport require energy from respiration?

Energy is required to move substances against the concentration gradient.

1.16 Core Practical: Investigate osmosis in potatoes

1.

What is the independent variable when investigating the effect of solution concentration on potato mass?

Concentration of the surrounding solution.

2.

Why should potato cylinders be cut to the same dimensions in an osmosis investigation?

To make the starting masses and surface areas comparable.

3.

Why should potato cylinders be blotted dry before their final mass is measured?

To remove surface water that would affect the final mass.

4.

What happens to the mass of a potato cylinder placed in a solution with a lower solute concentration than the potato cells?

Its mass increases.

5.

What happens to the mass of a potato cylinder placed in a solution with a higher solute concentration than the potato cells?

Its mass decreases.

6.

How can potato mass-change results be used to estimate the concentration of the potato cell sap?

The concentration where there is no net change in mass is approximately the concentration of the cell sap.

1.17 Calculate percentage gain and loss of mass in osmosis

1.

What equation is used to calculate percentage change in mass?

Percentage change = (change in mass ÷ original mass) × 100.

2.

What is the percentage gain in mass when a potato cylinder increases from 5.0 g to 6.0 g?

(1.0 ÷ 5.0) × 100 = 20% gain.

3.

What is the percentage loss in mass when a potato cylinder decreases from 8.0 g to 6.0 g?

(2.0 ÷ 8.0) × 100 = 25% loss.

4.

What is the percentage change in mass when a potato cylinder increases from 4.0 g to 4.8 g?

(0.8 ÷ 4.0) × 100 = 20% gain.

5.

What is the percentage change in mass when a potato cylinder decreases from 10.0 g to 7.5 g?

(2.5 ÷ 10.0) × 100 = 25% loss.

6.

Why is percentage change in mass useful when comparing osmosis results from potato cylinders with different starting masses?

It allows results from different starting masses to be compared fairly.

2.1 Describe mitosis as part of the cell cycle, including the stages interphase, prophase, metaphase, anaphase and telophase and cytokinesis

1.

What happens to the DNA during interphase of the cell cycle?

DNA is replicated so each chromosome has two copies of its genetic information.

2.

What happens to the chromosomes during prophase of mitosis?

Chromosomes condense and become visible; the nuclear membrane breaks down.

3.

What happens to the chromosomes during metaphase of mitosis?

Chromosomes line up at the equator of the cell.

4.

What happens to the chromosomes during anaphase of mitosis?

Sister chromatids are pulled to opposite poles.

5.

What happens to the chromosomes during telophase of mitosis?

New nuclear membranes form around the chromosomes at each pole.

6.

What is cytokinesis, and when does it occur during the cell cycle?

Cytokinesis is division of the cytoplasm, producing two daughter cells.

2.2 Describe the importance of mitosis in growth, repair and asexual reproduction

1.

How does mitosis allow an organism to grow?

It produces more body cells.

2.

How does mitosis replace damaged cells during tissue repair?

It produces new cells to replace damaged cells.

3.

Why is mitosis important for replacing old or worn-out cells?

It replaces cells that are no longer functioning effectively.

4.

Why is mitosis involved in asexual reproduction?

It produces new organisms from one parent without fertilisation.

5.

Why does asexual reproduction by mitosis produce genetically identical offspring?

There is no fusion of gametes, so the offspring are genetically identical apart from mutations.

6.

Which type of cell division is responsible for growth and tissue repair in multicellular organisms?

Mitosis.

2.3 Describe the division of a cell by mitosis as the production of two daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell, and that this results in the formation of two genetically identical diploid body cells

1.

How many daughter cells are produced by mitosis?

Two.

2.

How does the chromosome number of each daughter cell compare with the parent cell after mitosis?

It is the same as the parent cell.

3.

Why are the daughter cells produced by mitosis genetically identical to the parent cell?

DNA is replicated before division and the copies are separated equally.

4.

What type of cells are produced by mitosis: haploid or diploid cells?

Diploid cells.

5.

How does the genetic information in the nuclei of the two daughter cells compare with each other after mitosis?

They have identical sets of chromosomes.

6.

Why must DNA be replicated before mitosis occurs?

So each daughter cell receives a complete identical set of chromosomes.

2.4 Describe cancer as the result of changes in cells that lead to uncontrolled cell division

1.

What is cancer?

A disease caused by uncontrolled cell division.

2.

What happens to cell division when a cell becomes cancerous?

Cell division becomes uncontrolled.

3.

How can changes in cells lead to uncontrolled cell division?

Mutations can affect genes controlling cell division.

4.

Why can uncontrolled cell division result in the formation of a tumour?

A mass of abnormally dividing cells can form a tumour.

5.

How does uncontrolled cell division differ from normal cell division?

Normal cell division is controlled; cancerous cell division is uncontrolled.

6.

Why can cancerous cells damage surrounding tissues?

They can invade and damage surrounding tissues.

2.5 Describe growth in organisms, including cell division and differentiation in animals and cell division, elongation and differentiation in plants

1.

How does cell division contribute to growth in animals?

Cell division increases cell number.

2.

What is cell differentiation?

A process in which cells become specialised.

3.

How does cell differentiation contribute to growth in animals?

Differentiation produces specialised cells needed for different tissues and functions.

4.

How does cell division contribute to growth in plants?

Cell division increases cell number.

5.

How does cell elongation contribute to growth in plants?

Cells increase in length, increasing the size of the plant.

6.

How does cell differentiation contribute to growth in plants?

Cells become specialised for different plant functions.

2.6 Explain the importance of cell differentiation in the development of specialised cells

1.

What is cell differentiation?

The process by which cells become specialised.

2.

Why is cell differentiation important in multicellular organisms?

It allows multicellular organisms to develop different cell types.

3.

How does differentiation allow cells to become specialised?

Different genes are expressed so cells develop different structures and functions.

4.

Why do specialised cells have structures adapted to particular functions?

Their structures allow them to perform particular functions efficiently.

5.

How does cell differentiation contribute to the formation of different tissues?

Groups of specialised cells form tissues.

6.

Why cannot a multicellular organism function effectively if all of its cells remain unspecialised?

It would not have the range of specialised cells needed for different functions.

2.7 Demonstrate an understanding of the use of percentiles charts to monitor growth

1.

What is a percentile chart used for in biology?

To compare an individual's growth with a reference population.

2.

How can a child's height be monitored using a percentile chart?

Plot the child's measurements against age.

3.

What does it mean if a child's height is on the 50th percentile?

About 50% of children are below that measurement and 50% are above it.

4.

What does a change in a child's position across percentile lines indicate?

It may indicate a change in the pattern of growth.

5.

Why can percentile charts be used to identify unusual patterns of growth?

Measurements far outside the usual range or unusual changes in position can be identified.

6.

Why should a person's growth be monitored over time rather than using a single measurement?

It shows the pattern and rate of growth over time.

2.8 Describe the function of embryonic stem cells, stem cells in animals and meristems in plants

1.

What is an embryonic stem cell?

An unspecialised cell from an early embryo that can differentiate into many cell types.

2.

Why can embryonic stem cells differentiate into many different cell types?

They have the ability to differentiate into many different specialised cells.

3.

What is the function of stem cells in adult animals?

They replace and repair damaged or worn-out cells.

4.

Where are meristem cells found in plants?

At regions of active plant growth, such as root and shoot tips.

5.

What is the function of meristem cells in plants?

They divide to produce new cells for plant growth.

6.

How do meristem cells contribute to plant growth?

They produce cells that elongate and differentiate.

2.9 Discuss the potential benefits and risks associated with the use of stem cells in medicine

1.

How could stem cells be used to replace damaged or diseased cells?

They can replace damaged or diseased cells.

2.

How could stem cells potentially help treat paralysis or damage to nervous tissue?

They could replace damaged nervous tissue and restore some function.

3.

How could stem cells potentially be used to treat diseases such as diabetes?

They could replace insulin-producing cells.

4.

What is one risk associated with using stem cells in medicine?

They may cause unwanted immune responses or uncontrolled growth.

5.

Why could uncontrolled stem cell division increase the risk of tumour formation?

Uncontrolled division can produce tumours.

6.

Why are embryonic stem cells considered ethically controversial?

Embryos are destroyed when embryonic stem cells are obtained, raising ethical concerns.

2.10B Describe the structures and functions of the brain including the cerebellum, cerebral hemispheres and medulla oblongata

1.

What is the function of the cerebellum?

Controls coordination, balance and fine movement.

2.

What is the function of the cerebral hemispheres?

Responsible for conscious thought, memory, intelligence and voluntary actions.

3.

What is the function of the medulla oblongata?

Controls involuntary functions such as breathing and heart rate.

4.

Which part of the brain is responsible for coordinating movement and balance?

Cerebellum.

5.

Which part of the brain is responsible for conscious thought, memory and intelligence?

Cerebral hemispheres.

6.

Which part of the brain controls involuntary activities such as breathing and heart rate?

Medulla oblongata.

2.11B Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using CT scanning and PET scanning to investigate brain function

1.

Why is it difficult to investigate brain tissue directly?

The skull protects the brain and direct access would damage tissue.

2.

What does a CT scan allow scientists and doctors to examine inside the skull?

It provides detailed images of structures inside the skull.

3.

How does a CT scan produce an image of the brain?

X-rays are taken from different angles and combined to produce cross-sectional images.

4.

What does a PET scan allow scientists to investigate in the brain?

It shows areas of brain activity.

5.

How does a PET scan show which areas of the brain are active?

A radioactive tracer is taken up more in active areas and detected by the scanner.

6.

Why are CT and PET scans useful alternatives to directly accessing brain tissue?

They allow the brain to be investigated without directly accessing the tissue.

2.12B Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system, including spinal injuries and brain tumours

1.

Why is damage to the brain difficult to treat?

The brain is complex and damaged neurones are difficult to replace.

2.

Why can damage to the spinal cord cause long-term loss of movement or sensation?

Damage can prevent electrical signals travelling between the brain and body.

3.

Why can brain tumours be difficult to treat surgically?

The tumour may be close to important brain tissue.

4.

Why can surgery on the brain damage healthy nervous tissue?

Healthy tissue may be damaged during surgery.

5.

Why can damage to neurones be difficult to repair?

Neurones have limited ability to regenerate and reconnect correctly.

6.

Why are treatments for brain tumours limited by the location of the tumour?

Removing the tumour may damage areas responsible for essential functions.

2.13 Explain the structure and function of sensory receptors, sensory neurones, relay neurones in the CNS, motor neurones and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters

1.

What is the function of a sensory receptor?

Detect a stimulus.

2.

What is the function of a sensory neurone?

Carry electrical impulses from receptors to the CNS.

3.

What is the function of a relay neurone in the central nervous system?

Connect sensory neurones to motor neurones within the CNS.

4.

What is the function of a motor neurone?

Carry impulses from the CNS to effectors.

5.

What is the function of the myelin sheath around an axon?

Insulates the axon and increases the speed of impulse transmission.

6.

How do neurotransmitters transmit a signal across a synapse?

Neurotransmitters diffuse across the synaptic gap and bind to receptors on the next neurone, triggering an electrical impulse.

2.14 Explain the structure and function of a reflex arc including sensory, relay and motor neurones

1.

What is a reflex action?

A rapid, automatic response to a stimulus.

2.

What is the correct pathway of a reflex arc from a receptor to an effector?

Receptor → sensory neurone → relay neurone → motor neurone → effector.

3.

What is the role of a sensory neurone in a reflex arc?

Carries the impulse from the receptor to the CNS.

4.

What is the role of a relay neurone in a reflex arc?

Passes the impulse from the sensory neurone to the motor neurone.

5.

What is the role of a motor neurone in a reflex arc?

Carries the impulse from the CNS to the effector.

6.

Why are reflex actions rapid and automatic?

The pathway is short and the response does not require conscious thought.

2.15B Explain the structure and function of the eye as a sensory receptor including the role of the cornea and lens, the iris, and rod and cone cells in the retina

1.

What is the function of the cornea in the eye?

Refracts light as it enters the eye.

2.

What is the function of the lens in the eye?

Focuses light onto the retina.

3.

What is the function of the iris?

Controls the size of the pupil and therefore the amount of light entering the eye.

4.

What is the function of rod cells in the retina?

Work in low light and detect light intensity.

5.

What is the function of cone cells in the retina?

Detect colour and work best in brighter light.

6.

How do rod and cone cells allow the eye to detect light and colour?

Rods detect light intensity and cones detect different wavelengths of visible light.

2.16B Describe defects of the eye including cataracts, long-sightedness, short-sightedness and colour blindness

1.

What is a cataract?

Clouding of the lens.

2.

How does a cataract affect vision?

Vision becomes blurred or cloudy.

3.

What is long-sightedness?

Difficulty seeing nearby objects clearly; the image forms behind the retina.

4.

What is short-sightedness?

Difficulty seeing distant objects clearly; the image forms in front of the retina.

5.

What is colour blindness?

A condition in which some colours are difficult to distinguish.

6.

Why does colour blindness affect a person's ability to distinguish certain colours?

Some cone cells or their pigments do not function normally.

2.17B Explain how cataracts, long-sightedness and short-sightedness can be corrected

1.

How can cataracts be treated to restore clear vision?

Replace the cloudy lens with an artificial lens.

2.

How do convex lenses correct long-sightedness?

A convex lens converges light before it enters the eye.

3.

How do concave lenses correct short-sightedness?

A concave lens diverges light before it enters the eye.

4.

Why does a convex lens help focus light onto the retina in a long-sighted eye?

It increases convergence so the image moves onto the retina.

5.

Why does a concave lens help focus light onto the retina in a short-sighted eye?

It reduces convergence so the image moves back onto the retina.

6.

Where should light be focused for a person to see a clear image?

On the retina.

3.1B Explain some of the advantages and disadvantages of asexual reproduction, including the lack of need to find a mate, a rapid reproductive cycle, but no variation in the population

1.

What is asexual reproduction?

Reproduction involving one parent and no fusion of gametes.

2.

Why does asexual reproduction not require an organism to find a mate?

Only one parent is required.

3.

Why can asexual reproduction produce offspring rapidly?

No mating or fertilisation is needed, so offspring can be produced quickly.

4.

Why are offspring produced by asexual reproduction genetically very similar to the parent?

They are produced by mitosis from one parent and are genetically identical apart from mutations.

5.

What is a disadvantage of having little or no genetic variation in a population?

A change in the environment could affect most or all individuals in the same way.

6.

What is one advantage and one disadvantage of asexual reproduction?

Advantage: rapid reproduction without finding a mate. Disadvantage: little or no genetic variation.

3.2B Explain some of the advantages and disadvantages of sexual reproduction, including variation in the population, but the requirement to find a mate

1.

What is sexual reproduction?

Reproduction involving the fusion of male and female gametes.

2.

Why does sexual reproduction produce genetic variation in offspring?

Gametes from two parents combine genetic information.

3.

Why can genetic variation increase a population's ability to survive environmental changes?

Some individuals may have characteristics better suited to the changed environment.

4.

Why does sexual reproduction usually require organisms to find a mate?

Gametes from two organisms must meet and fuse.

5.

Why can sexual reproduction be slower than asexual reproduction?

Finding a mate and producing gametes takes time and energy.

6.

What is one advantage and one disadvantage of sexual reproduction?

Advantage: genetic variation. Disadvantage: a mate is required and reproduction can be slower.

3.3 Explain the role of meiotic cell division, including the production of four daughter cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes

1.

What is the role of meiosis in sexual reproduction?

Produces gametes for sexual reproduction.

2.

How many daughter cells are produced by meiosis?

Four.

3.

How does the chromosome number of a meiotic daughter cell compare with the original cell?

It has half the chromosome number.

4.

What is the chromosome number of a human gamete compared with a human body cell?

A gamete is haploid, while a body cell is diploid.

5.

Why are the gametes produced by meiosis genetically different from each other?

Chromosome combinations and crossing over create genetic variation.

6.

What type of cells are produced by meiosis: haploid or diploid cells?

Haploid cells.

3.4 Describe DNA as a polymer made up of two strands coiled to form a double helix, complementary base pairs joined by weak hydrogen bonds, and nucleotides consisting of a sugar, phosphate group and base

1.

What shape does a DNA molecule have?

A double helix.

2.

What holds the two strands of a DNA molecule together?

Weak hydrogen bonds between complementary bases.

3.

Which four bases are found in DNA?

Adenine, thymine, cytosine and guanine.

4.

Which bases are complementary in DNA?

A pairs with T; C pairs with G.

5.

What three components make up a DNA nucleotide?

A sugar, phosphate group and base.

6.

How are nucleotides joined together to form a DNA strand?

Nucleotides join through their sugar and phosphate groups to form the strand.

3.5 Describe the genome as the entire DNA of an organism and a gene as a section of a DNA molecule that codes for a specific protein

1.

What is a genome?

The entire DNA of an organism.

2.

What is a gene?

A section of DNA that codes for a specific protein.

3.

How is a gene related to the production of a protein?

The gene contains the base sequence that determines the amino acid sequence of the protein.

4.

How does the genome differ from a single gene?

The genome contains all the organism's DNA; a gene is one section of that DNA.

5.

Where is genetic information stored in a cell?

In the DNA of the cells.

6.

Why can different genes code for different proteins?

They contain different base sequences that specify different amino acid sequences.

3.6 Explain how DNA can be extracted from fruit

1.

Why is detergent used when extracting DNA from fruit?

It breaks down cell membranes.

2.

Why is salt added during a fruit DNA extraction?

It helps separate DNA from proteins and other cell material.

3.

Why is the fruit mashed or blended during DNA extraction?

It breaks up the tissue and releases cell contents.

4.

What is the purpose of filtering the fruit mixture during DNA extraction?

To remove larger solid pieces while allowing dissolved material through.

5.

Why is cold ethanol or ice-cold alcohol added during DNA extraction?

DNA is insoluble in cold ethanol, so it precipitates out.

6.

What appearance does the extracted DNA usually have?

A white, cloudy or stringy material.

3.7B Explain how the order of bases in a section of DNA decides the order of amino acids in the protein and that these fold to produce specifically shaped proteins such as enzymes

1.

How does the base sequence of a gene determine the amino acid sequence of a protein?

The base sequence is read in groups that specify the order of amino acids.

2.

What is the relationship between the sequence of amino acids and the shape of a protein?

The amino acid sequence determines how the protein folds and therefore its three-dimensional shape.

3.

Why does changing the base sequence of a gene potentially change the protein produced?

It can change the amino acid sequence.

4.

Why is the specific shape of an enzyme important for its function?

The active site must have a specific shape to bind the substrate.

5.

How can the amino acid sequence determine the shape of an enzyme?

Interactions between amino acids cause the protein to fold into a particular shape.

6.

Why can a change in DNA sometimes affect the function of a protein?

A changed protein shape can alter its activity.

3.8B Describe the stages of protein synthesis, including transcription and translation

1.

What is transcription in protein synthesis?

Copying the base sequence of a gene into mRNA.

2.

What is the role of RNA polymerase during transcription?

Separates the DNA strands and joins complementary RNA nucleotides.

3.

What is produced when RNA polymerase transcribes a gene?

An mRNA molecule.

4.

Where does mRNA attach during translation?

A ribosome.

5.

What is the role of codons in protein synthesis?

They are three-base sequences that specify amino acids.

6.

What is the role of tRNA in protein synthesis?

It carries amino acids to the ribosome and matches them to the codons.

3.9B Describe how genetic variants in the non-coding DNA of a gene can affect phenotype by influencing the binding of RNA polymerase and altering the quantity of protein produced

1.

What is non-coding DNA?

DNA that does not directly code for the amino acid sequence of a protein.

2.

How can a genetic variant in non-coding DNA affect the binding of RNA polymerase?

It can make RNA polymerase bind more or less effectively.

3.

How can altered RNA polymerase binding affect transcription?

It can increase or decrease the rate of transcription.

4.

How can a genetic variant in non-coding DNA alter the quantity of protein produced?

More or less mRNA may be produced, leading to more or less protein.

5.

Why can changing the amount of a protein affect an organism's phenotype?

Proteins affect cell processes and characteristics.

6.

How can a genetic variant affect phenotype without changing the amino acid sequence of a protein?

It can change the amount of protein produced without changing the protein's amino acid sequence.

3.10B Describe how genetic variants in the coding DNA of a gene can affect phenotype by altering the sequence of amino acids and therefore the activity of the protein produced

1.

What is coding DNA?

DNA containing the sequence that codes for a protein.

2.

How can a genetic variant in coding DNA change the amino acid sequence of a protein?

It can change the base sequence and therefore the amino acid sequence.

3.

How can changing the amino acid sequence affect the shape of a protein?

The altered amino acid sequence can change protein folding.

4.

How can a change in protein shape affect its activity?

The altered shape can change how well the protein functions.

5.

Why can a genetic variant in coding DNA cause a change in phenotype?

A changed protein can alter a characteristic.

6.

How could a mutation in the coding DNA of an enzyme affect the enzyme's activity?

It could alter the active site so the enzyme works less effectively or not at all.

3.11B Describe the work of Gregor Mendel in discovering the basis of genetics and recognise the difficulties of understanding inheritance before the mechanism was discovered

1.

What organism did Gregor Mendel use to investigate inheritance?

Pea plants.

2.

What did Mendel's experiments demonstrate about the inheritance of characteristics?

Characteristics are inherited through discrete factors, now understood as genes and alleles.

3.

Why were pea plants useful for Mendel's genetic experiments?

They have clear contrasting characteristics and can be cross-pollinated.

4.

Why was inheritance difficult to understand before Mendel's work?

Genes, chromosomes and DNA had not yet been discovered.

5.

Why did Mendel's work provide evidence that characteristics are inherited as discrete factors?

Different inherited factors could be followed through generations.

6.

Why was Mendel's work not fully appreciated when it was first published?

The mechanism of inheritance was not understood and the significance of his work was not recognised at the time.

3.12 Explain why there are differences in the inherited characteristics as a result of alleles

1.

What is an allele?

Different forms of the same gene.

2.

Why can different alleles of the same gene produce different inherited characteristics?

They can contain different base sequences and therefore influence characteristics differently.

3.

How can an individual inherit different alleles of the same gene?

One allele comes from each parent.

4.

Why can siblings have different inherited characteristics?

They can inherit different allele combinations from their parents.

5.

How does sexual reproduction contribute to differences in inherited characteristics?

It mixes genetic information from two parents and creates new allele combinations.

6.

How can different combinations of alleles produce different phenotypes?

Different allele combinations can lead to different phenotypes.

3.13 Explain the terms chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype, gamete and zygote

1.

What is a chromosome?

A long DNA molecule containing many genes.

2.

What is a gene?

A section of DNA coding for a specific protein.

3.

What is an allele?

A different form of a gene.

4.

What is the difference between a dominant allele and a recessive allele?

A dominant allele is expressed when present; a recessive allele is only expressed when no dominant allele is present.

5.

What is the difference between a homozygous genotype and a heterozygous genotype?

Homozygous means two identical alleles; heterozygous means two different alleles.

6.

What are the meanings of genotype, phenotype, gamete and zygote?

Genotype = allele combination; phenotype = observable characteristics; gamete = haploid sex cell; zygote = diploid cell formed by fertilisation.

3.14 Explain monohybrid inheritance using genetic diagrams, Punnett squares and family pedigrees

1.

What is a monohybrid cross?

A genetic cross involving one gene.

2.

What information does a Punnett square show?

The possible allele combinations of offspring.

3.

How can a genetic diagram be used to predict the genotypes of offspring?

Combine the alleles from the two parents in the possible gametes.

4.

How can a genetic diagram be used to predict the phenotypes of offspring?

Determine the characteristic associated with each genotype.

5.

What symbols are commonly used to represent dominant and recessive alleles in a genetic diagram?

Capital letter for dominant allele and corresponding lowercase letter for recessive allele.

6.

What information can a family pedigree show about the inheritance of a characteristic?

It shows how a characteristic may be inherited through a family.

3.15 Describe how the sex of offspring is determined at fertilisation, using genetic diagrams

1.

Which sex chromosomes does a human female normally have?

XX.

2.

Which sex chromosomes does a human male normally have?

XY.

3.

Which sex chromosome can a human egg cell carry?

X.

4.

Which sex chromosome can a human sperm cell carry?

X or Y.

5.

How does fertilisation determine the sex chromosome combination of a human offspring?

An X sperm gives XX; a Y sperm gives XY.

6.

What is the probability of a human child being genetically male or genetically female?

50% genetically female and 50% genetically male, assuming equal probability.

3.16 Calculate and analyse outcomes using probabilities, ratios and percentages from monohybrid crosses and pedigree analysis for dominant and recessive traits

1.

What is the probability of an offspring inheriting a particular genotype from a given Punnett square?

Number of favourable outcomes ÷ total possible outcomes.

2.

How can a Punnett square be used to calculate the expected percentage of offspring with a particular phenotype?

Count the relevant offspring in the Punnett square and express as a fraction, ratio or percentage.

3.

What phenotypic ratio is expected from a heterozygous dominant × heterozygous dominant monohybrid cross?

3 dominant : 1 recessive.

4.

What genotypic ratio is expected from a heterozygous × heterozygous monohybrid cross?

1 AA : 2 Aa : 1 aa.

5.

What percentage of offspring are expected to show a recessive phenotype from Aa × Aa?

25%.

6.

How can a pedigree be used to determine whether a characteristic is likely to be dominant or recessive?

Look at the pattern of affected and unaffected individuals across generations.

3.17B Describe the inheritance of the ABO blood groups with reference to codominance and multiple alleles

1.

What are the three alleles that determine the ABO blood group system?

I^A, I^B and i.

2.

What does it mean that the ABO blood group system has multiple alleles?

More than two alleles exist for the same gene in the population.

3.

Which ABO alleles are codominant?

I^A and I^B.

4.

What blood group results from the genotype IAIB?

AB.

5.

What blood group results from the genotype IAi?

A.

6.

What blood group results from the genotype ii?

O.

3.18B Explain how sex-linked genetic disorders are inherited

1.

What is a sex-linked genetic disorder?

A disorder caused by an allele on a sex chromosome, usually the X chromosome.

2.

Why are X-linked recessive disorders more common in males than females?

Males have only one X chromosome, so a recessive allele on it is expressed.

3.

Why can a male inherit an X-linked disorder from his mother?

His X chromosome comes from his mother.

4.

Why can a female be a carrier of an X-linked recessive disorder without showing the disorder?

She has one normal dominant allele and one recessive allele.

5.

How can a carrier mother and an unaffected father have a son with an X-linked recessive disorder?

A carrier mother can pass the recessive X-linked allele to her son.

6.

Why cannot a father pass an X-linked allele directly to his son?

A son receives the Y chromosome from his father.

3.19 State that most phenotypic features are the result of multiple genes rather than single gene inheritance

1.

What does it mean when a characteristic is controlled by multiple genes?

Several genes contribute to the characteristic.

2.

Why are most human phenotypic features not controlled by a single gene?

Most characteristics depend on the combined effects of many genes.

3.

Give one example of a human characteristic influenced by multiple genes.

Height.

4.

Why can characteristics controlled by many genes show a wide range of phenotypes?

Different combinations of alleles produce many possible phenotypes.

5.

How can multiple genes contribute to variation in human height?

Different allele combinations contribute small effects to height.

6.

How does polygenic inheritance differ from single-gene inheritance?

Polygenic inheritance involves many genes; single-gene inheritance mainly involves one gene.

3.20 Describe the causes of variation that influence phenotype, including genetic and environmental variation

1.

What is genetic variation?

Differences in DNA or allele combinations between individuals.

2.

How can mutations cause genetic variation?

Mutations create new DNA sequences and potentially new alleles.

3.

How does sexual reproduction produce genetic variation?

It creates new combinations of alleles.

4.

What is environmental variation?

Variation caused by differences in environmental conditions.

5.

How can an organism's environment affect its phenotype?

Factors such as diet, temperature and lifestyle can affect characteristics.

6.

What is an example of a characteristic influenced by both genetic and environmental factors?

Height.

3.21 Discuss the outcomes of the Human Genome Project and its potential applications within medicine

1.

What was the main aim of the Human Genome Project?

To determine the sequence of bases in human DNA and identify genes.

2.

What information did the Human Genome Project provide about human DNA?

Information about the base sequence and location of human genes.

3.

How could knowledge of the human genome help identify genes associated with inherited diseases?

Scientists can compare genomes to identify genetic variants associated with disease.

4.

How could genome information be used to improve the diagnosis of genetic disorders?

It can help identify genetic mutations linked to disorders.

5.

How could knowledge of a person's genome contribute to personalised medicine?

Treatment can be tailored according to a person's genetic information.

6.

What is one potential ethical concern associated with the use of human genome information?

Privacy or discrimination based on genetic information.

3.22 State that there is usually extensive genetic variation within a population of a species and that these arise through mutations

1.

What is genetic variation within a population?

Differences in alleles and DNA between individuals in the same population.

2.

What is a mutation?

A change in the DNA base sequence.

3.

How can mutations create new alleles?

A mutation can produce a new DNA sequence that forms a new allele.

4.

Why can mutations increase genetic variation within a population?

Each new allele adds to the genetic differences within the population.

5.

Why does sexual reproduction help produce genetic variation in a population?

It combines alleles from two parents to form different offspring.

6.

Why is genetic variation important for the survival of a species when environments change?

Variation increases the chance that some individuals can survive environmental change.

3.23 State that most genetic mutations have no effect on the phenotype, some mutations have a small effect on the phenotype and, rarely, a single mutation will significantly affect the phenotype

1.

Why do most genetic mutations have no effect on phenotype?

They may occur in non-coding DNA or not change the protein's function.

2.

Why can some genetic mutations have a small effect on phenotype?

They may slightly alter protein function.

3.

Why can a single mutation rarely have a large effect on phenotype?

A mutation can greatly alter an important protein or its production.

4.

How can a mutation in a gene affect the protein produced?

It can change the DNA sequence used to produce the protein.

5.

Why might a mutation that changes a protein's function significantly affect phenotype?

A major change in protein function can significantly alter a characteristic.

6.

Why is the effect of a mutation dependent on the gene and DNA sequence affected?

Different genes have different functions and different DNA changes have different effects.

4.1B Describe the work of Charles Darwin and Alfred Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on modern biology

1.

What did Charles Darwin contribute to the development of the theory of evolution by natural selection?

He developed the theory of evolution by natural selection.

2.

What did Alfred Wallace contribute to the development of the theory of evolution by natural selection?

He independently developed the theory of natural selection and communicated his ideas alongside Darwin.

3.

What observations helped Darwin develop his theory of natural selection?

Variation within populations and observations of organisms in different environments helped Darwin develop the theory.

4.

Why is Darwin's theory of natural selection important to modern biology?

It explains how populations change over generations and is a central idea in modern biology.

5.

How did Darwin and Wallace independently contribute to the theory of evolution?

Both independently developed ideas about natural selection.

6.

How did the theory of natural selection change scientific understanding of how species change over time?

It replaced the idea that species were fixed and showed that populations change over time through natural selection.

4.2 Explain Charles Darwin's theory of evolution by natural selection

1.

What is natural selection?

Individuals with advantageous inherited characteristics are more likely to survive and reproduce.

2.

Why is there variation between individuals in a population?

Mutations and sexual reproduction create genetic variation.

3.

Why do organisms with advantageous characteristics have a greater chance of surviving and reproducing?

They are better adapted to the environment, so they are more likely to survive and reproduce.

4.

How are advantageous alleles passed to future generations?

They are passed to offspring during reproduction.

5.

How can natural selection cause a characteristic to become more common in a population over many generations?

Their alleles become more common over successive generations.

6.

How can natural selection eventually lead to the evolution of a new species?

Accumulated genetic differences can become large enough for populations to become reproductively isolated.

4.3 Explain how the emergence of resistant organisms supports Charles Darwin's theory of evolution including antibiotic resistance in bacteria

1.

How can antibiotic resistance arise in a bacterial population?

A mutation can produce a resistance allele.

2.

Why does an antibiotic kill susceptible bacteria but not bacteria with a resistance allele?

Susceptible bacteria are killed or inhibited, while resistant bacteria survive.

3.

How does antibiotic use create a selection pressure on bacterial populations?

The antibiotic creates selection pressure by favouring resistant bacteria.

4.

How can antibiotic-resistant bacteria become more common over successive generations?

Resistant bacteria survive and reproduce, passing the allele to offspring.

5.

Why does antibiotic resistance provide evidence supporting Darwin's theory of natural selection?

It shows that advantageous inherited characteristics become more common through natural selection.

6.

Why should antibiotics not be used unnecessarily?

Unnecessary use increases selection for resistant bacteria.

4.4 Describe the evidence for human evolution, based on fossils, including Ardi, Lucy and Richard Leakey's discoveries

1.

What is a fossil?

The preserved remains or traces of past organisms.

2.

What does the 4.4-million-year-old Ardi fossil provide evidence about?

It provides evidence about an early human ancestor living about 4.4 million years ago.

3.

What does the 3.2-million-year-old Lucy fossil provide evidence about?

It provides evidence about an early hominin living about 3.2 million years ago.

4.

What did Richard Leakey's discovery of 1.6-million-year-old fossils contribute to our understanding of human evolution?

They provided evidence of early human ancestors and changes in human anatomy over time.

5.

How can differences between fossils from different time periods provide evidence for human evolution?

Different features at different ages show changes in organisms over time.

6.

Why does the fossil record provide evidence that humans have changed over time?

Fossils from different periods show that human ancestors have changed over time.

4.5 Describe the evidence for human evolution based on stone tools

1.

How does the development of stone tools provide evidence for human evolution?

Increasingly complex tools suggest increasing skill and changes in behaviour over time.

2.

How have stone tools changed over time?

They generally became more complex and better made.

3.

What can increasingly complex stone tools suggest about changes in human ancestors?

They suggest increased intelligence, skill and behavioural development.

4.

How can scientists determine the age of a stone tool from its environment?

By examining the rock layers or deposits in which they are found and using dating methods.

5.

Why can the position of a stone tool within different rock layers provide information about its age?

Lower rock layers are generally older than higher layers.

6.

How can dating evidence from stone tools help scientists investigate human evolution?

It provides evidence about the development of human behaviour over time.

4.6B Describe how the anatomy of the pentadactyl limb provides scientists with evidence for evolution

1.

What is a pentadactyl limb?

A limb with five digits based on a common skeletal pattern.

2.

What basic bone pattern is shared by pentadactyl limbs?

The same basic arrangement of bones.

3.

Which types of vertebrates have pentadactyl limbs?

Many vertebrates, including mammals, birds, reptiles and amphibians.

4.

Why does the similar underlying structure of pentadactyl limbs provide evidence for common ancestry?

Similar structures suggest that the organisms may have inherited them from a common ancestor.

5.

How can pentadactyl limbs have similar structures but different functions?

The bones have been modified for different functions.

6.

What does variation in the pentadactyl limb among vertebrates provide evidence for?

Evidence for common ancestry and divergent evolution.

4.7 Describe how genetic analysis has led to the suggestion of the three domains rather than the five kingdoms classification method

1.

What is biological classification?

Organising organisms into groups based on shared characteristics and evolutionary relationships.

2.

What are the three domains used to classify organisms?

Bacteria, Archaea and Eukarya.

3.

What are the five kingdoms of the older classification system?

Prokaryotae, Protoctista, Fungi, Plantae and Animalia.

4.

How has genetic analysis changed the classification of organisms?

DNA and molecular comparisons revealed relationships that were not clear from physical characteristics alone.

5.

Why can comparing DNA sequences provide evidence of evolutionary relationships?

More similar DNA sequences suggest a more recent common ancestor.

6.

Why does genetic evidence support classification into three domains?

Genetic differences support the separation of organisms into three major evolutionary groups.

4.8 Explain selective breeding and its impact on food plants and domesticated animals

1.

What is selective breeding?

Choosing parents with desired characteristics and breeding them.

2.

What are the main steps involved in selective breeding?

Select parents with desired traits, breed them, select offspring with the trait and repeat over generations.

3.

How can selective breeding increase milk production in cattle?

Breed cattle that produce the most milk and repeatedly select high-producing offspring.

4.

How can selective breeding produce crop plants with desirable characteristics?

Select plants with desirable traits such as high yield and breed them over generations.

5.

How can repeated selective breeding increase the frequency of desirable alleles?

Individuals carrying the desirable alleles are more likely to be selected as parents.

6.

What is one disadvantage of selective breeding in domesticated animals or crops?

Reduced genetic variation and increased risk of inherited health problems or disease.

4.9B Describe the process of tissue culture and its advantages in medical research and plant breeding programmes

1.

What is tissue culture?

Growing cells or tissues in a controlled nutrient medium.

2.

How are cells used to produce genetically identical organisms during plant tissue culture?

Plant cells divide and form new plants genetically identical to the parent.

3.

Why are small pieces of plant tissue suitable for tissue culture?

Many plant cells retain the ability to divide and differentiate.

4.

How can tissue culture rapidly produce large numbers of plants with desirable characteristics?

Small pieces of tissue can produce many plants in a short time.

5.

How can tissue culture be used in medical research?

It can provide cells or tissues for controlled studies of biological processes and diseases.

6.

What is one advantage of using tissue culture in plant breeding programmes?

Large numbers of genetically identical plants with desirable characteristics can be produced quickly.

4.10 Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics

1.

What is genetic engineering?

Deliberately modifying an organism's DNA to introduce a desired characteristic.

2.

What is the purpose of modifying an organism's genome during genetic engineering?

To introduce a gene that gives a desirable characteristic.

3.

How can a gene from one organism be introduced into another organism?

Isolate the desired gene and insert it into the recipient organism's DNA using a suitable vector.

4.

Why can genetic engineering produce organisms with desirable characteristics?

The organism expresses the introduced gene and develops the desired trait.

5.

How does genetic engineering differ from selective breeding?

Genetic engineering directly changes DNA; selective breeding selects existing variation.

6.

What is a genetically modified organism?

An organism whose genetic material has been altered using genetic engineering.

4.11 Describe the main stages of genetic engineering including the use of restriction enzymes, ligase, sticky ends and vectors

1.

What is the role of a restriction enzyme in genetic engineering?

It cuts DNA at specific base sequences.

2.

What are sticky ends?

Short single-stranded sections of DNA left after cutting.

3.

Why are sticky ends useful when inserting a gene into DNA?

They can pair with complementary sticky ends on another DNA molecule.

4.

What is the role of DNA ligase in genetic engineering?

It joins DNA fragments together.

5.

What is a vector in genetic engineering?

A carrier used to transfer a gene into a host cell, such as a plasmid.

6.

What are the main stages used to insert a desired gene into an organism using genetic engineering?

Isolate the desired gene, cut DNA with restriction enzymes, join the gene into a vector using ligase, then transfer the vector into the host cell.

4.12B Explain the advantages and disadvantages of genetic engineering to produce GM organisms including the introduction of genes for insect resistance from Bacillus thuringiensis into crop plants

1.

What is one advantage of genetically modifying crops to produce insect resistance?

Reduced crop damage and increased yield.

2.

How can a gene from Bacillus thuringiensis give a crop plant insect resistance?

The Bt gene codes for a protein that is toxic to certain insect pests.

3.

How can insect-resistant GM crops reduce the use of chemical insecticides?

Fewer chemical insecticides may be needed.

4.

What is one potential environmental risk of growing insect-resistant GM crops?

The gene or its effects could affect non-target organisms or biodiversity.

5.

What is one potential disadvantage of genetically modified crops for farmers or consumers?

GM crops may be expensive to develop, and there may be concerns about consumer acceptance.

6.

Why is the use of GM crops a subject of scientific and ethical debate?

Benefits, environmental risks, safety, economic effects and ethical concerns must all be considered.

4.13B Explain the advantages and disadvantages of agricultural solutions to the demands of a growing human population, including use of fertilisers and biological control

1.

Why are fertilisers used in agriculture?

They provide mineral ions needed for plant growth.

2.

How can fertilisers increase crop yield?

They replace mineral ions in the soil, increasing plant growth and yield.

3.

What is biological control?

Using one organism to control the population of another organism, such as a pest.

4.

How can biological control reduce crop damage caused by pests?

A biological control organism reduces the pest population.

5.

What is one environmental disadvantage of excessive fertiliser use?

Nutrient pollution and eutrophication can occur.

6.

What is one advantage and one disadvantage of using biological control?

Advantage: reduces chemical pesticide use. Disadvantage: the control organism may affect non-target species or become difficult to control.

4.14 Evaluate the benefits and risks of genetic engineering and selective breeding in modern agriculture and medicine, including practical and ethical implications

1.

What is one benefit of genetic engineering in agriculture?

It can introduce desirable traits such as pest resistance or improved yield.

2.

What is one risk of genetic engineering in agriculture?

Possible environmental effects, such as effects on non-target species or biodiversity.

3.

What is one benefit of selective breeding in agriculture?

It can increase useful characteristics in crops and livestock.

4.

What is one risk of selective breeding in domesticated animals?

Reduced genetic variation can increase inherited disorders and disease susceptibility.

5.

What is one potential medical benefit of genetic engineering?

It can produce useful proteins or treatments for disease.

6.

What practical and ethical issues should be considered when using genetic engineering or selective breeding?

Safety, cost, effectiveness, environmental impact, animal welfare, consent and ethical concerns.

5.1 Describe health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the World Health Organization (WHO)

1.

How does the World Health Organization define health?

Health is a state of complete physical, mental and social well-being, not merely the absence of disease or infirmity.

2.

What does physical well-being mean in the WHO definition of health?

Being physically healthy and functioning normally.

3.

What does mental well-being mean in the WHO definition of health?

Having good psychological and emotional well-being.

4.

What does social well-being mean in the WHO definition of health?

Being able to interact and function positively within society.

5.

Why does being free from disease not necessarily mean that a person is considered completely healthy?

A person may have no disease but still have poor physical, mental or social well-being.

6.

Which international organisation defines health as complete physical, mental and social well-being?

World Health Organization (WHO).

5.2 Describe the difference between communicable and non-communicable diseases

1.

What is a communicable disease?

A disease that can be transmitted between organisms.

2.

What is a non-communicable disease?

A disease that cannot be transmitted between organisms.

3.

How are communicable diseases transmitted between organisms?

Through pathogens by routes such as droplets, contaminated food or water, direct contact or vectors.

4.

Why can non-communicable diseases not be transmitted between people?

They are not caused by transmissible pathogens.

5.

Give one example of a communicable disease.

Tuberculosis.

6.

Give one example of a non-communicable disease.

Cancer.

5.3 Explain why the presence of one disease can lead to a higher susceptibility to other diseases

1.

Why can having one disease increase a person's susceptibility to another disease?

It may weaken the immune system or damage body defences.

2.

How can a disease weaken the immune system?

It can reduce the body's ability to destroy pathogens.

3.

Why does destruction of white blood cells increase susceptibility to other infections?

Fewer white blood cells are available to respond to pathogens.

4.

How can HIV infection increase susceptibility to other diseases?

HIV attacks immune cells, weakening the immune system.

5.

Why can a weakened immune system make it more difficult to fight pathogens?

The body is less able to detect and destroy pathogens.

6.

How can one disease indirectly increase the risk of developing another disease?

One disease can weaken defences, making another infection more likely.

5.4 Describe a pathogen as a disease-causing organism, including viruses, bacteria, fungi and protists

1.

What is a pathogen?

An organism that causes disease.

2.

What is a bacterial pathogen?

A bacterium that causes disease.

3.

What is a viral pathogen?

A virus that causes disease.

4.

What is a fungal pathogen?

A fungus that causes disease.

5.

What is a protist pathogen?

A protist that causes disease.

6.

Which four groups of pathogens are required by the Edexcel specification?

Viruses, bacteria, fungi and protists.

5.5 Describe some common infections, including cholera, tuberculosis, Chalara ash dieback, malaria, HIV, stomach ulcers caused by Helicobacter and Ebola

1.

Which type of pathogen causes cholera, and what is a major symptom of cholera?

Bacterium; severe diarrhoea and dehydration.

2.

Which type of pathogen causes tuberculosis, and what part of the body can tuberculosis damage?

Bacterium; it can damage the lungs.

3.

Which type of pathogen causes Chalara ash dieback, and what symptoms does it cause in ash trees?

Fungus; it causes lesions and dieback of ash trees.

4.

Which type of pathogen causes malaria, and which organs can malaria damage?

Protist; it can damage red blood cells and the liver.

5.

Which type of pathogen causes HIV infection, and what cells does HIV destroy?

Virus; it destroys helper T cells.

6.

Which bacterium can cause stomach ulcers, and which virus causes Ebola?

Helicobacter pylori; Ebola is caused by a virus.

5.6 Explain how pathogens are spread and how this spread can be reduced or prevented

1.

How is cholera commonly spread?

Through contaminated food or water.

2.

How is tuberculosis commonly spread?

In droplets from coughs and sneezes.

3.

How can the spread of Chalara ash dieback occur?

Through infected plants, spores or movement of infected plant material.

4.

How is malaria transmitted from one person to another?

By mosquitoes acting as vectors.

5.

How can stomach ulcers caused by Helicobacter be spread?

Through close contact and contaminated food or other routes of transmission.

6.

How is Ebola spread between people?

Through contact with infected blood or body fluids.

5.7B Describe the lifecycle of a virus, including lysogenic and lytic pathways

1.

What happens when a virus attaches to a suitable host cell?

It attaches to a receptor and enters or injects its genetic material into the host cell.

2.

What happens to viral genetic material during viral replication?

The viral genome is copied using the host cell's machinery.

3.

What happens during the lytic pathway of a virus?

Viral components are produced and new viruses form; the host cell eventually bursts.

4.

What happens during the lysogenic pathway of a virus?

Viral DNA becomes incorporated into the host DNA and is copied when the host cell divides.

5.

How can viral genetic material remain inside a host cell during the lysogenic pathway?

It becomes part of the host cell's DNA.

6.

What event causes the lysogenic pathway to enter the lytic pathway?

A trigger can activate the viral DNA, causing it to enter the lytic pathway.

5.8 Explain how sexually transmitted infections (STIs) are spread and how this spread can be reduced or prevented, including Chlamydia and HIV

1.

What is a sexually transmitted infection?

An infection mainly spread through sexual contact.

2.

How is Chlamydia commonly transmitted?

Through sexual contact with an infected person.

3.

How is HIV commonly transmitted?

Through infected blood, semen, vaginal fluids or breast milk, including sexual contact.

4.

How can condoms reduce the spread of STIs?

They act as a barrier that reduces contact with infected body fluids.

5.

Why can testing and treatment help reduce the spread of Chlamydia?

Infected people can be identified and treated, reducing transmission.

6.

Why can reducing contact with infected body fluids reduce HIV transmission?

Reducing exposure to infected blood and other body fluids reduces transmission.

5.9B Describe how some plants defend themselves against attack from pests and pathogens by physical barriers, including the leaf cuticle and cell wall

1.

What is the function of the waxy leaf cuticle in plant defence?

It forms a waxy waterproof barrier.

2.

How does the leaf cuticle reduce the entry of pathogens into a plant?

It reduces the ability of pathogens to enter the leaf.

3.

How does the plant cell wall help defend against pathogens?

It provides a strong barrier around the plant cell.

4.

Why does the physical structure of a plant cell wall make it difficult for pathogens to enter?

It is strong and difficult for pathogens to penetrate.

5.

How do physical barriers protect plants before pathogens enter their cells?

They prevent or reduce pathogen entry before infection is established.

6.

Which two physical barriers are specifically required for plant defence in the Edexcel specification?

The leaf cuticle and cell wall.

5.10B Describe how plants defend themselves against attack from pests and pathogens by producing chemicals, some of which can be used to treat human diseases or relieve symptoms

1.

How can plants defend themselves against pests using chemicals?

They produce chemicals that repel or harm pests.

2.

How can plants defend themselves against pathogens using chemicals?

They produce chemicals that inhibit or kill pathogens.

3.

Why can plant-produced chemicals be useful in medicine?

Some have useful biological effects in humans.

4.

How can plant chemicals be used to treat human diseases?

They can be developed into medicines.

5.

How can plant chemicals be used to relieve symptoms of human diseases?

They can reduce symptoms by affecting biological processes causing them.

6.

Why can producing defensive chemicals increase a plant's ability to survive pathogen or pest attack?

It reduces damage and increases the chance of survival and reproduction.

5.11B Describe different ways plant diseases can be detected and identified, in the lab and in the field

1.

Why should possible environmental causes be eliminated when diagnosing a plant disease?

To avoid confusing disease with a non-infectious cause such as mineral deficiency.

2.

How can the distribution of affected plants in a field help identify a plant disease?

Clusters or patterns of affected plants can suggest how a disease is spreading.

3.

What can visible symptoms tell scientists when identifying a plant disease?

Symptoms such as leaf spots, discolouration, wilting or lesions.

4.

How can laboratory diagnostic tests identify a plant pathogen?

Tests can detect the pathogen or its genetic material.

5.

Why is it useful to combine field observations with laboratory diagnostic testing?

Field observations provide context and laboratory tests provide more specific evidence.

6.

What four approaches can be used to detect and identify plant diseases?

Visual symptoms, distribution patterns, laboratory testing and molecular or genetic tests.

5.12 Describe how the physical barriers and chemical defences of the human body provide protection from pathogens

1.

How does the skin act as a physical barrier against pathogens?

It forms a physical barrier preventing pathogens from entering.

2.

How does mucus help protect the human body from pathogens?

It traps pathogens and particles.

3.

How do cilia help protect the respiratory system from pathogens?

They move mucus and trapped pathogens away from the lungs.

4.

How does lysozyme help defend the body against pathogens?

It breaks down bacterial cell walls.

5.

How does hydrochloric acid in the stomach help destroy pathogens?

It provides an acidic environment that kills many pathogens.

6.

Which physical and chemical defences protect humans from pathogens before a specific immune response occurs?

Skin, mucus, cilia, lysozyme and hydrochloric acid.

5.13 Explain the role of the specific immune system of the human body in defence against disease

1.

What happens when a person is exposed to a pathogen for the first time?

Specific lymphocytes recognise antigens and begin an immune response.

2.

What are antigens?

Molecules on the surface of pathogens that are recognised by the immune system.

3.

How do antigens trigger the production of specific antibodies?

Specific lymphocytes produce antibodies complementary to the antigen.

4.

What is the role of memory lymphocytes?

They remain in the body and respond rapidly if the same pathogen enters again.

5.

Why does the secondary immune response occur more rapidly than the primary response?

Memory lymphocytes are already present and quickly produce a stronger response.

6.

How does the production of memory lymphocytes provide long-term immunity to a pathogen?

They allow a rapid secondary response that can prevent illness.

5.14 Explain the body's response to immunisation using an inactive form of a pathogen

1.

What is immunisation?

The process of making a person immune using a vaccine.

2.

Why is an inactive form of a pathogen used in a vaccine?

It provides antigens without causing the full disease.

3.

How does a vaccine trigger an immune response?

The antigens trigger a specific immune response.

4.

What happens to antibody production after vaccination?

Specific antibody-producing cells are activated and antibodies are produced.

5.

Why does vaccination lead to the production of memory lymphocytes?

They provide long-term immune memory.

6.

Why can a vaccinated person produce antibodies more rapidly when exposed to the pathogen later?

Memory lymphocytes recognise the pathogen and produce a rapid antibody response.

5.15B Discuss the advantages and disadvantages of immunisation, including the concept of herd immunity

1.

What is herd immunity?

Protection of a population when enough people are immune to reduce disease transmission.

2.

How does a high vaccination rate reduce the spread of a communicable disease?

There are fewer susceptible people for the pathogen to infect.

3.

How does herd immunity help protect people who cannot be vaccinated?

Reduced transmission lowers the chance of exposure.

4.

What is one advantage of immunisation?

It reduces the spread and incidence of communicable disease.

5.

What is one disadvantage or risk associated with immunisation?

Some people may experience side effects or, rarely, serious reactions.

6.

Why can vaccination programmes reduce the number of people infected during an outbreak?

High vaccination coverage reduces transmission and the size of outbreaks.

5.16 Explain that antibiotics can only be used to treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism

1.

Why are antibiotics effective against bacterial infections?

They target bacterial cell processes, such as cell wall synthesis, that can be disrupted without normally damaging human cells.

2.

Why do antibiotics not treat viral infections?

Viruses do not have the bacterial cell structures or processes targeted by antibiotics.

3.

What is the target of an antibiotic within a bacterial cell?

Processes or structures such as bacterial cell wall synthesis or bacterial protein synthesis.

4.

Why can antibiotics inhibit bacterial cell processes without normally damaging human cells?

The targets are different from those in human cells.

5.

Why would taking antibiotics for a viral infection not cure the infection?

The virus is unaffected by antibacterial drugs.

6.

Why is it important to use antibiotics only when they are needed for bacterial infections?

To reduce unnecessary selection for antibiotic-resistant bacteria.

5.17B Explain the aseptic techniques used in culturing microorganisms in the laboratory

1.

What is the purpose of using an autoclave when preparing sterile growth medium?

To kill microorganisms and sterilise the medium and equipment.

2.

Why are Petri dishes sterilised before microorganisms are cultured?

To prevent unwanted microorganisms contaminating the culture.

3.

Why are sterile inoculating loops used to transfer microorganisms?

To transfer microorganisms without introducing contaminants.

4.

Why should Petri dishes and culture vials be kept covered?

To reduce contamination from the air and surroundings.

5.

How does aseptic technique reduce contamination of a microbial culture?

It prevents unwanted microorganisms entering the culture.

6.

What is the purpose of using aseptic techniques when culturing microorganisms?

To maintain a pure culture and protect against contamination.

5.18B Core Practical: Investigate the effects of antiseptics, antibiotics or plant extracts on microbial cultures

1.

How can the effectiveness of an antimicrobial substance be tested using a microbial culture?

Place measured amounts of the substances onto a microbial culture and compare the areas where growth is inhibited.

2.

What does a clear zone around an antimicrobial disc on agar indicate?

It shows that microbial growth has been inhibited.

3.

Why should the diameter of the clear zone be measured when comparing antimicrobial substances?

A larger clear zone indicates greater antimicrobial effectiveness.

4.

Why should the concentration of the antimicrobial substance be controlled or recorded?

So differences in results can be linked to the antimicrobial rather than concentration.

5.

Why should sterile technique be used when investigating antimicrobial substances?

To prevent contamination and protect the investigator.

6.

How can repeated measurements improve the reliability of an investigation into antimicrobial effectiveness?

They allow a mean to be calculated and reduce the effect of random error.

5.19B Calculate cross-sectional areas of bacterial cultures and clear agar jelly using πr²

1.

What equation is used to calculate the area of a circular bacterial culture?

Area = πr².

2.

What measurements are needed to calculate the cross-sectional area of a circular bacterial culture?

The radius.

3.

How can the radius of a bacterial culture be calculated from its diameter?

Radius = diameter ÷ 2.

4.

What is the cross-sectional area of a circular clear zone with a radius of 5 mm?

Area = π × 5² = 78.5 mm².

5.

Why must the radius rather than the diameter be used in the equation πr²?

The equation uses radius squared.

6.

How can the calculated area of a clear zone be used to compare antimicrobial effectiveness?

Larger area generally indicates greater antimicrobial effectiveness.

5.20 Describe that the process of developing new medicines, including antibiotics, has many stages, including discovery, development, preclinical and clinical testing

1.

What is the discovery stage of developing a new medicine?

Finding a substance that may have a useful biological effect.

2.

What happens during the development stage of medicine development?

Refining and testing the substance to produce a suitable medicine.

3.

What is preclinical testing?

Testing for safety, toxicity and effectiveness using cells, tissues and organisms before human trials.

4.

What is clinical testing?

Testing safety and effectiveness in humans.

5.

Why are medicines tested before they are given to large numbers of humans?

To ensure they are safe and work effectively.

6.

What are the main stages involved in developing a new medicine?

Discovery → development → preclinical testing → clinical testing.

5.21B Describe the production of monoclonal antibodies

1.

What type of cell is used to produce the desired antibody during monoclonal antibody production?

Lymphocytes.

2.

Why can the lymphocytes used in monoclonal antibody production not be used directly to produce large quantities of antibodies?

They do not divide indefinitely in culture.

3.

What is a hybridoma cell?

A cell made by fusing a lymphocyte with a tumour cell.

4.

How are hybridoma cells produced?

Fuse a lymphocyte producing the desired antibody with a tumour cell.

5.

Why are hybridoma cells useful for producing monoclonal antibodies?

They can divide repeatedly while producing the same antibody.

6.

How do hybridoma cells produce large quantities of identical antibodies?

They divide repeatedly and all the cells produce the same antibody.

5.22B Explain the use of monoclonal antibodies

1.

How are monoclonal antibodies used in pregnancy tests?

They bind to pregnancy hormones so a test can detect them.

2.

How can monoclonal antibodies be used to locate blood clots?

They can bind to substances associated with clots and carry a detectable marker.

3.

How can monoclonal antibodies be used to locate cancer cells?

They can bind to antigens found on cancer cells.

4.

How can monoclonal antibodies be used to treat cancer?

They can deliver toxic substances or radioactive material to cancer cells.

5.

Why can monoclonal antibodies target specific cells more precisely than some conventional drug treatments?

They bind to specific antigens on particular cells.

6.

What is one advantage of using monoclonal antibodies compared with radiotherapy for targeting specific cells?

They can target specific cells while reducing damage to nearby healthy tissue.

5.23 Describe that many non-communicable human diseases are caused by the interaction of a number of factors

1.

What is a non-communicable disease?

A disease that cannot be transmitted between organisms.

2.

Why can many non-communicable diseases be caused by several interacting factors?

Different risk factors can act together to increase disease risk.

3.

Which type of disease includes cardiovascular disease?

Non-communicable disease.

4.

Which types of cancer can be influenced by multiple factors?

For example, lung and colorectal cancer can involve several risk factors.

5.

How can nutrition influence the risk of non-communicable disease?

Poor diet can increase disease risk through effects such as obesity or nutrient deficiency.

6.

Which types of diseases listed in the Edexcel specification can result from interactions between multiple factors?

Cardiovascular disease, many cancers, and some liver and lung diseases.

5.24 Explain the effect of lifestyle factors on non-communicable diseases at local, national and global levels

1.

What is the equation for calculating BMI?

BMI = mass ÷ height².

2.

What does a high BMI indicate about a person's body mass relative to their height?

A high body mass relative to height.

3.

How can exercise and diet affect the risk of obesity?

Healthy diet and regular exercise reduce the risk of obesity.

4.

How can poor nutrition contribute to malnutrition?

An inadequate or unbalanced diet can lead to nutrient deficiencies or excess energy intake.

5.

How can excessive alcohol consumption increase the risk of liver disease?

It increases the risk of liver damage and liver disease.

6.

How can smoking increase the risk of cardiovascular disease?

It damages the cardiovascular system and increases the risk of cardiovascular disease.

5.25 Evaluate some different treatments for cardiovascular disease, including life-long medication, surgical procedures and lifestyle changes

1.

How can life-long medication be used to treat cardiovascular disease?

Drugs can lower blood pressure, reduce cholesterol or reduce clot formation.

2.

How can surgical procedures treat cardiovascular disease?

Procedures such as stents, angioplasty or bypass surgery can improve blood flow.

3.

How can lifestyle changes reduce the risk or severity of cardiovascular disease?

Improving diet, increasing exercise and stopping smoking can reduce risk.

4.

What is one advantage of using medication to treat cardiovascular disease?

It can control risk factors without invasive surgery.

5.

What is one advantage and one risk of using surgical procedures to treat cardiovascular disease?

Advantage: can restore blood flow. Risk: complications and damage during surgery.

6.

Why might lifestyle changes be recommended alongside medication or surgery for cardiovascular disease?

Lifestyle changes can reduce underlying risk factors and improve the effectiveness of other treatments.

6.1 Describe photosynthetic organisms as the main producers of food and therefore biomass

1.

What are photosynthetic organisms, and why are they described as the main producers of food and biomass?

They make organic food molecules using photosynthesis and form the base of most food chains.

2.

Why are green plants and algae important producers in ecosystems?

They produce food and biomass that can be transferred to consumers.

3.

How does photosynthesis allow plants and algae to produce food?

They use light energy to convert carbon dioxide and water into glucose.

4.

Why does the glucose produced by photosynthetic organisms contribute to biomass?

Glucose can be used to make larger biological molecules and plant tissues.

5.

What is meant by the term biomass in the context of photosynthetic organisms?

The mass of living biological material.

6.

Why do consumers ultimately depend on photosynthetic organisms for food and biomass?

Consumers obtain biomass and energy by feeding on them directly or indirectly.

6.2 Describe photosynthesis in plants and algae as an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen

1.

What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen.

2.

Why is photosynthesis described as an endothermic reaction?

It takes in energy from the surroundings.

3.

What form of energy is transferred to the plant during photosynthesis?

Light energy.

4.

Which two substances are the reactants in photosynthesis?

Carbon dioxide and water.

5.

Which two substances are produced during photosynthesis?

Glucose and oxygen.

6.

Where does the light energy used in photosynthesis come from?

The Sun.

6.3 Explain the effect of temperature, light intensity and carbon dioxide concentration as limiting factors on the rate of photosynthesis

1.

How does increasing temperature affect the rate of photosynthesis when temperature is a limiting factor?

It increases the rate until another factor becomes limiting or the temperature becomes too high.

2.

Why does increasing light intensity increase the rate of photosynthesis at low light intensities?

More light energy is available for photosynthesis.

3.

Why does increasing carbon dioxide concentration increase the rate of photosynthesis when carbon dioxide is limiting?

More carbon dioxide is available for the photosynthetic reactions.

4.

What happens to the rate of photosynthesis when a limiting factor is increased beyond the point where another factor becomes limiting?

The rate reaches a plateau because another factor becomes limiting.

5.

What is meant by a limiting factor in photosynthesis?

A factor that limits the rate of photosynthesis when it is in shortest supply.

6.

How can temperature, light intensity and carbon dioxide concentration each limit the rate of photosynthesis?

Each can become the factor that limits the rate when the others are sufficient.

6.4 Explain the interactions of temperature, light intensity and carbon dioxide concentration in limiting the rate of photosynthesis

1.

How can increasing light intensity fail to increase the rate of photosynthesis?

Another factor, such as carbon dioxide concentration or temperature, may be limiting.

2.

How can increasing carbon dioxide concentration fail to increase the rate of photosynthesis?

Another factor, such as light intensity or temperature, may be limiting.

3.

Why must temperature, light intensity and carbon dioxide concentration be considered together when investigating photosynthesis?

The factors affect the same process and the limiting factor can change depending on conditions.

4.

How can two limiting factors interact to determine the rate of photosynthesis?

Increasing one factor may increase the rate until another factor becomes limiting.

5.

What would happen to the rate of photosynthesis if light intensity and carbon dioxide concentration were high but temperature was too low?

The rate remains low because temperature is limiting.

6.

Why does changing one environmental factor sometimes have little effect on the rate of photosynthesis?

Another factor may already be limiting the process.

6.5 Core Practical: Investigate the effect of light intensity on the rate of photosynthesis

1.

How could you investigate the effect of light intensity on the rate of photosynthesis?

Place an aquatic plant at different distances from a light source and measure the photosynthesis rate.

2.

How could the rate of photosynthesis be measured in an investigation using an aquatic plant?

Count bubbles of oxygen or measure oxygen volume produced per unit time.

3.

What variable should be changed when investigating the effect of light intensity on photosynthesis?

Light intensity, usually changed by varying the distance from the light source.

4.

Which variables should be controlled when investigating the effect of light intensity on photosynthesis?

Temperature, carbon dioxide concentration, plant species and amount of plant.

5.

Why should the distance between the light source and plant be measured accurately?

Light intensity depends on distance from the source.

6.

Why should the investigation be repeated at each light intensity?

To calculate a mean and identify anomalous results.

6.6 Explain how the rate of photosynthesis is directly proportional to light intensity and inversely proportional to the distance from a light source, including the use of the inverse square law calculation

1.

How is the rate of photosynthesis related to light intensity when light intensity is the limiting factor?

It is directly proportional when light intensity is the limiting factor.

2.

How is light intensity related to the distance from a light source?

Light intensity decreases as distance increases.

3.

What happens to light intensity when the distance from a light source is doubled?

It becomes one quarter as great.

4.

What is the inverse square law for light intensity?

Light intensity ∝ 1 ÷ distance².

5.

If the distance from a light source is tripled, by what factor does the light intensity change?

It becomes one ninth as great.

6.

How can the inverse square law be used to compare photosynthesis rates at different distances from a light source?

Calculate relative light intensity using 1 ÷ distance² and compare the corresponding rates.

6.7 Explain how the structure of the root hair cells is adapted to absorb water and mineral ions

1.

How does the long extension of a root hair cell help it absorb substances from the soil?

It increases surface area and contact with soil water.

2.

Why does a root hair cell have a large surface area?

A large surface area increases the rate of absorption.

3.

How does the thin surface of a root hair cell help water absorption?

It gives a short diffusion path for water.

4.

How are mineral ions absorbed into root hair cells?

They are absorbed by active transport when their concentration is lower in the soil than in the root cells.

5.

Why do root hair cells contain many mitochondria?

Active transport of mineral ions requires energy.

6.

How is the structure of a root hair cell adapted for absorbing water and mineral ions?

Long extension, large surface area, thin surface and many mitochondria adapt the cell for absorption.

6.8 Explain how the structures of the xylem and phloem are adapted to their function in the plant, including: a lignified dead cells in xylem transporting water and minerals through the plant b living cells in phloem using energy to transport sucrose around the plant

1.

How are xylem vessels adapted to transport water and mineral ions through a plant?

They form long hollow tubes with no end walls and lignified walls, allowing water and mineral ions to move through them.

2.

Why are xylem vessels made from dead cells?

The absence of cell contents leaves a continuous pathway.

3.

What is the function of lignin in xylem vessels?

It strengthens the vessels and prevents them collapsing.

4.

How are phloem tissues adapted to transport sucrose around a plant?

Living phloem cells are arranged in tubes and transport sucrose around the plant.

5.

Why do phloem cells require energy to transport sucrose?

Active translocation of sucrose requires energy.

6.

What are the key structural and functional differences between xylem and phloem?

Xylem is made of dead lignified cells and carries water and minerals; phloem is living tissue and carries sucrose.

6.9 Explain how water and mineral ions are transported through the plant by transpiration, including the structure and function of the stomata

1.

What is transpiration?

Loss of water vapour from leaves.

2.

How does transpiration help transport water through a plant?

Water loss creates a pull that draws water up through the xylem.

3.

How does water move from the roots to the leaves through the xylem?

Water moves upward through the xylem as part of the transpiration stream.

4.

What is the function of stomata in a plant?

They allow gas exchange and control water vapour loss.

5.

How does water vapour leave a leaf through the stomata?

Water evaporates from leaf cells and diffuses out through the stomata.

6.

How do stomata control the movement of gases and water vapour into and out of a leaf?

Guard cells open and close the stomata, controlling gas exchange and water vapour loss.

6.10 Describe how sucrose is transported around the plant by translocation

1.

What is translocation in plants?

Movement of sucrose through the phloem.

2.

Which substance is transported through the phloem by translocation?

Sucrose.

3.

From where to where can sucrose be transported by translocation?

Between sources and sinks around the plant.

4.

Why is translocation important for plants?

It supplies cells with sugars needed for respiration, growth and storage.

5.

Which tissue transports sucrose around a plant?

Phloem.

6.

How does translocation differ from the transport of water in the xylem?

Water is mainly transported upward in xylem, while sucrose can be transported from sources to sinks in phloem.

6.11B Explain how the structure of a leaf is adapted for photosynthesis and gas exchange

1.

How is the broad shape of a leaf adapted for photosynthesis?

It provides a large surface area for absorbing light.

2.

How are the palisade cells adapted for photosynthesis?

They contain many chloroplasts and are near the upper surface where light intensity is high.

3.

How does the thin structure of a leaf help gas exchange?

Gases have a short diffusion distance.

4.

How do stomata allow gas exchange in a leaf?

They allow carbon dioxide to enter and oxygen and water vapour to leave.

5.

How are air spaces inside the leaf adapted for gas exchange?

They provide a large internal surface area for gas diffusion.

6.

How is the structure of a leaf adapted to maximise photosynthesis while allowing efficient gas exchange?

Large surface area, thin structure, chloroplast-rich palisade cells, stomata and air spaces all improve photosynthesis and gas exchange.

6.12 Explain the effect of environmental factors on the rate of water uptake by a plant, to include light intensity, air movement and temperature

1.

How does increasing light intensity affect the rate of water uptake by a plant?

It increases.

2.

How does increasing air movement affect the rate of water uptake by a plant?

It increases.

3.

How does increasing temperature affect the rate of water uptake by a plant?

It usually increases.

4.

Why does increased air movement usually increase transpiration and water uptake?

It removes water vapour from around the leaf, maintaining a concentration gradient.

5.

Why does increasing temperature usually increase transpiration and water uptake?

It increases evaporation and diffusion of water vapour.

6.

How do light intensity, air movement and temperature affect water uptake by a plant?

Greater light intensity, air movement and temperature generally increase water uptake by increasing transpiration.

6.13 Demonstrate an understanding of rate calculations for transpiration

1.

How is the rate of transpiration calculated from the amount of water lost and the time taken?

Rate of water loss = amount of water lost ÷ time.

2.

A plant loses 6 cm³ of water in 3 hours. What is its mean rate of water loss?

6 ÷ 3 = 2 cm³/hour.

3.

A plant loses 0.8 g of water in 20 minutes. What is its rate of water loss in g/min?

0.8 ÷ 20 = 0.04 g/min.

4.

Why is the time unit important when calculating the rate of transpiration?

It determines the unit and value of the rate.

5.

How could a change in mass be used to calculate the rate of water loss from a plant?

Measure the decrease in mass over a known time and divide by time.

6.

What measurements are needed to calculate the rate of transpiration?

Amount of water lost and time taken.

6.14B Explain how plants are adapted to survive in extreme environments including the effect of leaf size and shape, the cuticle and stomata

1.

How does a small leaf size help a plant survive in a dry environment?

It reduces surface area and therefore water loss.

2.

How can leaf shape reduce water loss in plants adapted to extreme environments?

A suitable shape can reduce exposed surface area and water loss.

3.

How does a thick waxy cuticle help a plant survive in dry conditions?

It reduces evaporation of water from the leaf.

4.

How can the position or number of stomata reduce water loss?

Fewer or sunken stomata reduce water loss.

5.

Why might plants adapted to dry environments have fewer stomata?

Fewer stomata reduce the pathways for water vapour to leave.

6.

How do leaf size, leaf shape, the cuticle and stomata help plants survive extreme environments?

They reduce water loss while allowing enough gas exchange for survival.

6.15B Explain how plant hormones control and coordinate plant growth and development, including the role of auxins in phototropisms and gravitropisms

1.

What is the role of plant hormones in controlling and coordinating plant growth?

They act as chemical messengers controlling growth and development.

2.

What is a phototropism?

Growth response to light.

3.

How do auxins cause a plant shoot to grow towards light?

Auxin accumulates on the shaded side of the shoot and stimulates greater cell elongation there, causing bending towards light.

4.

What is a gravitropism?

Growth response to gravity.

5.

How do auxins cause plant roots to respond to gravity?

Auxin causes roots to grow downwards by affecting cell elongation.

6.

How do auxins coordinate growth responses in plant shoots and roots?

Auxin distribution causes unequal growth on different sides of shoots and roots.

6.16B Describe the commercial uses of auxins, gibberellins and ethene in plants, including: a auxins in weedkillers and rooting powders b gibberellins in germination, fruit and flower formation and the production of seedless fruit c ethene in fruit ripening

1.

How are auxins used commercially as weedkillers?

Selective auxin weedkillers cause rapid abnormal growth in weeds.

2.

How are auxins used commercially in rooting powders?

Auxins stimulate root formation in cuttings.

3.

How are gibberellins used commercially to promote germination?

They can stimulate germination.

4.

How are gibberellins used commercially in fruit and flower formation and the production of seedless fruit?

They can promote fruit and flower formation and produce seedless fruit.

5.

How is ethene used commercially in fruit ripening?

It is used to control and speed up fruit ripening.

6.

What are the main commercial uses of auxins, gibberellins and ethene?

Auxins: weedkillers and rooting powders; gibberellins: germination, fruit and flower formation and seedless fruit; ethene: fruit ripening.

7.1 Describe where hormones are produced and how they are transported from endocrine glands to their target organs, including the pituitary gland, thyroid gland, pancreas, adrenal glands, ovaries and testes

1.

Where are hormones produced in the human body?

In endocrine glands.

2.

How are hormones transported from endocrine glands to their target organs?

In the blood.

3.

What is the function of the pituitary gland as an endocrine gland?

It releases hormones that control other endocrine glands and body processes.

4.

What is the function of the thyroid gland as an endocrine gland?

It produces thyroxine, which affects metabolic rate.

5.

Which hormones are associated with the pancreas, adrenal glands, ovaries and testes?

Pancreas: insulin and glucagon; adrenal glands: adrenalin; ovaries: oestrogen and progesterone; testes: testosterone.

6.

What are the target organs of hormones and how do hormones affect them?

Target organs contain cells that respond to particular hormones, producing specific effects.

7.2 Explain that adrenalin is produced by the adrenal glands to prepare the body for fight or flight, including: a increased heart rate b increased blood pressure c increased blood flow to the muscles d raised blood sugar levels by stimulating the liver to change glycogen into glucose

1.

Where is adrenalin produced in the human body?

Adrenal glands.

2.

What is the role of adrenalin in the fight-or-flight response?

It prepares the body for rapid action.

3.

How does adrenalin affect heart rate during the fight-or-flight response?

It increases heart rate.

4.

How does adrenalin affect blood pressure during the fight-or-flight response?

It increases blood pressure.

5.

How does adrenalin increase blood flow to muscles during the fight-or-flight response?

It increases blood supply to the muscles.

6.

How does adrenalin increase blood glucose concentration during the fight-or-flight response?

It stimulates the liver to convert glycogen into glucose, increasing blood glucose concentration.

7.3 Explain how thyroxine controls metabolic rate as an example of negative feedback, including: a low levels of thyroxine stimulates production of TRH in hypothalamus b this causes release of TSH from the pituitary gland c TSH acts on the thyroid to produce thyroxine d when thyroxine levels are normal thyroxine inhibits the release of TRH and the production of TSH

1.

What is the role of thyroxine in controlling metabolic rate?

It controls the rate of metabolism.

2.

What happens to TRH production when thyroxine levels are low?

TRH production increases.

3.

What effect does TRH have on the pituitary gland?

It stimulates release of TSH.

4.

What effect does TSH have on the thyroid gland?

It stimulates the thyroid gland to produce thyroxine.

5.

What happens to TRH and TSH production when thyroxine levels return to normal?

Thyroxine inhibits TRH release and TSH production.

6.

Why is thyroxine regulation an example of negative feedback?

The response reduces the original change and returns thyroxine levels towards normal.

7.4 Describe the stages of the menstrual cycle, including the roles of the hormones oestrogen and progesterone, in the control of the menstrual cycle

1.

What happens to the uterus lining during menstruation?

The uterus lining is shed.

2.

What happens to the uterus lining during the first part of the menstrual cycle?

The lining thickens.

3.

What role does oestrogen have in repairing and maintaining the uterus lining?

It stimulates repair and thickening of the uterus lining.

4.

What happens during ovulation in the menstrual cycle?

An egg is released from the ovary.

5.

What role does progesterone have after ovulation?

It maintains the uterus lining.

6.

What happens to progesterone levels if fertilisation does not occur?

Progesterone levels fall.

7.5 Explain the interactions of oestrogen, progesterone, FSH and LH in the control of the menstrual cycle, including the repair and maintenance of the uterus wall, ovulation and menstruation

1.

What role does FSH play at the beginning of the menstrual cycle?

It stimulates an ovarian follicle to mature and begin producing oestrogen.

2.

What role does oestrogen play in the menstrual cycle?

It helps repair and thicken the uterus lining.

3.

How does oestrogen affect FSH production during the menstrual cycle?

High oestrogen reduces FSH and causes an increase in LH leading to ovulation.

4.

What role does LH play in causing ovulation?

A rise in LH causes ovulation.

5.

What role does progesterone play in maintaining the uterus lining?

It maintains the uterus lining.

6.

How do changes in progesterone and oestrogen levels cause menstruation?

Falling progesterone and oestrogen levels cause the lining to break down, resulting in menstruation.

7.6 Explain how hormonal contraception influences the menstrual cycle and prevents pregnancy

1.

How does hormonal contraception prevent pregnancy?

It changes hormone levels to prevent ovulation and reduce the chance of fertilisation.

2.

How can hormonal contraception prevent ovulation?

Hormones suppress the release of FSH and LH.

3.

How can hormonal contraception affect FSH and LH levels?

They reduce FSH and LH production.

4.

How can hormonal contraception alter the uterus lining?

It can make the uterus lining less suitable for implantation.

5.

How can hormonal contraception make it more difficult for sperm to reach an egg?

Some hormonal methods thicken cervical mucus.

6.

Why does hormonal contraception reduce the chance of fertilisation and pregnancy?

They make ovulation, fertilisation and implantation less likely.

7.7 Evaluate hormonal and barrier methods of contraception

1.

What is a hormonal method of contraception?

A method that uses hormones to prevent pregnancy.

2.

What is a barrier method of contraception?

A method that physically prevents sperm reaching the egg.

3.

How does the contraceptive pill prevent pregnancy?

It suppresses FSH and LH, preventing ovulation.

4.

How does a condom prevent pregnancy?

It acts as a physical barrier preventing sperm entering the female reproductive tract.

5.

What are advantages of hormonal contraception compared with barrier contraception?

They are generally more effective when used correctly and do not require use at the time of intercourse for some methods.

6.

What are advantages and disadvantages of barrier contraception compared with hormonal contraception?

Barrier methods do not alter hormone levels and condoms also reduce STI transmission, but they must be used correctly each time.

7.8 Explain the use of hormones in Assisted Reproductive Technology (ART) including IVF and clomifene therapy

1.

What is the role of hormones in IVF treatment?

They stimulate and control egg development and ovulation.

2.

How are hormones used to stimulate egg production during IVF?

Hormones stimulate the ovaries to mature several follicles.

3.

What is IVF?

Fertilisation occurs outside the body and an embryo is transferred to the uterus.

4.

Why are hormones used to control ovulation during IVF?

To control the timing of egg maturation and ovulation.

5.

What is clomifene therapy used to treat?

It is used to stimulate ovulation in women who do not ovulate normally.

6.

How does clomifene therapy increase the chance of ovulation?

It stimulates release of FSH and LH, encouraging ovulation.

7.9 Explain the importance of maintaining a constant internal environment in response to internal and external change

1.

What is meant by maintaining a constant internal environment?

Keeping conditions inside the body within narrow limits.

2.

Why must organisms maintain a constant internal environment?

Cells and enzymes need stable conditions to function effectively.

3.

How can changes in external temperature affect the internal environment?

It can cause the internal temperature to rise or fall.

4.

How can changes in blood glucose concentration affect the internal environment?

It can affect cell respiration and enzyme activity.

5.

How can changes in water concentration affect the internal environment?

It changes water balance and cell function.

6.

What is homeostasis and why is it important for cells?

Homeostasis is the maintenance of a stable internal environment and is essential for normal cell function.

7.10B Explain the importance of homeostasis, including: a thermoregulation – the effect on enzyme activity b osmoregulation – the effect on animal cells

1.

What is homeostasis?

Maintenance of a stable internal environment.

2.

Why is thermoregulation important for enzyme activity?

Enzymes work best within a narrow temperature range.

3.

What can happen to enzymes if body temperature becomes too high?

They can denature.

4.

What is osmoregulation?

Control of water concentration.

5.

Why is osmoregulation important for animal cells?

It prevents cells gaining or losing too much water.

6.

What can happen to animal cells if the water concentration of their surroundings changes significantly?

They may swell and burst or shrink, depending on the surrounding water concentration.

7.11B Explain how thermoregulation takes place, with reference to the function of the skin, including: a the role of the dermis b the role of the epidermis c the role of the hypothalamus

1.

What is the function of the dermis in thermoregulation?

It contains blood vessels, sweat glands and temperature receptors involved in heat loss.

2.

What is the function of the epidermis in the skin?

It forms the outer protective layer of the skin.

3.

What role does the hypothalamus play in thermoregulation?

It monitors body temperature and coordinates responses.

4.

How does the hypothalamus detect changes in body temperature?

Temperature receptors provide information about body temperature to the hypothalamus.

5.

How does the skin help maintain a constant body temperature?

It changes blood flow and sweating to control heat loss.

6.

How do the dermis, epidermis and hypothalamus work together in thermoregulation?

The hypothalamus detects changes and coordinates responses in the skin, while the dermis contains structures that produce heat loss and the epidermis provides protection.

7.12B Explain how thermoregulation takes place, with reference to: a shivering b vasoconstriction c vasodilation

1.

How does shivering increase body temperature?

Rapid muscle contractions release heat.

2.

What is vasoconstriction?

Narrowing of blood vessels near the skin.

3.

How does vasoconstriction reduce heat loss from the body?

Less blood flows near the surface, reducing heat loss.

4.

What is vasodilation?

Widening of blood vessels near the skin.

5.

How does vasodilation increase heat loss from the body?

More blood flows near the surface, increasing heat loss.

6.

How do shivering, vasoconstriction and vasodilation help maintain body temperature?

They reduce or increase heat loss to keep body temperature near normal.

7.13 Explain how the hormone insulin controls blood glucose concentration

1.

Where is insulin produced?

Pancreas.

2.

What happens to insulin secretion when blood glucose concentration increases?

It increases.

3.

How does insulin reduce blood glucose concentration?

It causes cells to take up more glucose and stimulates glycogen formation.

4.

How does insulin affect the uptake of glucose by body cells?

It increases uptake of glucose by cells.

5.

How does insulin affect glycogen formation in the liver?

It stimulates glucose to be converted into glycogen for storage.

6.

Why does insulin help maintain a stable blood glucose concentration?

It lowers blood glucose when it rises above the normal range.

7.14 Explain how blood glucose concentration is regulated by glucagon

1.

Where is glucagon produced?

Pancreas.

2.

What happens to glucagon secretion when blood glucose concentration becomes too low?

It increases.

3.

How does glucagon increase blood glucose concentration?

It stimulates the liver to break down glycogen to glucose.

4.

What effect does glucagon have on glycogen in the liver?

It causes glycogen to be converted into glucose.

5.

How do insulin and glucagon work together to regulate blood glucose concentration?

Insulin lowers blood glucose; glucagon raises it.

6.

Why is glucagon important during periods when blood glucose concentration is low?

It prevents blood glucose concentration becoming too low.

7.15 Explain the cause of type 1 diabetes and how it is controlled

1.

What causes type 1 diabetes?

The immune system destroys insulin-producing cells in the pancreas.

2.

Why does a person with type 1 diabetes have insufficient insulin?

The cells producing insulin are destroyed.

3.

How does type 1 diabetes affect blood glucose concentration?

It causes blood glucose concentration to rise.

4.

How can type 1 diabetes be controlled?

Insulin injections, monitoring blood glucose, diet and exercise.

5.

Why must people with type 1 diabetes monitor their blood glucose concentration?

To adjust insulin treatment and avoid dangerously high or low glucose levels.

6.

How does insulin treatment help a person with type 1 diabetes?

It replaces the insulin the body cannot produce adequately.

7.16 Explain the cause of type 2 diabetes and how it is controlled

1.

What causes type 2 diabetes?

Body cells become less responsive to insulin, often linked to genetic factors and obesity.

2.

What is insulin resistance?

Reduced sensitivity of cells to insulin.

3.

How does type 2 diabetes affect blood glucose concentration?

Blood glucose concentration remains too high.

4.

How can changes in diet help control type 2 diabetes?

A healthy diet can help reduce excess body mass and improve blood glucose control.

5.

How can regular exercise help control type 2 diabetes?

It can improve insulin sensitivity and help control blood glucose.

6.

How can medication be used to control type 2 diabetes?

Drugs can improve insulin action or reduce blood glucose concentration.

7.17 Evaluate the correlation between body mass and type 2 diabetes including waist:hip calculations and BMI, using the BMI equation

1.

What is the relationship between increased body mass and the risk of developing type 2 diabetes?

Greater body mass, particularly excess body fat, is associated with increased risk.

2.

What does BMI measure?

A measure comparing body mass with height.

3.

What is the equation used to calculate BMI?

BMI = mass in kg ÷ height in m².

4.

How is waist-to-hip ratio calculated?

Waist-to-hip ratio = waist circumference ÷ hip circumference.

5.

Why can BMI and waist-to-hip ratio be useful when assessing the risk of type 2 diabetes?

They can indicate body fat distribution and help assess disease risk.

6.

What are limitations of using BMI to assess an individual's risk of type 2 diabetes?

BMI does not distinguish fat from muscle and does not directly measure body fat distribution.

7.18B Describe the structure of the urinary system

1.

What are the main organs of the human urinary system?

Kidneys, ureters, bladder and urethra.

2.

What is the function of the kidneys in the urinary system?

Filter the blood and produce urine.

3.

What is the function of the ureters?

Carry urine from the kidneys to the bladder.

4.

What is the function of the bladder?

Stores urine.

5.

What is the function of the urethra?

Carries urine out of the body.

6.

What is the pathway taken by urine from the kidneys to outside the body?

Kidneys → ureters → bladder → urethra → outside the body.

7.19B Explain how the structure of the nephron is related to its function in filtering the blood and forming urine including: a filtration in the glomerulus and Bowman's capsule b selective reabsorption of glucose c reabsorption of water

1.

What is a nephron?

The functional unit of the kidney.

2.

Where does filtration of the blood occur in a nephron?

In the glomerulus and Bowman's capsule.

3.

What happens to small molecules during filtration in the glomerulus and Bowman's capsule?

Small molecules and water are forced out of the blood into the filtrate.

4.

Where is glucose selectively reabsorbed in the nephron?

In the proximal convoluted tubule.

5.

Why is glucose normally completely reabsorbed from the filtrate?

Glucose is useful and normally needs to be returned to the blood.

6.

How is water reabsorbed from the filtrate during urine formation?

Water is reabsorbed by osmosis from the filtrate into the blood.

7.20B Explain the effect of ADH on the permeability of the collecting duct in regulating the water content of the blood

1.

Where is ADH produced and released?

It is produced in the hypothalamus and released by the pituitary gland.

2.

What happens to ADH levels when the water content of the blood is too low?

ADH levels increase.

3.

How does ADH affect the permeability of the collecting duct?

It increases the permeability of the collecting duct.

4.

How does increased ADH concentration affect water reabsorption?

More water is reabsorbed into the blood.

5.

What happens to the volume and concentration of urine when ADH levels increase?

Urine volume decreases and urine becomes more concentrated.

6.

What happens to ADH levels when the water content of the blood is too high?

ADH levels decrease.

7.21B Describe the treatments for kidney failure, including kidney dialysis and organ donation

1.

What is kidney failure?

The kidneys can no longer adequately filter the blood and regulate water and ion balance.

2.

How does kidney dialysis help a person with kidney failure?

It removes waste substances and excess water from the blood.

3.

What substances are removed from the blood during dialysis?

Urea and excess ions or water.

4.

What are the disadvantages of long-term kidney dialysis?

It is time-consuming, requires regular treatment and can restrict lifestyle.

5.

How can a kidney transplant treat kidney failure?

A healthy donated kidney takes over the filtration function.

6.

What are the advantages and disadvantages of receiving a donated kidney?

Advantage: can restore kidney function without repeated dialysis. Disadvantage: rejection and lifelong treatment may be required.

7.22B State that urea is produced from the breakdown of excess amino acids in the liver

1.

Where is urea produced?

Liver.

2.

From what substances is urea produced?

Excess amino acids.

3.

Why is urea produced from excess amino acids?

They cannot be stored, so they are broken down.

4.

Why can excess amino acids not simply be stored in the body?

Excess amino acids cannot be stored in the same way as glucose or fat.

5.

What happens to excess amino acids before urea is produced?

Their amino groups are removed by deamination.

6.

Which organ removes urea from the blood and forms it into urine?

Kidneys.

8.1 Describe the need to transport substances into and out of a range of organisms, including oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea

1.

Why do multicellular organisms need to transport substances into and out of their cells?

They are too large to rely on diffusion alone over long distances.

2.

Why do multicellular organisms need to transport oxygen to their cells?

Oxygen is needed for aerobic respiration.

3.

Why do multicellular organisms need to transport carbon dioxide away from their cells?

It is produced by respiration and must be removed to prevent harmful accumulation.

4.

Why do multicellular organisms need to transport water and mineral ions around the body?

They are needed for metabolism and other cell processes.

5.

Why do multicellular organisms need to transport dissolved food molecules to their cells?

They provide nutrients and energy sources for cells.

6.

Why does urea need to be transported away from cells?

Urea is a waste product that must be removed because it is toxic at high concentrations.

8.2 Explain the need for exchange surfaces and a transport system in multicellular organisms including the calculation of surface area : volume ratio

1.

Why do multicellular organisms need specialised exchange surfaces?

To provide a large area for rapid exchange of substances.

2.

Why do multicellular organisms need transport systems?

To move substances between exchange surfaces and cells.

3.

Why does a large surface area : volume ratio increase the efficiency of exchange?

A large surface area compared with volume gives more area for exchange per unit volume.

4.

How is surface area : volume ratio calculated?

Surface area : volume ratio = surface area ÷ volume.

5.

How does an organism's size affect its surface area : volume ratio?

As size increases, surface area : volume ratio decreases.

6.

Why can simple diffusion alone be insufficient to supply the needs of large multicellular organisms?

Diffusion distances become too large and the surface area : volume ratio becomes too small.

8.3 Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

1.

How are alveoli adapted to provide a large surface area for gas exchange?

There are many alveoli, giving a large surface area.

2.

How does the thin wall of an alveolus increase the rate of gas exchange?

The wall is one cell thick, giving a short diffusion distance.

3.

How does the blood supply around alveoli maintain a concentration gradient for diffusion?

Continuous blood flow removes oxygen and brings carbon dioxide, maintaining a concentration gradient.

4.

How does ventilation of the lungs maintain a concentration gradient for gas exchange?

Ventilation replaces air, maintaining concentration gradients.

5.

How does oxygen diffuse from the alveoli into the blood?

Oxygen diffuses down its concentration gradient from the alveoli into the blood.

6.

How does carbon dioxide diffuse from the blood into the alveoli?

Carbon dioxide diffuses down its concentration gradient from the blood into the alveoli.

8.4B Describe the factors affecting the rate of diffusion, including surface area, concentration gradient and diffusion distance

1.

How does increasing surface area affect the rate of diffusion?

It increases the rate.

2.

How does increasing the concentration gradient affect the rate of diffusion?

It increases the rate.

3.

How does increasing diffusion distance affect the rate of diffusion?

It decreases the rate.

4.

Why does a larger surface area allow substances to diffuse more quickly?

More particles can cross the surface at the same time.

5.

Why does a steeper concentration gradient increase the rate of diffusion?

There is a greater difference in concentration between the two sides.

6.

Why does a shorter diffusion distance increase the rate of diffusion?

Particles travel a shorter distance.

8.5B Calculate the rate of diffusion using Fick's law: surface area concentration difference diffusion thickness of membrane rate of × α

1.

What factors are directly proportional to the rate of diffusion according to Fick's law?

Surface area and concentration difference.

2.

What factor is inversely proportional to the rate of diffusion according to Fick's law?

Membrane thickness.

3.

How does doubling the surface area affect the rate of diffusion if all other factors remain constant?

It doubles.

4.

How does doubling the concentration difference affect the rate of diffusion if all other factors remain constant?

It doubles.

5.

How does doubling the thickness of a membrane affect the rate of diffusion if all other factors remain constant?

It halves.

6.

How can Fick's law be used to calculate a change in the rate of diffusion?

Rate ∝ (surface area × concentration difference) ÷ membrane thickness.

8.6 Explain how the structure of the blood is related to its function: a red blood cells (erythrocytes) b white blood cells (phagocytes and lymphocytes) c plasma d platelets

1.

How is the structure of a red blood cell adapted for transporting oxygen?

They are biconcave, have no nucleus and contain haemoglobin, giving a large surface area for oxygen transport.

2.

How are phagocytes adapted to defend the body against pathogens?

They can change shape and engulf pathogens by phagocytosis.

3.

How are lymphocytes adapted to defend the body against pathogens?

They have receptors that recognise antigens and produce specific antibodies.

4.

What is the function of plasma in the blood?

It transports dissolved substances such as nutrients, hormones, carbon dioxide and urea.

5.

What is the function of platelets in the blood?

They help blood clot to prevent blood loss and entry of pathogens.

6.

How does the structure of blood allow it to transport substances and defend the body?

Each component has structures adapted for transport, defence or clotting.

8.7 Explain how the structure of the blood vessels is related to their function

1.

How is the structure of an artery adapted to withstand high blood pressure?

Thick muscular and elastic walls withstand high pressure.

2.

How is the structure of a vein adapted to return blood to the heart?

They have thin walls, a large lumen and valves to help return blood at low pressure.

3.

How are valves in veins adapted to prevent the backflow of blood?

They prevent blood flowing backwards.

4.

How is the structure of a capillary adapted for exchange of substances with tissues?

They are very narrow and have walls one cell thick.

5.

Why do capillaries have walls that are only one cell thick?

They provide a short diffusion distance.

6.

How do the structures of arteries, veins and capillaries differ according to their functions?

Arteries have thick walls and small lumens; veins have thinner walls, larger lumens and valves; capillaries have one-cell-thick walls.

8.8 Explain how the structure of the heart and circulatory system is related to its function, including the role of the major blood vessels, the valves and the relative thickness of chamber walls

1.

How does the structure of the heart allow it to pump blood around the body?

Muscular chambers contract to pump blood and valves maintain one-way flow.

2.

What is the function of the major blood vessels connected to the heart?

Arteries carry blood away from the heart, veins return blood and the pulmonary vessels carry blood to and from the lungs.

3.

What is the function of the valves in the heart?

They prevent backflow.

4.

Why is the wall of the left ventricle thicker than the wall of the right ventricle?

It pumps blood to the whole body at high pressure.

5.

Why are the walls of the atria thinner than the walls of the ventricles?

The atria only push blood into the ventricles, so they need less force.

6.

How does the circulatory system ensure that oxygenated and deoxygenated blood are transported to the correct locations?

The left and right sides are separated, and the pulmonary and systemic circuits keep oxygenated and deoxygenated blood apart.

8.9 Describe cellular respiration as an exothermic reaction which occurs continuously in living cells to release energy for metabolic processes, including aerobic and anaerobic respiration

1.

What is cellular respiration?

A series of reactions that release energy from glucose.

2.

Why is cellular respiration described as an exothermic reaction?

It releases energy to the surroundings.

3.

Why does cellular respiration occur continuously in living cells?

Cells need a continuous energy supply for metabolic processes.

4.

What is the purpose of the energy released by cellular respiration?

It powers processes such as active transport, movement, growth and synthesis.

5.

What is aerobic respiration?

Respiration using oxygen to release energy from glucose.

6.

What is anaerobic respiration?

Respiration without oxygen.

8.10 Compare the process of aerobic respiration with the process of anaerobic respiration

1.

What is the difference between aerobic and anaerobic respiration?

Aerobic respiration uses oxygen and releases more energy; anaerobic respiration occurs without oxygen and releases less energy.

2.

Which type of respiration requires oxygen?

Aerobic respiration.

3.

Which type of respiration releases more energy per glucose molecule?

Aerobic respiration.

4.

What are the products of aerobic respiration?

Carbon dioxide and water.

5.

What are the products of anaerobic respiration in human muscle cells?

Lactic acid.

6.

Why does anaerobic respiration occur during vigorous exercise?

Oxygen cannot be supplied quickly enough to meet the muscles' energy demand.

8.11 Core Practical: Investigate the rate of respiration in living organisms

1.

How can the rate of respiration in a living organism be investigated experimentally?

Measure oxygen uptake or carbon dioxide production over time, for example using a respirometer.

2.

What measurement could be taken to determine the rate of respiration in a respiration experiment?

Change in gas volume or pressure over time.

3.

Why should temperature be controlled when investigating the rate of respiration?

Temperature affects respiration rate.

4.

Why is a control experiment needed when investigating the rate of respiration?

It shows whether changes are due to respiration rather than apparatus effects.

5.

How can the rate of respiration be calculated from experimental data?

Rate = change in measurement ÷ time.

6.

What variables should be controlled when investigating the rate of respiration in living organisms?

Temperature, amount of organism, species, food availability and apparatus conditions.

8.12 Calculate heart rate, stroke volume and cardiac output, using the equation cardiac output = stroke volume × heart rate

1.

What is meant by heart rate?

Number of heart beats per minute.

2.

What is meant by stroke volume?

Volume of blood pumped by the heart in one beat.

3.

What is meant by cardiac output?

Volume of blood pumped by the heart per minute.

4.

How is cardiac output calculated from stroke volume and heart rate?

Cardiac output = stroke volume × heart rate.

5.

What happens to cardiac output if heart rate increases while stroke volume remains constant?

It increases.

6.

What happens to cardiac output if stroke volume increases while heart rate remains constant?

It increases.

9.1 Describe the different levels of organisation from individual organisms, populations, communities, to the whole ecosystem

1.

What is an organism in an ecosystem?

An individual living thing.

2.

What is a population in an ecosystem?

All organisms of one species living in an area.

3.

What is a community in an ecosystem?

All the populations of different species living together in an area.

4.

What is an ecosystem?

A community and the abiotic environment interacting.

5.

What is the difference between a population and a community?

A population contains one species; a community contains many species.

6.

What is the correct order of organisation from an individual organism to an ecosystem?

Organism → population → community → ecosystem.

9.2 Explain how communities can be affected by abiotic and biotic factors, including: a temperature, light, water, pollutants b competition, predation

1.

How can temperature affect the organisms present in a community?

It affects enzyme activity, survival and reproduction.

2.

How can light intensity affect the organisms present in a community?

It affects photosynthesis and the organisms that can survive.

3.

How can water availability affect the organisms present in a community?

It affects the availability of water for organisms.

4.

How can pollutants affect the organisms present in a community?

They can damage or kill organisms and reduce population sizes.

5.

How can competition affect the size of populations within a community?

Competition for resources can reduce population size.

6.

How can predation affect the size of populations within a community?

Predators reduce prey populations and can affect population balance.

9.3 Describe the importance of interdependence in a community

1.

What is meant by interdependence between organisms in a community?

Organisms depend on other organisms for resources or survival.

2.

Why are organisms in a community dependent on other organisms?

They rely on food, pollination, shelter, reproduction or other interactions.

3.

How can a change in one population affect other populations in a community?

Changes in one population can alter food availability or competition for others.

4.

How does interdependence contribute to the stability of a community?

Interactions between populations can help maintain a balance.

5.

How can removing one species affect an interdependent community?

Other populations may increase or decrease.

6.

Why can changes in the population of one species have effects throughout a community?

Food webs and other dependencies link populations together.

9.4 Describe how the survival of some organisms is dependent on other species, including parasitism and mutualism

1.

What is parasitism?

A relationship where one organism benefits and the host is harmed.

2.

How does a parasite benefit from its host?

It obtains nutrients or another resource from the host.

3.

How can parasitism affect the survival of a host organism?

It can weaken the host and reduce its survival or reproduction.

4.

What is mutualism?

A relationship where both organisms benefit.

5.

How do both organisms benefit from a mutualistic relationship?

Both gain an advantage such as food, protection or transport.

6.

Why can the survival of some organisms depend on a mutualistic relationship with another species?

The relationship may provide an essential resource that neither organism can obtain as effectively alone.

9.5 Core Practical: Investigate the relationship between organisms and their environment using field-work techniques, including quadrats and belt transects

1.

How is a quadrat used to investigate the distribution of organisms in a habitat?

It is placed over an area to sample organisms and estimate abundance or distribution.

2.

Why should quadrats be placed randomly when investigating the distribution of organisms?

To avoid bias and give every location an equal chance of being sampled.

3.

How is a belt transect used to investigate changes in the distribution of organisms across a habitat?

A series of quadrats is placed along a line to show changes across the habitat.

4.

Why are several quadrats used when investigating organisms in a habitat?

To obtain more representative data.

5.

How can a belt transect be used to investigate the effect of an environmental gradient on organisms?

Compare abundance at different positions along the gradient.

6.

What measurements can be collected using quadrats and belt transects during ecological fieldwork?

Number of organisms, percentage cover, frequency or abundance at different locations.

9.6 Explain how to determine the number of organisms in a given area using raw data from field-work techniques, including quadrats and belt transects

1.

How can the number of organisms in a given area be estimated using quadrat data?

Calculate the mean number per quadrat and scale it up to the total habitat area.

2.

How can the mean number of organisms per quadrat be calculated?

Mean = total number of organisms counted ÷ number of quadrats.

3.

How can the estimated total number of organisms in a habitat be calculated from quadrat data?

Mean organisms per quadrat × number of quadrats that would cover the habitat.

4.

How can quadrat data be used to estimate population density?

Population density = number of organisms ÷ area sampled.

5.

How can belt transect data be used to determine how organism numbers change across a habitat?

Compare counts or percentage cover at different positions along the transect.

6.

Why does using multiple quadrats improve the reliability of an estimate of organism numbers?

It reduces the effect of random variation and gives a more representative sample.

9.7B Explain how some energy is transferred to less useful forms at each trophic level and that this affects the number of organisms at each trophic level, limits the length of a food chain and determines the shape of a pyramid of biomass in an ecosystem

1.

Why is less energy available at each successive trophic level in a food chain?

Energy is lost through respiration, movement, heat and waste at each level.

2.

How is energy transferred to less useful forms at each trophic level?

It is dissipated mainly as thermal energy through respiration, and energy is lost in waste and uneaten material.

3.

Why does the amount of energy available affect the number of organisms at each trophic level?

Less available energy means less biomass can be supported.

4.

Why are food chains usually limited in length?

There is progressively less energy available at higher trophic levels.

5.

How does energy transfer between trophic levels affect the shape of a pyramid of biomass?

Biomass decreases at higher trophic levels.

6.

Why does a pyramid of biomass usually become narrower at higher trophic levels?

Less energy and biomass are available to support organisms at higher levels.

9.8B Calculate the efficiency of energy transfers between trophic levels and percentage calculations of biomass

1.

How is the efficiency of an energy transfer between trophic levels calculated?

Efficiency = energy transferred to next level ÷ energy entering the level × 100.

2.

How is the percentage change in biomass calculated?

Percentage change = change ÷ original × 100.

3.

How can the efficiency of energy transfer be calculated when the energy entering and leaving a trophic level are known?

Divide energy transferred out by energy transferred in and multiply by 100.

4.

What percentage efficiency results when 2000 kJ of energy enters a trophic level and 200 kJ is transferred to the next trophic level?

(200 ÷ 2000) × 100 = 10%.

5.

What percentage of biomass is transferred if a trophic level contains 500 kg of biomass and 50 kg is transferred to the next trophic level?

(50 ÷ 500) × 100 = 10%.

6.

Why is the efficiency of energy transfer between trophic levels usually less than 100%?

Energy is lost through respiration, movement, waste, death and uneaten material.

9.9 Explain the positive and negative human interactions within ecosystems and their impacts on biodiversity, including: a fish farming b introduction of non-indigenous species c eutrophication

1.

How can fish farming have positive effects on food production?

It provides a controlled source of fish for food.

2.

How can fish farming negatively affect biodiversity?

Waste, disease and escaped fish can affect natural ecosystems and biodiversity.

3.

How can introducing a non-indigenous species affect biodiversity?

It may compete with native species, prey on them or introduce disease.

4.

Why can a non-indigenous species become invasive?

It may have no natural predators or competitors and spread rapidly.

5.

What is eutrophication?

Nutrient enrichment of water caused by substances such as nitrates and phosphates.

6.

How can eutrophication reduce biodiversity in an aquatic ecosystem?

It can cause algal blooms, followed by oxygen depletion and death of aquatic organisms.

9.10 Explain the benefits of maintaining local and global biodiversity, including the conservation of animal species and the impact of reforestation

1.

What is biodiversity?

The variety of different species and genetic variation.

2.

Why is maintaining biodiversity important for ecosystems?

It increases ecosystem stability and provides resources and ecosystem services.

3.

How can conserving animal species help maintain biodiversity?

It prevents species extinction and maintains food webs.

4.

What are the benefits of maintaining global biodiversity?

It provides genetic resources, ecosystem services and resilience to environmental change.

5.

How can reforestation increase biodiversity?

It creates habitats and increases the number of species that can survive.

6.

How can reforestation benefit ecosystems and the environment?

It can absorb carbon dioxide, reduce soil erosion and restore habitats.

9.11B Describe the biological factors affecting levels of food security, including: a increasing human population b increasing animal farming and the increased meat and fish consumption c the impact of new pests and pathogens d environmental change caused by human activity e sustainability issues, e.g. use of land for biofuel production and the cost of agricultural inputs

1.

How can an increasing human population affect global food security?

More people require more food.

2.

How can increasing animal farming affect food security?

It uses large amounts of land, water and feed.

3.

How can increased meat and fish consumption affect food security?

Increased demand can place greater pressure on food resources and ecosystems.

4.

How can new pests and pathogens reduce food security?

They can reduce crop or livestock yields.

5.

How can environmental change caused by human activity affect food security?

Climate change, pollution, deforestation and habitat destruction can reduce agricultural productivity.

6.

How can the use of land for biofuel production and the cost of agricultural inputs affect food security?

Land used for biofuels may not be available for food, while expensive fertilisers, fuel or pesticides can increase food production costs.

9.12 Describe how different materials cycle through the abiotic and biotic components of an ecosystem

1.

What is meant by an abiotic component of an ecosystem?

A non-living part of an ecosystem.

2.

What is meant by a biotic component of an ecosystem?

A living part of an ecosystem.

3.

How do materials move between abiotic and biotic components of an ecosystem?

Through processes such as feeding, excretion, decomposition and gas exchange.

4.

Why must materials be recycled within ecosystems?

The supply of materials is finite within an ecosystem.

5.

Which processes allow materials to move between living organisms and the non-living environment?

Photosynthesis, respiration, feeding, excretion and decomposition.

6.

How do material cycles help maintain ecosystems?

They return nutrients and other materials to organisms and the environment.

9.13 Explain the importance of the carbon cycle, including the processes involved and the role of microorganisms as decomposers

1.

Why is the carbon cycle important to ecosystems?

It recycles carbon between organisms and the atmosphere and provides carbon for biological molecules.

2.

How does photosynthesis remove carbon dioxide from the atmosphere?

Plants absorb carbon dioxide during photosynthesis.

3.

How does respiration return carbon dioxide to the atmosphere?

Organisms release carbon dioxide during respiration.

4.

How does combustion return carbon dioxide to the atmosphere?

Burning fuels or biomass releases carbon dioxide.

5.

How do microorganisms act as decomposers in the carbon cycle?

They break down dead organisms and waste.

6.

How does decomposition return carbon compounds to the environment?

Decomposers break down organic material and release carbon dioxide through respiration, returning carbon compounds to the environment.

9.14 Explain the importance of the water cycle, including the processes involved and the production of potable water in areas of drought including desalination

1.

Why is the water cycle important to ecosystems?

It recycles water needed by living organisms and ecosystems.

2.

How does evaporation contribute to the water cycle?

Liquid water changes to water vapour.

3.

How does condensation contribute to the water cycle?

Water vapour cools and forms liquid droplets.

4.

How does precipitation return water to the Earth's surface?

Rain or other forms of precipitation return water to the surface.

5.

How can desalination produce potable water in areas affected by drought?

Remove dissolved salts from seawater to produce freshwater.

6.

Why is desalination useful in areas where freshwater supplies are limited?

It provides an additional source of freshwater where natural supplies are insufficient.

9.15 Explain how nitrates are made available for plant uptake, including the use of fertilisers, crop rotation and the role of bacteria in the nitrogen cycle

1.

Why do plants need nitrate ions?

They are needed to make amino acids and proteins.

2.

How can fertilisers increase the availability of nitrates for plant uptake?

They add nitrate ions or compounds that provide them to the soil.

3.

How does crop rotation increase the availability of nitrates in soil?

Growing legumes increases nitrogen fixation, improving soil nitrogen for later crops.

4.

What role do bacteria play in making nitrates available to plants?

They convert nitrogen between different compounds in the nitrogen cycle.

5.

How do nitrogen-fixing bacteria contribute to the nitrogen cycle?

They convert atmospheric nitrogen into nitrogen compounds that can enter the soil.

6.

Why are bacteria important for maintaining the supply of nitrogen compounds available to plants?

They make nitrogen compounds available in forms plants can absorb.

9.16B Evaluate the use of indicator species as evidence to assess the level of pollution, including: a polluted water – bloodworm, sludgeworm b clean water – freshwater shrimps, stonefly c air quality – different species of lichen, blackspot fungus on roses

1.

What are indicator species?

Organisms whose presence or absence indicates particular environmental conditions.

2.

Which organisms can indicate polluted water?

Bloodworms and sludgeworms.

3.

Which organisms can indicate clean water?

Freshwater shrimps and stoneflies.

4.

How can different species of lichen be used to assess air quality?

Different lichen species vary in their tolerance to air pollution.

5.

How can blackspot fungus on roses be used as an indicator of air quality?

Its presence or absence can indicate air pollution levels.

6.

Why are indicator species useful for assessing levels of pollution?

They provide biological evidence of environmental conditions over time.

9.17B Explain the effects of temperature, water content and oxygen availability on the rate of decomposition in food preservation

1.

How does temperature affect the rate of decomposition during food preservation?

Lower temperature slows enzyme activity and microbial growth.

2.

How does water content affect the rate of decomposition during food preservation?

Lower water availability reduces microbial activity and slows decomposition.

3.

How does oxygen availability affect the rate of decomposition during food preservation?

Less oxygen can reduce aerobic microbial respiration and slow decomposition.

4.

Why does reducing temperature slow decomposition during food preservation?

Microorganisms and enzymes work more slowly at lower temperatures.

5.

Why does reducing water availability slow decomposition during food preservation?

Microorganisms have less available water for growth and activity.

6.

Why can reducing oxygen availability slow the decomposition of food?

Many decomposers require oxygen for aerobic respiration.

9.18B Explain the effects of temperature, water content and oxygen availability on the rate of decomposition in composting

1.

How does temperature affect the rate of decomposition during composting?

Increasing temperature within a suitable range increases decomposition rate.

2.

How does water content affect the rate of decomposition during composting?

Too little water slows decomposition; sufficient moisture allows decomposers to function.

3.

How does oxygen availability affect the rate of decomposition during composting?

More oxygen supports aerobic decomposers.

4.

Why does increasing temperature within suitable limits increase the rate of decomposition in composting?

Microorganisms become more active at suitable higher temperatures.

5.

Why is sufficient water important for decomposition during composting?

Water is needed for cell processes and microbial activity.

6.

Why is oxygen availability important for aerobic decomposition during composting?

Aerobic decomposers require oxygen for respiration and efficient decomposition.

9.19B Calculate rate changes in the decay of biological material

1.

How is the rate of decay of biological material calculated?

Rate of decay = change in mass ÷ time.

2.

What measurements are needed to calculate the rate of decay?

Change in mass and time taken.

3.

How can the rate of decay be calculated from a change in mass over a given time?

Divide the mass lost by the time taken.

4.

A biological material loses 30 g of mass in 10 days; what is its average rate of decay?

30 ÷ 10 = 3 g/day.

5.

A biological material loses 48 g of mass in 12 hours; what is its average rate of decay?

48 ÷ 12 = 4 g/hour.

6.

How can rates of decay be compared when biological materials are decomposing under different conditions?

Calculate rates using the same units and compare the values.

Biology

Edexcel GCSE Triple Science: Biology

Topic 1 – Key concepts in biology

1.1 Explain how the sub-cellular structures of eukaryotic and prokaryotic cells are related to their functions, including animal cells, plant cells and bacteria

1.2 Describe how specialised cells are adapted to their function, including sperm cells, egg cells and ciliated epithelial cells

1.3 Explain how changes in microscope technology, including electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures

1.4 Demonstrate an understanding of number, size and scale, including the use of estimations and explain when they should be used

1.5 Demonstrate an understanding of the relationship between quantitative units in relation to cells, including milli, micro, nano, pico and calculations with numbers written in standard form

1.6 Core Practical: Investigate biological specimens using microscopes, including magnification calculations and labelled scientific drawings from observations

1.7 Explain the mechanism of enzyme action including the active site and enzyme specificity

1.8 Explain how enzymes can be denatured due to changes in the shape of the active site

1.9 Explain the effects of temperature, substrate concentration and pH on enzyme activity

1.10 Core Practical: Investigate the effect of pH on enzyme activity

1.11 Demonstrate an understanding of rate calculations for enzyme activity

1.12 Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates, proteins and lipids and their breakdown into sugars, amino acids and fatty acids and glycerol

1.13B Core Practical: Investigate the use of chemical reagents to identify starch, reducing sugars, proteins and fats

1.14B Explain how the energy contained in food can be measured using calorimetry

1.15 Explain how substances are transported into and out of cells, including by diffusion, osmosis and active transport

1.16 Core Practical: Investigate osmosis in potatoes

1.17 Calculate percentage gain and loss of mass in osmosis

Topic 2 – Cells and control

2.1 Describe mitosis as part of the cell cycle, including the stages interphase, prophase, metaphase, anaphase and telophase and cytokinesis

2.2 Describe the importance of mitosis in growth, repair and asexual reproduction

2.3 Describe the division of a cell by mitosis as the production of two daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell, and that this results in the formation of two genetically identical diploid body cells

2.4 Describe cancer as the result of changes in cells that lead to uncontrolled cell division

2.5 Describe growth in organisms, including cell division and differentiation in animals and cell division, elongation and differentiation in plants

2.6 Explain the importance of cell differentiation in the development of specialised cells

2.7 Demonstrate an understanding of the use of percentiles charts to monitor growth

2.8 Describe the function of embryonic stem cells, stem cells in animals and meristems in plants

2.9 Discuss the potential benefits and risks associated with the use of stem cells in medicine

2.10B Describe the structures and functions of the brain including the cerebellum, cerebral hemispheres and medulla oblongata

2.11B Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using CT scanning and PET scanning to investigate brain function

2.12B Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system, including spinal injuries and brain tumours

2.13 Explain the structure and function of sensory receptors, sensory neurones, relay neurones in the CNS, motor neurones and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters

2.14 Explain the structure and function of a reflex arc including sensory, relay and motor neurones

2.15B Explain the structure and function of the eye as a sensory receptor including the role of the cornea and lens, the iris, and rod and cone cells in the retina

2.16B Describe defects of the eye including cataracts, long-sightedness, short-sightedness and colour blindness

2.17B Explain how cataracts, long-sightedness and short-sightedness can be corrected

Topic 3 – Genetics

3.1B Explain some of the advantages and disadvantages of asexual reproduction, including the lack of need to find a mate, a rapid reproductive cycle, but no variation in the population

3.2B Explain some of the advantages and disadvantages of sexual reproduction, including variation in the population, but the requirement to find a mate

3.3 Explain the role of meiotic cell division, including the production of four daughter cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes

3.4 Describe DNA as a polymer made up of two strands coiled to form a double helix, complementary base pairs joined by weak hydrogen bonds, and nucleotides consisting of a sugar, phosphate group and base

3.5 Describe the genome as the entire DNA of an organism and a gene as a section of a DNA molecule that codes for a specific protein

3.6 Explain how DNA can be extracted from fruit

3.7B Explain how the order of bases in a section of DNA decides the order of amino acids in the protein and that these fold to produce specifically shaped proteins such as enzymes

3.8B Describe the stages of protein synthesis, including transcription and translation

3.9B Describe how genetic variants in the non-coding DNA of a gene can affect phenotype by influencing the binding of RNA polymerase and altering the quantity of protein produced

3.10B Describe how genetic variants in the coding DNA of a gene can affect phenotype by altering the sequence of amino acids and therefore the activity of the protein produced

3.11B Describe the work of Gregor Mendel in discovering the basis of genetics and recognise the difficulties of understanding inheritance before the mechanism was discovered

3.12 Explain why there are differences in the inherited characteristics as a result of alleles

3.13 Explain the terms chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype, gamete and zygote

3.14 Explain monohybrid inheritance using genetic diagrams, Punnett squares and family pedigrees

3.15 Describe how the sex of offspring is determined at fertilisation, using genetic diagrams

3.16 Calculate and analyse outcomes using probabilities, ratios and percentages from monohybrid crosses and pedigree analysis for dominant and recessive traits

3.17B Describe the inheritance of the ABO blood groups with reference to codominance and multiple alleles

3.18B Explain how sex-linked genetic disorders are inherited

3.19 State that most phenotypic features are the result of multiple genes rather than single gene inheritance

3.20 Describe the causes of variation that influence phenotype, including genetic and environmental variation

3.21 Discuss the outcomes of the Human Genome Project and its potential applications within medicine

3.22 State that there is usually extensive genetic variation within a population of a species and that these arise through mutations

3.23 State that most genetic mutations have no effect on the phenotype, some mutations have a small effect on the phenotype and, rarely, a single mutation will significantly affect the phenotype

Topic 4 – Natural selection and genetic modification

4.1B Describe the work of Charles Darwin and Alfred Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on modern biology

4.2 Explain Charles Darwin's theory of evolution by natural selection

4.3 Explain how the emergence of resistant organisms supports Charles Darwin's theory of evolution including antibiotic resistance in bacteria

4.4 Describe the evidence for human evolution, based on fossils, including Ardi, Lucy and Richard Leakey's discoveries

4.5 Describe the evidence for human evolution based on stone tools

4.6B Describe how the anatomy of the pentadactyl limb provides scientists with evidence for evolution

4.7 Describe how genetic analysis has led to the suggestion of the three domains rather than the five kingdoms classification method

4.8 Explain selective breeding and its impact on food plants and domesticated animals

4.9B Describe the process of tissue culture and its advantages in medical research and plant breeding programmes

4.10 Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics

4.11 Describe the main stages of genetic engineering including the use of restriction enzymes, ligase, sticky ends and vectors

4.12B Explain the advantages and disadvantages of genetic engineering to produce GM organisms including the introduction of genes for insect resistance from Bacillus thuringiensis into crop plants

4.13B Explain the advantages and disadvantages of agricultural solutions to the demands of a growing human population, including use of fertilisers and biological control

4.14 Evaluate the benefits and risks of genetic engineering and selective breeding in modern agriculture and medicine, including practical and ethical implications

Topic 5 – Health, disease and the development of medicines

5.1 Describe health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the World Health Organization (WHO)

5.2 Describe the difference between communicable and non-communicable diseases