OCR Triple Science: Biology — Recall & Retrieval

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

1.

What type of microscope is commonly used to view cells in school laboratories?

Light microscope.

2.

What are the main parts of a light microscope used to observe cells?

Eyepiece lens, objective lenses, stage, stage clips, coarse focus wheel, fine focus wheel, light source (or mirror).

3.

Why are stains used when viewing cells with a light microscope?

To increase contrast so cell structures are easier to see.

4.

Why are thin sections of specimens used when preparing slides for microscopy?

So light can pass through the specimen, producing a clearer image.

5.

How is magnification calculated when using a light microscope?

Magnification = image size ÷ actual size.

6.

How can a light microscope be used to compare different types of cells?

A light microscope can be used to compare the appearance and visible structures of different cell types.

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

1.

What are the main sub-cellular structures found in eukaryotic and prokaryotic cells?

Eukaryotic cells contain a nucleus, cytoplasm, cell membrane, ribosomes and mitochondria; plant cells also contain a cell wall, chloroplasts and a permanent vacuole; prokaryotic cells have cytoplasm, cell membrane, cell wall, ribosomes, circular DNA and plasmids.

2.

What is the function of the nucleus, genetic material and chromosomes?

The nucleus contains genetic material (DNA) organised into chromosomes, which control the activities of the cell.

3.

What are the functions of mitochondria, chloroplasts and ribosomes?

Mitochondria are the site of aerobic respiration, chloroplasts are the site of photosynthesis and ribosomes are the site of protein synthesis.

4.

What is the function of the cell membrane and why is it selectively permeable?

The cell membrane controls the movement of substances into and out of the cell because it is selectively permeable.

5.

What are plasmids and where are they found?

Plasmids are small circular rings of DNA found in prokaryotic cells.

6.

How do the sub-cellular structures of plant, animal and prokaryotic cells differ?

Plant cells contain chloroplasts, a cell wall and a permanent vacuole; animal cells do not. Prokaryotic cells lack a nucleus and membrane-bound organelles but contain circular DNA and plasmids.

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

1.

What is an electron microscope?

A microscope that uses electrons instead of light to produce images.

2.

How does an electron microscope differ from a light microscope?

It uses electrons rather than light and has a much higher resolution.

3.

What is meant by the resolution of a microscope?

Resolution is the ability to distinguish two points that are close together as separate.

4.

Why does a transmission electron microscope have a higher resolution than a light microscope?

Electrons have a much shorter wavelength than light, giving a higher resolution.

5.

How has electron microscopy increased our understanding of sub-cellular structures?

It has allowed scientists to see much smaller sub-cellular structures in greater detail.

6.

Which cell structures can be seen using an electron microscope but not clearly with a light microscope?

Ribosomes, membranes and other ultrastructural details that cannot be seen clearly with a light microscope.

B1.2a Describe DNA as a polymer

1.

What is DNA?

DNA is the genetic material found in cells.

2.

What is meant by the term polymer?

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

3.

Why is DNA described as a polymer?

DNA consists of many repeating nucleotide monomers joined together.

4.

What smaller repeating units make up a DNA polymer?

Nucleotides.

5.

How does the polymer structure of DNA allow it to store genetic information?

The sequence of nucleotides stores genetic information.

6.

Why is DNA important in living organisms?

It carries the genetic instructions needed to make proteins and control cell activities.

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

1.

What is the overall shape of a DNA molecule?

Double helix.

2.

How many strands make up a DNA molecule?

Two strands.

3.

What is meant by the term double helix?

Two strands twisted around each other.

4.

How are the two strands of DNA arranged?

They run alongside each other in a spiral.

5.

Why is DNA described as a double-stranded molecule?

It consists of two complementary nucleotide strands.

6.

How does the double helix structure help distinguish DNA from other biological molecules?

The twisted two-stranded structure distinguishes DNA from other biological molecules.

B1.2c Describe that DNA is made from four different nucleotides; each nucleotide consisting of a common sugar and phosphate group with one of four different bases attached to the sugar

1.

What is a nucleotide?

The basic building block (monomer) of DNA.

2.

What are the three parts of a DNA nucleotide?

A sugar, a phosphate group and a nitrogen-containing base.

3.

What are the four bases found in DNA?

Adenine (A), thymine (T), cytosine (C) and guanine (G).

4.

Which bases pair together in a DNA molecule?

Adenine pairs with thymine, and cytosine pairs with guanine.

5.

Why are A-T and G-C known as complementary base pairs?

Because each base only pairs with its specific complementary base.

6.

How do complementary base pairs help maintain the structure of DNA?

Complementary base pairing holds the two DNA strands together.

B1.2d Recall a simple description of protein synthesis

1.

What is protein synthesis?

The process of making proteins from genetic information.

2.

What happens to the DNA molecule at the start of protein synthesis?

The DNA unzips and one strand is used as a template.

3.

What is the role of mRNA during transcription?

mRNA carries a copy of the genetic code from the nucleus to the ribosome.

4.

Where do transcription and translation occur in a cell?

Transcription occurs in the nucleus; translation occurs at ribosomes in the cytoplasm.

5.

What is the role of tRNA during translation?

tRNA carries specific amino acids to the ribosome.

6.

How is the sequence of amino acids determined during protein synthesis?

The sequence of DNA bases determines the order of amino acids.

B1.2e Explain simply how the structure of DNA affects the proteins made in protein synthesis

1.

What is meant by the genetic code?

The sequence of DNA bases that determines the amino acid sequence.

2.

What is a DNA triplet code?

A sequence of three DNA bases that codes for one amino acid.

3.

How does the sequence of DNA bases determine the sequence of amino acids in a protein?

Each DNA triplet codes for a specific amino acid, determining the protein produced.

4.

Why does changing the DNA base sequence change the protein produced?

A different base sequence changes the amino acid sequence, producing a different protein.

5.

How does the structure of DNA influence the structure of proteins?

The DNA base sequence determines the amino acid sequence and therefore the protein's structure.

6.

Why is the order of amino acids important in a protein?

The order of amino acids determines the protein's shape and function.

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

1.

What is the purpose of investigating enzyme activity?

To investigate how different factors affect enzyme activity.

2.

How can the rate of an enzyme-controlled reaction be measured?

By measuring the amount of product formed or substrate used over time.

3.

Which variables can be changed when investigating enzyme activity?

Temperature, pH, substrate concentration or enzyme concentration.

4.

Which variables should be controlled in an enzyme investigation?

All variables except the independent variable should be controlled.

5.

Why should enzyme investigations be repeated?

To improve reliability and identify anomalous results.

6.

How can the results of an enzyme investigation be presented and analysed?

Results can be presented in tables and graphs and analysed by comparing reaction rates.

B1.2g Explain the mechanism of enzyme action

1.

What is an enzyme?

A biological catalyst that speeds up chemical reactions without being used up.

2.

What is meant by the active site of an enzyme?

The region of an enzyme where the substrate binds.

3.

How does the lock-and-key hypothesis explain enzyme specificity?

Only a substrate with a complementary shape fits into the active site.

4.

What role do enzymes play in metabolism?

They catalyse metabolic reactions in living organisms.

5.

How does temperature, pH, substrate concentration and enzyme concentration affect the rate of an enzyme-controlled reaction?

Temperature, pH, substrate concentration and enzyme concentration all affect reaction rate; very high temperatures or extreme pH can denature enzymes.

6.

Why does the rate of an enzyme-controlled reaction eventually stop increasing under some conditions?

Another factor becomes limiting or all active sites become occupied, so the rate reaches a maximum.

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

1.

What is cellular respiration?

The chemical process that releases energy from glucose to produce ATP.

2.

Why is cellular respiration described as a universal process?

It occurs in all living cells.

3.

Why does cellular respiration occur continuously in living cells?

Cells require a continuous supply of ATP, so respiration occurs continuously.

4.

What is ATP?

Adenosine triphosphate (ATP), the cell's energy transfer molecule.

5.

How does cellular respiration supply ATP to cells?

Respiration releases energy which is used to produce ATP.

6.

Why is ATP essential for living organisms?

ATP provides energy for processes such as active transport, muscle contraction and protein synthesis.

B1.3b Describe cellular respiration as an exothermic reaction

1.

What is meant by an exothermic reaction?

A reaction that releases energy to the surroundings.

2.

Why is cellular respiration described as an exothermic reaction?

It releases energy from glucose.

3.

What happens to energy during cellular respiration?

Energy is released and transferred to ATP, with some lost as heat.

4.

How is the energy released during respiration used by cells?

To power metabolic processes in cells.

5.

How does cellular respiration differ from an endothermic reaction?

Endothermic reactions absorb energy, whereas respiration releases energy.

6.

Why is the release of energy during respiration essential for life?

Cells need a continuous energy supply for life processes.

B1.3c Compare the processes of aerobic respiration and anaerobic respiration

1.

What is aerobic respiration?

Respiration using oxygen to release energy from glucose.

2.

What is anaerobic respiration?

Respiration without oxygen to release energy from glucose.

3.

What are the differences between aerobic and anaerobic respiration in terms of the conditions required?

Aerobic respiration requires oxygen; anaerobic respiration does not.

4.

What are the substrates and products of aerobic and anaerobic respiration in animals and in plants or fungi?

Aerobic: glucose + oxygen → carbon dioxide + water. Anaerobic (animals): glucose → lactic acid. Anaerobic (plants and fungi): glucose → ethanol + carbon dioxide.

5.

How do the ATP yields of aerobic and anaerobic respiration compare?

Aerobic respiration releases much more ATP than anaerobic respiration.

6.

Why is aerobic respiration generally more efficient than anaerobic respiration?

Aerobic respiration completely breaks down glucose, releasing more energy.

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

1.

What are carbohydrates?

Molecules made from sugar monomers.

2.

What is meant by the terms monomer and polymer?

A monomer is a small repeating unit; a polymer is a large molecule made from many monomers.

3.

How are sugars used to synthesise carbohydrates?

Sugars join together to form carbohydrate polymers.

4.

How are carbohydrates broken down into sugars?

Carbohydrates are broken down into simple sugars.

5.

Why are sugars important in living organisms?

Sugars are used in respiration and to build carbohydrates.

6.

How are monomers and polymers involved in the synthesis and breakdown of carbohydrates?

Monomers join to form carbohydrate polymers, and polymers can be broken back down into monomers.

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

1.

What are amino acids?

The monomers that make up proteins.

2.

How are amino acids used to synthesise proteins?

Amino acids join together to form proteins.

3.

How are proteins broken down into amino acids?

Proteins are broken down into amino acids.

4.

Why are proteins important in living organisms?

Proteins are needed for growth, repair and making enzymes.

5.

How are monomers and polymers involved in the synthesis and breakdown of proteins?

Monomers (amino acids) join to form protein polymers, which can later be broken down.

6.

Why are amino acids essential for growth and repair?

They are needed to make new proteins for growth and tissue repair.

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

1.

What are lipids?

Lipids are biological molecules including fats and oils.

2.

What are the building blocks of lipids?

Fatty acids and glycerol.

3.

How are fatty acids and glycerol used to synthesise lipids?

Fatty acids combine with glycerol to form lipids.

4.

How are lipids broken down into fatty acids and glycerol?

Lipids are broken down into fatty acids and glycerol.

5.

Why are lipids important in living organisms?

Lipids are important for energy storage, insulation and cell membranes.

6.

Why are fatty acids and glycerol essential for the synthesis and breakdown of lipids?

They are the monomers required to build and break down lipid molecules.

B1.4a Describe the importance of mitosis in growth, repair and asexual reproduction

1.

What is mitosis?

Cell division producing two genetically identical daughter cells.

2.

Why is mitosis important for the growth of multicellular organisms?

It increases the number of cells for growth.

3.

How does mitosis repair damaged or worn-out tissues?

It replaces damaged or worn-out cells.

4.

How does mitosis produce genetically identical cells?

DNA is copied before division so each daughter cell receives identical chromosomes.

5.

Why is mitosis important in asexual reproduction?

It produces genetically identical offspring from one parent.

6.

Why is it important that chromosome number is maintained during mitosis?

It ensures each new cell has the correct chromosome number.

B1.4b Describe the main stages of the cell cycle, including DNA replication and mitosis

1.

What are the main stages of the cell cycle?

Cell growth, DNA replication, mitosis and cytokinesis.

2.

What happens during DNA replication?

DNA is copied to produce two identical sets of chromosomes.

3.

What happens during mitosis?

The nucleus divides to produce two genetically identical nuclei.

4.

What happens during cytokinesis?

The cytoplasm and cell membrane divide to form two cells.

5.

Why must DNA be replicated before mitosis occurs?

So each daughter cell receives a complete set of chromosomes.

6.

What is the outcome of one complete cell cycle?

Two genetically identical daughter cells with the same chromosome number as the parent cell.

B1.4c Describe stem cells as unspecialised cells that can divide and differentiate into specialised cells

1.

What is a stem cell?

An unspecialised cell that can divide and differentiate.

2.

What is meant by the term differentiation?

The process by which a cell becomes specialised.

3.

Why are stem cells described as unspecialised cells?

They have not yet developed a specialised function.

4.

How can stem cells become specialised cells?

By switching specific genes on and off during differentiation.

5.

Where are stem cells found in animals and plants?

Animal stem cells are found in embryos and some adult tissues; plant stem cells are found in meristems.

6.

Why are stem cells important for growth and repair?

They provide new specialised cells for growth and tissue repair.

B1.4d Explain the potential benefits, risks and ethical issues associated with the use of stem cells in medicine

1.

How can stem cells be used to treat disease or injury?

They can replace damaged cells and tissues to treat disease or injury.

2.

What are the potential benefits of using stem cells in medicine?

Potential treatments for diseases and damaged tissues.

3.

What are the potential risks of stem cell treatments?

Rejection, tumour formation or infection.

4.

Why can stem cells from embryos cause ethical concerns?

Because embryos are destroyed to obtain embryonic stem cells.

5.

How do adult stem cells differ from embryonic stem cells in medical use?

Adult stem cells are less controversial but can form fewer cell types than embryonic stem cells.

6.

Why is the use of stem cells considered both a scientific and an ethical issue?

Stem cells offer major medical benefits but raise ethical concerns, especially when embryos are used.

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

1.

What are photosynthetic organisms?

Organisms that carry out photosynthesis, such as green plants and algae.

2.

Why are photosynthetic organisms described as producers?

They make their own food by photosynthesis.

3.

How do photosynthetic organisms make food?

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

4.

What is biomass?

The total mass of living material.

5.

Why are photosynthetic organisms the main source of biomass on Earth?

They produce the organic material that forms the base of food chains.

6.

Why is photosynthesis essential for almost all life on Earth?

Most organisms depend directly or indirectly on photosynthesis for food and oxygen.

B1.4b Describe the process of photosynthesis

1.

What is photosynthesis?

The process by which plants make glucose using light energy.

2.

What are the reactants needed for photosynthesis?

Carbon dioxide and water.

3.

What are the products of photosynthesis?

Glucose and oxygen.

4.

Why is photosynthesis described as a two-stage process?

Light energy is absorbed and used to make glucose from carbon dioxide and water.

5.

Where in a plant cell does photosynthesis take place?

In the chloroplasts.

6.

What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen.

B1.4c Describe photosynthesis as an endothermic reaction

1.

What is an endothermic reaction?

A reaction that absorbs energy from the surroundings.

2.

Why is photosynthesis described as an endothermic reaction?

Because it absorbs light energy.

3.

What is the source of energy for photosynthesis?

Light from the Sun.

4.

What happens to light energy during photosynthesis?

Light energy is converted into chemical energy stored in glucose.

5.

How does photosynthesis differ from respiration in terms of energy transfer?

Photosynthesis absorbs energy, whereas respiration releases energy.

6.

Why is the absorption of energy essential for photosynthesis?

Energy is needed to convert carbon dioxide and water into glucose.

B1.4d Describe experiments to investigate photosynthesis

1.

What is the purpose of investigating photosynthesis experimentally?

To investigate the conditions needed for photosynthesis or the rate of photosynthesis.

2.

How can a plant be tested for starch after photosynthesis?

Boil the leaf in water, heat it in ethanol, rinse it, add iodine solution and observe the colour change.

3.

Why is a leaf boiled in water before testing it for starch?

To kill the cells and stop chemical reactions.

4.

Why is a leaf heated in ethanol before adding iodine solution?

To remove chlorophyll so the iodine colour change can be seen clearly.

5.

What colour does iodine solution turn if starch is present?

Blue-black.

6.

How do starch test experiments show that photosynthesis has occurred?

Starch is produced during photosynthesis, so a blue-black colour shows that photosynthesis has occurred.

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

1.

How does temperature affect the rate of photosynthesis?

The rate increases with temperature up to the optimum, then decreases as enzymes denature.

2.

How does light intensity affect the rate of photosynthesis?

The rate increases as light intensity increases until another factor becomes limiting.

3.

How does carbon dioxide concentration affect the rate of photosynthesis?

The rate increases as carbon dioxide concentration increases until another factor becomes limiting.

4.

Why does the rate of photosynthesis eventually stop increasing as light intensity increases?

Another factor becomes limiting.

5.

Why does the rate of photosynthesis eventually stop increasing as carbon dioxide concentration increases?

Another factor becomes limiting.

6.

Why does photosynthesis have an optimum temperature?

Above the optimum temperature, enzymes involved in photosynthesis become denatured.

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

1.

What is meant by a limiting factor?

The factor in shortest supply that limits the rate of photosynthesis.

2.

How can light intensity act as a limiting factor in photosynthesis?

If light intensity is too low, increasing other factors will have little effect.

3.

How can carbon dioxide concentration act as a limiting factor in photosynthesis?

If carbon dioxide concentration is too low, increasing other factors will have little effect.

4.

How can temperature act as a limiting factor in photosynthesis?

If temperature is too low or too high, enzyme activity limits photosynthesis.

5.

How can graphs be used to identify the limiting factor in photosynthesis?

Graphs show where increasing one factor no longer increases the rate because another factor has become limiting.

6.

Why can changing one limiting factor have no effect if another factor is limiting the rate of photosynthesis?

Because another factor has become the limiting factor.

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

1.

What is diffusion?

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

2.

What is osmosis?

The net movement of water molecules through a partially permeable membrane from a region of higher water potential (dilute solution) to a region of lower water potential (more concentrated solution).

3.

What is active transport?

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

4.

In which direction do substances move during diffusion, osmosis and active transport in relation to the concentration gradient?

Diffusion and osmosis move down a concentration (or water potential) gradient; active transport moves against the concentration gradient.

5.

Which substances are transported into and out of cells by diffusion, osmosis and active transport?

Diffusion transports oxygen and carbon dioxide; osmosis transports water; active transport transports substances such as mineral ions and glucose.

6.

What is meant by water potential, and how does it affect the movement of water by osmosis?

Water potential describes the tendency of water molecules to move. Water moves by osmosis from a region of higher water potential to a region of lower water potential.

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

1.

What is mitosis?

Cell division producing two genetically identical daughter cells.

2.

What happens during the cell growth stage of the cell cycle?

The cell grows and increases the number of sub-cellular structures.

3.

What happens during DNA replication in the cell cycle?

DNA is copied to produce identical chromosomes.

4.

Why does further cell growth occur before mitosis?

The cell grows further and prepares for mitosis.

5.

What happens to chromosomes during mitosis?

Chromosomes separate so each new nucleus receives one copy of every chromosome.

6.

Why is mitosis important for the growth of multicellular organisms?

It increases the number of genetically identical cells for growth.

B2.1c Explain the importance of cell differentiation

1.

What is cell differentiation?

The process by which cells become specialised for specific functions.

2.

Why is cell differentiation important in multicellular organisms?

It allows cells to carry out different functions efficiently.

3.

How does cell differentiation allow organisms to become more efficient?

Different specialised cells perform different jobs within the organism.

4.

What is a specialised cell?

A cell adapted to carry out a particular function.

5.

What are examples of specialised cells in animals and plants?

Examples include red blood cells, nerve cells, root hair cells and palisade cells.

6.

Why are specialised cells needed in multicellular organisms?

Different tissues and organs require cells with specialised functions.

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

1.

What are stem cells?

Unspecialised cells that can divide and differentiate.

2.

Where are stem cells found in embryonic animals?

In the embryo.

3.

Where are stem cells found in adult animals?

In tissues such as bone marrow.

4.

What are meristems?

Regions of actively dividing cells in plants.

5.

Where are meristems found in plants?

At the tips of roots and shoots.

6.

How do stem cells in animals differ from meristems in plants?

Animal stem cells are found in embryos and some adult tissues, whereas plant meristems continue producing new cells throughout life.

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?

They can differentiate into almost any type of specialised cell.

2.

What is the function of adult stem cells?

They replace and repair damaged cells in certain tissues.

3.

What is the function of meristems in plants?

They produce new cells for growth and differentiation.

4.

How do stem cells produce different cell types?

By dividing and then differentiating into specialised cell types.

5.

Why are stem cells important for development, growth and repair?

They are essential for development, growth and tissue repair.

6.

Why are meristems important for plant growth?

They allow plants to continue growing throughout life.

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

1.

What are embryonic stem cells?

Stem cells from embryos that can form almost any cell type.

2.

What are adult stem cells?

Stem cells found in certain adult tissues that can produce a limited range of cell types.

3.

How does the range of cell types produced by embryonic stem cells differ from that of adult stem cells?

Embryonic stem cells can produce many more cell types than adult stem cells.

4.

Why are embryonic stem cells considered less specialised than adult stem cells?

They have not yet become specialised.

5.

Why are adult stem cells usually limited to producing certain cell types?

They have already become partly specialised.

6.

How do the abilities of embryonic stem cells and adult stem cells differ?

Embryonic stem cells have the ability to divide and develop into almost any cell type in the human body, whereas adult stem cells are more limited in the cell types they can produce.

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 surface area : volume ratio of an organism?

The amount of surface area compared with the volume of an organism.

2.

How does increasing size affect an organism's surface area : volume ratio?

Surface area : volume ratio decreases as size increases.

3.

Why do multicellular organisms require specialised exchange surfaces?

Because diffusion alone is too slow to meet the needs of all cells.

4.

Why do multicellular organisms require transport systems?

To transport substances efficiently to and from cells throughout the organism.

5.

How do diffusion distances change as organisms become larger?

Diffusion distances become larger as organisms increase in size.

6.

How does surface area : volume ratio explain the need for exchange surfaces and transport systems in multicellular organisms?

A smaller surface area : volume ratio and larger diffusion distances mean specialised exchange surfaces and transport systems are required.

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.

Why is oxygen transported into organisms?

For aerobic respiration.

2.

Why is carbon dioxide transported out of organisms?

As a waste product of respiration.

3.

Why is water transported into and out of organisms?

For metabolic reactions and to maintain water balance.

4.

Why are dissolved food molecules transported around organisms?

To provide energy and raw materials for growth and respiration.

5.

Why are mineral ions transported into organisms?

For healthy growth and the synthesis of important molecules.

6.

Why is urea transported out of the body?

Urea is removed because it is a waste product produced from the breakdown of excess amino acids.

B2.2c Describe the human circulatory system

1.

What is the function of the human circulatory system?

To transport substances such as oxygen, nutrients, carbon dioxide and urea around the body.

2.

How is the human circulatory system linked to the gaseous exchange system?

Blood transports oxygen from the lungs and carbon dioxide back to the lungs.

3.

Why do mammals have a double circulatory system?

To keep oxygenated and deoxygenated blood separate and maintain high blood pressure to the body.

4.

What are the two circuits of the human circulatory system?

The pulmonary circulation and the systemic circulation.

5.

How are blood vessels arranged in the human circulatory system?

The heart pumps blood through arteries, capillaries and veins.

6.

How does the arrangement of the circulatory system help to transport substances around the body?

Its arrangement allows rapid transport of substances to and from all body cells.

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

1.

How is cardiac muscle adapted to enable the heart to pump blood continuously?

Cardiac muscle contains many mitochondria and contracts continuously without tiring.

2.

What are the names and functions of the valves, chambers and blood vessels entering and leaving the heart?

Valves prevent backflow of blood; atria receive blood; ventricles pump blood; the vena cava and pulmonary vein enter the heart; the aorta and pulmonary artery leave the heart.

3.

How is the structure of an artery adapted to its function?

Thick muscular walls and elastic tissue withstand high pressure.

4.

How is the structure of a vein adapted to its function?

Thin walls, a large lumen and valves help return blood at low pressure.

5.

How is the structure of a capillary adapted to its function?

Thin walls, a narrow lumen and a large surface area allow efficient diffusion.

6.

How do the structures of the heart and blood vessels enable the circulatory system to function effectively?

Their specialised structures enable efficient circulation of blood throughout the body.

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

1.

How are red blood cells adapted to transport oxygen?

They contain haemoglobin, have a biconcave shape and lack a nucleus, increasing space for haemoglobin.

2.

Why do red blood cells contain haemoglobin?

Haemoglobin binds reversibly with oxygen to transport it.

3.

What substances are transported by plasma?

Carbon dioxide, urea, glucose, amino acids, hormones and dissolved ions.

4.

Why is plasma important for transporting dissolved substances around the body?

It transports dissolved substances throughout the body.

5.

How do the adaptations of red blood cells differ from those of plasma?

Red blood cells transport oxygen, whereas plasma transports dissolved substances.

6.

How do red blood cells and plasma work together to transport substances in the blood?

Red blood cells carry oxygen while plasma transports many other substances around the body.

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.

How are water and mineral ions taken up by plants?

Water enters by osmosis and mineral ions are absorbed mainly by active transport.

2.

How are root hair cells adapted to absorb water efficiently?

They have a large surface area and thin cell walls for efficient osmosis.

3.

How are root hair cells adapted to absorb mineral ions efficiently?

They contain many mitochondria to supply energy for active transport.

4.

Why do root hair cells have a large surface area?

To increase the rate of absorption.

5.

Why is active transport needed for the uptake of some mineral ions?

Because mineral ions are often absorbed against the concentration gradient.

6.

How does the structure of a root hair cell relate to its function in water and mineral ion uptake?

Their adaptations maximise the uptake of water and mineral ions from the soil.

B2.2g Describe the processes of transpiration and translocation

1.

What is transpiration?

The loss of water vapour from leaves through the stomata.

2.

What is translocation?

The movement of dissolved sugars and other organic substances through the phloem.

3.

What is the function of the stomata in transpiration?

They allow gas exchange and regulate water loss.

4.

What substances are transported by translocation?

Dissolved sugars, mainly sucrose, and other organic substances.

5.

How do transpiration and translocation differ?

Transpiration moves water in the xylem; translocation moves sugars in the phloem.

6.

How do transpiration and translocation help plants survive?

They transport water, minerals and food to where they are needed in the plant.

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

1.

What is the function of xylem tissue?

To transport water and mineral ions from the roots to the rest of the plant.

2.

What is the function of phloem tissue?

To transport dissolved sugars and other organic substances.

3.

How is xylem adapted to transport water and mineral ions?

Xylem vessels are dead, hollow, strengthened with lignin and have no end walls.

4.

How is phloem adapted to transport dissolved sugars and other organic substances?

Phloem consists of living cells with sieve plates and companion cells.

5.

How do the structures of xylem and phloem differ?

Xylem transports water and minerals; phloem transports dissolved sugars and other organic substances.

6.

How do the adaptations of xylem and phloem enable them to carry out their functions?

Their specialised structures allow efficient transport of different substances throughout the plant.

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

1.

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

Increasing light intensity increases water uptake.

2.

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

Greater air movement increases water uptake.

3.

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

Increasing temperature increases water uptake up to a point.

4.

Why does increasing light intensity increase water uptake?

Light opens stomata, increasing transpiration.

5.

Why does increasing air movement affect the rate of water uptake?

Moving air removes water vapour around the leaf, maintaining a diffusion gradient.

6.

Why do changes in environmental factors affect the rate of water uptake by a plant?

Environmental factors affect transpiration, which changes the rate of water uptake.

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?

A piece of apparatus used to estimate the rate of water uptake by a plant.

2.

How does a simple potometer measure the rate of water uptake?

By measuring the movement of an air bubble in a capillary tube over time.

3.

How can a potometer be used to investigate the effect of light intensity on water uptake?

Change the light intensity while keeping other variables constant and measure bubble movement.

4.

How can a potometer be used to investigate the effect of temperature or air movement on water uptake?

Change temperature or air movement while keeping other variables constant and measure bubble movement.

5.

How is the rate of water uptake calculated using measurements from a potometer?

Rate = distance moved (or volume of water taken up) ÷ time.

6.

Why is a potometer used to estimate the rate of transpiration rather than measure transpiration directly?

It measures water uptake, which is used as an estimate of transpiration because not all water taken up is lost by transpiration.

B3.1a Describe the structure of the nervous system

1.

What is the Central Nervous System (CNS)?

The brain and spinal cord.

2.

What are the functions of sensory neurones, relay neurones and motor neurones?

Sensory neurones carry impulses from receptors to the CNS; relay neurones carry impulses within the CNS; motor neurones carry impulses from the CNS to effectors.

3.

What are sensory receptors and what is their function?

They detect stimuli.

4.

What is a synapse and what is its role in the nervous system?

A tiny gap between neurones where neurotransmitters transmit nerve impulses.

5.

What are effectors and how do they respond to nerve impulses?

Muscles or glands that bring about a response.

6.

How are the Central Nervous System, neurones, receptors, synapses and effectors organised to form the nervous system?

Receptors detect stimuli, sensory neurones carry impulses to the CNS, relay neurones process the information, motor neurones carry impulses to effectors, and effectors produce the response.

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

1.

Why does the nervous system connect to all parts of the body?

To detect and respond to changes throughout the body.

2.

How do sensory receptors detect changes in the internal or external environment?

They detect stimuli and convert them into nerve impulses.

3.

How are nerve impulses transmitted through the nervous system to produce a response?

Nerve impulses travel from receptors to the CNS and then to effectors.

4.

What is the role of the Central Nervous System in coordinating responses?

It processes information and coordinates the response.

5.

Why are different sensory receptors needed in the nervous system?

Different receptors detect different types of stimuli.

6.

How do the components of the nervous system work together to produce a coordinated response?

Receptors, neurones, the CNS and effectors work together to produce coordinated responses.

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

1.

What is a reflex action?

A rapid, automatic response to a stimulus.

2.

What are the stages of a reflex arc?

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

3.

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

It carries nerve impulses from the receptor to the CNS.

4.

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

It passes impulses between sensory and motor neurones within the CNS.

5.

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

The motor neurone carries impulses to the effector, which produces the response.

6.

How does the structure of a reflex arc enable a rapid automatic response?

It follows a short pathway through the CNS, allowing a rapid automatic response.

B3.1d Explain how the main structures of the eye are related to their functions

1.

What is the function of the cornea in the human eye?

It refracts light entering the eye.

2.

How does the iris control the amount of light entering the eye?

The iris changes the size of the pupil to control light entering the eye.

3.

What is the function of the pupil?

It is the opening that allows light into the eye.

4.

How do the lens, ciliary body and suspensory ligaments work together to focus light onto the retina?

The ciliary muscles alter the shape of the lens by changing the tension in the suspensory ligaments to focus light on the retina.

5.

What are the functions of the retina and the optic nerve?

The retina contains light receptors and the optic nerve carries impulses to the brain.

6.

How are the main structures of the eye adapted to enable vision?

Each structure is adapted to focus light accurately onto the retina for clear vision.

B3.1e Describe common defects of the eye and explain how some of these problems may be overcome

1.

What is colour blindness?

An inability to distinguish certain colours.

2.

What causes short-sightedness (myopia)?

The eye is too long or the lens is too powerful, so distant images focus in front of the retina.

3.

What causes long-sightedness (hyperopia)?

The eye is too short or the lens is not powerful enough, so near images focus behind the retina.

4.

How can short-sightedness be corrected?

Concave (diverging) lenses.

5.

How can long-sightedness be corrected?

Convex (converging) lenses.

6.

How do corrective lenses overcome defects of the eye?

Corrective lenses alter the path of light so images focus on the retina.

B3.1f Describe the structure and function of the brain

1.

What is the function of the cerebrum?

Conscious thought, intelligence, memory and voluntary actions.

2.

What is the function of the cerebellum?

Coordination of balance and muscular movement.

3.

What is the function of the medulla?

Control of unconscious activities such as breathing and heart rate.

4.

What are the roles of the hypothalamus and the pituitary gland?

The hypothalamus regulates internal conditions and links the nervous and endocrine systems; the pituitary gland releases hormones.

5.

How do different regions of the brain work together to control the body?

Different regions perform specialised functions and work together to coordinate the body.

6.

How is the structure of the brain related to its functions?

Different brain regions are specialised for different functions.

B3.1g Explain some of the difficulties of investigating brain function

1.

Why is it difficult to investigate the function of different parts of the brain?

The brain is complex and difficult to study without causing damage.

2.

Why can case studies be useful when investigating brain function?

They provide information about the functions of damaged brain regions.

3.

What are the limitations of using case studies to investigate brain function?

They are limited because every injury is different and evidence may not apply to everyone.

4.

What ethical issues must be considered when researching the human brain?

The risk of harming patients and the need for informed consent.

5.

Why can ethical considerations limit brain research?

Ethical restrictions limit the types of investigations that can be carried out.

6.

How do practical and ethical difficulties affect investigations into brain function?

Both practical and ethical issues make research into brain function difficult.

B3.1h Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system

1.

Why is damage to nervous tissue often difficult to repair?

Nervous tissue has very limited ability to regenerate.

2.

Why can damage to surrounding nervous tissue limit treatment?

Surgery may damage nearby healthy nervous tissue.

3.

Why is it difficult for surgeons to access some parts of the nervous system?

Many areas are difficult to reach safely without causing damage.

4.

Why can diseases of the brain and nervous system be difficult to treat?

Nervous tissue is difficult to repair and treatments are often limited.

5.

What are the main limitations of current treatments for damage to the brain and nervous system?

Treatments may not fully restore lost function.

6.

How do the properties of nervous tissue make treatment of brain and nervous system disorders challenging?

The delicate nature and poor regenerative ability of nervous tissue make treatment difficult.

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

1.

What is hormonal coordination?

Coordination of body functions using hormones.

2.

What is the endocrine system?

A system of glands that secrete hormones.

3.

What is the function of hormones in the human body?

Hormones act as chemical messengers.

4.

How are hormones transported around the body?

They are transported in the bloodstream.

5.

What are endocrine glands and what do they do?

They produce and release hormones.

6.

How do hormones act on target organs and cells with specific receptors?

Hormones only affect target organs or cells with specific receptors.

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

1.

What is the function of thyroxine in the body?

It regulates metabolic rate, growth and development.

2.

How is thyroxine an example of a negative feedback system?

Thyroxine levels are controlled by negative feedback.

3.

What is the function of adrenaline in the body?

It prepares the body for a fight-or-flight response.

4.

How does adrenaline prepare the body for a fight-or-flight response?

It increases heart rate, breathing rate and blood glucose concentration.

5.

Why is negative feedback important in controlling thyroxine levels?

It keeps thyroxine levels within a normal range.

6.

How do the roles of thyroxine and adrenaline differ?

Thyroxine regulates metabolism, whereas adrenaline prepares the body for emergencies.

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

1.

What is the role of oestrogen in the menstrual cycle?

It rebuilds the uterine lining and stimulates LH release while inhibiting FSH.

2.

What is the role of progesterone in the menstrual cycle?

It maintains the uterine lining after ovulation.

3.

What is the role of FSH in human reproduction?

It stimulates egg maturation in the ovaries.

4.

What is the role of testosterone in human reproduction?

It stimulates sperm production and male secondary sexual characteristics.

5.

How do hormones control the menstrual cycle?

Hormones regulate egg maturation, ovulation and maintenance of the uterus.

6.

Why are hormones essential for human reproduction?

They control the reproductive processes required for successful reproduction.

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

1.

How does FSH influence the menstrual cycle?

It stimulates egg maturation and oestrogen production.

2.

What is the role of LH in the menstrual cycle?

It triggers ovulation.

3.

How does oestrogen affect the release of FSH and LH?

Oestrogen inhibits FSH and stimulates LH.

4.

What is the role of progesterone after ovulation?

It maintains the uterine lining and inhibits FSH and LH.

5.

How do FSH, LH, oestrogen and progesterone interact to control the menstrual cycle?

They interact through positive and negative feedback to regulate the menstrual cycle.

6.

Why are changes in hormone levels necessary throughout the menstrual cycle?

They ensure the correct timing of egg maturation, ovulation and preparation of the uterus.

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

1.

How are hormones used in contraception?

Hormones are used to prevent ovulation or reduce the chance of fertilisation.

2.

How do hormonal methods of contraception prevent pregnancy?

Hormonal methods prevent pregnancy by inhibiting FSH and LH, preventing ovulation.

3.

What are examples of non-hormonal methods of contraception?

Examples include condoms, diaphragms and copper IUDs.

4.

What are the advantages and disadvantages of hormonal contraception?

Advantages include high effectiveness and convenience; disadvantages include possible side effects and no protection against STIs.

5.

What are the advantages and disadvantages of non-hormonal contraception?

Advantages include no hormonal side effects; condoms also reduce STI transmission, but some methods are less effective if not used correctly.

6.

How does the effectiveness of hormonal contraception compare with non-hormonal contraception?

Hormonal contraception is generally more effective, while non-hormonal methods may avoid hormonal side effects and some protect against STIs.

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

1.

How are hormones used to treat infertility?

Hormones are used to stimulate egg maturation and ovulation.

2.

What is the role of fertility drugs in reproductive technology?

Fertility drugs contain FSH and/or LH to stimulate egg development and ovulation.

3.

How can hormones stimulate ovulation?

FSH stimulates egg maturation and LH triggers ovulation.

4.

Why may hormonal treatment be used before assisted reproduction?

To increase the chance of successful fertilisation.

5.

How do modern reproductive technologies help people with infertility?

They increase the chance of pregnancy in people experiencing infertility.

6.

What are the advantages and limitations of using hormones to treat infertility?

Hormonal treatments can improve fertility but may increase the risk of multiple pregnancies and other side effects.

B3.2g Explain how plant hormones are important in the control and coordination of plant growth and development, with reference to the role of auxins in phototropisms and gravitropisms

1.

What is the function of auxins in plants?

Auxins stimulate cell elongation in plant shoots.

2.

How do auxins cause phototropism?

Auxins accumulate on the shaded side, causing greater cell elongation so the shoot bends towards the light.

3.

How do auxins cause gravitropism?

Auxins accumulate on the lower side of shoots, causing the shoot to grow upwards.

4.

Why does an unequal distribution of auxin cause plant shoots to bend?

Cells with more auxin elongate more, causing bending.

5.

How do auxins coordinate plant growth and development?

Auxins coordinate growth by controlling cell elongation.

6.

How are auxins involved in both phototropism and gravitropism?

Unequal auxin distribution causes growth responses to light and gravity.

B3.2h Describe some of the variety of effects of plant hormones, relating to auxins, gibberellins and ethene

1.

How do auxins affect plant growth?

They stimulate cell elongation and root development.

2.

What is the role of gibberellins in seed germination?

They stimulate seed germination.

3.

How do gibberellins affect plant growth?

They stimulate stem growth.

4.

What is the role of ethene in fruit ripening?

It stimulates fruit ripening.

5.

How does ethene affect flower opening and the shedding of leaves?

It promotes flower opening and leaf fall.

6.

How do the effects of auxins, gibberellins and ethene differ?

Auxins mainly control growth responses, gibberellins promote growth and germination, and ethene controls fruit ripening and ageing.

B3.2i Describe some of the different ways in which people use plant hormones to control plant growth

1.

How are selective herbicides used to control plant growth?

Selective herbicides kill broad-leaved weeds without harming grasses.

2.

How are plant hormones used to produce root cuttings?

Auxins stimulate root formation in cuttings.

3.

How are plant hormones used to produce seedless (parthenocarpic) fruit?

Plant hormones stimulate fruit development without fertilisation.

4.

How can plant hormones be used to alter seed dormancy?

Gibberellins can break seed dormancy and stimulate germination.

5.

Why are plant hormones useful in agriculture and horticulture?

They improve crop production and plant propagation.

6.

How are different plant hormones used to control plant growth?

Different plant hormones are used to control growth, germination, rooting and fruit production.

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

1.

What is meant by maintaining a constant internal environment?

Homeostasis.

2.

Why is homeostasis important for living organisms?

It keeps conditions suitable for enzyme-controlled metabolic reactions.

3.

Why must metabolic reactions occur at appropriate rates?

Metabolic reactions depend on enzymes working at their optimum conditions.

4.

How can internal changes affect the body's internal environment?

Internal changes such as exercise alter body temperature and blood glucose concentration.

5.

How can external changes affect the body's internal environment?

External changes such as environmental temperature affect body temperature.

6.

Why is maintaining a constant internal environment essential for survival?

Maintaining stable internal conditions allows cells and enzymes to function effectively.

B3.3b Describe the function of the skin in the control of body temperature

1.

How does the skin detect changes in external temperature?

Thermoreceptors in the skin detect temperature changes.

2.

How does sweating help to control body temperature?

Sweat evaporates, removing heat from the body.

3.

How does shivering help to maintain body temperature?

Muscle contractions generate heat.

4.

What is vasodilation and how does it help cool the body?

Blood vessels widen, increasing blood flow near the skin to lose heat.

5.

What is vasoconstriction and how does it help conserve body heat?

Blood vessels narrow, reducing blood flow near the skin to conserve heat.

6.

How does the skin help maintain a constant body temperature?

Sweating, shivering, vasodilation and vasoconstriction help maintain body temperature.

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

1.

What is the function of insulin?

It lowers blood glucose concentration.

2.

When is insulin released into the bloodstream?

When blood glucose concentration becomes too high.

3.

How does insulin lower blood glucose concentration?

It increases the uptake of glucose by cells and stimulates conversion of glucose to glycogen.

4.

What effect does insulin have on liver and muscle cells?

They convert glucose into glycogen for storage.

5.

Why is insulin important for homeostasis?

It prevents blood glucose concentration from becoming too high.

6.

How does insulin help maintain a constant blood sugar level?

Insulin lowers blood glucose concentration back towards normal levels.

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

1.

What is the function of glucagon?

It raises blood glucose concentration.

2.

When is glucagon released?

When blood glucose concentration becomes too low.

3.

How does glucagon increase blood glucose concentration?

It stimulates the breakdown of glycogen into glucose.

4.

How do insulin and glucagon work together?

Insulin lowers blood glucose while glucagon raises it.

5.

Why are both insulin and glucagon needed to regulate blood sugar?

They maintain blood glucose concentration within a normal range.

6.

How do insulin and glucagon maintain blood glucose by negative feedback?

They work together through negative feedback to regulate blood glucose concentration.

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

1.

What is type 1 diabetes?

A condition where the pancreas produces little or no insulin.

2.

What is type 2 diabetes?

A condition where body cells no longer respond properly to insulin.

3.

How is type 1 diabetes treated?

Insulin injections, careful monitoring of blood glucose and controlled diet.

4.

How can type 2 diabetes be managed or treated?

Lifestyle changes such as diet and exercise, and medication if required.

5.

What are the main differences between type 1 and type 2 diabetes?

Type 1 involves lack of insulin production; Type 2 involves insulin resistance and is often linked to lifestyle.

6.

Why do the treatments for type 1 and type 2 diabetes differ?

Because the causes of the two conditions are different (Type 1 born with little to no insulin vs Type 2 cells not responsive/are resistant to insulin).

B3.3f Explain the effect on cells of osmotic changes in body fluids

1.

What happens to cells when body fluids have a higher water potential than the cells?

Water enters the cells by osmosis, causing them to swell and possibly burst (lysis).

2.

What happens to cells when body fluids have a lower water potential than the cells?

Water leaves the cells by osmosis, causing them to shrink (crenate).

3.

What happens to cells when body fluids have the same water potential as the cells?

There is no net movement of water into or out of the cells.

4.

What is meant by lysis?

The bursting of an animal cell when too much water enters by osmosis.

5.

Why can cells shrink when water leaves by osmosis?

Water moves out of the cell by osmosis into the surrounding fluid.

6.

How do osmotic changes in body fluids affect animal cells?

Animal cells swell, shrink or remain unchanged depending on the water potential of the surrounding body fluids.

B3.3g Describe the function of the kidneys in maintaining the water balance of the body

1.

What is the function of the kidneys in maintaining water balance?

They regulate the body's water content by controlling how much water is reabsorbed.

2.

How do the kidneys vary the amount of water excreted?

By changing the amount of water reabsorbed into the blood.

3.

How do the kidneys change the concentration of urine?

By varying the amount of water reabsorbed before urine is produced.

4.

Why is regulating water balance important?

To maintain homeostasis and normal cell function.

5.

How do the kidneys respond when the body is dehydrated?

They reabsorb more water, producing a smaller volume of concentrated urine.

6.

How do the kidneys help maintain homeostasis?

They regulate water content by adjusting the concentration and volume of urine.

B3.3h Describe the gross structure of the kidney and the structure of the kidney tubule

1.

What are the main structures of the kidney?

Cortex, medulla, pelvis and kidney tubules (nephrons).

2.

What is the function of the cortex and medulla?

The cortex contains filtration units; the medulla contains loops of the kidney tubules where water balance is regulated.

3.

What is the role of the kidney tubule?

It filters blood and selectively reabsorbs useful substances.

4.

How is the kidney tubule adapted for reabsorption?

It has a large surface area and a good blood supply for efficient reabsorption.

5.

What is filtered from the blood into the kidney tubule?

Water, glucose, ions, urea and other small molecules.

6.

How do the structures of the kidney enable it to maintain water balance?

Filtration followed by selective reabsorption enables the kidneys to regulate water balance.

B3.3i Describe the effect of ADH on the permeability of the kidney tubules

1.

What is ADH?

Antidiuretic hormone.

2.

How does ADH affect the permeability of the kidney tubules?

It increases the permeability of the kidney tubules to water.

3.

How does ADH affect the amount of water reabsorbed into the blood?

More water is reabsorbed into the bloodstream.

4.

How does ADH affect the concentration of urine?

Urine becomes more concentrated and its volume decreases.

5.

How is ADH controlled by negative feedback?

ADH secretion changes in response to blood water content through negative feedback.

6.

How does ADH help maintain water balance in the body?

ADH regulates water reabsorption to maintain water balance.

B3.3j Explain the response of the body to different temperature and osmotic challenges

1.

How does the body respond to high rates of sweating and dehydration?

More ADH is released, more water is reabsorbed and concentrated urine is produced.

2.

How does the body respond to drinking excessive amounts of water?

Less ADH is released, less water is reabsorbed and dilute urine is produced.

3.

How does the body respond to a high salt intake?

More water is conserved by increasing ADH release.

4.

How does the sensation of thirst help maintain water balance?

It encourages water intake when blood water potential falls.

5.

How do the kidneys respond to different osmotic challenges?

They alter the amount of water reabsorbed according to the body's needs.

6.

How do negative feedback mechanisms maintain water balance and body temperature during different environmental challenges?

Negative feedback regulates body temperature and water balance despite changing environmental conditions.

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

1.

What does it mean when a material cycles through an ecosystem?

Materials move repeatedly between living organisms and the non-living environment.

2.

What are the abiotic components of an ecosystem?

Non-living parts of the ecosystem, such as air, water and soil.

3.

What are the biotic components of an ecosystem?

Living organisms within the ecosystem.

4.

How do materials move between the abiotic and biotic components of an ecosystem?

Materials are taken up by organisms and returned to the environment through processes such as decomposition.

5.

Which materials are named in the OCR specification as examples of materials that cycle through ecosystems?

Carbon and nitrogen.

6.

Why must materials such as carbon and nitrogen be continuously recycled in ecosystems?

They are needed continuously by living organisms and must be recycled because supplies are limited.

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?

They act as decomposers, recycling materials.

2.

What is decomposition?

The breakdown of dead organisms and waste.

3.

How do microorganisms act as decomposers?

They break down dead material and release nutrients back into the environment.

4.

Why are decomposers essential for recycling materials in ecosystems?

They recycle nutrients for reuse by plants and other organisms.

5.

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

They release nutrients from dead organisms and waste into the soil and atmosphere.

6.

How does the action of microorganisms help maintain the cycling of materials through an ecosystem?

Their decomposition activities maintain the continuous recycling of materials in ecosystems.

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?

It recycles carbon needed for photosynthesis and other biological molecules.

2.

Why is the water cycle important to living organisms?

It recycles water needed for life processes.

3.

How do the carbon and water cycles help to maintain habitats?

They maintain suitable environmental conditions for living organisms.

4.

How do the carbon and water cycles ensure the availability of fresh water?

The water cycle continuously recycles fresh water.

5.

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

They recycle essential materials required by living organisms.

6.

Describe the main stages of both the carbon cycle and the water cycle.

Carbon cycle: photosynthesis, feeding, respiration, decomposition and combustion. Water cycle: evaporation, condensation, precipitation and transpiration.

B4.1d Explain the effect of factors such as temperature, water content and oxygen availability on rate of decomposition

1.

How does temperature affect the rate of decomposition?

Higher temperatures increase decomposition up to an optimum.

2.

How does water content affect the rate of decomposition?

More water generally increases decomposition.

3.

How does oxygen availability affect the rate of decomposition?

More oxygen increases aerobic decomposition.

4.

What is the difference between aerobic and anaerobic decomposition?

Aerobic decomposition uses oxygen; anaerobic decomposition occurs without oxygen.

5.

Why do microorganisms decompose materials more quickly under favourable conditions?

Their enzymes work more effectively under favourable conditions.

6.

Explain how temperature, water content and oxygen availability together affect the rate of decomposition.

Warm, moist and oxygen-rich conditions produce the fastest rates of decomposition.

B4.1e Describe different levels of organisation in an ecosystem

1.

What is an individual organism?

A single living organism.

2.

What is a population?

All the organisms of one species living in the same area.

3.

What is a community?

All the populations of different species living and interacting in the same area.

4.

What is an ecosystem?

A community together with the abiotic (non-living) environment.

5.

Arrange the following in order of increasing level of organisation: community, ecosystem, individual organism and population.

Individual organism → Population → Community → Ecosystem.

6.

What is the difference between a population, a community and an ecosystem?

A population contains one species, a community contains all the populations in an area, and an ecosystem includes the community and the abiotic environment.

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

1.

What are abiotic factors in an ecosystem?

Non-living factors in an ecosystem.

2.

How can temperature, light intensity, moisture level and soil pH affect a community?

Temperature, light intensity, moisture level and soil pH affect the size and distribution of communities.

3.

What are biotic factors in an ecosystem?

Living factors in an ecosystem.

4.

How can predators affect the size of a community?

Predators reduce the size of prey populations.

5.

How can food availability affect a community?

Food availability affects the size of populations because organisms compete for resources.

6.

Explain how abiotic and biotic factors together determine the size and distribution of communities.

Abiotic and biotic factors together determine the size and distribution of communities.

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

1.

What is meant by interdependence in a community?

Organisms depend on each other for survival.

2.

What is predation?

One organism kills and eats another organism.

3.

What is mutualism?

A relationship in which both organisms benefit.

4.

What is parasitism?

A relationship in which one organism benefits and the other is harmed.

5.

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

Changes to one population can affect all the other organisms in the community.

6.

Why does competition occur between organisms living in the same community?

Competition occurs when organisms require the same limited resources, such as food, water, light, space or mates.

B4.1h Describe the differences between the trophic levels of organisms within an ecosystem

1.

What is a trophic level?

The feeding position of an organism in a food chain.

2.

What is a producer?

An organism that makes its own food, usually by photosynthesis.

3.

What is a consumer?

An organism that obtains energy by feeding on other organisms.

4.

How do producers and consumers occupy different trophic levels?

Producers occupy the first trophic level; consumers occupy higher trophic levels.

5.

How is energy transferred from one trophic level to the next?

Energy is transferred by feeding.

6.

Explain how trophic levels describe feeding relationships within an ecosystem.

Trophic levels describe the feeding relationships and transfer of energy through an ecosystem.

B4.1i Describe pyramids of biomass and explain, with examples, how biomass is lost between the different trophic levels

1.

What is a pyramid of biomass?

A diagram showing the biomass at each trophic level.

2.

Why is there less biomass at each successive trophic level?

Biomass is lost between trophic levels.

3.

How is biomass lost by egestion?

Biomass is lost in faeces and undigested material.

4.

How is biomass lost by excretion?

Biomass is lost in waste products such as urea.

5.

How is biomass lost through respiration?

Biomass is lost because materials are respired to release energy.

6.

Explain, using egestion, excretion and respiration, why pyramids of biomass become narrower at higher trophic levels.

Egestion, excretion and respiration reduce the biomass available for transfer to the next trophic level.

B4.1j Calculate the efficiency of biomass transfers between trophic levels and explain how this affects the number of trophic levels in a food chain

1.

What is meant by the efficiency of biomass transfer between trophic levels?

The percentage of biomass transferred from one trophic level to the next.

2.

State the equation used to calculate the percentage efficiency of biomass transfer.

Percentage efficiency = (Biomass transferred ÷ Biomass available) × 100.

3.

A producer level contains 5000 g of biomass and the primary consumers contain 500 g. Calculate the percentage efficiency of biomass transfer.

10%.

4.

A food chain has 1200 g of biomass at one trophic level and 180 g at the next. Calculate the efficiency of biomass transfer.

15%.

5.

Why is biomass transfer between trophic levels never 100% efficient?

Because biomass is lost by egestion, excretion and respiration.

6.

Explain how the efficiency of biomass transfer limits the number of trophic levels in a food chain.

Since only a small proportion of biomass is transferred at each trophic level, food chains usually contain only a limited number of trophic levels.

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

1.

What is a gamete?

A sex cell (sperm or egg) containing a haploid set of chromosomes.

2.

What is the difference between a chromosome, a gene and an allele (variant)?

A chromosome is a long DNA molecule; a gene is a section of DNA that codes for a protein; an allele (variant) is a different version of a gene.

3.

What is meant by the terms dominant and recessive?

A dominant allele is expressed if present; a recessive allele is only expressed when two copies are present.

4.

What is the difference between homozygous and heterozygous?

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

5.

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

Genotype is the genetic makeup of an organism; phenotype is its observable characteristics.

6.

An organism has the genotype Bb, where B is dominant for brown eyes and b is recessive for blue eyes. What is the organism's phenotype?

Brown eyes.

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

1.

What is a genome?

The complete genetic material of an organism.

2.

What does the genome contain?

All of an organism's DNA, including all of its genes.

3.

How is the genome different from a chromosome?

A chromosome is one DNA molecule; the genome is the complete set of DNA.

4.

How is the genome different from a gene?

A gene is a section of DNA; the genome includes every gene.

5.

Does every cell in an organism usually contain the same genome?

Yes, almost all cells contain the same genome.

6.

Why is the genome important for an organism?

It contains the instructions for the development and functioning of the organism.

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

1.

How does the genome influence an organism's phenotype?

Genes provide the instructions that influence characteristics.

2.

How can the environment influence an organism's phenotype?

Environmental factors can affect how characteristics develop.

3.

What is meant by discontinuous variation?

Variation with distinct categories and no intermediates.

4.

What is meant by continuous variation?

Variation showing a continuous range of values.

5.

Give one example of discontinuous variation and one example of continuous variation.

Discontinuous: blood group. Continuous: height.

6.

Explain how both genes and the environment together determine an organism's phenotype.

Phenotype is determined by the interaction between genes and the environment.

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?

A change in the DNA sequence.

2.

Where do all genetic variants come from?

Mutations.

3.

What effect do most mutations have on phenotype?

Most have no effect.

4.

What effect do some mutations have on phenotype?

Some affect the phenotype.

5.

What effect do very few mutations have on phenotype?

Very few determine the phenotype.

6.

Explain why different mutations can have different effects on an organism's phenotype.

Different mutations affect different genes or gene expression, so their effects vary.

B5.1e Describe how genetic variants may influence phenotype

1.

How can a mutation in coding DNA alter an organism's phenotype?

It may change the amino acid sequence and the protein produced.

2.

How can changing the structure of a protein affect its function?

It may change the protein's shape and function.

3.

How can a mutation affecting the active site of an enzyme influence phenotype?

It may alter the shape of the active site so the enzyme no longer works properly.

4.

How can a mutation in non-coding DNA affect phenotype?

It may affect gene expression.

5.

How can changes in non-coding DNA alter whether a gene is expressed?

They can alter whether, when or how much a gene is expressed.

6.

Explain the difference between mutations in coding DNA and non-coding DNA.

Coding DNA mutations alter proteins directly; non-coding DNA mutations alter gene expression.

B5.1f Explain some of the advantages and disadvantages of asexual and sexual reproduction in a range of organisms

1.

State one advantage and one disadvantage of asexual reproduction.

Advantage: only one parent is needed and reproduction is rapid. Disadvantage: little or no genetic variation.

2.

State one advantage and one disadvantage of sexual reproduction.

Advantage: produces genetic variation. Disadvantage: requires two parents and is slower.

3.

How does the number of offspring produced differ between asexual and sexual reproduction?

Asexual reproduction usually produces more offspring.

4.

Which type of reproduction usually allows organisms to reproduce more quickly?

Asexual reproduction.

5.

Why is genetic variation an advantage in changing environments?

Genetic variation increases the chance that some individuals will survive environmental change.

6.

Explain why environmental pressures can make sexual reproduction advantageous despite producing fewer offspring more slowly.

Sexual reproduction produces variation that increases survival in changing environments despite being slower.

B5.1g Explain the terms haploid and diploid

1.

What is meant by the term haploid?

A cell containing one set of chromosomes.

2.

What is meant by the term diploid?

A cell containing two sets of chromosomes.

3.

Which human cells are haploid?

Sperm and egg cells.

4.

Which human cells are diploid?

Body cells.

5.

How do the chromosome numbers of haploid and diploid cells differ?

Haploid cells have half the chromosome number of diploid cells.

6.

Why must gametes be haploid?

So fertilisation restores the normal diploid chromosome number.

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

1.

What is meiosis?

Cell division that produces haploid gametes.

2.

Why does meiosis halve the chromosome number?

To produce gametes with half the normal chromosome number.

3.

What cells are produced by meiosis?

Gametes.

4.

Why is halving the chromosome number necessary before fertilisation?

So fertilisation restores the diploid chromosome number.

5.

How does fertilisation restore the diploid chromosome number?

Fertilisation combines two haploid gametes to produce a diploid zygote.

6.

Why is meiosis a source of genetic variation?

Meiosis produces genetically varied gametes through independent assortment and recombination.

B5.1i 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?

The inheritance of a characteristic controlled by one gene.

2.

How does a homozygous dominant genotype differ from a homozygous recessive genotype?

Homozygous dominant has two dominant alleles (e.g. TT); homozygous recessive has two recessive alleles (e.g. tt).

3.

How does a heterozygous genotype affect phenotype when one allele is dominant?

The dominant phenotype is expressed.

4.

Explain why dominant alleles mask recessive alleles in heterozygous individuals.

A dominant allele masks the effect of a recessive allele.

5.

A homozygous dominant (TT) plant is crossed with a homozygous recessive (tt) plant. What are the genotypes and phenotypes of the offspring?

Genotypes: all Tt. Phenotypes: all show the dominant characteristic.

6.

Explain how homozygous and heterozygous crosses demonstrate dominant and recessive inheritance.

Homozygous and heterozygous crosses show how dominant alleles are expressed and recessive alleles are only expressed when homozygous.

B5.1j Predict the results of single gene crosses

1.

What is a Punnett square?

A diagram used to predict the possible genotypes of offspring.

2.

How is a Punnett square used to predict offspring genotypes?

By placing the parental alleles around the grid and combining them.

3.

Complete a Punnett square for the cross Bb × Bb.

BB, Bb, Bb, bb.

4.

A Bb × Bb cross produces four possible offspring. Calculate the probability of an offspring having the recessive phenotype.

25% (1 in 4).

5.

A TT × Tt cross is carried out. Calculate the probability of producing a homozygous dominant offspring.

50% (2 in 4).

6.

Why are Punnett squares useful for predicting inheritance but not the exact outcomes of individual families?

They predict probabilities, not the exact outcome of individual families.

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

1.

Which chromosomes determine sex in humans?

The X and Y chromosomes.

2.

What sex chromosomes does a female have?

XX.

3.

What sex chromosomes does a male have?

XY.

4.

Why can sperm determine the sex of a baby but eggs cannot?

Eggs always carry an X chromosome, whereas sperm carry either X or Y.

5.

Complete a Punnett square for an XX × XY cross and state the probability of a male child.

XX, XX, XY, XY → 50% male.

6.

Explain why the chance of a baby being male or female is approximately 50%.

Half of the sperm carry X chromosomes and half carry Y chromosomes.

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

1.

What is meant by multiple gene inheritance?

A characteristic controlled by more than one gene.

2.

Why are most phenotypic characteristics controlled by more than one gene?

Because many characteristics are influenced by several genes acting together.

3.

Give an example of a characteristic controlled by multiple genes.

Height.

4.

How does multiple gene inheritance differ from single gene inheritance?

Single gene inheritance is controlled by one gene; multiple gene inheritance is controlled by several genes.

5.

Why does multiple gene inheritance often produce continuous variation?

Because the combined effects of many genes produce a range of phenotypes.

6.

Why are relatively few characteristics controlled by a single gene?

Because most characteristics are influenced by several genes rather than just one.

B5.1m Describe the development of our understanding of genetics

1.

Who was Gregor Mendel?

An Austrian monk and scientist.

2.

What investigations did Mendel carry out?

Investigations into inheritance using pea plants.

3.

What did Mendel discover about inheritance?

That characteristics are inherited through discrete units (genes).

4.

Why were Mendel's ideas not accepted immediately?

His ideas were ahead of the available scientific evidence and technology.

5.

How did later scientific discoveries support Mendel's work?

The discovery of chromosomes, genes and DNA supported his conclusions.

6.

Explain why Mendel is considered the founder of modern genetics.

His work laid the foundations of modern genetics and our understanding of inheritance.

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

1.

What is genetic variation?

Differences in alleles between individuals of the same species.

2.

Why is there usually extensive genetic variation within a population?

Because mutations and sexual reproduction produce different allele combinations.

3.

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

It allows populations to adapt to changing environments.

4.

Does every individual in a population have the same alleles? Explain your answer.

No. Individuals usually have different combinations of alleles.

5.

How does genetic variation make individuals within a population different from one another?

Different alleles produce different characteristics.

6.

Why is genetic variation essential for evolution by natural selection?

It provides the variation on which natural selection acts.

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

1.

What is the difference between an artificial classification system and a natural classification system?

Artificial classification is based on observable features; natural classification is based on evolutionary relationships.

2.

What is molecular phylogenetics?

The study of evolutionary relationships using DNA and molecular evidence.

3.

How is DNA sequencing used to classify organisms?

By comparing DNA base sequences to determine how closely related organisms are.

4.

Why have developments in biology changed classification systems?

New evidence from genetics and molecular biology has improved classification.

5.

Why can DNA evidence provide a more accurate classification than appearance alone?

DNA evidence is more reliable because it is less affected by environmental factors than appearance.

6.

Explain how molecular phylogenetics has improved scientists' understanding of relationships between organisms.

Molecular phylogenetics has produced classification systems that better reflect evolutionary relationships.

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 meant by natural selection?

The process in which individuals with advantageous inherited characteristics are more likely to survive and reproduce.

2.

What role do mutations play in evolution?

Mutations produce new genetic variants.

3.

Why are some phenotypes better suited to an environment than others?

They are better adapted to survive and reproduce in that environment.

4.

How are advantageous alleles passed on through natural selection?

Individuals with advantageous alleles survive, reproduce and pass them to their offspring.

5.

Explain how natural selection causes advantageous variants to become more common in a population over time.

Advantageous alleles become more common over many generations.

6.

Describe the sequence of events from mutation to natural selection and evolution.

Mutation creates variation; natural selection favours advantageous variants, leading to 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 evolution?

A change in the inherited characteristics of a population over time.

2.

Why does evolution occur in populations rather than individuals?

Because populations contain genetic variation whereas individuals do not evolve genetically during their lifetime.

3.

How does natural selection cause inherited characteristics to change over time?

Individuals with advantageous characteristics reproduce more successfully, changing allele frequencies over generations.

4.

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

Continued natural selection and isolation can eventually produce a new species.

5.

Why does speciation usually occur over many generations?

Because many generations are needed for sufficient genetic changes to accumulate.

6.

Explain how natural selection can result in speciation.

Natural selection gradually changes populations until they may become reproductively isolated and form new species.

B5.2e Describe the evidence for evolution

1.

How do fossils provide evidence for evolution?

Fossils show that organisms have changed over time.

2.

How does antibiotic resistance in bacteria provide evidence for evolution?

Antibiotic resistance develops through natural selection.

3.

Why do resistant bacteria become more common after antibiotics are used?

Resistant bacteria survive treatment, reproduce and pass on resistance alleles.

4.

What does the fossil record show about organisms over time?

The fossil record shows the appearance, change and extinction of organisms over time.

5.

Explain how antibiotic resistance develops through natural selection.

Random mutations produce resistant bacteria, which survive antibiotics and reproduce.

6.

Explain why fossils and antibiotic-resistant bacteria both support the theory of evolution.

Fossils and antibiotic-resistant bacteria both provide evidence that evolution occurs through natural selection.

B5.2f Describe the work of Darwin and Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on modern biology

1.

Who were Charles Darwin and Alfred Russel Wallace?

Scientists who developed the theory of evolution by natural selection.

2.

What theory did Darwin and Wallace develop?

The theory of evolution by natural selection.

3.

Why were Darwin's ideas not immediately accepted?

There was insufficient scientific evidence at the time and many people held conflicting beliefs.

4.

How has the theory of evolution by natural selection influenced modern biology?

It underpins modern biology and explains the diversity of life.

5.

What is a seed bank, and why is it important for conserving biodiversity?

A collection of seeds stored to conserve plant biodiversity and genetic diversity.

6.

Explain the importance of the work of Darwin and Wallace to our understanding of evolution today.

Their work transformed our understanding of evolution and forms the basis of modern evolutionary biology.

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 the difference between the distribution and abundance of organisms in a habitat?

Distribution is where organisms are found; abundance is the number of organisms present.

2.

How are random sampling and transect sampling used to investigate the distribution of organisms?

Random sampling estimates abundance; transects investigate changes in distribution across a habitat.

3.

What are quadrats, pooters, nets and identification keys, and how are they used during ecological fieldwork?

Quadrats sample plants or slow-moving organisms; pooters collect small invertebrates; nets collect flying or aquatic organisms; identification keys identify species.

4.

How does the capture–recapture method estimate the size of a population?

A sample is captured, marked, released, recaptured and the proportion of marked organisms is used to estimate population size.

5.

A 1 m² quadrat contains 12 daisies. If the field has an area of 250 m², estimate the total number of daisies using scaling up.

3000 daisies.

6.

Explain how field investigations can be used to determine the numbers and distribution of organisms in a habitat.

Field investigations use sampling techniques and scaling up to estimate the abundance and distribution of organisms in habitats.

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

1.

What is meant by biodiversity?

The variety of different species in an ecosystem or on Earth.

2.

Give two examples of positive human interactions with ecosystems.

Habitat conservation and captive breeding programmes.

3.

Give two examples of negative human interactions with ecosystems.

Deforestation and overhunting.

4.

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

They protect species, habitats and genetic diversity.

5.

How do land use and hunting threaten biodiversity?

They destroy habitats, reduce populations and may cause extinctions.

6.

Explain how both positive and negative human activities affect biodiversity.

Human activities can either conserve or reduce biodiversity depending on how ecosystems are managed.

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

1.

Why is maintaining biodiversity important?

It maintains stable ecosystems and preserves resources for future generations.

2.

What are the challenges of gaining international agreements for conservation schemes?

Different countries may have different priorities, costs and environmental policies.

3.

Why must conservation schemes be monitored?

To determine whether they are effective.

4.

What is ecotourism?

Tourism that conserves the environment and benefits local communities.

5.

How can ecotourism help conserve biodiversity?

It provides income that encourages conservation of habitats and wildlife.

6.

Explain why maintaining biodiversity involves both benefits and challenges.

Conserving biodiversity has environmental and economic benefits but requires international cooperation and long-term monitoring.

B6.1d Evaluate the evidence for the impact of environmental changes on the distribution of organisms, with reference to water and atmospheric gases

1.

How can changes in water availability affect the distribution of organisms?

Changes in water availability can alter where organisms can survive.

2.

How can changes in atmospheric gases affect the distribution of organisms?

Changes in atmospheric gases, such as carbon dioxide, can affect the distribution of organisms.

3.

What evidence might scientists collect to investigate changes in the distribution of organisms?

Distribution surveys, long-term monitoring and environmental measurements.

4.

Why is it important to evaluate the quality of evidence before drawing conclusions about environmental change?

Reliable evidence is needed before identifying causes of environmental change.

5.

A survey shows that a plant species has disappeared from areas that have become much drier over the last 20 years. What conclusion can be drawn, and what additional evidence would strengthen it?

Drier conditions may have contributed to the disappearance, but further evidence from repeated surveys and environmental data would strengthen the conclusion.

6.

Evaluate the evidence that changes in water availability and atmospheric gases can affect where organisms are found.

Conclusions should be based on sufficient, reliable evidence linking environmental changes with changes in organism distribution.

B6.2a Describe some of the biological factors affecting levels of food security

1.

What is meant by food security?

Having enough safe and nutritious food for the population.

2.

How does an increasing human population affect food security?

More people require more food.

3.

How can changing diets in wealthier populations affect global food security?

Increased demand for meat means more crops are used to feed livestock.

4.

How do new pests and pathogens reduce food security?

They reduce crop and livestock yields.

5.

How can environmental change affect food production?

Climate change and extreme weather can reduce food production.

6.

Explain how sustainability and the cost of agricultural inputs can affect food security.

Sustainability and the cost of agricultural inputs affect the amount of food that can be produced.

B6.2b Describe and explain some possible agricultural solutions to the demands of the growing human population

1.

What is hydroponics, and how can it increase food production?

Growing plants without soil using nutrient solutions.

2.

What is biological control?

The use of living organisms to control pests.

3.

How can gene technology increase food production?

By introducing desirable genes into crops.

4.

How do fertilisers improve crop yields?

They replace mineral ions needed for plant growth.

5.

How do pesticides help increase food production?

They reduce crop losses caused by pests.

6.

Explain how hydroponics, biological control, gene technology, fertilisers and pesticides can help meet the demands of a growing human population.

Hydroponics, biological control, gene technology, fertilisers and pesticides can all increase food production.

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

1.

What is selective breeding?

Choosing parents with desirable characteristics and breeding them together.

2.

How is selective breeding carried out?

Repeatedly breed individuals showing the desired characteristics over many generations.

3.

What are the benefits of selectively breeding food plants?

Higher yields, disease resistance and improved quality.

4.

What are the benefits of selectively breeding domesticated animals?

Faster growth, higher milk yield or greater meat production.

5.

What are some disadvantages or risks of selective breeding?

Reduced genetic variation and increased risk of inherited disorders.

6.

Explain the overall impact of selective breeding on agriculture.

Selective breeding has increased agricultural productivity but may reduce genetic diversity.

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

1.

What is genetic engineering?

Modifying an organism's genome by inserting genes for desirable characteristics.

2.

What is meant by modifying an organism's genome?

Changing the DNA of an organism.

3.

What is a desirable characteristic?

A useful inherited characteristic.

4.

How does genetic engineering differ from selective breeding?

Genetic engineering directly changes DNA, whereas selective breeding relies on choosing parents.

5.

Give one example of a desirable characteristic that can be introduced by genetic engineering.

Herbicide resistance (or insect resistance).

6.

Explain how genetic engineering can produce organisms with desirable characteristics.

Genetic engineering introduces specific genes to produce organisms with desirable characteristics.

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

1.

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

To cut DNA at specific base sequences.

2.

What are sticky ends?

Short overhanging DNA ends that can join with complementary DNA.

3.

What is the role of DNA ligase?

To join DNA fragments together.

4.

Why are plasmids used as vectors in genetic engineering?

They carry the desired gene into host cells.

5.

Why are host bacteria and antibiotic resistance markers used during genetic engineering?

Bacteria replicate the modified plasmid, and antibiotic resistance markers identify successfully modified cells.

6.

Describe the main steps involved in genetic engineering, including restriction enzymes, sticky ends, ligase, plasmids, host bacteria and antibiotic resistance markers.

The required gene is cut out using restriction enzymes, inserted into a plasmid with DNA ligase, transferred into bacteria and identified using antibiotic resistance markers.

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

1.

Give two possible benefits of using gene technology in agriculture.

Increased crop yields; crops resistant to pests or disease.

2.

Give two possible risks of using gene technology in agriculture.

Reduced genetic diversity; possible effects on wild species or ecosystems.

3.

What practical considerations should be considered before using gene technology?

Safety, environmental impact, cost and effectiveness.

4.

What ethical considerations are associated with gene technology?

Concerns about modifying organisms, animal welfare and ownership of GM organisms.

5.

Why do scientists and governments evaluate both the benefits and risks before approving genetically modified organisms?

To ensure the benefits outweigh the risks to people and the environment.

6.

Explain why the use of gene technology in modern agriculture remains controversial.

Gene technology has the potential to improve food production but must be carefully assessed for environmental, ethical and safety risks.

B6.2g Describe and explain some possible biotechnological solutions to the demands of the growing human population

1.

What is meant by biotechnology?

The use of living organisms or biological processes to produce useful products.

2.

What is genetic modification (GM)?

Altering an organism's DNA to introduce desirable characteristics.

3.

How can genetically modified crops help increase food production?

They may be resistant to pests, diseases or herbicides, increasing yields.

4.

How can genetically modified livestock help meet the demands of a growing population?

They may grow faster, resist disease or produce more food.

5.

Give one example of how genetic modification has been used in agriculture.

Bt maize (or Golden Rice).

6.

Explain how biotechnology, including genetic modification, can help address the demands of a growing human population.

Biotechnology, including genetic modification, can increase food production and help meet the demands of a growing population.

B6.3a Describe the relationship between health and disease

1.

What is meant by health?

A state of physical and mental well-being.

2.

What is meant by disease?

A condition that impairs normal body function.

3.

How can disease affect a person's physical health?

It can reduce the body's ability to function normally.

4.

Can a person have poor health without having an infectious disease? Explain your answer.

Yes. Poor health can result from non-communicable diseases, mental illness or poor lifestyle.

5.

How can having a disease reduce overall health?

Disease reduces overall physical or mental well-being.

6.

Explain the relationship between health and disease.

Health and disease are closely linked because disease reduces normal body function and well-being.

B6.3b Describe different types of diseases

1.

What is a communicable disease?

A disease caused by pathogens that can be passed between organisms.

2.

What is a non-communicable disease?

A disease that cannot be passed between organisms.

3.

Give one example of a communicable disease.

Measles.

4.

Give one example of a non-communicable disease.

Coronary heart disease.

5.

What is the main difference between communicable and non-communicable diseases?

Communicable diseases are infectious; non-communicable diseases are not.

6.

Explain why communicable diseases can spread between organisms but non-communicable diseases cannot.

Pathogens spread communicable diseases, whereas non-communicable diseases have non-infectious causes.

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

1.

How can HIV increase the risk of tuberculosis?

HIV weakens the immune system, increasing susceptibility to tuberculosis.

2.

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

HPV infection increases the risk of cervical cancer.

3.

Why can one disease increase the likelihood of developing another disease?

One disease can weaken the body or damage tissues, increasing the risk of another disease.

4.

Which diseases are used by OCR as examples of disease interactions?

HIV/AIDS and tuberculosis; HPV and cervical cancer.

5.

Explain why people with weakened immune systems are more likely to develop additional diseases.

They are less able to defend against pathogens and disease.

6.

Explain how communicable diseases can influence the development of non-communicable diseases.

Communicable diseases can increase the likelihood of developing other communicable or non-communicable diseases.

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

1.

Which four groups of pathogens cause communicable diseases?

Viruses, bacteria, protists and fungi.

2.

How are communicable diseases spread between animals?

By direct contact, air, water, contaminated food or vectors.

3.

How are communicable diseases spread between plants?

By wind, water, insect vectors, direct contact or contaminated soil.

4.

Why does increasing the number of pathogens increase the chance of disease spread?

More pathogens increase the chance of transmission.

5.

A disease infects 45 people in a village of 900 people. Calculate the percentage of the population infected.

5%.

6.

Explain how viruses, bacteria, protists and fungi spread communicable diseases in animals and plants.

Pathogens spread through various routes, allowing communicable diseases to infect animals and plants.

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

1.

How can detecting antigens help reduce the spread of disease?

They identify infected individuals by detecting pathogen antigens.

2.

How can DNA testing be used to identify disease?

It identifies pathogen DNA.

3.

How can visual identification help detect disease?

Visible symptoms can indicate disease.

4.

Why is early detection important in controlling communicable diseases?

It allows infected organisms to be isolated or treated before the disease spreads.

5.

Explain how identifying infected organisms helps reduce disease spread.

Detecting infected organisms reduces opportunities for transmission.

6.

Describe how antigen testing, DNA testing and visual identification are used to reduce or prevent the spread of communicable diseases.

Antigen testing, DNA testing and visual identification help detect disease early and reduce its spread.

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

1.

Name one viral, one bacterial and one fungal human infection.

Viral: measles; bacterial: Salmonella food poisoning; fungal: athlete's foot.

2.

What causes HIV/AIDS?

HIV, a virus that attacks the immune system.

3.

Which viral plant disease is specified by OCR?

Tobacco mosaic virus (TMV).

4.

Which fungal plant disease is specified by OCR?

Barley powdery mildew (Erysiphe graminis).

5.

Which bacterial plant disease is specified by OCR?

Crown gall disease (Agrobacterium tumefaciens).

6.

State the pathogen responsible for tobacco mosaic virus (TMV), barley powdery mildew (Erysiphe graminis) and crown gall disease (Agrobacterium tumefaciens).

TMV – virus; barley powdery mildew – fungus; crown gall disease – bacterium.

B6.3g Describe physical plant defence responses to disease

1.

What is the function of the leaf cuticle?

It forms a protective barrier that reduces pathogen entry and water loss.

2.

How does the cell wall help defend plants against disease?

It provides a strong barrier that helps prevent pathogens entering plant cells.

3.

Why is the leaf cuticle considered a physical defence?

Because it physically blocks pathogens from entering the plant.

4.

Why is the cell wall considered a physical defence?

Because it acts as a tough physical barrier against infection.

5.

Explain how physical barriers reduce infection in plants.

They reduce the likelihood of pathogens entering plant tissues.

6.

Describe the physical defence responses of plants against disease.

Plants use physical barriers such as the waxy cuticle and cell walls to defend against disease.

B6.3h Describe chemical plant defence responses

1.

What are antimicrobial substances?

Chemicals produced by plants that kill or inhibit microorganisms.

2.

How do antimicrobial substances protect plants?

They kill pathogens or stop their growth.

3.

Why are antimicrobial substances considered chemical defences?

Because they protect the plant using chemical substances rather than physical barriers.

4.

Give the function of antimicrobial substances in plants.

To destroy or inhibit pathogens.

5.

Explain how antimicrobial substances help prevent disease.

They reduce infection by killing or preventing the growth of microorganisms.

6.

Describe the chemical defence responses of plants against disease.

Plants produce antimicrobial chemicals that help protect them against disease.

B6.3i Describe different ways plant diseases can be detected and identified, in the lab and in the field

1.

How can DNA from a pathogen be used to identify plant disease?

By testing for pathogen DNA.

2.

How can antigens be used to detect plant disease?

By detecting pathogen antigens.

3.

How can observation be used to diagnose plant disease in the field?

By observing visible symptoms.

4.

How is microscopy used to identify plant disease?

By identifying pathogens under a microscope.

5.

What is the difference between laboratory and field diagnosis of plant diseases?

Laboratory diagnosis uses tests such as DNA analysis or microscopy; field diagnosis relies mainly on observation of symptoms.

6.

Describe how plant diseases can be detected and identified in both the laboratory and the field.

Plant diseases can be identified using DNA testing, antigen testing, microscopy and field observations.

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

1.

What is the role of white blood cells?

To defend the body against pathogens.

2.

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

Phagocytosis, producing antibodies and producing antitoxins.

3.

What is the role of platelets?

To help blood clot.

4.

How does blood clotting help defend the body against disease?

It seals wounds, preventing pathogen entry and reducing blood loss.

5.

Explain how white blood cells are adapted to protect the body from pathogens.

White blood cells recognise pathogens, destroy them and produce antibodies and antitoxins.

6.

Explain how white blood cells and platelets work together to defend the body.

White blood cells defend against infection, while platelets prevent pathogen entry by clotting blood.

B6.3k Describe the non-specific defence systems of the human body against pathogens

1.

What is meant by a non-specific defence system?

Defences that act against any pathogen rather than a specific one.

2.

Give four examples of non-specific defences in the human body.

Skin, mucus, cilia and stomach acid.

3.

How does the skin help prevent infection?

It forms a physical barrier to pathogens.

4.

How does stomach acid protect the body from pathogens?

It kills many pathogens that enter with food.

5.

Explain how mucus and cilia help defend the respiratory system.

Mucus traps pathogens and cilia move the mucus out of the airways.

6.

Describe the non-specific defence systems of the human body against pathogens.

Physical and chemical barriers help prevent pathogens entering the body.

B6.3l Explain the role of the immune system of the human body in defence against disease

1.

What is the role of the immune system?

To detect and destroy pathogens.

2.

How do white blood cells recognise pathogens?

By recognising foreign antigens on their surface.

3.

What are antibodies?

Proteins that bind specifically to antigens.

4.

What are antitoxins?

Chemicals that neutralise toxins produced by pathogens.

5.

How do memory cells provide immunity?

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

6.

Explain how the immune system protects the body from disease.

The immune system recognises pathogens, destroys them and provides long-term immunity through memory cells.

B6.3m Describe how monoclonal antibodies are produced

1.

What is a monoclonal antibody?

Identical antibodies produced by identical immune cells.

2.

Which cells are fused to produce monoclonal antibodies?

B-lymphocytes and tumour cells.

3.

What is a hybridoma?

A fused cell formed from a B-lymphocyte and a tumour cell.

4.

Why are hybridoma cells useful?

They divide rapidly and produce one type of antibody.

5.

How are large quantities of monoclonal antibodies produced?

By growing hybridoma cells in culture.

6.

Describe the process used to produce monoclonal antibodies.

B-lymphocytes are fused with tumour cells to form hybridomas, which produce large quantities of identical antibodies.

B6.3n Describe some of the ways in which monoclonal antibodies can be used

1.

How are monoclonal antibodies used in pregnancy testing?

They detect the hormone hCG in urine.

2.

How can monoclonal antibodies be used to detect prostate cancer?

They bind to specific antigens on prostate cancer cells to detect the disease.

3.

How can monoclonal antibodies be used to target cancer cells?

They can carry drugs or radioactive substances directly to cancer cells.

4.

Why are monoclonal antibodies useful in disease detection?

They bind specifically to target antigens, making disease detection highly accurate.

5.

Explain why monoclonal antibodies can target specific antigens.

Because they have a specific complementary shape to one antigen.

6.

Describe the uses of monoclonal antibodies in pregnancy testing, disease detection and treating disease.

Monoclonal antibodies are used in pregnancy testing, disease diagnosis and targeted treatments.

B6.3o Explain the use of vaccines and medicines in the prevention and treatment of disease

1.

How do vaccines help prevent disease?

They stimulate the immune system to produce memory cells without causing disease.

2.

What is the difference between antibiotics, antivirals and antiseptics?

Antibiotics kill bacteria; antivirals slow the replication of viruses; antiseptics kill microorganisms on external surfaces.

3.

Why do antibiotics not work against viruses?

Because viruses reproduce inside body cells and antibiotics only target bacteria.

4.

How do vaccines produce immunity?

They stimulate the production of memory cells that respond rapidly to future infections.

5.

Explain how medicines can help treat disease.

Medicines prevent, control or treat disease depending on their mode of action.

6.

Compare the roles of vaccines, antibiotics, antivirals and antiseptics in preventing and treating disease.

Vaccines prevent disease by producing immunity, while medicines such as antibiotics, antivirals and antiseptics treat or control infections.

B6.3p Explain the aseptic techniques used in culturing organisms

1.

Why is alcohol used during aseptic technique?

To disinfect equipment and kill microorganisms.

2.

Why are inoculating loops flamed before use?

To sterilise the loop before transferring microorganisms.

3.

Why are glassware and growth media autoclaved?

To sterilise equipment and culture media before use.

4.

Why is culturing often carried out near a Bunsen burner?

The updraught from the flame reduces contamination by airborne microorganisms.

5.

A Petri dish has a clear circular area with a radius of 12 mm. Calculate the area of the clear zone. Give your answer in mm². (Use πr².)

≈452 mm² (π × 12² ≈ 452.4 mm²).

6.

Describe the aseptic techniques used when culturing microorganisms.

Aseptic techniques involve sterilising equipment, minimising contamination and safely culturing microorganisms.

B6.3q Describe the processes of discovery and development of potential new medicines

1.

What is preclinical testing?

Laboratory testing using cells, tissues and animals.

2.

What is clinical testing?

Testing new medicines in humans.

3.

Why are new medicines first tested in the laboratory?

To assess safety and potential effectiveness before use in humans.

4.

Why are clinical trials carried out in humans?

To test safety, effectiveness and the correct dosage.

5.

Why must new medicines be tested for safety, effectiveness and dosage?

To ensure medicines are safe, effective and used at appropriate doses.

6.

Describe the stages involved in developing a new medicine.

New medicines are developed through preclinical testing followed by phased clinical trials.

B6.3r Recall that many non-communicable human diseases are caused by the interaction of a number of factors

1.

Why do many non-communicable diseases have more than one cause?

Because genetic, lifestyle and environmental factors all contribute.

2.

Give four non-communicable diseases listed in the specification.

Cardiovascular disease, cancer, type 2 diabetes and liver disease.

3.

How can lifestyle contribute to cardiovascular disease?

Poor diet, smoking and lack of exercise increase the risk.

4.

How can nutrition influence the risk of type 2 diabetes?

Poor nutrition and obesity increase the risk.

5.

Why can both genetic and environmental factors contribute to disease?

Genetic inheritance and environmental influences both affect disease risk.

6.

Explain why many non-communicable diseases result from the interaction of several factors.

Most non-communicable diseases result from several interacting genetic, lifestyle and environmental factors.

B6.3s Evaluate some different treatments for cardiovascular disease

1.

Give one lifestyle treatment for cardiovascular disease.

Regular exercise (or a healthier diet/stop smoking).

2.

Give one medical treatment for cardiovascular disease.

Statins.

3.

Give one surgical treatment for cardiovascular disease.

Coronary artery bypass surgery (or inserting a stent).

4.

Why might lifestyle changes be recommended before surgery?

They are less invasive and may reduce the need for surgery.

5.

A study shows that after treatment A, 72 out of 90 patients improved. Calculate the percentage of patients who improved.

80%.

6.

Evaluate the advantages and disadvantages of lifestyle, medical and surgical treatments for cardiovascular disease.

Lifestyle changes have few side effects but require commitment; medicines can be effective but may have side effects; surgery can be highly effective but carries greater risk and cost.

B6.3t Analyse the effect of lifestyle factors on the incidence of non-communicable diseases at local, national and global levels

1.

Which lifestyle factors does the specification identify as affecting the incidence of non-communicable diseases?

Lack of exercise, poor diet, alcohol consumption and smoking.

2.

How can a lack of exercise increase the risk of non-communicable diseases?

It increases the risk of obesity, cardiovascular disease and type 2 diabetes.

3.

How can poor diet contribute to non-communicable diseases?

It increases the risk of obesity, cardiovascular disease and type 2 diabetes.

4.

How do alcohol consumption and smoking affect the incidence of non-communicable diseases?

Smoking increases the risk of lung cancer and cardiovascular disease; excessive alcohol increases the risk of liver disease and other illnesses.

5.

A town has 2,500 adults. 375 have a smoking-related disease. Calculate the percentage of adults affected.

15%.

6.

Analyse how exercise, diet, alcohol and smoking influence the incidence of non-communicable diseases at local, national and global levels.

Lifestyle factors increase the incidence of non-communicable diseases locally, nationally and globally by increasing exposure to disease risk factors.

B6.3u Describe cancer as the result of changes in cells that lead to uncontrolled growth and division

1.

What is cancer?

A disease caused by uncontrolled cell growth and division.

2.

What changes occur in cells that can lead to cancer?

Mutations that disrupt normal control of the cell cycle.

3.

Why is uncontrolled cell division harmful?

It forms tumours and can damage healthy tissues.

4.

How do tumours form?

Uncontrolled cell division produces a mass of abnormal cells.

5.

What is the difference between normal cell division and uncontrolled cell division?

Normal cell division is regulated; cancer cell division is uncontrolled.

6.

Describe how cancer develops as a result of changes in cells leading to uncontrolled growth and division.

Cancer develops when mutations cause cells to divide uncontrollably, forming tumours.

B6.3v Discuss potential benefits and risks associated with the use of stem cells in medicine

1.

What are stem cells?

Unspecialised cells that can divide and differentiate into specialised cell types.

2.

How can stem cells be used in tissue transplantation?

They can replace damaged or diseased cells and tissues.

3.

Why can transplanted tissues be rejected by the immune system?

The immune system recognises the transplanted tissue as foreign and attacks it.

4.

Give two potential benefits of using stem cells in medicine.

Replace damaged tissues; potential treatments for diseases such as paralysis or diabetes.

5.

Give two potential risks or ethical concerns associated with using stem cells.

Risk of immune rejection; ethical concerns over the use of embryonic stem cells.

6.

Discuss the benefits and risks of using stem cells in medicine, including tissue transplantation and rejection.

Stem cells have the potential to treat disease by replacing damaged tissues, but there are risks such as immune rejection and ethical concerns.

B6.3w Explain some of the possible benefits and risks of using gene technology in medicine

1.

Give two possible benefits of using gene technology in medicine.

Treat inherited disorders; produce medicines such as insulin.

2.

Give two possible risks of using gene technology in medicine.

Unexpected side effects; ethical concerns about altering genes.

3.

What practical considerations should be considered before using gene technology in medicine?

Safety, effectiveness and long-term effects.

4.

What ethical considerations are associated with using gene technology in medicine?

Concerns about modifying human genes and the possible effects on future generations.

5.

Why must gene technology be carefully tested before it is widely used?

To ensure it is safe, effective and that the benefits outweigh the risks.

6.

Explain why the use of gene technology in medicine has both potential benefits and potential risks.

Gene technology offers major medical benefits but must be carefully evaluated for safety, ethical and practical reasons.

B6.3x Discuss the potential importance for medicine of our increasing understanding of the human genome

1.

How can understanding the human genome help predict the likelihood of developing certain diseases?

It can identify people who are at increased genetic risk of certain diseases.

2.

What is meant by drugs that are targeted to genomes?

Medicines designed to work with a person's genetic makeup.

3.

How could knowledge of the human genome improve the treatment of disease?

It can lead to more effective and personalised treatments.

4.

Why might genome-based medicine be more effective than a single treatment for everyone?

Because treatments can be matched to an individual's genes rather than using the same treatment for everyone.

5.

Give one potential benefit and one limitation of using genome information in medicine.

Increased understanding of the human genome allows improved prediction, prevention and personalised treatment of disease.

6.

Discuss the importance of increasing knowledge of the human genome for predicting disease risk and developing targeted drug treatments.

Knowledge of the human genome helps identify genetic variants that increase the risk of disease, allowing earlier diagnosis and prevention. It also allows scientists to develop targeted drugs designed to treat specific genetic causes of disease, making treatments more effective and reducing side effects.

Biology

Paper 1

B1 – Cell Level Systems