IGCSE Biology syllabus checklist

CoreEvery candidate

• 1.1Describe the characteristics of living organisms: movement as an action by an organism or part of an organism causing a change of position or place.
• 1.1Describe respiration as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
• 1.1Describe sensitivity as the ability to detect and respond to changes in the internal or external environment.
• 1.1Describe growth as a permanent increase in size and dry mass.
• 1.1Describe reproduction as the processes that make more of the same kind of organism.
• 1.1Describe excretion as the removal of the waste products of metabolism and substances in excess of requirements.
• 1.1Describe nutrition as the taking in of materials for energy, growth and development.
• 1.2State that organisms can be classified into groups by the features that they share.
• 1.2Describe a species as a group of organisms that can reproduce to produce fertile offspring.
• 1.2Describe the binomial system of naming species as an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and the species.
• 1.2Construct and use dichotomous keys based on identifiable features.
• 1.3State the main features used to place animals and plants into the appropriate kingdoms.
• 1.3State the main features used to place organisms into groups within the animal kingdom: the main groups of vertebrates (mammals, birds, reptiles, amphibians, fish) and the main groups of arthropods (myriapods, insects, arachnids, crustaceans).
• 1.3Classify organisms using the features identified for the animal kingdom groups.

SupplementExtended candidates only

• 1.2Explain that classification systems aim to reflect evolutionary relationships.
• 1.2Explain that the sequences of bases in DNA are used as a means of classification.
• 1.2Explain that groups of organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor.
• 1.3State the main features used to place all organisms into one of the five kingdoms: animal, plant, fungus, prokaryote and protoctist.
• 1.3State the main features used to place organisms into groups within the plant kingdom, limited to ferns and flowering plants (dicotyledons and monocotyledons).
• 1.3Classify organisms using the features identified for the five kingdoms and the plant groups.
• 1.3State the features of viruses, limited to a protein coat and genetic material.

CoreEvery candidate

• 2.1Describe and compare the structure of a plant cell with an animal cell: cell wall, cell membrane, nucleus, cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles.
• 2.1Describe the structure of a bacterial cell: cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids.
• 2.1Identify the cell structures listed for plant, animal and bacterial cells in diagrams and images.
• 2.1Describe the functions of the cell structures listed for plant, animal and bacterial cells.
• 2.1State that new cells are produced by division of existing cells.
• 2.1State that specialised cells have specific functions: ciliated cells (movement of mucus in the trachea and bronchi), root hair cells (absorption), palisade mesophyll cells (photosynthesis), neurones (conduction of electrical impulses), red blood cells (transport of oxygen) and sperm and egg cells (reproduction).
• 2.1Describe the meaning of the terms cell, tissue, organ, organ system and organism, illustrated by syllabus examples.
• 2.2State and use the formula: magnification = image size ÷ actual size.
• 2.2Calculate magnification and size of biological specimens using millimetres as units.

SupplementExtended candidates only

• 2.2Convert measurements between millimetres (mm) and micrometres (µm).

CoreEvery candidate

• 3.1Describe diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration (down a concentration gradient), as a result of their random movement.
• 3.1State that the energy for diffusion comes from the kinetic energy of random movement of molecules and ions.
• 3.1State that some substances move into and out of cells by diffusion through the cell membrane.
• 3.1Describe the importance of diffusion of gases and solutes in living organisms.
• 3.1Investigate the factors that influence diffusion, limited to: surface area, temperature, concentration gradient and distance.
• 3.2Describe the role of water as a solvent in organisms with reference to digestion, excretion and transport.
• 3.2State that water diffuses through partially permeable membranes by osmosis.
• 3.2State that water moves into and out of cells by osmosis through the cell membrane.
• 3.2Investigate osmosis using materials such as dialysis tubing.
• 3.2Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations.
• 3.2State that plants are supported by the pressure of water inside the cells pressing outwards on the cell wall.
• 3.3Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (against a concentration gradient), using energy from respiration.

SupplementExtended candidates only

• 3.2Describe osmosis as the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.
• 3.2Explain the effects on plant cells of immersing them in solutions of different concentrations by using the terms turgid, turgor pressure, plasmolysis and flaccid.
• 3.2Explain the importance of water potential and osmosis in the uptake and loss of water by organisms.
• 3.3Explain the importance of active transport as a process for movement of molecules or ions across membranes, including ion uptake by root hairs.
• 3.3State that protein carriers move molecules or ions across a membrane during active transport.

CoreEvery candidate

• 4.1List the chemical elements that make up carbohydrates, fats and proteins.
• 4.1State that large molecules are made from smaller molecules: starch, glycogen and cellulose from glucose; proteins from amino acids; fats and oils from fatty acids and glycerol.
• 4.1Describe the use of iodine solution to test for starch.
• 4.1Describe the use of Benedict’s solution to test for reducing sugars.
• 4.1Describe the use of the biuret test for proteins.
• 4.1Describe the use of the ethanol emulsion test for fats and oils.
• 4.1Describe the use of the DCPIP test for vitamin C.
• 5.1Describe a catalyst as a substance that increases the rate of a chemical reaction and is not changed by the reaction.
• 5.1Describe enzymes as proteins that are involved in all metabolic reactions, where they function as biological catalysts.
• 5.1Describe why enzymes are important in all living organisms in terms of a reaction rate necessary to sustain life.
• 5.1Describe enzyme action with reference to the shape of the active site of an enzyme being complementary to its substrate and the formation of products.
• 5.1Investigate and describe the effect of changes in temperature and pH on enzyme activity, with reference to optimum temperature and denaturation.

SupplementExtended candidates only

• 4.1Describe the structure of a DNA molecule: two strands coiled together to form a double helix; each strand contains chemicals called bases; bonds between pairs of bases hold the strands together; the bases always pair up in the same way — A with T, and C with G.
• 5.1Explain enzyme action with reference to active site, enzyme-substrate complex, substrate and product.
• 5.1Explain the specificity of enzymes in terms of the complementary shape and fit of the active site with the substrate.
• 5.1Explain the effect of changes in temperature on enzyme activity in terms of kinetic energy, shape and fit, frequency of effective collisions and denaturation.
• 5.1Explain the effect of changes in pH on enzyme activity in terms of shape and fit and denaturation.

CoreEvery candidate

• 6.1Describe photosynthesis as the process by which plants synthesise carbohydrates from raw materials using energy from light.
• 6.1State the word equation for photosynthesis: carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll.
• 6.1State that chlorophyll is a green pigment that is found in chloroplasts.
• 6.1State that chlorophyll transfers energy from light into energy in chemicals, for the synthesis of carbohydrates.
• 6.1Outline the subsequent use and storage of the carbohydrates made in photosynthesis: starch as an energy store; cellulose to build cell walls; glucose used in respiration to provide energy; sucrose for transport in the phloem; nectar to attract insects for pollination.
• 6.1Explain the importance of nitrate ions for making amino acids and magnesium ions for making chlorophyll.
• 6.1Investigate the need for chlorophyll, light and carbon dioxide for photosynthesis, using appropriate controls.
• 6.1Investigate and describe the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis.
• 6.1Investigate and describe the effect of light and dark conditions on gas exchange in an aquatic plant using hydrogencarbonate indicator solution.
• 6.2State that most leaves have a large surface area and are thin, and explain how these features are adaptations for photosynthesis.
• 6.2Identify in diagrams and images the structures in the leaf of a dicotyledonous plant: chloroplasts, cuticle, guard cells and stomata, upper and lower epidermis, palisade mesophyll, spongy mesophyll, air spaces, vascular bundles, xylem and phloem.
• 6.2Explain how the structures of the leaf adapt it for photosynthesis.

SupplementExtended candidates only

• 6.1State the balanced chemical equation for photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
• 6.1Identify and explain the limiting factors of photosynthesis in different environmental conditions.

CoreEvery candidate

• 7.1Describe what is meant by a balanced diet.
• 7.1State the principal dietary sources and describe the importance of carbohydrates, fats and oils, proteins, vitamins C and D, mineral ions calcium and iron, fibre (roughage) and water.
• 7.1State the causes of scurvy and rickets.
• 7.2Identify the main organs of the digestive system: alimentary canal (mouth, oesophagus, stomach, small intestine — duodenum and ileum, large intestine — colon, rectum, anus) and associated organs (salivary glands, pancreas, liver, gall bladder).
• 7.2Describe the functions of the organs of the digestive system in relation to ingestion, digestion, absorption, assimilation and egestion.
• 7.3Describe physical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules.
• 7.3State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion.
• 7.3Identify the types of human teeth: incisors, canines, premolars and molars.
• 7.3Describe the structure of human teeth: enamel, dentine, pulp, nerves, blood vessels and cement; teeth are embedded in bone and gums.
• 7.3Describe the functions of the types of human teeth in physical digestion of food.
• 7.3Describe the function of the stomach in physical digestion.
• 7.4Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules.
• 7.4State the role of chemical digestion in producing small soluble molecules that can be absorbed.
• 7.4Describe the functions of enzymes: amylase breaks down starch to simple reducing sugars; proteases break down protein to amino acids; lipase breaks down fats and oils to fatty acids and glycerol.
• 7.4State where in the digestive system amylase, protease and lipase are secreted and where they act.
• 7.4Describe the functions of hydrochloric acid in gastric juice: killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity.
• 7.5State that the small intestine is the region where nutrients are absorbed.
• 7.5State that most water is absorbed from the small intestine but some is also absorbed from the colon.

SupplementExtended candidates only

• 7.3Outline the role of bile in emulsifying fats and oils to increase the surface area for chemical digestion.
• 7.4Describe the digestion of starch: amylase breaks down starch to maltose; maltase breaks down maltose to glucose on the membranes of the epithelium lining the small intestine.
• 7.4Describe the digestion of protein by proteases: pepsin breaks down protein in the acidic conditions of the stomach; trypsin breaks down protein in the alkaline conditions of the small intestine.
• 7.4Explain that bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum, to provide a suitable pH for enzyme action.
• 7.5Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine.
• 7.5Describe the structure of a villus.
• 7.5Describe the roles of capillaries and lacteals in villi.

CoreEvery candidate

• 8.1State the functions of xylem (transport of water and mineral ions, and support) and phloem (transport of sucrose and amino acids).
• 8.1Identify the position of xylem and phloem in sections of roots, stems and leaves of non-woody dicotyledonous plants.
• 8.2Identify root hair cells in diagrams and images and state their functions.
• 8.2State that the large surface area of root hairs increases the uptake of water and mineral ions.
• 8.2Outline the pathway of water through the root, stem and leaf: root hair cells, root cortex cells, xylem, mesophyll cells.
• 8.2Investigate, using a suitable stain, the pathway of water through the above-ground parts of a plant.
• 8.3Describe transpiration as the loss of water vapour from leaves.
• 8.3State that water evaporates from the surfaces of mesophyll cells into air spaces and then diffuses out of the leaves through the stomata as water vapour.
• 8.3Investigate and describe the effects of variation of temperature and wind speed on transpiration rate.

SupplementExtended candidates only

• 8.1Relate the structure of xylem vessels to their function: thick walls with lignin; no cell contents; cells joined end to end with no cross walls to form a long continuous tube.
• 8.3Explain how water vapour loss is related to the large internal surface area provided by interconnecting air spaces between mesophyll cells and the size and number of stomata.
• 8.3Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by forces of attraction between water molecules.
• 8.3Explain the effects on the rate of transpiration of varying temperature, wind speed and humidity.
• 8.3Explain how and why wilting occurs.
• 8.4Describe translocation as the movement of sucrose and amino acids in phloem from sources to sinks.
• 8.4Describe sources (parts of plants that release sucrose or amino acids) and sinks (parts that use or store them).
• 8.4Explain why some parts of a plant may act as a source and a sink at different times.

CoreEvery candidate

• 9.1Describe the circulatory system as a system of blood vessels with a pump and valves to ensure one-way flow of blood.
• 9.2Identify the structures of the mammalian heart: muscular wall, septum, left and right ventricles, left and right atria, one-way valves and coronary arteries.
• 9.2State that blood is pumped away from the heart in arteries and returns to the heart in veins.
• 9.2State that the activity of the heart may be monitored by ECG, pulse rate and listening to sounds of valves closing.
• 9.2Investigate and describe the effect of physical activity on the heart rate.
• 9.2Describe coronary heart disease as blockage of coronary arteries, and state the possible risk factors: diet, lack of exercise, stress, smoking, genetic predisposition, age and sex.
• 9.2Discuss the roles of diet and exercise in reducing the risk of coronary heart disease.
• 9.3Describe the structure of arteries, veins and capillaries: relative thickness of wall, diameter of the lumen and the presence of valves in veins.
• 9.3State the functions of capillaries.
• 9.3Identify the main blood vessels to and from the heart (vena cava, aorta, pulmonary artery, pulmonary vein), the lungs (pulmonary artery and vein) and the kidney (renal artery and vein).
• 9.4List the components of blood: red blood cells, white blood cells, platelets and plasma.
• 9.4Identify red and white blood cells in photomicrographs and diagrams.
• 9.4State the functions of red blood cells (transport of oxygen, role of haemoglobin), white blood cells (phagocytosis and antibody production), platelets (clotting) and plasma (transport of blood cells, ions, nutrients, urea, hormones and carbon dioxide).
• 9.4State the roles of blood clotting as preventing blood loss and the entry of pathogens.

SupplementExtended candidates only

• 9.1Describe the single circulation of a fish.
• 9.1Describe the double circulation of a mammal.
• 9.1Explain the advantages of a double circulation.
• 9.2Identify the atrioventricular and semilunar valves in the mammalian heart.
• 9.2Explain the relative thickness of the muscle walls of the left and right ventricles, and of the atria compared to the ventricles.
• 9.2Explain the importance of the septum in separating oxygenated and deoxygenated blood.
• 9.2Describe the functioning of the heart in terms of the contraction of muscles of the atria and ventricles and the action of the valves.
• 9.3Explain how the structure of arteries and veins is related to the pressure of the blood that they transport.
• 9.3Explain how the structure of capillaries is related to their functions.
• 9.3Identify the main blood vessels to and from the liver: hepatic artery, hepatic veins and hepatic portal vein.
• 9.4Identify lymphocytes and phagocytes in photomicrographs and diagrams.
• 9.4State the functions of lymphocytes (antibody production) and phagocytes (engulfing pathogens by phagocytosis).
• 9.4Describe the process of clotting as the conversion of fibrinogen to fibrin to form a mesh.

CoreEvery candidate

• 10.1Describe a pathogen as a disease-causing organism.
• 10.1Describe a transmissible disease as a disease in which the pathogen can be passed from one host to another.
• 10.1State that a pathogen is transmitted by direct contact (including blood and other body fluids) or indirectly (including contaminated surfaces, food, animals and air).
• 10.1Describe the body defences: skin, hairs in the nose, mucus, stomach acid, white blood cells.
• 10.1Explain the importance in controlling the spread of disease of: a clean water supply, hygienic food preparation, good personal hygiene, waste disposal, sewage treatment (details of stages not required).

SupplementExtended candidates only

• 10.1Describe active immunity as defence against a pathogen by antibody production in the body.
• 10.1State that each pathogen has its own antigens, which have specific shapes.
• 10.1Describe antibodies as proteins that bind to antigens, leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.
• 10.1State that specific antibodies have complementary shapes that fit specific antigens.
• 10.1Explain that active immunity is gained after an infection by a pathogen or by vaccination.
• 10.1Outline the process of vaccination: weakened pathogens or their antigens are put into the body; the antigens stimulate an immune response by lymphocytes which produce antibodies; memory cells are produced that give long-term immunity.
• 10.1Explain the role of vaccination in controlling the spread of diseases.
• 10.1Explain that passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk.
• 10.1Explain the importance of breast-feeding for the development of passive immunity in infants.
• 10.1State that memory cells are not produced in passive immunity.
• 10.1Describe cholera as a disease caused by a bacterium transmitted in contaminated water.
• 10.1Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of ions from the blood.

CoreEvery candidate

• 11.1Describe the features of gas exchange surfaces in humans: large surface area, thin surface, good blood supply, good ventilation with air.
• 11.1Identify the parts of the breathing system: lungs, diaphragm, ribs, intercostal muscles, larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries.
• 11.1Investigate the differences in composition between inspired and expired air using limewater as a test for carbon dioxide.
• 11.1Describe the differences in composition between inspired and expired air: oxygen, carbon dioxide and water vapour.
• 11.1Investigate and describe the effects of physical activity on the rate and depth of breathing.
• 12.1State the uses of energy in living organisms: muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses, maintenance of a constant body temperature.
• 12.1Investigate and describe the effect of temperature on respiration in yeast.
• 12.2Describe aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.
• 12.2State the word equation: glucose + oxygen → carbon dioxide + water.
• 12.3Describe anaerobic respiration as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.
• 12.3State that anaerobic respiration releases much less energy per glucose molecule than aerobic respiration.
• 12.3State the word equation in yeast: glucose → alcohol + carbon dioxide.
• 12.3State the word equation in muscles during vigorous exercise: glucose → lactic acid.

SupplementExtended candidates only

• 11.1Identify the internal and external intercostal muscles.
• 11.1State the function of cartilage in the trachea.
• 11.1Explain the role of the ribs, internal and external intercostal muscles and the diaphragm in producing volume and pressure changes in the thorax leading to ventilation of the lungs.
• 11.1Explain the differences in composition between inspired and expired air.
• 11.1Explain the link between physical activity and the rate and depth of breathing: increased carbon dioxide concentration in the blood detected by the brain leads to increased rate and greater depth of breathing.
• 11.1Explain the role of goblet cells, mucus and ciliated cells in protecting the breathing system from pathogens and particles.
• 12.2State the balanced chemical equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.
• 12.3State the balanced chemical equation in yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.
• 12.3State that lactic acid builds up in muscles and blood during vigorous exercise, causing an oxygen debt.
• 12.3Outline how the oxygen debt is removed after exercise: continuation of fast heart rate to transport lactic acid in the blood from the muscles to the liver; continuation of deeper and faster breathing to supply oxygen for aerobic respiration of lactic acid; aerobic respiration of lactic acid in the liver.

CoreEvery candidate

• 13.1State that carbon dioxide is excreted through the lungs.
• 13.1State that the kidneys excrete urea and excess water and ions.
• 13.1Identify the kidneys, ureters, bladder and urethra in diagrams and images.

SupplementExtended candidates only

• 13.1Identify the structure of the kidney: cortex and medulla.
• 13.1Outline the structure and function of a nephron and its associated blood vessels: the glomerulus filters water, glucose, urea and ions from the blood; the nephron reabsorbs all of the glucose, some of the ions and most of the water back into the blood; urine is formed containing urea, excess water and excess ions (details of these processes not required).
• 13.1Describe the role of the liver in the assimilation of amino acids by converting them to proteins.
• 13.1State that urea is formed in the liver from excess amino acids.
• 13.1Describe deamination as the removal of the nitrogen-containing part of amino acids to form urea.
• 13.1Explain the importance of excretion, limited to toxicity of urea.

CoreEvery candidate

• 14.1State that electrical impulses travel along neurones.
• 14.1Describe the mammalian nervous system: the central nervous system (CNS) consisting of the brain and spinal cord; the peripheral nervous system (PNS) consisting of nerves outside the brain and spinal cord.
• 14.1Describe the role of the nervous system as coordination and regulation of body functions.
• 14.1Identify sensory, relay and motor neurones in diagrams and images.
• 14.1Describe a simple reflex arc: receptor, sensory neurone, relay neurone, motor neurone, effector.
• 14.1Describe a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands).
• 14.1Describe a synapse as a junction between two neurones.
• 14.2Describe sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature, chemicals.
• 14.2Identify the structures of the eye: cornea, iris, pupil, lens, retina, optic nerve, blind spot.
• 14.2Describe the function of each part: cornea — refracts light; iris — controls how much light enters the pupil; lens — focuses light on to the retina; retina — contains light receptors, some sensitive to light of different colours; optic nerve — carries impulses to the brain.
• 14.2Explain the pupil reflex, limited to changes in light intensity and pupil diameter.
• 14.3Describe a hormone as a chemical substance produced by a gland, carried by the blood, which alters the activity of one or more specific target organs.
• 14.3Identify specific endocrine glands and state the hormones they secrete: adrenal glands — adrenaline; pancreas — insulin; testes — testosterone; ovaries — oestrogen.
• 14.3Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects: increased breathing rate, increased heart rate, increased pupil diameter.
• 14.3Compare nervous and hormonal control: speed of action and duration of effect.
• 14.4Describe homeostasis as the maintenance of a constant internal environment.
• 14.4State that insulin decreases blood glucose concentration.
• 14.5Describe gravitropism as a response in which parts of a plant grow towards or away from gravity.
• 14.5Describe phototropism as a response in which parts of a plant grow towards or away from the direction of the light source.
• 14.5Investigate and describe gravitropism and phototropism in shoots and roots.
• 15.1Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body.
• 15.1Describe the use of antibiotics for the treatment of bacterial infections.
• 15.1State that some bacteria are resistant to antibiotics, which reduces their effectiveness.
• 15.1State that antibiotics kill bacteria but do not affect viruses.

SupplementExtended candidates only

• 14.1Describe the structure of a synapse: vesicles containing neurotransmitter molecules, the synaptic gap, receptor proteins.
• 14.1Describe the events at a synapse: an impulse stimulates release of neurotransmitter molecules from vesicles into the synaptic gap; the neurotransmitter molecules diffuse across the gap; they bind with receptor proteins on the next neurone; an impulse is then stimulated in the next neurone.
• 14.1State that synapses ensure that impulses travel in one direction only.
• 14.2Explain the pupil reflex in terms of the antagonistic action of circular and radial muscles in the iris.
• 14.2Explain accommodation to view near and distant objects in terms of contraction and relaxation of ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light.
• 14.2Describe the distribution of rods and cones in the retina.
• 14.2Outline the function of rods and cones: greater sensitivity of rods for night vision; three different kinds of cones absorbing light of different colours for colour vision.
• 14.2Identify the position of the fovea and state its function.
• 14.3State that glucagon is secreted by the pancreas.
• 14.3Describe the role of adrenaline in the control of metabolic activity: increasing blood glucose concentration, increasing heart rate.
• 14.4Explain the concept of homeostatic control by negative feedback with reference to a set point.
• 14.4Describe the control of blood glucose concentration by the liver and the roles of insulin and glucagon.
• 14.4Outline the treatment of Type 1 diabetes.
• 14.4Identify in diagrams and images of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels, fatty tissue.
• 14.4Describe the maintenance of a constant internal body temperature in mammals: insulation, sweating, shivering and the role of the brain.
• 14.4Describe the maintenance of a constant internal body temperature in terms of vasodilation and vasoconstriction of arterioles supplying skin surface capillaries.
• 14.5Explain phototropism and gravitropism of a shoot as examples of the chemical control of plant growth.
• 14.5Explain the role of auxin in controlling shoot growth: auxin is made in the shoot tip; auxin diffuses through the plant from the shoot tip; auxin is unequally distributed in response to light and gravity; auxin stimulates cell elongation.
• 15.1Explain how using antibiotics only when essential can limit the development of resistant bacteria such as MRSA.

CoreEvery candidate

• 16.1Describe asexual reproduction as a process resulting in the production of genetically identical offspring from one parent.
• 16.1Identify examples of asexual reproduction in diagrams, images and information provided.
• 16.2Describe sexual reproduction as a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.
• 16.2Describe fertilisation as the fusion of the nuclei of gametes.
• 16.3Identify and draw the parts of an insect-pollinated flower: sepals, petals, stamens, filaments, anthers, carpels, style, stigma, ovary, ovules.
• 16.3State the functions of these structures.
• 16.3Identify and describe the anthers and stigmas of a wind-pollinated flower.
• 16.3Distinguish between the pollen grains of insect-pollinated and wind-pollinated flowers.
• 16.3Describe pollination as the transfer of pollen grains from an anther to a stigma.
• 16.3State that fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule.
• 16.3Describe the structural adaptations of insect-pollinated and wind-pollinated flowers.
• 16.3Investigate and describe the environmental conditions that affect germination of seeds: water, oxygen and a suitable temperature.
• 16.4Identify on diagrams and state the functions of the male reproductive system: testes, scrotum, sperm ducts, prostate gland, urethra, penis.
• 16.4Identify on diagrams and state the functions of the female reproductive system: ovaries, oviducts, uterus, cervix, vagina.
• 16.4Describe fertilisation as the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell).
• 16.4State that in early development, the zygote forms an embryo which is a ball of cells that implants into the lining of the uterus.
• 16.4Identify on diagrams and state the functions of the following in the development of the fetus: umbilical cord, placenta, amniotic sac, amniotic fluid.
• 16.5Describe the roles of testosterone and oestrogen in the development and regulation of secondary sexual characteristics during puberty.
• 16.5Describe the menstrual cycle in terms of changes in the ovaries and in the lining of the uterus.
• 16.6Describe a sexually transmitted infection (STI) as an infection transmitted through sexual contact.
• 16.6State that human immunodeficiency virus (HIV) is a pathogen that causes an STI.
• 16.6State that HIV infection may lead to AIDS.
• 16.6Describe the methods of transmission of HIV.
• 16.6Explain how the spread of STIs is controlled.

SupplementExtended candidates only

• 16.1Discuss the advantages and disadvantages of asexual reproduction to a population of a species in the wild and to crop production.
• 16.2State that nuclei of gametes are haploid and the nucleus of a zygote is diploid.
• 16.2Discuss the advantages and disadvantages of sexual reproduction to a population of a species in the wild and to crop production.
• 16.3Describe self-pollination as the transfer of pollen grains from the anther of a flower to the stigma of the same flower or a different flower on the same plant.
• 16.3Describe cross-pollination as the transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.
• 16.3Discuss the potential effects of self-pollination and cross-pollination on a population, in terms of variation, capacity to respond to changes in the environment and reliance on pollinators.
• 16.3Describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (details of production of endosperm and development not required).
• 16.4Explain the adaptive features of sperm: flagellum, mitochondria, enzymes in the acrosome.
• 16.4Explain the adaptive features of egg cells: energy stores, the jelly coat that changes at fertilisation.
• 16.4Compare male and female gametes in terms of size, structure, motility and numbers.
• 16.4Describe the function of the placenta and umbilical cord in relation to the exchange of dissolved nutrients, gases and excretory products between the blood of the mother and the blood of the fetus.
• 16.4State that some pathogens and toxins can pass across the placenta and affect the fetus.
• 16.5Describe the sites of production of oestrogen and progesterone in the menstrual cycle and in pregnancy.
• 16.5Explain the role of hormones in controlling the menstrual cycle and pregnancy: FSH, LH, progesterone, oestrogen.

CoreEvery candidate

• 17.1State that chromosomes are made of DNA, which contains genetic information in the form of genes.
• 17.1Define a gene as a length of DNA that codes for a protein.
• 17.1Define an allele as an alternative form of a gene.
• 17.1Describe the inheritance of sex in humans with reference to X and Y chromosomes.
• 17.4Describe inheritance as the transmission of genetic information from generation to generation.
• 17.4Describe genotype as the genetic make-up of an organism in terms of the alleles present.
• 17.4Describe phenotype as the observable features of an organism.
• 17.4Describe homozygous as having two identical alleles of a particular gene.
• 17.4State that two identical homozygous individuals that breed together will be pure-breeding.
• 17.4Describe heterozygous as having two different alleles of a particular gene.
• 17.4State that a heterozygous individual will not be pure-breeding.
• 17.4Describe a dominant allele as an allele that is expressed if it is present in the genotype.
• 17.4Describe a recessive allele as an allele that is only expressed when there is no dominant allele of the gene present.
• 17.4Interpret pedigree diagrams for the inheritance of a given characteristic.
• 17.4Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1:1 and 3:1 ratios.
• 17.4Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes.

SupplementExtended candidates only

• 17.1State that the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein (details of nucleotide structure not required).
• 17.1Explain that different sequences of amino acids give different shapes to protein molecules.
• 17.1Explain that DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters.
• 17.1Explain how a protein is made: the gene remains in the nucleus; messenger RNA (mRNA) is a copy of a gene; mRNA molecules are made in the nucleus and move to the cytoplasm; the mRNA passes through ribosomes; the ribosome assembles amino acids into protein molecules; the specific sequence of amino acids is determined by the sequence of bases in the mRNA (details of transcription/translation not required).
• 17.1Explain that most body cells contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs.
• 17.1Describe a haploid nucleus as a nucleus containing a single set of chromosomes.
• 17.1Describe a diploid nucleus as a nucleus containing two sets of chromosomes.
• 17.1State that in a diploid cell there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs.
• 17.2Describe mitosis as nuclear division giving rise to genetically identical cells (stages not required).
• 17.2State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction.
• 17.2State that the exact replication of chromosomes occurs before mitosis.
• 17.2State that during mitosis the copies of chromosomes separate, maintaining the chromosome number in each daughter cell.
• 17.2Describe stem cells as unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions.
• 17.3State that meiosis is involved in the production of gametes.
• 17.3Describe meiosis as a reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells (stages not required).
• 17.4Explain how to use a test cross to identify an unknown genotype.
• 17.4Describe codominance as a situation in which both alleles in heterozygous organisms contribute to the phenotype.
• 17.4Explain the inheritance of ABO blood groups: phenotypes A, B, AB and O; alleles Iᴬ, Iᴮ and Iᵒ.
• 17.4Describe a sex-linked characteristic as a feature in which the gene responsible is located on a sex chromosome, making the characteristic more common in one sex than the other.
• 17.4Describe red-green colour blindness as an example of sex linkage.
• 17.4Use genetic diagrams to predict the results of monohybrid crosses involving codominance or sex linkage and calculate phenotypic ratios.

CoreEvery candidate

• 18.1Describe variation as differences between individuals of the same species.
• 18.1State that continuous variation results in a range of phenotypes between two extremes; examples: body length, body mass.
• 18.1State that discontinuous variation results in a limited number of phenotypes with no intermediates; examples: ABO blood groups, seed shape in peas, seed colour in peas.
• 18.1State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment.
• 18.1Investigate and describe examples of continuous and discontinuous variation.
• 18.1Describe mutation as genetic change.
• 18.1State that mutation is the way in which new alleles are formed.
• 18.1State that ionising radiation and some chemicals increase the rate of mutation.
• 18.2Describe an adaptive feature as an inherited feature that helps an organism to survive and reproduce in its environment.
• 18.2Interpret images or other information about a species to describe its adaptive features.
• 18.3Describe natural selection with reference to: genetic variation within populations; production of many offspring; struggle for survival including competition for resources; a greater chance of reproduction by individuals better adapted to the environment; these individuals pass on their alleles to the next generation.
• 18.3Describe selective breeding with reference to: selection by humans of individuals with desirable features; crossing these individuals to produce the next generation; selection of offspring showing the desirable features.
• 18.3Outline how selective breeding by artificial selection is carried out over many generations to improve crop plants and domesticated animals, and apply this to given contexts.

SupplementExtended candidates only

• 18.1Describe gene mutation as a random change in the base sequence of DNA.
• 18.1State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations.
• 18.2Explain the adaptive features of hydrophytes and xerophytes to their environments.
• 18.3Describe adaptation as the process, resulting from natural selection, by which populations become more suited to their environment over many generations.
• 18.3Describe the development of strains of antibiotic-resistant bacteria as an example of natural selection.
• 18.3Outline the differences between natural and artificial selection.

CoreEvery candidate

• 19.1State that the Sun is the principal source of energy input to biological systems.
• 19.1Describe the flow of energy through living organisms, including light energy from the Sun and chemical energy in organisms, and its eventual transfer to the environment.
• 19.2Describe a food chain as showing the transfer of energy from one organism to the next, beginning with a producer.
• 19.2Construct and interpret simple food chains.
• 19.2Describe a food web as a network of interconnected food chains and interpret food webs.
• 19.2Describe a producer as an organism that makes its own organic nutrients, usually using energy from sunlight through photosynthesis.
• 19.2Describe a consumer as an organism that gets its energy by feeding on other organisms.
• 19.2State that consumers may be classed as primary, secondary, tertiary and quaternary according to their position in a food chain.
• 19.2Describe a herbivore as an animal that gets its energy by eating plants.
• 19.2Describe a carnivore as an animal that gets its energy by eating other animals.
• 19.2Describe a decomposer as an organism that gets its energy from dead or waste organic material.
• 19.2Use food chains and food webs to describe the impact humans have through overharvesting of food species and through introducing foreign species to a habitat.
• 19.2Draw, describe and interpret pyramids of numbers and pyramids of biomass.
• 19.2Discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain.
• 19.2Describe a trophic level as the position of an organism in a food chain, food web or ecological pyramid.
• 19.2Identify the trophic levels in food webs, food chains and ecological pyramids: producers, primary, secondary, tertiary and quaternary consumers.
• 19.3Describe the carbon cycle: photosynthesis, respiration, feeding, decomposition, formation of fossil fuels, combustion.
• 19.4Describe a population as a group of organisms of one species living in the same area at the same time.
• 19.4Describe a community as all of the populations of different species in an ecosystem.
• 19.4Describe an ecosystem as a unit containing the community of organisms and their environment, interacting together.
• 19.4Identify and state the factors affecting the rate of population growth: food supply, competition, predation, disease.
• 19.4Identify the lag, exponential (log), stationary and death phases in the sigmoid curve of population growth for a population growing in an environment with limited resources.
• 19.4Interpret graphs and diagrams of population growth.
• 20.1Describe how humans have increased food production: agricultural machinery to use larger areas of land and improve efficiency; chemical fertilisers to improve yields; insecticides to improve quality and yield; herbicides to reduce competition with weeds; selective breeding to improve production by crop plants and livestock.
• 20.1Describe the advantages and disadvantages of large-scale monocultures of crop plants.
• 20.1Describe the advantages and disadvantages of intensive livestock production.
• 20.2Describe biodiversity as the number of different species that live in an area.
• 20.2Describe the reasons for habitat destruction: increased area for housing, crop plant production and livestock production; extraction of natural resources; freshwater and marine pollution.
• 20.2State that through altering food webs and food chains, humans can have a negative impact on habitats.
• 20.2Explain the undesirable effects of deforestation as an example of habitat destruction: reducing biodiversity, extinction, loss of soil, flooding, increase of carbon dioxide in the atmosphere.
• 20.3Describe the effects of untreated sewage and excess fertiliser on aquatic ecosystems.
• 20.3Describe the effects of non-biodegradable plastics in aquatic and terrestrial ecosystems.
• 20.3Describe the sources and effects of pollution of the air by methane and carbon dioxide: the enhanced greenhouse effect and climate change.
• 20.4Describe a sustainable resource as one which is produced as rapidly as it is removed from the environment so that it does not run out.
• 20.4State that some resources can be conserved and managed sustainably: forests and fish stocks.
• 20.4Explain why organisms become endangered or extinct: climate change, habitat destruction, hunting, overharvesting, pollution, introduced species.
• 20.4Describe how endangered species can be conserved: monitoring and protecting species and habitats; education; captive breeding programmes; seed banks.

SupplementExtended candidates only

• 19.2Draw, describe and interpret pyramids of energy.
• 19.2Discuss the advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain.
• 19.2Explain why the transfer of energy from one trophic level to another is often not efficient.
• 19.2Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels.
• 19.2Explain why it is more energy efficient for humans to eat crop plants than to eat livestock fed on crop plants.
• 19.3Describe the nitrogen cycle with reference to: decomposition of plant and animal protein to ammonium ions; nitrification; nitrogen fixation by lightning and bacteria; absorption of nitrate ions by plants; production of amino acids and proteins; feeding and digestion of proteins; deamination; denitrification.
• 19.3State the roles of microorganisms in the nitrogen cycle: decomposition, nitrification, nitrogen fixation, denitrification (generic names of individual bacteria not required).
• 19.4Explain the factors that lead to each phase in the sigmoid curve of population growth, making reference to the role of limiting factors.
• 20.3Explain the process of eutrophication of water: increased availability of nitrate and other ions; increased growth of producers; increased decomposition after death of producers; increased aerobic respiration by decomposers; reduction in dissolved oxygen; death of organisms requiring dissolved oxygen in water.
• 20.4Explain how forests can be conserved using education, protected areas, quotas and replanting.
• 20.4Explain how fish stocks can be conserved using education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring.
• 20.4Describe the reasons for conservation programmes: maintaining or increasing biodiversity; reducing extinction; protecting vulnerable ecosystems; maintaining ecosystem functions — nutrient cycling and resource provision including food, drugs, fuel and genes.
• 20.4Describe the use of artificial insemination (AI) and in vitro fertilisation (IVF) in captive breeding programmes.
• 20.4Explain the risks to a species if its population size decreases, reducing genetic variation (knowledge of genetic drift not required).

CoreEvery candidate

• 21.1State that bacteria are useful in biotechnology and genetic modification due to their rapid reproduction rate and their ability to make complex molecules.
• 21.2Describe the role of anaerobic respiration in yeast during the production of ethanol for biofuels.
• 21.2Describe the role of anaerobic respiration in yeast during bread-making.
• 21.2Describe the use of pectinase in fruit juice production.
• 21.2Investigate and describe the use of biological washing powders that contain enzymes.
• 21.3Describe genetic modification as changing the genetic material of an organism by removing, changing or inserting individual genes.
• 21.3Outline examples of genetic modification: insertion of human genes into bacteria to produce human proteins; insertion of genes into crop plants to confer resistance to herbicides; insertion of genes into crop plants to confer resistance to insect pests; insertion of genes into crop plants to improve nutritional qualities.

SupplementExtended candidates only

• 21.1Discuss why bacteria are useful in biotechnology and genetic modification: few ethical concerns over their manipulation and growth; the presence of plasmids.
• 21.2Explain the use of lactase to produce lactose-free milk.
• 21.2Describe how fermenters can be used for the large-scale production of useful products by bacteria and fungi, including insulin, penicillin and mycoprotein.
• 21.2Describe and explain the conditions that need to be controlled in a fermenter: temperature, pH, oxygen, nutrient supply, waste products.
• 21.3Outline the process of genetic modification using bacterial production of a human protein as an example: isolation of the DNA making up a human gene using restriction enzymes, forming sticky ends; cutting of bacterial plasmid DNA with the same restriction enzymes, forming complementary sticky ends; insertion of human DNA into bacterial plasmid DNA using DNA ligase to form a recombinant plasmid; insertion of recombinant plasmids into bacteria (specific details not required); multiplication of bacteria containing recombinant plasmids; expression in bacteria of the human gene to make the human protein.
• 21.3Discuss the advantages and disadvantages of genetically modifying crops, including soya, maize and rice.