OCR Combined Science: Biology — Recall & Retrieval

B1.1a Describe how light microscopes and staining can be used to view cells

1.

Name the three main parts of a light microscope used to illuminate, support and magnify a specimen.

The three main parts are the lenses, which magnify the specimen; the stage, which supports the specimen; and the lamp, which illuminates the specimen.

2.

State the functions of the lenses, stage and lamp in a light microscope.

The lenses magnify the specimen, the stage supports the microscope slide, and the lamp provides light that passes through the specimen.

3.

Describe how a biological specimen is prepared using a microscope slide and cover slip.

A thin specimen is placed on a microscope slide, a drop of liquid or stain is added if required, and a cover slip is carefully lowered over the specimen.

4.

Why are stains used when viewing colourless cells or specimens under a light microscope?

Stains are used to increase contrast, making colourless cells and their structures easier to see.

5.

Explain how stains can help scientists distinguish between different cell structures or tissues.

Different stains bind to particular cell structures or tissues, causing them to appear different colours and allowing scientists to distinguish between structures.

6.

State how the total magnification of a light microscope is calculated and calculate the magnification when a ×10 eyepiece lens and a ×40 objective lens are used.

Total magnification = eyepiece magnification × objective magnification. For a ×10 eyepiece and ×40 objective: 10 × 40 = ×400.

B1.1b Explain how the main sub-cellular structures of eukaryotic cells (plants and animals) and prokaryotic cells are related to their functions

1.

Explain the functions of the nucleus, genetic material and chromosomes in a eukaryotic cell.

The nucleus contains the cell's genetic material, which is organised into chromosomes. Chromosomes contain genes that provide instructions for making proteins and controlling cell activities.

2.

Compare the location and arrangement of genetic material in eukaryotic and prokaryotic cells.

In eukaryotic cells, genetic material is enclosed within a nucleus and arranged into linear chromosomes. In prokaryotic cells, genetic material is not enclosed in a nucleus and consists mainly of a circular DNA molecule in the cytoplasm.

3.

What are plasmids, where are they found and what type of information can they carry?

Plasmids are small, circular DNA molecules found in prokaryotic cells. They carry additional genetic information, such as genes for antibiotic resistance.

4.

Explain how mitochondria are related to their function in cellular respiration.

Mitochondria are the site of aerobic cellular respiration, where energy is transferred to produce ATP. Their internal membranes provide a large surface area for reactions involved in respiration.

5.

Explain how chloroplasts are related to their function, including the role of chlorophyll.

Chloroplasts are the site of photosynthesis in plant cells. They contain chlorophyll, which absorbs light energy needed for photosynthesis.

6.

Explain the functions of the cell membrane and ribosomes, including receptor molecules, the selective barrier and protein synthesis.

The cell membrane is a selectively permeable barrier that controls the movement of substances into and out of the cell and contains receptor molecules involved in cell signalling. Ribosomes are the site of protein synthesis.

B1.1c Explain how electron microscopy has increased our understanding of sub-cellular structures

1.

What is meant by the resolution of a microscope?

Resolution is the ability of a microscope to distinguish between two points that are close together as separate points.

2.

How does the resolution of a transmission electron microscope compare with the resolution of a light microscope?

A transmission electron microscope (TEM) has a much higher resolution than a light microscope, allowing much smaller structures to be distinguished.

3.

Explain why a transmission electron microscope can reveal smaller sub-cellular structures than a light microscope.

A TEM uses a beam of electrons, which have a much shorter wavelength than visible light. This gives the electron microscope a much higher resolution.

4.

State two sub-cellular structures that can be seen in greater detail using an electron microscope.

Structures that can be seen in greater detail using an electron microscope include ribosomes and the internal membranes of mitochondria.

5.

Compare the structures that may be visible in a light micrograph with those visible in an electron micrograph.

A light micrograph can show larger structures such as the nucleus, cell wall, chloroplasts and vacuole, whereas an electron micrograph can reveal much smaller structures and detailed internal organisation.

6.

Explain how images produced by electron microscopes have increased scientists’ understanding of the internal structure and organisation of cells.

Electron microscopes have allowed scientists to observe smaller sub-cellular structures and their detailed internal organisation, improving understanding of how cell structures are arranged and how they relate to cell functions.

B1.2a Describe DNA as a polymer

1.

What is DNA?

DNA (deoxyribonucleic acid) is the molecule that carries genetic information in living organisms.

2.

What is meant by the term polymer?

A polymer is a large molecule made from many smaller repeating units called monomers.

3.

Explain why DNA is described as a polymer.

DNA is described as a polymer because it is a large molecule made from many repeating nucleotide monomers joined together.

4.

What smaller repeating units make up a DNA molecule?

DNA is made up of repeating units called nucleotides.

5.

Where is DNA found inside a eukaryotic cell?

In a eukaryotic cell, DNA is found mainly in the nucleus, where it is organised into chromosomes.

6.

Explain why DNA is important for living organisms.

DNA is important because it stores genetic information, including the instructions needed to make proteins and control the characteristics and activities of cells.

B1.2b Describe DNA as being made up of two strands forming a double helix

1.

How many strands make up a DNA molecule?

A DNA molecule consists of two strands.

2.

What is meant by the term double helix?

A double helix is a structure consisting of two strands twisted around each other in a spiral shape.

3.

Describe the overall shape of a DNA molecule.

DNA has the shape of a twisted ladder, with two strands forming the sides and paired bases forming the rungs.

4.

Explain how the two strands of DNA are arranged.

The two DNA strands run alongside each other and are held together by bonds between complementary bases.

5.

State the name given to the structure formed by the two DNA strands.

The two strands form a double helix.

6.

Explain why the double helix structure is important for storing genetic information.

The double helix provides a stable structure for storing genetic information while allowing the strands to separate when the DNA needs to be copied.

B1.2c Describe experiments that can be used to investigate enzymatic reactions

1.

What is an enzyme?

An enzyme is a biological catalyst, usually a protein, that speeds up a chemical reaction without being used up.

2.

Describe a practical method that could be used to investigate the activity of an enzyme.

An enzyme investigation could involve mixing an enzyme with its substrate under controlled conditions and measuring the rate of reaction, such as by measuring the time taken for a particular product to form or substrate to disappear.

3.

State the independent variable in an investigation of enzyme activity.

The independent variable is the factor deliberately changed, such as temperature, pH or substrate concentration.

4.

State the dependent variable that would be measured during an enzyme investigation.

The dependent variable is the rate of the enzyme-controlled reaction, determined from measurements taken during the experiment.

5.

Name two control variables that should be kept constant during an enzyme investigation.

Two control variables could be the volume or concentration of enzyme and the volume or concentration of substrate. Other factors, such as temperature or pH, may also need to be controlled depending on the independent variable.

6.

Explain how the results of an enzyme investigation could be presented and analysed using tables, calculations or graphs.

Results can be recorded in a table, used to calculate reaction rates, and plotted on a graph to identify patterns and determine the conditions that produce the highest enzyme activity.

B1.2d Explain the mechanism of enzyme action

1.

Explain the role of enzymes in metabolism.

Enzymes control metabolic reactions by acting as biological catalysts, increasing the rate of reactions in cells.

2.

What is the active site of an enzyme?

The active site is the specific region of an enzyme where the substrate binds and the reaction takes place.

3.

Explain the lock and key hypothesis and how it describes enzyme specificity.

The lock and key hypothesis states that an enzyme's active site has a specific shape that is complementary to its substrate, so only a particular substrate can bind effectively to that enzyme.

4.

Describe how temperature and pH affect the rate of enzyme-controlled reactions.

As temperature increases, enzyme activity generally increases until an optimum temperature is reached. Above the optimum, bonds maintaining the enzyme's structure can break, changing the shape of the active site and denaturing the enzyme. Enzymes also have an optimum pH; extreme pH values can alter the active site and reduce activity.

5.

Explain how substrate concentration and enzyme concentration affect the rate of enzyme-controlled reactions.

Increasing substrate concentration generally increases the reaction rate until all active sites are occupied and the enzyme becomes the limiting factor. Increasing enzyme concentration generally increases the reaction rate if sufficient substrate is available.

6.

Explain why enzymes are described as biological catalysts, referring to the active site, enzyme specificity and the factors affecting enzyme activity.

Enzymes are biological catalysts because they speed up metabolic reactions without being used up. Their specific active sites bind particular substrates, giving enzymes specificity. Enzyme activity is affected by factors including temperature, pH, substrate concentration and enzyme concentration.

B1.3a Describe cellular respiration as a universal chemical process, continuously occurring in all living cells that supply ATP

1.

What is cellular respiration?

Cellular respiration is a series of chemical reactions in cells that transfer energy from glucose to make ATP.

2.

Why is cellular respiration described as a universal chemical process?

Cellular respiration is described as a universal chemical process because it occurs in all living organisms.

3.

In which living cells does cellular respiration occur?

Cellular respiration occurs continuously in all living cells.

4.

What molecule is supplied by cellular respiration to provide energy for cellular processes?

Cellular respiration supplies ATP (adenosine triphosphate), which provides energy for cellular processes.

5.

Explain why cells require a continuous supply of ATP.

Cells require a continuous supply of ATP because ATP is constantly used to provide energy for cellular processes and must therefore be continually resynthesised.

6.

Explain why cellular respiration must occur continuously, even when an organism is resting.

Cellular respiration must occur continuously because cells constantly require energy for processes such as active transport, movement, growth and synthesis, even when an organism is resting.

B1.3b Describe cellular respiration as an exothermic reaction

1.

What is meant by an exothermic reaction?

An exothermic reaction is a chemical reaction that releases energy to the surroundings, usually as heat.

2.

Explain why cellular respiration is an exothermic reaction.

Cellular respiration is exothermic because the chemical reactions involved release energy from glucose.

3.

What happens to the energy released during cellular respiration?

Some of the energy released during respiration is transferred to ATP, while some is released as heat to the surroundings.

4.

How does the energy released during respiration benefit living organisms?

The energy released during respiration provides the energy needed for cellular processes, such as active transport, movement, growth and synthesis.

5.

Compare an exothermic reaction with an endothermic reaction.

An exothermic reaction releases energy to the surroundings, whereas an endothermic reaction takes in energy from the surroundings.

6.

Give one example of evidence that shows energy is released during respiration.

Evidence for energy release during respiration includes an increase in temperature, such as when heat produced by respiring organisms is detected.

B1.3c Compare the processes of aerobic and anaerobic respiration in plants/fungi and animals

1.

Compare the conditions required for aerobic and anaerobic respiration.

Aerobic respiration requires oxygen, whereas anaerobic respiration occurs without oxygen.

2.

State the reactants (substrates) used in aerobic respiration.

The substrates for aerobic respiration are glucose and oxygen.

3.

Compare the products formed during anaerobic respiration in animals with those formed in plants and fungi.

In animals, anaerobic respiration produces lactic acid. In plants and fungi, anaerobic respiration produces ethanol and carbon dioxide.

4.

Which type of respiration produces the greatest yield of ATP? Explain your answer.

Aerobic respiration produces the greatest yield of ATP because glucose is broken down more completely in the presence of oxygen.

5.

Complete a table comparing aerobic respiration, anaerobic respiration in animals, and anaerobic respiration in plants/fungi, including the conditions, substrates, products and ATP yield.

Aerobic: oxygen present, glucose + oxygen, carbon dioxide + water, high ATP yield. Anaerobic in animals: oxygen unavailable/insufficient, glucose, lactic acid, low ATP yield. Anaerobic in plants/fungi: oxygen unavailable/insufficient, glucose, ethanol + carbon dioxide, low ATP yield.

6.

Explain why organisms carry out anaerobic respiration even though it produces much less ATP than aerobic respiration.

Organisms carry out anaerobic respiration when oxygen is unavailable or insufficient, because it still releases some energy from glucose and produces ATP, although much less than aerobic respiration.

B1.3d Explain the importance of sugars in the synthesis and breakdown of carbohydrates

1.

What is meant by the terms monomer and polymer?

A monomer is a small molecule that can join with other monomers to form a polymer. A polymer is a large molecule made from many smaller repeating units.

2.

Which monomers join together to form carbohydrates?

Simple sugars such as glucose are the monomers used to build carbohydrates.

3.

Explain how carbohydrates are synthesised from sugars.

Carbohydrates are synthesised when sugar molecules are joined together to form larger carbohydrate molecules.

4.

Explain how carbohydrates are broken down into sugars.

Carbohydrates are broken down by breaking the bonds between their sugar units, producing smaller sugars such as glucose.

5.

Why is the synthesis and breakdown of carbohydrates important in living organisms?

Carbohydrate synthesis allows organisms to store and use energy, while carbohydrate breakdown provides sugars that can be used in processes such as cellular respiration.

6.

Explain why carbohydrates are described as polymers.

Carbohydrates are described as polymers because complex carbohydrates can consist of many sugar monomers joined together.

B1.3e Explain the importance of amino acids in the synthesis and breakdown of proteins

1.

What is meant by the terms monomer and polymer in relation to proteins?

In proteins, a monomer is an amino acid and a polymer is a protein made from many amino acids joined together.

2.

What are the monomers that make up proteins?

The monomers that make up proteins are amino acids.

3.

Explain how amino acids are joined together to synthesise proteins.

Amino acids are joined together by chemical bonds to form long chains called polypeptides, which fold to form proteins.

4.

Explain how proteins are broken down into amino acids.

Proteins are broken down by breaking the bonds between amino acids, producing individual amino acids.

5.

Why are amino acids important for the growth and repair of living organisms?

Amino acids are needed to synthesise proteins required for growth and repair of tissues and cells.

6.

Explain why proteins are described as polymers.

Proteins are described as polymers because they are large molecules made from many amino acid monomers joined together.

B1.3f Explain the importance of fatty acids and glycerol in the synthesis and breakdown of lipids

1.

Name the molecules that join together to form a lipid.

A lipid is formed from fatty acids and glycerol.

2.

Explain how fatty acids and glycerol are combined to synthesise lipids.

Fatty acids and glycerol are joined together by chemical reactions to synthesise lipids.

3.

Explain how lipids are broken down into fatty acids and glycerol.

Lipids are broken down by breaking the bonds between fatty acids and glycerol, releasing fatty acids and glycerol.

4.

Why are lipids important in living organisms?

Lipids are important as energy stores, provide insulation and form an important component of cell membranes.

5.

Compare the synthesis and breakdown of lipids with the synthesis and breakdown of carbohydrates.

Carbohydrates are made from sugar units, whereas lipids are made from fatty acids and glycerol. Both can be synthesised into larger molecules and broken down into smaller molecules.

6.

Explain why fatty acids and glycerol are essential building blocks of lipids.

Fatty acids and glycerol are essential building blocks of lipids because they combine to form the structure of lipid molecules and are released when lipids are broken down.

B1.4a Describe photosynthetic organisms as the main producers of food and therefore biomass for life on Earth

1.

What are photosynthetic organisms?

Photosynthetic organisms are organisms that use light energy to make organic substances, such as glucose, by photosynthesis.

2.

Give two examples of photosynthetic organisms.

Examples of photosynthetic organisms include green plants and algae.

3.

Explain why photosynthetic organisms are described as the main producers of food.

Photosynthetic organisms are the main producers of food because they make organic food molecules from carbon dioxide and water using light energy.

4.

What is meant by the term biomass?

Biomass is the total mass of living biological material in an organism, population or ecosystem.

5.

Explain why most food chains depend on photosynthetic organisms.

Most food chains depend on photosynthetic organisms because they produce organic food molecules that provide energy and biomass for other organisms.

6.

Explain why life on Earth depends on photosynthetic organisms.

Life on Earth depends on photosynthetic organisms because they provide food and biomass, and photosynthesis also releases oxygen needed for aerobic respiration.

B1.4b Describe the process of photosynthesis

1.

State the word equation for photosynthesis.

Carbon dioxide + water → glucose + oxygen.

2.

Identify the reactants and products of photosynthesis.

The reactants are carbon dioxide and water. The products are glucose and oxygen.

3.

Explain why photosynthesis is described as a two-stage process.

Photosynthesis can be described as a two-stage process because light energy is captured and used to drive reactions that ultimately produce glucose.

4.

Where in the cell does photosynthesis take place?

Photosynthesis takes place in the chloroplasts of photosynthetic cells.

5.

Explain the role of chloroplasts in photosynthesis.

Chloroplasts contain chlorophyll, which absorbs light energy needed to drive photosynthesis.

6.

Describe the process of photosynthesis from the entry of the reactants to the production of glucose and oxygen.

Carbon dioxide enters the leaf through the stomata and water is transported to the leaves through the xylem. Chlorophyll absorbs light energy, which is used to convert carbon dioxide and water into glucose, with oxygen released as a by-product.

B1.4c Describe photosynthesis as an endothermic reaction

1.

What is meant by an endothermic reaction?

An endothermic reaction is a chemical reaction that takes in energy from the surroundings.

2.

Explain why photosynthesis is an endothermic reaction.

Photosynthesis is endothermic because it requires an input of light energy to convert carbon dioxide and water into glucose and oxygen.

3.

What is the source of energy for photosynthesis?

The source of energy for photosynthesis is light energy from the Sun.

4.

Compare an endothermic reaction with an exothermic reaction.

An endothermic reaction takes in energy from the surroundings, whereas an exothermic reaction releases energy to the surroundings.

5.

Explain what happens to light energy during photosynthesis.

During photosynthesis, light energy is absorbed by chlorophyll and transferred into chemical energy stored in glucose.

6.

Give one piece of evidence that shows photosynthesis requires an input of energy.

Evidence that photosynthesis requires an input of energy is that photosynthesis only occurs when a suitable light source is available; plants exposed to light produce starch, whereas areas kept in darkness do not.

B1.4d Describe experiments to investigate photosynthesis

1.

Describe how a plant can be tested for starch to investigate photosynthesis.

To test a leaf for starch, boil the leaf in water, then heat it in ethanol in a water bath to remove chlorophyll. Rinse it in water and add iodine solution. A blue-black colour indicates starch.

2.

Why is part of a leaf covered with opaque material during a starch test?

Part of a leaf is covered with an opaque material to prevent light reaching that area, allowing it to be compared with an exposed area.

3.

Explain why a plant is destarched before investigating photosynthesis.

A plant is destarched by keeping it in darkness for a sufficient period of time, so that stored starch is used up before the investigation.

4.

Describe the purpose of iodine solution in a photosynthesis investigation.

Iodine solution is used to test for starch; it turns blue-black when starch is present.

5.

State what result would show that photosynthesis has occurred.

A blue-black colour shows that starch is present, providing evidence that photosynthesis has occurred.

6.

Explain how a starch test demonstrates the consequences of excluding light from a photosynthesising plant.

If the exposed part of a leaf turns blue-black but the covered part does not, this shows that excluding light prevents starch formation and therefore demonstrates that light is required for photosynthesis.

B1.4e Explain the effect of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis

1.

Explain how increasing light intensity affects the rate of photosynthesis.

Increasing light intensity generally increases the rate of photosynthesis because more light energy is available, until another factor becomes limiting and the rate levels off.

2.

Explain how carbon dioxide concentration affects the rate of photosynthesis.

Increasing carbon dioxide concentration generally increases the rate of photosynthesis because carbon dioxide is a reactant, until another factor becomes limiting.

3.

Explain how temperature affects the rate of photosynthesis.

As temperature increases, the rate of photosynthesis generally increases because enzyme-controlled reactions occur faster, up to an optimum temperature. Above the optimum, enzymes can become denatured and the rate decreases.

4.

Why does increasing one factor not always increase the rate of photosynthesis?

Increasing one factor does not always increase the rate because another factor may have become the limiting factor.

5.

Predict what would happen to the rate of photosynthesis if light intensity, carbon dioxide concentration or temperature were reduced.

Reducing light intensity or carbon dioxide concentration will generally decrease the rate of photosynthesis. Reducing temperature below the optimum will also decrease the rate.

6.

Explain how an investigation could be carried out to measure the effect of one factor on the rate of photosynthesis while keeping the other factors constant.

Change one factor, such as light intensity, while keeping temperature and carbon dioxide concentration constant. Measure the rate of photosynthesis, for example by measuring the volume of oxygen produced in a fixed time, and repeat the experiment at different values of the independent variable.

B1.4f Explain the interaction of temperature, light intensity and carbon dioxide concentration in limiting the rate of photosynthesis using graphs depicting the effects of the limiting factors

1.

What is meant by a limiting factor?

A limiting factor is a factor that, when in short supply, limits the rate of a process.

2.

Explain how light intensity can become the limiting factor for photosynthesis.

Light intensity can become the limiting factor when there is insufficient light energy for photosynthesis. Increasing light intensity then increases the rate until another factor becomes limiting.

3.

Explain how carbon dioxide concentration can become the limiting factor for photosynthesis.

Carbon dioxide concentration can become the limiting factor when there is insufficient carbon dioxide for photosynthesis. Increasing carbon dioxide concentration then increases the rate until another factor becomes limiting.

4.

Explain how temperature can become the limiting factor for photosynthesis.

Temperature can become a limiting factor when it is too low for enzyme-controlled reactions to occur rapidly. Increasing temperature increases the rate up to an optimum, beyond which the rate decreases because enzymes become denatured.

5.

Describe how a graph of photosynthesis changes when the limiting factor is increased and another factor becomes limiting.

On a graph, increasing the limiting factor initially causes the rate of photosynthesis to increase. The graph then levels off when another factor becomes limiting.

6.

Explain how graphs can be used to identify which factor is limiting the rate of photosynthesis under different conditions.

Graphs can identify the limiting factor by showing which variable causes the rate of photosynthesis to increase when it is increased. Once increasing that variable no longer increases the rate, another factor is limiting.

B2.1a Explain how substances are transported into and out of cells through diffusion, osmosis and active transport

1.

Compare diffusion, osmosis and active transport.

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane. Active transport is the movement of substances against a concentration gradient using energy.

2.

Explain how concentration gradients affect the movement of substances during diffusion.

During diffusion, particles move down their concentration gradient, from an area of higher concentration to an area of lower concentration, until they become more evenly distributed.

3.

Explain how water moves by osmosis, using the term water potential.

During osmosis, water molecules move from a region of higher water potential to lower water potential through a partially permeable membrane.

4.

Give one example of a substance transported by diffusion, one by osmosis and one by active transport.

Oxygen can be transported by diffusion, water by osmosis, and mineral ions can be transported by active transport.

5.

Explain the direction of movement of substances during diffusion, osmosis and active transport.

Diffusion moves particles from high to low concentration, osmosis moves water from high to low water potential, and active transport moves substances from low to high concentration.

6.

Explain why active transport requires energy whereas diffusion and osmosis do not.

Active transport requires energy because substances are moved against their concentration gradient, whereas diffusion and osmosis are passive processes that do not require energy from respiration.

B2.1b Describe the process of mitosis in growth, including the cell cycle

1.

What is the purpose of mitosis?

Mitosis produces new cells for growth, repair and replacement of damaged or worn-out cells.

2.

State the stages of the cell cycle in the correct order.

The cell cycle consists of cell growth, DNA replication, mitosis and cell division.

3.

What happens during DNA replication?

During DNA replication, the DNA molecule is copied so that each chromosome has two identical copies of its genetic information.

4.

Explain what happens to chromosomes during mitosis.

During mitosis, the chromosomes are separated so that one copy of each chromosome moves to each end of the cell.

5.

Explain how mitosis produces two genetically identical daughter cells.

Mitosis produces two genetically identical daughter cells because the DNA is replicated before mitosis and the replicated chromosomes are evenly separated between the two new cells.

6.

Explain why mitosis is important for growth and repair in multicellular organisms.

Mitosis is important for growth and repair because it produces new genetically identical cells, increasing cell number and replacing damaged or old cells.

B2.1c Explain the importance of cell differentiation

1.

What is meant by cell differentiation?

Cell differentiation is the process by which an unspecialised cell develops into a cell with a specialised structure and function.

2.

Explain why cell differentiation allows organisms to become more efficient.

Cell differentiation allows cells to become specialised for particular functions, making the organism more efficient.

3.

What is a specialised cell?

A specialised cell is a cell that has structures and features adapted to perform a particular function.

4.

Give three examples of specialised cells and state one function of each.

Red blood cells transport oxygen, nerve cells transmit electrical impulses, and root hair cells absorb water and mineral ions from the soil.

5.

Explain how cell differentiation produces specialised cells.

Cell differentiation occurs when cells develop different structures and functions due to different genes being expressed, producing specialised cells.

6.

Explain why multicellular organisms require many different specialised cell types.

Multicellular organisms require many specialised cell types because different cells perform different functions, allowing complex organisms to carry out all the processes needed for survival.

B2.1d Recall that stem cells are present in embryonic and adult animals, and meristems in plants

1.

What is a stem cell?

A stem cell is an unspecialised cell that can divide and produce new cells that can differentiate into specialised cell types.

2.

Where are embryonic stem cells found?

Embryonic stem cells are found in the early embryo.

3.

Where are adult stem cells found?

Adult stem cells are found in certain tissues and organs, such as bone marrow.

4.

Where are stem cells found in plants?

In plants, stem cells are found in meristems, particularly at the tips of roots and shoots.

5.

What is a meristem?

A meristem is a region of actively dividing, unspecialised plant cells that can differentiate into different plant cell types.

6.

Compare the locations of stem cells in embryonic animals, adult animals and plants.

Embryonic stem cells are found in early embryos, adult stem cells are found in particular tissues such as bone marrow, and plant stem cells are found in meristems.

B2.1e Describe the functions of stem cells in embryonic and adult animals, and meristems in plants

1.

What is the function of embryonic stem cells?

Embryonic stem cells divide and differentiate to produce the different specialised cell types needed to form the developing organism.

2.

What is the function of adult stem cells?

Adult stem cells produce new cells for growth and repair and replacement of damaged or worn-out cells in particular tissues.

3.

What is the function of meristems in plants?

Meristems produce new plant cells that can differentiate into different types of specialised plant cells, allowing plants to grow.

4.

Explain how stem cells contribute to development, growth and repair.

Stem cells contribute to development, growth and repair by dividing to produce new cells and differentiating into specialised cell types.

5.

Explain why stem cells are able to produce a range of different cell types.

Stem cells can produce a range of cell types because they are unspecialised cells that can divide and differentiate into specialised cells.

6.

Compare the roles of embryonic stem cells, adult stem cells and plant meristems.

Embryonic stem cells contribute to the development of the whole organism, adult stem cells mainly maintain and repair particular tissues, and plant meristems produce cells responsible for plant growth and development.

B2.1f Describe the difference between embryonic and adult stem cells in animals

1.

Compare embryonic and adult stem cells.

Embryonic stem cells are found in early embryos and can differentiate into a wide range of specialised cell types. Adult stem cells are found in particular tissues and generally have a more limited ability to differentiate.

2.

Which type of stem cell can differentiate into the greatest variety of cell types?

Embryonic stem cells can differentiate into the greatest variety of cell types.

3.

Explain why embryonic stem cells have greater potential than adult stem cells.

Embryonic stem cells have greater potential because they are less specialised and can differentiate into many different types of cell.

4.

State one similarity between embryonic and adult stem cells.

Both embryonic and adult stem cells are unspecialised cells that can divide and differentiate into specialised cells.

5.

Give one example of a use for adult stem cells in the body.

Adult stem cells can be used to produce new blood cells from bone marrow stem cells, helping to replace damaged or diseased blood cells.

6.

Explain why embryonic stem cells are particularly important during early development.

Embryonic stem cells are particularly important during early development because they can differentiate into many different specialised cell types needed to form the developing organism.

B2.2a Explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area : volume ratio

1.

What is meant by the term surface area : volume ratio?

The surface area : volume ratio compares the total surface area of an organism or object with its total volume.

2.

Calculate the surface area, volume and surface area : volume ratio of a cube with sides measuring 3 cm.

For a cube with sides of 3 cm: surface area = 6 × 3² = 54 cm²; volume = 3³ = 27 cm³; surface area : volume ratio = 54 : 27 = 2 : 1.

3.

Explain how the surface area : volume ratio changes as an organism increases in size.

As an organism increases in size, its volume increases faster than its surface area, so its surface area : volume ratio decreases.

4.

Explain why cells in large multicellular organisms cannot obtain enough oxygen and nutrients by diffusion alone.

Large multicellular organisms have a small surface area : volume ratio, so there is not enough surface area for sufficient oxygen and nutrients to enter all cells by diffusion alone.

5.

Explain why increasing diffusion distance reduces the efficiency of diffusion in large organisms.

A greater diffusion distance means substances take longer to diffuse, reducing the rate and efficiency of diffusion.

6.

Explain why multicellular organisms require specialised exchange surfaces and transport systems, making reference to surface area : volume ratio and diffusion distance.

Large multicellular organisms require specialised exchange surfaces with a large surface area and short diffusion distances, together with transport systems, because their low surface area : volume ratio makes diffusion alone insufficient to supply all cells.

B2.2b Describe some of the substances transported into and out of a range of organisms in terms of the requirements of those organisms

1.

Name four substances that are transported into or out of living organisms.

Four substances transported into or out of organisms are oxygen, carbon dioxide, water and dissolved food molecules.

2.

Explain why oxygen is transported into animal cells.

Oxygen is transported into animal cells for use in aerobic respiration, which releases energy and produces ATP.

3.

Explain why carbon dioxide is transported out of animal cells.

Carbon dioxide is transported out of animal cells because it is a waste product of aerobic respiration and can be harmful if it accumulates.

4.

Explain why water must be transported into and around living organisms.

Water must be transported into and around organisms because it is needed for chemical reactions, transport and maintaining cells, and is a raw material for photosynthesis in plants.

5.

Explain why dissolved food molecules are transported to cells throughout the body.

Dissolved food molecules such as glucose and amino acids are transported to cells so they can be used for respiration, growth, repair and synthesis of biological molecules.

6.

Compare the substances transported into and out of plants and animals, explaining why each substance is required.

Plants transport water and mineral ions into the plant and sugars away from photosynthesising tissues, while animals transport substances such as oxygen, glucose and amino acids to cells and carry carbon dioxide and urea away as waste products.

B2.2b Describe some of the substances transported into and out of a range of organisms in terms of the requirements of those organisms (2)

1.

Name six substances that are transported into or out of living organisms.

Six substances transported into or out of living organisms are oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea.

2.

Explain why oxygen is transported into animal cells.

Oxygen is transported into animal cells for aerobic respiration, allowing energy to be transferred to ATP.

3.

Explain why carbon dioxide is transported out of animal cells.

Carbon dioxide is transported out of animal cells because it is a waste product of aerobic respiration.

4.

Explain why water and dissolved food molecules must be transported around multicellular organisms.

Water and dissolved food molecules must be transported around multicellular organisms because cells require water for chemical reactions and transport, while food molecules provide materials and energy for respiration, growth and repair.

5.

Explain why mineral ions are transported into plants.

Mineral ions are transported into plants because they are needed for healthy growth and the production of substances such as proteins and chlorophyll.

6.

Explain why urea is transported out of the body and identify where it is produced.

Urea is transported out of the body because it is a nitrogen-containing waste product. It is produced in the liver when excess amino acids are broken down.

B2.2c Describe the human circulatory system

1.

What is the main function of the human circulatory system?

The main function of the human circulatory system is to transport substances around the body, including oxygen, nutrients, carbon dioxide and waste products.

2.

Explain the relationship between the circulatory system and the gaseous exchange system.

The circulatory system transports oxygen from the lungs to body cells and carries carbon dioxide from body cells to the lungs for removal.

3.

What is meant by a double circulatory system?

A double circulatory system is a circulatory system in which blood passes through the heart twice during one complete circuit of the body.

4.

Describe the route taken by blood through the pulmonary and systemic circulations.

In the pulmonary circulation, blood travels from the right ventricle to the lungs and back to the left atrium. In the systemic circulation, blood travels from the left ventricle to the body and back to the right atrium.

5.

Explain why mammals require a double circulatory system.

Mammals require a double circulatory system because it allows blood to be pumped to the lungs for oxygenation and then pumped at high pressure to the rest of the body, supporting their high metabolic demands.

6.

Describe the arrangement of the blood vessels that make up the human circulatory system.

The circulatory system consists of the heart and blood vessels, including arteries, veins and capillaries, which form a network connecting the heart, lungs and body tissues.

B2.2d Explain how the structure of the heart and the blood vessels are adapted to their functions

1.

Name the four chambers of the mammalian heart.

The four chambers are the right atrium, right ventricle, left atrium and left ventricle.

2.

Name the four main valves and the major blood vessels entering and leaving the heart.

The main valves are the tricuspid, pulmonary, mitral and aortic valves. Major vessels include the vena cava, pulmonary artery, pulmonary vein and aorta.

3.

Explain how cardiac muscle is adapted for its function.

Cardiac muscle is adapted to contract repeatedly and rhythmically, allowing the heart to pump blood continuously around the body.

4.

Compare the structures of arteries, veins and capillaries, referring to wall thickness, lumen diameter and the presence of valves.

Arteries have thick muscular and elastic walls and a relatively narrow lumen, with no valves. Veins have thinner walls, a wider lumen and valves. Capillaries have very thin walls, only one cell thick, and a very narrow lumen.

5.

Explain why arteries, veins and capillaries each have different structural adaptations.

Arteries need strong, elastic walls to withstand high pressure. Veins need valves to prevent backflow because blood pressure is lower. Capillaries have thin walls to provide a short diffusion distance for exchange of substances.

6.

Explain how the adaptations of the heart and blood vessels allow blood to be transported efficiently around the body.

The heart provides pressure to move blood around the body, while the specialised structures of arteries, veins and capillaries allow blood to be transported efficiently and substances exchanged with tissues.

B2.2e Explain how red blood cells and plasma are adapted to their transport functions in the blood

1.

Explain how red blood cells are adapted to transport oxygen.

Red blood cells contain haemoglobin, which binds to oxygen. They have a biconcave shape and no nucleus, allowing efficient oxygen transport.

2.

Explain why red blood cells have a biconcave shape.

Their biconcave shape provides a large surface area and short diffusion distance, allowing oxygen to diffuse into and out of the cell efficiently.

3.

Explain why mature red blood cells do not contain a nucleus.

Mature red blood cells have no nucleus, providing more space for haemoglobin and therefore increasing their oxygen-carrying capacity.

4.

State the function of plasma.

Plasma is the liquid component of blood that transports dissolved substances around the body.

5.

Name four substances transported by plasma.

Plasma transports substances including carbon dioxide, urea, glucose and amino acids. It also transports hormones and mineral ions.

6.

Explain how the adaptations of both red blood cells and plasma enable efficient transport throughout the body.

Red blood cells efficiently transport oxygen using haemoglobin, while plasma transports dissolved substances throughout the body, allowing materials and waste products to move efficiently between organs and tissues.

B2.2f Explain how water and mineral ions are taken up by plants, relating the structure of the root hair cells to their function

1.

Explain how water enters a root hair cell.

Water enters root hair cells by osmosis, moving from an area of higher water potential in the soil to lower water potential in the root hair cell through the partially permeable cell membrane.

2.

Explain how mineral ions enter a root hair cell.

Mineral ions enter root hair cells by active transport, moving from a lower concentration in the soil to a higher concentration inside the root hair cells using energy from respiration.

3.

Describe three adaptations of root hair cells that make them efficient at absorbing water and mineral ions.

Root hair cells have a large surface area, a long extension providing a short diffusion distance, and many mitochondria to provide energy for active transport.

4.

Explain why root hair cells have a large surface area.

Root hair cells have a large surface area, which provides more membrane through which water and mineral ions can be absorbed.

5.

Compare the uptake of water with the uptake of mineral ions into root hair cells.

Water enters root hair cells by osmosis down a water potential gradient without requiring energy, whereas mineral ions can enter by active transport against a concentration gradient using energy.

6.

Explain how the adaptations of root hair cells enable plants to absorb the substances needed for healthy growth.

The long extensions and large surface area of root hair cells increase absorption, while their mitochondria provide energy for active transport of mineral ions, allowing plants to obtain the water and minerals needed for growth.

B2.2g Describe the processes of transpiration and translocation

1.

Define the term transpiration.

Transpiration is the loss of water vapour from a plant, mainly through the stomata in the leaves.

2.

Define the term translocation.

Translocation is the transport of dissolved sugars, particularly sucrose, through the phloem from sources to sinks.

3.

Explain the role of the stomata during transpiration.

Stomata allow gas exchange and provide a route through which water vapour is lost from the leaves during transpiration.

4.

State the substances transported by the xylem during transpiration.

The xylem transports water and dissolved mineral ions from the roots to the rest of the plant.

5.

State the substances transported by the phloem during translocation.

The phloem transports dissolved sugars, such as sucrose, around the plant.

6.

Compare transpiration and translocation.

Transpiration is the loss of water vapour from leaves and is associated with the movement of water through the xylem, whereas translocation is the movement of dissolved sugars through the phloem.

B2.2h Explain how the structure of the xylem and phloem are adapted to their functions in the plant

1.

State the function of the xylem.

The xylem transports water and dissolved mineral ions from the roots to the rest of the plant.

2.

State the function of the phloem.

The phloem transports dissolved sugars, such as sucrose, around the plant.

3.

Describe two structural adaptations of xylem vessels that make them suitable for transporting water.

Xylem vessels are long, continuous hollow tubes with no end walls and have thick, lignified walls, providing strength and preventing collapse under tension.

4.

Describe two structural adaptations of phloem vessels that make them suitable for transporting dissolved sugars.

Phloem contains sieve tube elements with sieve plates that allow dissolved sugars to pass through. They are associated with companion cells, which provide the energy needed for transport.

5.

Compare the substances transported by xylem and phloem.

Xylem transports water and dissolved mineral ions, whereas phloem transports dissolved sugars, such as sucrose.

6.

Explain how the adaptations of xylem and phloem allow transport throughout the plant.

The hollow, strengthened structure of xylem vessels allows efficient movement of water, while the sieve tubes and companion cells of the phloem allow dissolved sugars to be transported throughout the plant.

B2.2i Explain the effect of a variety of environmental factors on the rate of water uptake by a plant

1.

Explain why increasing light intensity increases the rate of water uptake.

Increasing light intensity increases the rate of transpiration by causing stomata to open, increasing water loss from the leaves and therefore increasing water uptake from the roots.

2.

Explain why increasing temperature increases the rate of water uptake.

Increasing temperature increases the rate of evaporation and diffusion of water vapour from leaves, increasing transpiration and therefore water uptake.

3.

Explain why increasing air movement (wind speed) increases the rate of water uptake.

Increasing air movement removes water vapour from around the leaf, maintaining a steep water vapour concentration gradient and increasing transpiration and water uptake.

4.

A plant absorbs 2.4 cm³ of water per hour at 20°C and 4.8 cm³ per hour at 30°C. By what factor has the rate of water uptake increased?

The rate increases from 2.4 cm³/hour to 4.8 cm³/hour. 4.8 ÷ 2.4 = 2, so the rate has increased by a factor of 2.

5.

During an investigation, the rate of water uptake is 1.5 cm³/hour in still air and 3.6 cm³/hour in windy conditions. Calculate the increase in the rate of water uptake.

Increase = 3.6 − 1.5 = 2.1 cm³/hour.

6.

Predict and explain what would happen to the rate of water uptake if a plant was placed in a dark, cool room with no wind.

The rate of water uptake would decrease because low light reduces stomatal opening, low temperature reduces evaporation, and still air reduces the movement of water vapour away from the leaf.

B2.2j Describe how a simple potometer can be used to investigate factors that affect the rate of water uptake

1.

What is a potometer used to measure?

A potometer is used to estimate the rate of water uptake by a plant shoot.

2.

Describe how you would use a simple potometer to investigate the effect of light intensity on water uptake.

A leafy shoot is fitted into an airtight potometer containing water. A bubble is introduced into the capillary tube and the distance moved by the bubble is measured over a fixed time. The experiment is repeated at different light intensities while other factors are controlled.

3.

Explain why only one variable should be changed during a potometer investigation.

Only one variable should be changed so that any change in the rate of water uptake can be attributed to the independent variable being investigated.

4.

A bubble moves 36 mm in 9 minutes. Calculate the rate of water uptake in mm/min.

Rate = distance ÷ time = 36 ÷ 9 = 4 mm/min.

5.

A plant shoot has a mass of 18.0 g before an investigation and 16.2 g afterwards. Calculate the percentage loss in mass.

Mass lost = 18.0 − 16.2 = 1.8 g. Percentage loss = (1.8 ÷ 18.0) × 100 = 10%.

6.

A bubble moves 18 mm in 6 minutes at 20°C and 42 mm in 6 minutes at 30°C. Calculate the rate of water uptake at each temperature and identify which temperature resulted in the greater rate.

At 20°C: 18 ÷ 6 = 3 mm/min. At 30°C: 42 ÷ 6 = 7 mm/min. Therefore, 30°C produced the greater rate of water uptake.

B3.1a Describe the structure of the nervous system

1.

State the function of the central nervous system (CNS).

The central nervous system (CNS) consists of the brain and spinal cord and processes information and coordinates the body's responses.

2.

State the function of the brain in the nervous system.

The brain receives and processes information and coordinates responses to stimuli.

3.

State the function of the spinal cord.

The spinal cord carries nerve impulses between the brain and the rest of the nervous system and coordinates reflex responses.

4.

State the function of a sensory neurone.

A sensory neurone carries electrical impulses from sensory receptors to the CNS.

5.

State the function of a relay neurone.

A relay neurone carries electrical impulses between sensory and motor neurones within the CNS.

6.

State the function of a motor neurone.

A motor neurone carries electrical impulses from the CNS to effectors, such as muscles or glands.

B3.1b Explain how the components of the nervous system can produce a coordinated response

1.

Define the term stimulus.

A stimulus is a change in the environment that can be detected by an organism.

2.

Define the term receptor.

A receptor is a specialised cell or group of cells that detects a stimulus and produces a response in the form of a nerve impulse.

3.

Define the term effector.

An effector is a muscle or gland that produces a response to a nerve impulse.

4.

Explain the role of receptors in producing a coordinated response.

Receptors detect changes in the environment and generate electrical impulses in sensory neurones, which carry information to the CNS for processing.

5.

Explain the role of effectors in producing a coordinated response.

Effectors carry out the response coordinated by the nervous system. Muscles contract and glands secrete substances in response to nerve impulses.

6.

A person accidentally steps on a sharp drawing pin. Describe how the nervous system produces a coordinated response from the moment the stimulus is detected until the muscles contract.

The sharp drawing pin stimulates pain receptors in the foot. A sensory neurone carries impulses to the CNS, where a relay neurone passes the impulse to a motor neurone. The motor neurone carries the impulse to the leg muscles, causing them to contract and withdraw the foot.

B3.1c Explain how the structure of a reflex arc is related to its function

1.

Define the term reflex action.

A reflex action is a rapid, automatic response to a stimulus that does not require conscious thought.

2.

State the correct order of structures in a reflex arc.

The correct order is receptor → sensory neurone → relay neurone → motor neurone → effector.

3.

Explain why reflex actions are usually faster than voluntary actions.

Reflex actions are usually faster because the response is coordinated through the spinal cord rather than requiring conscious processing by the brain, reducing the distance and time involved.

4.

A person touches a hot pan and immediately removes their hand. Explain why this response is a reflex action.

Touching a hot pan causes heat receptors in the skin to detect the stimulus and initiate a rapid nerve pathway through the spinal cord, causing the arm muscles to contract and remove the hand without conscious thought.

5.

Explain how a relay neurone helps a reflex arc to function.

A relay neurone connects the sensory neurone to the motor neurone within the CNS, allowing the nerve impulse to pass rapidly from the receptor to the effector.

6.

A reflex response takes 0.15 s, while a voluntary response takes 0.48 s. Calculate how much faster the reflex response is than the voluntary response.

The reflex response is 0.33 s faster than the voluntary response. Calculation: 0.48 − 0.15 = 0.33 s.

B3.2a Describe the principles of hormonal coordination and control by the human endocrine system

1.

Define the term hormone.

A hormone is a chemical messenger produced by an endocrine gland and transported in the blood to a target organ or tissue.

2.

Explain why hormones are described as chemical messengers.

Hormones are described as chemical messengers because they carry information between different parts of the body and cause specific responses in target cells.

3.

State where hormones are produced in the endocrine system.

Hormones are produced by endocrine glands.

4.

State how hormones are transported around the body.

Hormones are transported around the body in the bloodstream.

5.

Define the term receptor.

A receptor is a protein on or inside a target cell that specifically binds to a particular hormone.

6.

Explain why a hormone affects only particular target cells or organs.

A hormone affects only particular target cells or organs because only cells with the specific receptor for that hormone can respond to it.

B3.2b Explain the roles of thyroxine and adrenaline in the body

1.

Name the endocrine gland that produces thyroxine.

Thyroxine is produced by the thyroid gland.

2.

State the role of thyroxine in controlling metabolic rate.

Thyroxine helps control the body's metabolic rate, increasing the rate at which chemical reactions occur.

3.

Explain how negative feedback controls the release of thyroxine.

Thyroxine release is controlled by negative feedback. When thyroxine levels become too high, the signals stimulating its production are reduced, lowering thyroxine production. When levels fall, stimulation increases.

4.

Name the endocrine gland that produces adrenaline.

Adrenaline is produced by the adrenal glands.

5.

Describe the effects of adrenaline on the body during a fight-or-flight response.

Adrenaline increases heart rate and breathing rate, increases blood flow to muscles, and increases blood glucose concentration, preparing the body for rapid action.

6.

Explain how the effects of adrenaline increase a person's chances of survival in a dangerous situation.

These effects increase survival chances by providing more oxygen and glucose to muscles, allowing the body to respond quickly to a dangerous situation.

B3.2c Describe the role of hormones in human reproduction including the control of the menstrual cycle

1.

State the role of follicle stimulating hormone (FSH) in female reproduction.

FSH (follicle stimulating hormone) stimulates the development and maturation of an ovarian follicle containing an egg.

2.

State the role of oestrogen in the menstrual cycle.

Oestrogen is produced by the developing follicle and helps rebuild the lining of the uterus. It also inhibits FSH release and, at high levels, stimulates the release of LH.

3.

State the role of progesterone in the menstrual cycle.

Progesterone maintains the lining of the uterus after ovulation and inhibits the release of FSH and LH.

4.

State the role of testosterone in male reproduction.

Testosterone is produced by the testes and stimulates sperm production and the development of male secondary sexual characteristics.

5.

Explain how oestrogen and progesterone prepare the uterus for pregnancy.

Oestrogen causes the uterus lining to thicken after menstruation, while progesterone maintains the thickened lining after ovulation so it is suitable for implantation.

6.

Explain how hormones control the menstrual cycle.

Hormones control the menstrual cycle by changing the levels of FSH, oestrogen, LH and progesterone, which regulate follicle development, ovulation and maintenance of the uterus lining.

B3.2d Explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle

1.

State the role of luteinising hormone (LH) in the menstrual cycle.

LH (luteinising hormone) causes ovulation, the release of a mature egg from the ovary.

2.

Explain how follicle stimulating hormone (FSH) and oestrogen interact during the menstrual cycle.

FSH stimulates the development of an ovarian follicle, which produces oestrogen. Rising oestrogen levels cause FSH release to decrease, while high oestrogen levels stimulate the release of LH.

3.

Explain how oestrogen affects the release of FSH and LH.

Oestrogen initially inhibits FSH release, reducing the development of additional follicles. When oestrogen reaches a high level, it causes a surge in LH, leading to ovulation.

4.

Explain how progesterone affects the release of FSH and LH.

Progesterone inhibits the release of FSH and LH, preventing another follicle from developing and another ovulation from occurring during the same menstrual cycle.

5.

Describe the sequence of hormonal changes that leads to ovulation.

FSH stimulates follicle development, the follicle produces increasing levels of oestrogen, high oestrogen levels trigger an LH surge, and the LH surge causes ovulation.

6.

Explain how FSH, LH, oestrogen and progesterone work together to control the menstrual cycle.

FSH stimulates follicle development, the follicle produces oestrogen, high oestrogen stimulates LH release, and LH causes ovulation. After ovulation, progesterone is produced and maintains the uterus lining while inhibiting FSH and LH.

B3.2e Explain the use of hormones in contraception and evaluate hormonal and non-hormonal methods of contraception

1.

State one example of a hormonal method of contraception.

One hormonal method of contraception is the combined oral contraceptive pill, which contains oestrogen and progesterone-like hormones.

2.

State one example of a non-hormonal method of contraception.

One non-hormonal method of contraception is a condom.

3.

Explain how hormonal contraception prevents pregnancy.

Hormonal contraception can prevent pregnancy by inhibiting FSH and LH, preventing ovulation. It can also thicken cervical mucus, making it more difficult for sperm to reach an egg.

4.

Explain how a non-hormonal method of contraception prevents pregnancy.

A condom prevents pregnancy by acting as a physical barrier, preventing sperm from entering the female reproductive system.

5.

Compare the effectiveness of hormonal and non-hormonal methods of contraception.

Hormonal methods can be highly effective when used correctly, while the effectiveness of non-hormonal methods varies. Barrier methods can also provide protection against sexually transmitted infections, which hormonal methods do not.

6.

Evaluate the advantages and disadvantages of hormonal and non-hormonal methods of contraception.

Hormonal contraception is generally effective and reversible but can cause side effects and requires correct use. Non-hormonal methods avoid hormone-related side effects, and condoms can protect against sexually transmitted infections, but some non-hormonal methods are less effective with typical use.

B3.2f Explain the use of hormones in modern reproductive technologies to treat infertility

1.

Define the term infertility.

Infertility is the inability to become pregnant after a prolonged period of regular unprotected sexual intercourse.

2.

State how hormones are used to stimulate egg maturation during fertility treatment.

Hormones such as FSH can be administered to stimulate the development and maturation of eggs in the ovaries.

3.

Explain how hormones can increase the chances of pregnancy during fertility treatment.

Hormone treatment can stimulate the maturation and release of eggs, increasing the number of eggs available for fertilisation and therefore increasing the chance of pregnancy.

4.

State one modern reproductive technology used to treat infertility.

One modern reproductive technology used to treat infertility is IVF (in vitro fertilisation).

5.

Explain how hormone treatment is used alongside modern reproductive technologies.

Hormones can be used to stimulate the ovaries to produce several mature eggs, which can then be collected and fertilised during IVF. Other hormones may then support the uterus lining.

6.

Explain why hormone treatments can be effective in treating infertility.

Hormone treatments can be effective because they can stimulate egg development and ovulation, correcting or overcoming problems with normal reproductive hormone levels and increasing the opportunity for fertilisation.

B3.3a Explain the importance of maintaining a constant internal environment in response to internal and external change

1.

Define the term homeostasis.

Homeostasis is the maintenance of a constant internal environment in response to internal and external changes.

2.

State why living organisms need to maintain a constant internal environment.

Living organisms need to maintain a constant internal environment so that cells and enzymes can function effectively.

3.

State two examples of internal conditions controlled by homeostasis.

Two examples of internal conditions controlled by homeostasis are blood glucose concentration and body temperature.

4.

Explain how changes in the external environment can affect the body's internal environment.

Changes in the external environment, such as changes in temperature, can affect internal conditions, so homeostatic mechanisms act to keep internal conditions within suitable limits.

5.

Explain why enzymes and other metabolic reactions require a constant internal environment.

Enzymes and other metabolic reactions require a constant internal environment because changes in conditions such as temperature and pH can alter enzyme activity and affect the rate of metabolic reactions.

6.

Explain why maintaining homeostasis is essential for survival.

Maintaining homeostasis is essential for survival because cells depend on stable internal conditions for normal enzyme activity, metabolism and other vital processes.

B3.3b Explain how insulin controls blood sugar levels in the body

1.

Name the organ that produces insulin.

Insulin is produced by the pancreas.

2.

State when insulin is released into the bloodstream.

Insulin is released into the bloodstream when blood glucose concentration becomes too high.

3.

Explain how insulin lowers blood glucose concentration.

Insulin lowers blood glucose concentration by causing cells to take up more glucose and by stimulating the liver to convert glucose into glycogen for storage.

4.

State what happens to excess glucose after insulin is released.

Excess glucose is converted into glycogen and stored mainly in the liver and muscles.

5.

Explain why blood glucose concentration must be kept within a narrow range.

Blood glucose concentration must be kept within a narrow range because cells require a constant supply of glucose for respiration, while excessively high or low concentrations can damage normal body function.

6.

Explain how insulin helps maintain homeostasis.

Insulin helps maintain homeostasis by reducing high blood glucose concentrations, returning them towards the normal level.

B3.3c Explain how glucagon interacts with insulin to control blood sugar levels in the body

1.

State when glucagon is released into the bloodstream.

Glucagon is released when blood glucose concentration falls too low.

2.

Name the organ that produces glucagon.

Glucagon is produced by the pancreas.

3.

Explain how glucagon increases blood glucose concentration.

Glucagon increases blood glucose concentration by causing the liver to convert stored glycogen into glucose, which is then released into the blood.

4.

Explain how insulin and glucagon have opposite effects on blood glucose concentration.

Insulin decreases blood glucose concentration, whereas glucagon increases blood glucose concentration.

5.

Explain how insulin and glucagon work together to maintain a constant blood glucose concentration.

When blood glucose is too high, insulin lowers it by promoting glucose uptake and glycogen formation. When blood glucose is too low, glucagon raises it by promoting glycogen breakdown and glucose release. Together they maintain blood glucose within a suitable range.

6.

Explain why the interaction between insulin and glucagon is an example of homeostasis.

The interaction is an example of homeostasis because insulin and glucagon counteract changes in blood glucose concentration, maintaining a relatively constant internal condition.

B3.3d Compare type 1 and type 2 diabetes and explain how they can be treated

1.

State the cause of type 1 diabetes.

Type 1 diabetes occurs when the pancreas produces little or no insulin because the insulin-producing cells are destroyed by the body's immune system.

2.

State the cause of type 2 diabetes.

Type 2 diabetes occurs when body cells become less responsive to insulin, often associated with factors such as being overweight and having a sedentary lifestyle.

3.

Compare type 1 diabetes with type 2 diabetes.

Type 1 diabetes involves a lack of insulin production and usually requires insulin treatment. Type 2 diabetes involves insulin resistance and can often initially be managed through lifestyle changes and medication.

4.

State one treatment used for type 1 diabetes.

A main treatment for type 1 diabetes is regular injections or administration of insulin.

5.

State two treatments used for type 2 diabetes.

Two treatments for type 2 diabetes are a controlled diet and increased physical activity. Medication may also be used.

6.

Explain why the treatment for type 1 diabetes differs from the treatment for type 2 diabetes.

Type 1 diabetes requires insulin because the body produces little or no insulin, whereas type 2 diabetes may be managed initially by lifestyle changes and medicines that improve blood glucose control because the body still produces some insulin.

B4.1a Recall that many different materials cycle through the abiotic and biotic components of an ecosystem

1.

What is meant by the abiotic and biotic components of an ecosystem?

Abiotic components are the non-living parts of an ecosystem, such as air, water, soil, temperature and light. Biotic components are the living parts of an ecosystem, including plants, animals and microorganisms.

2.

What does it mean for a material to cycle through the abiotic and biotic components of an ecosystem?

Materials cycle through an ecosystem by moving between the non-living environment and living organisms before eventually being returned to the environment and reused.

3.

What happens to materials when they move from the abiotic components into living organisms?

When materials move from abiotic components into living organisms, they are absorbed or taken in and used to build substances needed for growth and other life processes.

4.

What happens to materials when they move from biotic components back into the abiotic environment?

Materials move from biotic components back into the abiotic environment through processes such as respiration, excretion and decomposition.

5.

What are two examples of materials that cycle through ecosystems?

Two examples of materials that cycle through ecosystems are carbon and nitrogen.

6.

Why must materials such as carbon and nitrogen be continually recycled within ecosystems?

Carbon and nitrogen must be continually recycled because there is a limited supply of these materials in ecosystems and living organisms continually need them to build important biological molecules.

B4.1b Explain the role of microorganisms in the cycling of materials through an ecosystem

1.

What role do microorganisms play in the cycling of materials through an ecosystem?

Microorganisms act as decomposers, breaking down dead organisms and waste materials and returning substances to the environment so they can be reused by other organisms.

2.

What is decomposition, and what types of material are decomposed by microorganisms?

Decomposition is the breakdown of dead organic material and waste. Microorganisms decompose materials such as dead plants, dead animals, faeces and other organic waste.

3.

How do microorganisms act as decomposers in an ecosystem?

Microorganisms such as bacteria and fungi act as decomposers by feeding on and breaking down organic material using enzymes.

4.

How does decomposition return materials from dead organisms and waste to the abiotic environment?

During decomposition, microorganisms break down complex substances in dead organisms and waste into simpler substances. These materials are released back into the soil, water or atmosphere where they can be reused.

5.

How could you investigate the range of ecosystems and identify examples of microorganisms that act as decomposers within them?

Different ecosystems could be sampled and observations made of decaying material. Samples could be collected and examined to identify microorganisms such as bacteria and fungi associated with decomposition.

6.

Why are microorganisms acting as decomposers essential for the continued cycling of materials through an ecosystem?

Decomposer microorganisms are essential because they return materials from dead organisms and waste to the environment. Without decomposition, nutrients would remain locked within dead material and would not be available for reuse by other organisms.

B4.1c Explain the importance of the carbon cycle and the water cycle to living organisms

1.

Why is the carbon cycle important to living organisms?

The carbon cycle is important because carbon is required to make biological molecules such as carbohydrates, proteins and fats that are needed by living organisms.

2.

What are the main stages by which carbon is transferred between living organisms and the environment?

Carbon dioxide is removed from the atmosphere by plants during photosynthesis and incorporated into organic molecules. Carbon is transferred between organisms through feeding and returned to the atmosphere by respiration, decomposition and combustion.

3.

Why is the water cycle important to living organisms?

The water cycle is important because all living organisms require water for processes such as chemical reactions, transport of substances and maintaining cells.

4.

What are the main stages of the water cycle?

The main stages of the water cycle include evaporation, condensation, precipitation and the return of water to rivers, lakes and oceans through surface runoff and groundwater.

5.

How do the carbon and water cycles help maintain habitats and freshwater supplies?

The water cycle continually supplies freshwater to habitats through precipitation, while the carbon cycle provides carbon needed by producers and other organisms, helping maintain functioning ecosystems.

6.

How do the carbon and water cycles contribute to the flow of nutrients through ecosystems?

The carbon and water cycles continually move essential materials between organisms and the environment, making them available for uptake and use by living organisms throughout ecosystems.

B4.1d Describe different levels of organisation in an ecosystem from individual organisms to the whole ecosystem

1.

What is meant by an individual organism in an ecosystem?

An individual organism is one single living organism, such as one rabbit, one oak tree or one bacterium.

2.

What is a population, and how is it different from an individual organism?

A population is all the organisms of one species living in a particular area. It differs from an individual organism because it contains many organisms of the same species rather than just one.

3.

What is a community, and how is it different from a population?

A community consists of all the populations of different species living and interacting in a particular area, whereas a population contains organisms of only one species.

4.

What is an ecosystem, and how does it include both biotic and abiotic components?

An ecosystem consists of a community of living organisms interacting with each other and with the non-living, abiotic components of their environment.

5.

What is the correct order of organisation from an individual organism to the whole ecosystem?

The correct order of organisation is individual organism → population → community → ecosystem.

6.

How does the number of organisms change as you move from an individual organism to a population, community and ecosystem?

The number and variety of organisms generally increases from an individual organism to a population, then to a community and finally to an ecosystem, which contains many populations of different species.

B4.1e Explain how abiotic and biotic factors can affect communities

1.

How can temperature and light intensity affect the organisms present in a community?

Temperature can affect enzyme activity, growth and survival, while light intensity affects the rate of photosynthesis in plants. These factors therefore influence which organisms can survive and reproduce in a community.

2.

How can moisture level and soil pH affect the distribution and abundance of organisms in a community?

Moisture level affects the availability of water to organisms, while soil pH affects the availability of mineral ions and the conditions in which plants and microorganisms can survive. This affects their distribution and abundance.

3.

How can predators affect the size and distribution of populations within a community?

Predators can reduce the size of prey populations by consuming them. Changes in predator numbers can therefore affect both the abundance and distribution of prey populations.

4.

How can the availability of food affect populations within a community?

If more food is available, a population may be able to support more individuals and increase in size. If food becomes limited, competition increases and the population may decrease.

5.

How can sampling techniques be used to identify and investigate biotic factors in an ecosystem?

Sampling techniques such as quadrats and transects can be used to measure the abundance and distribution of organisms, allowing relationships between different organisms and other biotic factors to be investigated.

6.

How could you investigate the effect of an abiotic or biotic factor on the distribution and abundance of organisms in an ecosystem?

The abundance and distribution of organisms could be measured at different values of an environmental factor. For example, quadrats could be placed along a transect and the number of organisms recorded alongside measurements of an abiotic factor such as light intensity or soil moisture.

B4.1f Describe the importance of interdependence and competition in a community

1.

What is meant by interdependence between organisms in a community?

Interdependence means that organisms within a community depend on other organisms for resources and survival, such as food, shelter, pollination or reproduction.

2.

How does predation demonstrate interdependence between organisms?

Predation demonstrates interdependence because predators depend on prey as a source of food, while changes in predator populations can also affect the size of prey populations.

3.

What is mutualism, and how does it demonstrate interdependence?

Mutualism is a relationship between two different species in which both organisms benefit. For example, insects obtain food from flowers while helping the plants reproduce through pollination.

4.

What is parasitism, and how does it demonstrate interdependence?

Parasitism is a relationship in which one organism, the parasite, benefits while the host is harmed. The parasite depends on the host for resources such as food or shelter.

5.

Why is interdependence important for the survival of organisms within a community?

Interdependence is important because organisms rely on one another for resources and processes necessary for survival and reproduction. A change in one population can therefore affect other populations within the community.

6.

Why do organisms compete with one another, and which resources can they compete for?

Organisms compete because resources are limited. Animals may compete for food, water, territory and mates, while plants may compete for light, water, space and mineral ions.

B5.1a Explain the following terms: gamete, chromosome, gene, allele/variant, dominant, recessive, homozygous, heterozygous, genotype and phenotype

1.

What is a gamete, and how does its genetic content differ from that of a body cell?

A gamete is a sex cell, such as a sperm or egg cell, containing a haploid set of chromosomes, so it has half the chromosome number of a body cell.

2.

What are a chromosome, gene and allele/variant, and how are these terms related?

A chromosome is a long DNA molecule containing many genes. A gene is a section of DNA that codes for a particular protein or characteristic, while an allele/variant is a different version of a gene.

3.

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

A dominant allele is expressed in the phenotype when present in either a homozygous or heterozygous genotype. A recessive allele is only expressed when two copies are present.

4.

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

A homozygous genotype contains two identical alleles for a gene, whereas a heterozygous genotype contains two different alleles.

5.

What is the difference between an organism’s genotype and its phenotype?

An organism's genotype is the combination of alleles it possesses, whereas its phenotype is the observable characteristics resulting from its genotype and environmental influences.

6.

How can the alleles inherited by an offspring be used to determine its phenotype?

The alleles inherited from the parents determine the organism's genotype, which can be used to predict the phenotype, particularly when the alleles have known dominant and recessive relationships.

B5.1b Describe the genome as the entire genetic material of an organism

1.

What is meant by the term genome?

The genome is the entire genetic material of an organism.

2.

What does an organism’s genome consist of?

An organism's genome consists of all of its DNA, including all of its genes and other DNA sequences.

3.

How is the genome related to the chromosomes of an organism?

The genome is contained within the organism's complete set of chromosomes.

4.

How does a genome differ from an individual gene?

A genome contains all of an organism's genetic material, whereas an individual gene is only a specific section of DNA.

5.

Why can the genome be described as the entire genetic material of an organism?

The genome can be described as the entire genetic material because it contains all the DNA sequences inherited by an organism.

6.

Why is an organism’s genome important in determining its characteristics?

An organism's genome contains the genetic information that contributes to its characteristics and biological functions, although phenotype is also influenced by the environment.

B5.1c Describe that the genome, and its interaction with the environment, influence the development of the phenotype of an organism

1.

How does an organism’s genome influence the development of its phenotype?

The genome contains genes that provide instructions for proteins and therefore influences the characteristics that develop in an organism.

2.

How can environmental factors influence an organism’s phenotype?

Environmental factors such as diet, temperature, light and exercise can influence an organism's phenotype.

3.

How does the interaction between an organism’s genome and its environment affect its phenotype?

Phenotype results from the interaction between genetic factors and environmental factors, so organisms with similar genomes can develop different characteristics in different environments.

4.

What is discontinuous variation, and what is an example of it?

Discontinuous variation produces distinct categories with no intermediate values, such as blood group.

5.

What is continuous variation, and what are two examples?

Continuous variation produces a range of values, such as height and body mass.

6.

How do discontinuous and continuous variation differ?

Discontinuous variation has distinct categories, often determined mainly by genetic factors, whereas continuous variation has a range of values and is usually influenced by multiple genes and environmental factors.

B5.1d Recall that all variants arise from mutations, and that most have no effect on the phenotype, some influence phenotype and a very few determine phenotype

1.

What is a mutation, and how can it produce a new genetic variant?

A mutation is a change in the DNA base sequence that can create a new genetic variant or allele.

2.

What effect do most genetic variants have on an organism’s phenotype?

Most genetic variants have no observable effect on the phenotype.

3.

How can some genetic variants influence an organism’s phenotype?

Some genetic variants can influence the phenotype by changing the protein produced or how much of a protein is produced.

4.

What does it mean when a genetic variant determines an organism’s phenotype?

If a genetic variant determines the phenotype, the characteristic is directly determined by that particular genetic variant, with little or no influence from other genetic or environmental factors.

5.

Why do most mutations have no effect on the phenotype?

Most mutations have no effect because they may occur in DNA that does not affect protein production, or the change may not alter the function of the resulting protein.

6.

What are the three possible effects that a mutation can have on an organism’s phenotype?

A mutation can have no effect on the phenotype, influence the phenotype, or, very rarely, determine the phenotype.

B5.1e Explain the terms haploid and diploid

1.

What is meant by the term haploid?

Haploid means having one set of chromosomes.

2.

What is meant by the term diploid?

Diploid means having two sets of chromosomes, with one set inherited from each parent.

3.

How does the chromosome number of a haploid cell compare with that of a diploid cell?

A haploid cell has half the chromosome number of a diploid cell.

4.

Which cells in humans are haploid?

In humans, sperm and egg cells are haploid.

5.

Which cells in humans are diploid?

Most human body cells are diploid.

6.

Why must gametes be haploid?

Gametes must be haploid so that when two gametes fuse during fertilisation, the normal diploid chromosome number is restored rather than doubled in every generation.

B5.1f Explain the role of meiotic cell division in halving the chromosome number to form gametes

1.

What is the role of meiotic cell division in the formation of gametes?

Meiosis produces haploid gametes from diploid cells by reducing the chromosome number by half.

2.

How does meiosis halve the chromosome number when forming gametes?

During meiosis, chromosomes are replicated and then separated through two successive cell divisions, producing cells with half the original chromosome number.

3.

Why must meiosis produce haploid gametes from diploid cells?

Meiosis must produce haploid gametes so that fertilisation does not double the chromosome number in each generation.

4.

How does the fusion of two haploid gametes restore the diploid chromosome number?

Two haploid gametes fuse during fertilisation, combining their chromosome sets and restoring the diploid chromosome number.

5.

How does meiosis provide a source of genetic variation?

Meiosis produces genetic variation through processes including the random distribution of chromosomes into gametes and the production of genetically different gametes.

6.

How does meiosis help maintain the diploid chromosome number between generations?

Meiosis produces haploid gametes, so when two gametes fuse during fertilisation, the resulting offspring is diploid, maintaining the chromosome number between generations.

B5.1g Explain single gene inheritance in the context of homozygous and heterozygous crosses involving dominant and recessive genes

1.

What is meant by single gene inheritance?

Single gene inheritance is the inheritance of a characteristic controlled by a single gene with different alleles.

2.

What is the difference between a homozygous dominant, homozygous recessive and heterozygous genotype?

A homozygous dominant genotype has two dominant alleles, a homozygous recessive genotype has two recessive alleles, and a heterozygous genotype has one dominant and one recessive allele.

3.

How does a dominant allele affect the phenotype of a heterozygous organism?

In a heterozygous organism, the dominant allele is expressed in the phenotype.

4.

How does a recessive allele affect the phenotype when an organism is heterozygous?

In a heterozygous organism, the recessive allele is not expressed in the phenotype because its effect is masked by the dominant allele.

5.

How can the probability of a particular phenotype be predicted from a genetic cross?

The probability of a particular phenotype can be predicted by using a genetic cross or Punnett square to determine the possible offspring genotypes and their expected ratios.

6.

How could a coin toss or die roll be used to investigate probability in genetic inheritance?

A coin toss or die roll can model genetic probability by representing the random inheritance of alleles. Repeated trials can be used to compare experimental results with expected probabilities.

B5.1h Predict the results of single gene crosses

1.

What is a Punnett square used to predict in a single gene cross?

A Punnett square is used to predict the possible genotypes and phenotypes of offspring from a genetic cross.

2.

How are the possible gametes from each parent represented in a Punnett square?

The possible gametes from each parent are written along the top and side of the Punnett square.

3.

How can a Punnett square be used to determine the possible genotypes of offspring?

Combining the allele from each parent in each box gives the possible offspring genotypes.

4.

How can the possible phenotypes of offspring be determined from a Punnett square?

The phenotypes are determined by applying the dominant and recessive relationships to the predicted genotypes.

5.

How can the probability of an offspring having a particular phenotype be calculated from a Punnett square?

The probability of a particular phenotype is calculated by counting the relevant boxes and dividing by the total number of boxes, then expressing the result as a fraction, decimal or percentage.

6.

How would you use a Punnett square to predict the results of a cross between two heterozygous organisms?

For a cross between two heterozygous organisms, Aa × Aa, the predicted genotypes are AA, Aa, Aa and aa, giving a genotype ratio of 1 AA : 2 Aa : 1 aa and, where A is completely dominant, a phenotype ratio of 3 dominant : 1 recessive.

B5.1i Describe sex determination in humans using a genetic cross

1.

Which sex chromosomes are normally present in a human female?

A human female normally has two X chromosomes (XX).

2.

Which sex chromosomes are normally present in a human male?

A human male normally has one X chromosome and one Y chromosome (XY).

3.

Which sex chromosome does a human egg normally contain?

A human egg normally contains an X chromosome.

4.

Which sex chromosomes can a human sperm contain?

Human sperm can contain either an X chromosome or a Y chromosome.

5.

How does fertilisation determine whether a human embryo is genetically XX or XY?

If an X-bearing sperm fertilises an egg, the embryo is XX. If a Y-bearing sperm fertilises an egg, the embryo is XY.

6.

How can a Punnett square be used to predict the probability of a human offspring being XX or XY?

A cross between XX and XY gives XX, XY, XX and XY, so the predicted probability is 50% XX and 50% XY.

B5.1j Recall that most phenotypic features are the result of multiple genes rather than single gene inheritance

1.

What is meant by multiple gene inheritance?

Multiple gene inheritance occurs when a characteristic is influenced by two or more genes.

2.

Why are most phenotypic features determined by multiple genes rather than a single gene?

Most phenotypic features are determined by multiple genes because characteristics are often complex and involve the combined effects of many genes.

3.

How can multiple genes contribute to continuous variation?

Multiple genes can contribute to continuous variation because different combinations of alleles can produce many possible phenotypes across a range.

4.

Why can characteristics such as height and weight show a wide range of phenotypes?

Characteristics such as height and weight can show a wide range because they are influenced by multiple genes as well as environmental factors.

5.

How does multiple gene inheritance differ from single gene inheritance?

Single gene inheritance involves a characteristic mainly controlled by one gene, whereas multiple gene inheritance involves several genes contributing to a characteristic.

6.

Why is it important to consider multiple genes when explaining most phenotypic features?

Considering multiple genes is important because most phenotypic features are not controlled by a single gene and their expression can also be affected by environmental factors.

B5.2a State that there is usually extensive genetic variation within a population of a species

1.

What is meant by genetic variation within a population?

Genetic variation is the differences in alleles and inherited characteristics between individuals within a population.

2.

What is the difference between genetic variation and environmental variation?

Genetic variation is caused by differences in an individual's genes and alleles, whereas environmental variation is caused by differences in the conditions or experiences individuals are exposed to.

3.

Why can individuals of the same species have different alleles?

Individuals of the same species can have different alleles because mutations create new variants, which can be inherited.

4.

How can different alleles produce differences in the characteristics of individuals within a population?

Different alleles can produce different characteristics by causing differences in the proteins produced or their function.

5.

Why is genetic variation within a population necessary for natural selection to occur?

Genetic variation is necessary for natural selection because it provides differences in characteristics on which selection can act.

6.

What is the relationship between genetic variation and the ability of a population to adapt to environmental changes?

Greater genetic variation increases the likelihood that some individuals possess inherited characteristics that help them survive environmental changes, allowing the population to adapt.

B5.2b Describe the impact of developments in biology on classification systems

1.

What is a classification system used for?

A classification system is used to organise organisms into groups based on their similarities and differences and to show relationships between them.

2.

What is a natural classification system?

A natural classification system groups organisms according to their evolutionary relationships and shared characteristics.

3.

What is an artificial classification system?

An artificial classification system groups organisms using selected observable characteristics that may not reflect their evolutionary relationships.

4.

What is the main difference between natural and artificial classification systems?

Natural classification aims to reflect evolutionary relationships, whereas artificial classification groups organisms according to chosen observable features.

5.

What is molecular phylogenetics?

Molecular phylogenetics is the study of evolutionary relationships between organisms using molecular evidence, such as similarities and differences in DNA or protein sequences.

6.

How has DNA sequencing improved the classification of organisms and the identification of evolutionary relationships?

DNA sequencing allows scientists to compare genetic information directly, helping them identify evolutionary relationships and revise classifications when genetic evidence shows that organisms are more or less closely related than previously thought.

B5.2c Explain how evolution occurs through the natural selection of variants that have given rise to phenotypes best suited to their environment

1.

What is a mutation?

A mutation is a change in the DNA base sequence that can produce a new genetic variant.

2.

How can mutations produce new genetic variants?

Mutations alter DNA and can therefore create new alleles or genetic variants.

3.

How can genetic variants produce different phenotypes within a population?

Different genetic variants can affect the proteins produced by an organism, resulting in differences in phenotype.

4.

What happens to organisms with phenotypes that are better suited to their environment?

Organisms with phenotypes that are better suited to their environment are more likely to survive and reproduce successfully.

5.

How does natural selection cause advantageous variants to become more common in a population?

Individuals with advantageous variants are more likely to reproduce and pass these variants to their offspring, so the frequency of advantageous variants increases in the population over generations.

6.

How does natural selection lead to evolution over successive generations?

Natural selection causes advantageous inherited variants to become more common over successive generations, resulting in a change in the inherited characteristics of the population, which is evolution.

B5.2d Describe evolution as a change in the inherited characteristics of a population over time, through a process of natural selection, which may result in the formation of new species

1.

What is meant by evolution?

Evolution is a change in the inherited characteristics of a population over time.

2.

What changes in a population during evolution?

The frequency of different inherited characteristics and genetic variants changes within a population during evolution.

3.

How does natural selection cause the inherited characteristics of a population to change over time?

Natural selection favours individuals with advantageous inherited characteristics, causing these characteristics to become more common in the population over successive generations.

4.

Why can advantageous inherited characteristics become more common over successive generations?

Individuals with advantageous inherited characteristics are more likely to survive, reproduce and pass their alleles to their offspring, increasing their frequency in later generations.

5.

How can populations become sufficiently different through evolutionary change to form new species?

If populations become genetically and reproductively isolated and accumulate enough differences over many generations, they may become unable to interbreed successfully and produce fertile offspring, resulting in new species.

6.

What is meant by the formation of a new species?

The formation of a new species, or speciation, occurs when populations become sufficiently different through evolutionary change that they can no longer successfully interbreed to produce fertile offspring.

B5.2e Describe the evidence for evolution

1.

What is a fossil?

A fossil is the preserved remains, impressions or other evidence of an organism that lived in the past.

2.

How do fossils provide evidence that organisms have changed over time?

Fossils provide evidence that organisms have changed over time because fossils from different geological periods show different forms and characteristics, including transitional forms.

3.

What can differences between fossils from different geological periods show about evolution?

Differences between fossils from different geological periods can show that species have changed, appeared and become extinct over time.

4.

How does antibiotic resistance in bacteria provide evidence for evolution?

Antibiotic resistance in bacteria provides evidence for evolution because bacterial populations can change over generations as resistant variants are naturally selected.

5.

How does natural selection cause antibiotic-resistant bacteria to become more common in a population?

Antibiotics kill susceptible bacteria, while resistant bacteria survive and reproduce. The resistant bacteria therefore become more common in the population.

6.

What does the evolution of antibiotic resistance demonstrate about changes in inherited characteristics over generations?

The evolution of antibiotic resistance demonstrates that inherited characteristics can change in frequency over successive generations through natural selection.

B6.1a Explain how to carry out a field investigation into the distribution and abundance of organisms in a habitat and how to determine their numbers in a given area

1.

What is meant by the distribution of organisms within a habitat?

Distribution describes where organisms are found within a particular habitat.

2.

What is meant by the abundance of organisms within a habitat?

Abundance describes the number of organisms of a particular species present in a given area.

3.

How can random sampling using quadrats be used to investigate the distribution and abundance of organisms?

Random sampling using quadrats involves placing quadrats at randomly selected locations and counting or estimating the organisms present. Repeating this allows the distribution and abundance of organisms to be determined.

4.

How can a transect be used to investigate changes in the distribution of organisms across a habitat?

A transect is a line or belt across a habitat along which organisms are sampled at regular intervals to investigate how their distribution changes across the habitat.

5.

How can pooters, nets and keys be used to sample and identify organisms during a field investigation?

Pooters and nets can be used to collect organisms safely for sampling, while identification keys can be used to identify the organisms collected.

6.

How can scaling-up methods and capture-recapture be used to estimate the number of organisms in a given area or population?

Scaling up uses results from a representative sample to estimate the total number of organisms in a larger area. Capture-recapture involves capturing, marking and releasing organisms, then recapturing a sample to estimate the population size.

B6.1b Describe both positive and negative human interactions within ecosystems and explain their impact on biodiversity

1.

What is meant by biodiversity?

Biodiversity is the variety of different species of organisms in a particular habitat, ecosystem or on Earth.

2.

What are two positive ways in which humans can interact with ecosystems?

Two positive human interactions are conservation of habitats and protection or reintroduction of endangered species.

3.

What are two negative ways in which humans can interact with ecosystems?

Two negative human interactions are deforestation and hunting, which can reduce populations and destroy habitats.

4.

How can changes in land use threaten biodiversity?

Changes in land use, such as deforestation and urbanisation, can destroy or fragment habitats, reducing populations and causing species to become endangered or extinct.

5.

How can hunting threaten individual species and biodiversity?

Hunting can reduce the population size of species and, if excessive, can cause species to become endangered or extinct, reducing biodiversity.

6.

How can conservation of individual species and selected habitats help maintain biodiversity?

Conserving individual species and selected habitats can protect endangered populations, preserve habitats and prevent extinctions, helping to maintain biodiversity.

B6.1c Explain some of the benefits and challenges of maintaining local and global biodiversity

1.

What are two benefits of maintaining biodiversity?

Two benefits of maintaining biodiversity are maintaining stable ecosystems and providing resources such as food, medicines and raw materials.

2.

Why is maintaining biodiversity important for ecosystems?

Biodiversity is important because different species are interdependent, and greater biodiversity can make ecosystems more resilient to environmental changes.

3.

Why can it be difficult to gain agreements for conservation schemes?

It can be difficult to gain agreements for conservation schemes because conservation can conflict with economic interests, local people's needs and the use of land or natural resources.

4.

Why is monitoring conservation schemes important?

Monitoring conservation schemes is important to determine whether they are successfully protecting or increasing biodiversity and to identify changes that require further action.

5.

What is ecotourism?

Ecotourism is tourism that aims to minimise environmental damage while supporting the conservation of natural environments and local communities.

6.

How can ecotourism benefit biodiversity and local communities?

Ecotourism can provide income for local communities and funding for conservation, creating an economic incentive to protect habitats and biodiversity.

B6.2a Explain the impact of the selective breeding of food plants and domesticated animals

1.

What is selective breeding?

Selective breeding is the process of choosing parents with desirable characteristics and breeding them together so that their offspring are more likely to inherit those characteristics.

2.

How is selective breeding used to produce food plants with desirable characteristics?

Selective breeding in food plants involves choosing plants with desirable characteristics, breeding them, selecting offspring with the best characteristics and repeating the process over many generations.

3.

How is selective breeding used to produce domesticated animals with desirable characteristics?

Selective breeding in domesticated animals involves choosing animals with desirable characteristics as parents, breeding them and selecting offspring with the desired characteristics for further breeding.

4.

What desirable characteristics might be selected for in food plants?

Desirable characteristics in food plants can include high yield, disease resistance, larger fruits or seeds, improved nutritional value and tolerance to environmental conditions.

5.

What desirable characteristics might be selected for in domesticated animals?

Desirable characteristics in domesticated animals can include high milk or meat production, rapid growth, disease resistance and increased fertility.

6.

How can selective breeding affect the characteristics of food plants and domesticated animals?

Selective breeding increases the frequency of alleles associated with desirable characteristics, causing the characteristics of food plants and domesticated animals to change over successive generations.

B6.2b Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics

1.

What is genetic engineering?

Genetic engineering is the process of modifying an organism's genetic material to introduce a desired characteristic.

2.

What is modified during the process of genetic engineering?

The organism's genome, specifically its DNA, is modified during genetic engineering.

3.

How does genetic engineering introduce a desirable characteristic into an organism?

Genetic engineering introduces a desirable characteristic by inserting a gene responsible for the characteristic into the organism's genome, allowing the organism to produce the relevant protein.

4.

What is meant by a desirable characteristic in genetic engineering?

A desirable characteristic is a feature considered useful or beneficial, such as pest resistance, disease resistance or increased crop yield.

5.

How does genetic engineering differ from selective breeding?

Selective breeding involves choosing organisms with desirable characteristics and breeding them over generations, whereas genetic engineering directly modifies DNA by introducing a specific gene.

6.

Why can genetic engineering introduce characteristics that would be difficult to obtain through selective breeding?

Genetic engineering can introduce genes from different species, allowing characteristics that would not be available through normal breeding between closely related organisms to be introduced.

B6.2c Describe the main steps in the process of genetic engineering

1.

What is the role of restriction enzymes in genetic engineering?

Restriction enzymes cut DNA at specific base sequences, allowing the desired gene to be removed and the vector DNA to be cut.

2.

What are sticky ends?

Sticky ends are short, unpaired sections of DNA produced when restriction enzymes make staggered cuts in DNA. They can pair with complementary bases on another DNA fragment.

3.

What is the role of ligase in genetic engineering?

Ligase joins the DNA fragments together by forming bonds in the DNA backbone, joining the desired gene to the vector.

4.

What is a vector, and why can plasmids be used as vectors?

A vector is a carrier used to transfer a gene into a host cell. Plasmids are small circular DNA molecules found in bacteria and can be used as vectors because they can carry inserted genes into bacterial cells.

5.

How is a desired gene inserted into a plasmid and transferred into a host bacterium?

The desired gene and plasmid are cut using the same restriction enzyme so they have complementary sticky ends. The gene is joined to the plasmid using DNA ligase, and the genetically engineered plasmid is transferred into a host bacterium.

6.

How are antibiotic resistance markers used to select bacteria that have taken up the genetically engineered plasmid?

The plasmid contains an antibiotic resistance marker. Bacteria are grown in the presence of the corresponding antibiotic, so bacteria that have taken up the plasmid survive while bacteria without the plasmid are killed.

B6.2d Explain some of the possible benefits and risks of using gene technology in modern agriculture

1.

What are two potential benefits of using gene technology in modern agriculture?

Two potential benefits are increased crop yields and increased resistance to pests or diseases.

2.

How could genetic engineering increase crop yields?

Genetic engineering can increase crop yields by introducing genes that improve characteristics such as growth rate, disease resistance or tolerance to environmental conditions, reducing crop losses.

3.

How could genetic engineering improve crop resistance to pests or disease?

Genetic engineering can introduce genes that make crops resistant to pests or diseases, reducing damage to crops and potentially reducing the need for pesticides.

4.

What are two potential risks of using gene technology in modern agriculture?

Two potential risks are the spread of modified genes to wild populations and the possibility of unintended effects on ecosystems or non-target organisms.

5.

What practical considerations should be considered when using genetically modified organisms in agriculture?

Practical considerations include the cost of developing and producing GM organisms, effectiveness, effects on surrounding ecosystems, potential spread of genes and long-term monitoring.

6.

What ethical considerations should be considered when using genetically modified organisms in agriculture?

Ethical considerations include whether it is acceptable to modify organisms genetically, potential effects on animal welfare, ownership and control of genetically modified crops, and concerns about impacts on natural ecosystems.

B6.3a Describe the relationship between health and disease

1.

What is meant by health?

Health is a state of physical and mental well-being.

2.

What is meant by disease?

Disease is a condition that affects the normal functioning of an organism.

3.

How can disease affect the health of an individual?

Disease can reduce health by disrupting the normal functioning of cells, tissues or organs.

4.

How can poor health increase the likelihood of disease?

Poor health can increase the likelihood of disease because factors such as poor diet, lack of exercise and harmful substances can weaken body systems or increase risk.

5.

How can disease affect the normal functioning of the body?

Disease can interfere with normal body functions by damaging cells, disrupting organ function or preventing normal metabolic processes.

6.

Why can health and disease be considered closely related?

Health and disease are closely related because disease can reduce health, while factors affecting health can influence the likelihood of developing disease.

B6.3b Describe different types of diseases

1.

What is a communicable disease?

A communicable disease is a disease caused by a pathogen that can be transmitted between organisms.

2.

What is a non-communicable disease?

A non-communicable disease is a disease that cannot normally be transmitted between individuals.

3.

How are communicable diseases different from non-communicable diseases?

Communicable diseases can be transmitted between organisms by pathogens, whereas non-communicable diseases are not caused by transmissible pathogens.

4.

How are communicable diseases transmitted between individuals?

Communicable diseases can spread through routes such as airborne droplets, direct contact, contaminated food or water, sexual contact and vectors.

5.

Why are non-communicable diseases not normally transmitted between individuals?

Non-communicable diseases are not normally transmitted because they are generally caused by genetic, lifestyle or environmental factors rather than transmissible pathogens.

6.

Give one example of a communicable disease and one example of a non-communicable disease.

An example of a communicable disease is influenza, while an example of a non-communicable disease is coronary heart disease.

B6.3c Describe the interactions between different types of disease

1.

How does HIV affect the immune system?

HIV attacks cells of the immune system, particularly helper T cells, reducing the body's ability to defend itself against pathogens.

2.

How can HIV increase a person’s susceptibility to other diseases?

HIV can increase susceptibility to other diseases because it weakens the immune system, making it harder for the body to fight infections.

3.

What is tuberculosis?

Tuberculosis (TB) is a communicable disease caused by the bacterium Mycobacterium tuberculosis, which commonly affects the lungs.

4.

How can HIV and tuberculosis interact within an infected person?

HIV weakens the immune system, making a person more susceptible to developing tuberculosis and making TB infections more difficult to control.

5.

What is the relationship between HPV infection and cervical cancer?

Persistent infection with certain types of human papillomavirus (HPV) can cause changes in cervical cells that may develop into cervical cancer.

6.

How can infection with HPV increase the risk of developing cervical cancer?

Infection with high-risk HPV can increase the risk of cervical cancer because viral infection can cause abnormal changes in cervical cells, which may become cancerous.

B6.3d Explain how communicable diseases (caused by viruses, bacteria, protists and fungi) are spread in animals and plants

1.

What are the four types of pathogen that can cause communicable diseases?

The four main types of pathogen are viruses, bacteria, protists and fungi.

2.

How can viruses spread between animals and plants?

Viruses can spread between animals and plants through methods including airborne droplets, direct contact, body fluids and vectors.

3.

How can bacteria spread between animals and plants?

Bacteria can spread through air, water, food, direct contact, contaminated surfaces and vectors.

4.

How can protists and fungi spread between animals and plants?

Protists can be spread by vectors such as mosquitoes, while fungi can spread through airborne spores, direct contact or contaminated material.

5.

How can the number of pathogens and number of infected cases be used as measures of the spread of a communicable disease?

The number of pathogens and number of infected cases can be monitored over time to identify changes in the spread and prevalence of a communicable disease.

6.

How can the number of infected cases be estimated when monitoring the spread of a communicable disease?

The number of infected cases can be estimated by sampling a population, identifying infected individuals and using the sample results to estimate the number infected in the wider population.

B6.3e Explain how the spread of communicable diseases may be reduced or prevented in animals and plants

1.

How can detecting an antigen help identify a communicable disease?

Detecting an antigen can identify a pathogen because antigens are molecules associated with the surface of pathogens and can be detected using specific antibodies.

2.

How can DNA testing be used to detect a communicable disease?

DNA testing can detect a communicable disease by identifying specific DNA sequences belonging to the pathogen in a sample.

3.

How can visual identification be used to detect disease in plants?

Plant diseases can be detected by examining plants for visible symptoms, such as unusual spots, discolouration, distorted growth or abnormal leaves.

4.

How can early detection of a communicable disease help reduce its spread?

Early detection allows infected individuals or plants to be isolated or treated quickly, reducing opportunities for the pathogen to spread.

5.

How can the number of infected cases be used to assess whether measures are reducing the spread of a disease?

Comparing the number of infected cases before and after control measures can show whether the measures have reduced disease transmission.

6.

What measures can be used to reduce or prevent the spread of communicable diseases in animals and plants?

Spread can be reduced through measures such as vaccination, isolation, hygiene, controlling vectors, using appropriate medicines, removing infected plants and controlling movement of infected organisms.

B6.3f Describe a minimum of one common human infection, one plant disease and sexually transmitted infections in humans including HIV/AIDS

1.

What is one example of a common human viral infection, and which type of pathogen causes it?

Influenza is a common human viral infection caused by the influenza virus.

2.

What is one example of a common human bacterial infection, and which type of pathogen causes it?

Tuberculosis (TB) is a common human bacterial infection caused by the bacterium Mycobacterium tuberculosis.

3.

What is one example of a common human fungal infection, and which type of pathogen causes it?

Athlete's foot is a common fungal infection caused by a fungus.

4.

What is tobacco mosaic virus (TMV), and what type of pathogen causes it?

Tobacco mosaic virus (TMV) is a viral plant disease caused by a virus that can cause a characteristic mosaic pattern on leaves and reduce photosynthesis.

5.

What are barley powdery mildew and crown gall disease, and which pathogens cause them?

Barley powdery mildew is a fungal disease caused by a fungus, while crown gall disease is caused by the bacterium Agrobacterium.

6.

What is HIV/AIDS, and how is HIV transmitted as a sexually transmitted infection?

HIV/AIDS is caused by the human immunodeficiency virus (HIV), which attacks the immune system. HIV can be transmitted sexually through infected body fluids during unprotected sexual contact.

B6.3g Explain how white blood cells and platelets are adapted to their defence functions in the blood

1.

What role do white blood cells play in defending the body against pathogens?

White blood cells defend the body by detecting and destroying pathogens and producing substances that help protect against infection.

2.

What are the three main defence functions of white blood cells?

The three main defence functions are phagocytosis, antibody production and antitoxin production.

3.

How do white blood cells destroy pathogens by phagocytosis?

During phagocytosis, a white blood cell surrounds and engulfs a pathogen, enclosing it inside the cell before digesting it using enzymes.

4.

How do antibodies and antitoxins help defend the body against pathogens?

Antibodies bind specifically to antigens on pathogens, helping to destroy or neutralise them. Antitoxins neutralise toxins produced by pathogens.

5.

What role do platelets play in the defence of the body?

Platelets help blood to clot when blood vessels are damaged, preventing excessive blood loss and helping prevent pathogens from entering the body.

6.

How are platelets adapted to help prevent pathogens entering the body through damaged blood vessels?

Platelets gather at damaged blood vessels and help form a blood clot, creating a barrier that seals the wound and reduces the entry of pathogens.

B6.3h Describe the non-specific defence systems of the human body against pathogens

1.

What is meant by a non-specific defence system?

A non-specific defence system protects the body against a wide range of pathogens rather than targeting one specific pathogen.

2.

How does the skin act as a non-specific defence against pathogens?

The skin acts as a physical barrier that prevents pathogens from entering the body and produces substances that can inhibit microbial growth.

3.

How do hairs and mucus in the respiratory system help defend against pathogens?

Hairs in the nose trap particles and pathogens, while mucus traps them so they can be removed from the respiratory system.

4.

How do cilia help prevent pathogens entering the lungs?

Cilia are hair-like structures that move mucus containing trapped pathogens towards the throat, where it can be swallowed.

5.

How does hydrochloric acid in the stomach help defend against pathogens?

Hydrochloric acid in the stomach creates a highly acidic environment that kills many pathogens entering the digestive system.

6.

How does blood clotting help prevent pathogens entering the body through wounds?

Blood clotting seals damaged skin and blood vessels, preventing further blood loss and reducing the opportunity for pathogens to enter the body.

B6.3i Explain the role of the immune system of the human body in defence against disease

1.

What is the role of the immune system in defending the body against disease?

The immune system recognises and destroys pathogens and helps protect the body against infectious disease.

2.

How do white blood cells recognise pathogens?

White blood cells recognise pathogens by detecting foreign antigens on their surfaces.

3.

How do antibodies help destroy or neutralise pathogens?

Antibodies bind specifically to pathogen antigens and can neutralise pathogens or mark them for destruction.

4.

How do antitoxins help defend the body against pathogens?

Antitoxins bind to and neutralise toxins produced by pathogens, reducing their harmful effects.

5.

How can antibodies provide immunity against a specific pathogen?

Antibodies produced against a pathogen can remain available through memory cells, allowing a faster and stronger response if the same pathogen enters the body again.

6.

Why is the immune response specific to particular pathogens?

The immune response is specific because antibodies and immune cells recognise particular antigens found on specific pathogens.

B6.3j Explain the use of vaccines and medicines in the prevention and treatment of disease

1.

How do vaccines help prevent communicable diseases?

Vaccines introduce antigens from a pathogen into the body, stimulating an immune response without causing the disease. This produces memory cells that provide protection against future infection.

2.

How does vaccination lead to the production of antibodies and memory cells?

Vaccination stimulates the production of specific antibodies and memory cells, allowing a faster and stronger response when the pathogen is encountered again.

3.

What is the difference between an antibiotic and an antiviral?

An antibiotic is a medicine used to treat bacterial infections, whereas an antiviral is a medicine used to target viruses or reduce their replication.

4.

Why are antibiotics effective against bacteria but not viruses?

Antibiotics work against bacteria, which have cellular structures and processes that can be targeted by these drugs, but viruses reproduce inside host cells and do not have the same structures.

5.

What are antiseptics, and how are they used to prevent infection?

Antiseptics are substances that kill or inhibit microorganisms and are applied to skin or wounds to reduce the risk of infection.

6.

How are antibiotics, antivirals and antiseptics used in the prevention or treatment of disease?

Antibiotics treat bacterial infections, antivirals can reduce viral replication and antiseptics reduce microorganisms on body surfaces or wounds, helping prevent infection.

B6.3k Describe the processes of discovery and development of potential new medicines

1.

What is the purpose of preclinical testing when developing a new medicine?

Preclinical testing determines whether a potential medicine is sufficiently safe and potentially effective before it is tested on humans.

2.

What is the purpose of clinical testing when developing a new medicine?

Clinical testing investigates the safety, effectiveness and appropriate dosage of a medicine in humans.

3.

What is investigated during preclinical testing of a potential new medicine?

Preclinical testing investigates factors such as toxicity, effectiveness and appropriate dosage, initially using laboratory tests and sometimes animals.

4.

What is investigated during clinical testing of a potential new medicine?

Clinical testing investigates safety, effectiveness, dosage and side effects in human volunteers and patients.

5.

Why must a potential new medicine be tested for safety and effectiveness before it is widely used?

Testing is necessary to establish that a medicine is safe enough and effective enough before it is widely used.

6.

Why are aseptic techniques used when investigating the growth of bacterial cultures?

Aseptic techniques are used to prevent unwanted microorganisms contaminating bacterial cultures, ensuring that observed growth is due to the bacteria being investigated.

B6.3m Evaluate some different treatments for cardiovascular disease

1.

What lifestyle changes can be used to treat cardiovascular disease?

Lifestyle changes include increasing exercise, eating a balanced diet, stopping smoking and reducing alcohol consumption.

2.

What medical treatments can be used to treat cardiovascular disease?

Medical treatments include statins, drugs that reduce blood pressure and drugs that reduce blood clotting.

3.

What surgical treatments can be used to treat cardiovascular disease?

Surgical treatments include stents, coronary artery bypass surgery and heart valve replacement.

4.

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

Lifestyle changes can reduce risk factors such as high blood pressure, high cholesterol and obesity, reducing the risk or effects of cardiovascular disease.

5.

What are the benefits of using medical treatments for cardiovascular disease?

Medical treatments can reduce cholesterol, lower blood pressure or prevent blood clots, reducing the risk of serious cardiovascular events.

6.

What are the benefits and risks of using surgical treatments for cardiovascular disease?

Surgical treatments can restore or improve blood flow and heart function, but they can involve risks such as infection, bleeding and complications from surgery.

B6.3n Analyse the effect of lifestyle factors on the incidence of non-communicable diseases at local, national and global levels

1.

What is meant by the incidence of a disease?

Incidence is the number of new cases of a disease occurring in a population during a specified period.

2.

How can exercise affect the incidence of non-communicable diseases?

Regular exercise generally reduces the risk and incidence of several non-communicable diseases, including cardiovascular disease and type 2 diabetes.

3.

How can diet affect the incidence of non-communicable diseases?

A poor diet, particularly one high in saturated fat, salt and sugar, can increase the incidence of diseases such as cardiovascular disease and type 2 diabetes.

4.

How can alcohol consumption affect the incidence of non-communicable diseases?

Excessive alcohol consumption increases the risk and incidence of conditions including liver disease, cardiovascular disease and some cancers.

5.

How can smoking affect the incidence of non-communicable diseases?

Smoking increases the incidence of lung cancer, cardiovascular disease and chronic lung diseases.

6.

Why can the incidence of non-communicable diseases differ between local, national and global populations?

Incidence can differ between local, national and global populations because lifestyle factors such as diet, smoking, alcohol consumption and exercise vary between populations, along with genetic, environmental and socioeconomic factors.

B6.3o Describe cancer as the result of changes in cells that lead to uncontrolled growth and division

1.

What is cancer?

Cancer is a disease caused by changes in cells that result in uncontrolled growth and division.

2.

What changes occur in cells that can lead to cancer?

Changes to genes controlling cell growth and division can cause cells to divide when they should not.

3.

What is meant by uncontrolled cell growth?

Uncontrolled cell growth means cells continue to increase in number or size without normal regulation.

4.

What is meant by uncontrolled cell division?

Uncontrolled cell division means cells continue to divide repeatedly without the normal controls that regulate the cell cycle.

5.

How can uncontrolled growth and division lead to the formation of a tumour?

Uncontrolled growth and division can cause a mass of abnormal cells to form a tumour.

6.

How does cancer differ from normal cell growth and division?

Normal cell growth and division are controlled and regulated, whereas cancer cells can divide uncontrollably and may form tumours.

B6.3p Discuss potential benefits and risks associated with the use of stem cells in medicine

1.

What are stem cells?

Stem cells are unspecialised cells that can divide and differentiate into specialised cell types.

2.

How can stem cells be used in tissue transplantation?

Stem cells can be used to produce replacement cells or tissues that can be used in tissue transplantation to replace damaged or diseased tissue.

3.

What is one potential benefit of using stem cells in medicine?

A potential benefit is that stem cells could replace damaged cells and restore the function of tissues or organs, potentially treating diseases that currently have limited treatment options.

4.

What is one potential risk of using stem cells in medicine?

A potential risk is uncontrolled cell division, which could result in tumour formation.

5.

Why can tissue rejection occur after a transplant?

Tissue rejection can occur when the recipient's immune system recognises transplanted cells as foreign and attacks them.

6.

How can tissue rejection affect the success of stem cell treatments?

Tissue rejection can damage or destroy transplanted cells, reducing the effectiveness and success of the treatment.

B6.3q Explain some of the possible benefits and risks of using gene technology in medicine

1.

What is gene technology?

Gene technology involves modifying or manipulating an organism's genetic material to produce a desired effect.

2.

What is one potential benefit of using gene technology in medicine?

A potential benefit is the ability to treat genetic disorders by replacing, modifying or introducing genetic information.

3.

How could gene technology be used to treat or prevent disease?

Gene technology could be used to introduce a functional version of a faulty gene, allowing cells to produce a functional protein and reducing the effects of a genetic disorder.

4.

What is one potential risk of using gene technology in medicine?

A potential risk is that genetic modification could cause unintended changes, potentially producing harmful effects.

5.

What practical considerations should be considered when using gene technology in medicine?

Practical considerations include the cost, effectiveness, safety, availability and long-term effects of gene technology.

6.

What ethical considerations should be considered when using gene technology in medicine?

Ethical considerations include whether it is acceptable to alter human genetic material, the possibility of unequal access to treatment and concerns about unintended effects on individuals or future generations.

B6.3r Discuss the potential importance for medicine of our increasing understanding of the human genome

1.

What is the human genome?

The human genome is the complete set of genetic material in a human, including all of its genes and DNA sequences.

2.

How could knowledge of the human genome help predict the likelihood of developing particular diseases?

Knowledge of the human genome can help identify genetic variants associated with particular diseases, allowing doctors to estimate an individual's risk of developing certain conditions.

3.

How could knowledge of the human genome help doctors select treatments for diseases?

Genome information can help doctors choose treatments based on an individual's genetic characteristics, potentially improving effectiveness and reducing adverse effects.

4.

What are genome-targeted drugs?

Genome-targeted drugs are medicines designed to act on specific molecular targets associated with particular genetic characteristics or disease-causing changes.

5.

How could drugs targeted to specific genomes improve the treatment of disease?

Genome-targeted drugs could improve treatment by targeting disease processes more precisely, potentially increasing effectiveness and reducing effects on healthy cells.

6.

Why could increasing understanding of the human genome be important for the future of medicine?

Increasing understanding of the human genome could enable earlier diagnosis, improved prediction of disease risk, personalised treatments and development of new medicines, potentially improving prevention and treatment of disease.

Biology

Paper 1

B1 – Cell Level Systems