GCSE Biology specification checklist

FoundationEvery student

• 1.1Describe plant and animal cells (eukaryotic cells) as having a cell membrane, cytoplasm and genetic material enclosed in a nucleus, and bacterial cells (prokaryotic cells) as much smaller, with cytoplasm, a cell membrane surrounded by a cell wall, and genetic material that is a single DNA loop not enclosed in a nucleus, plus one or more small rings of DNA called plasmids.
• 1.2Explain how the main sub-cellular structures — nucleus, cell membrane, mitochondria, ribosomes, and in plant cells chloroplasts and a permanent vacuole, plus a cellulose cell wall — are related to their functions.
• 1.3Demonstrate an understanding of the scale and size of cells, make order-of-magnitude calculations including the use of standard form, and use the prefixes centi, milli, micro and nano.
• 1.4Explain how electron microscopy has increased our understanding of sub-cellular structures by giving far higher magnification and resolution than light microscopes.
• 1.5Explain how the structures of specialised cells — sperm, nerve and muscle cells in animals; root hair, xylem and phloem cells in plants — relate to their functions.
• 1.6Carry out the microscopy required practical: use a light microscope to observe, draw and label a selection of plant and animal cells, including a magnification scale.
• 1.7Use the equation magnification = image size ÷ real size, converting between millimetres, micrometres and nanometres.
• 1.8Describe the nucleus as containing chromosomes made of DNA, each chromosome carrying a large number of genes, with chromosomes normally found in pairs in body cells.
• 1.9Describe the cell cycle: the cell grows and copies its DNA before mitosis, one set of chromosomes is pulled to each end of the cell and the nucleus divides, then the cytoplasm and cell membrane divide to form two identical cells — important in growth and development of multicellular organisms.
• 1.10Describe the function of stem cells in embryos, in adult animals (bone marrow) and in the meristems of plants, and evaluate the benefits and risks of using stem cells in medicine, including therapeutic cloning.

FoundationEvery student

• 2.1Describe diffusion as the spreading out of particles of any substance in solution or of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration, through cell membranes.
• 2.2Describe examples of substances transported into and out of cells by diffusion, including oxygen and carbon dioxide in gas exchange and the waste product urea from cells into blood plasma, and explain how the concentration gradient, temperature and membrane surface area affect the rate of diffusion.
• 2.3Calculate and compare surface area to volume ratios, and explain why single-celled organisms can rely on diffusion alone while multicellular organisms need exchange surfaces and transport systems.
• 2.4Explain how the small intestine and lungs in mammals, gills in fish, and the roots and leaves in plants are adapted for exchanging materials — large surface area, thin membranes, and in animals an efficient blood supply and ventilation.
• 2.5Describe osmosis as the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• 2.6Carry out the osmosis required practical: investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue, calculating percentage gain and loss of mass and plotting and interpreting graphs.
• 2.7Describe active transport as moving substances from a more dilute solution to a more concentrated solution (against the concentration gradient) using energy released by respiration, and give examples: mineral ions absorbed into root hair cells from dilute soil solutions, and sugar molecules absorbed from the gut into the blood.
• 2.8Compare transport by diffusion, osmosis and active transport and explain the differences between the three processes.

FoundationEvery student

• 3.1Describe the hierarchy of organisation: cells as building blocks, a tissue as a group of cells with similar structure and function, organs as aggregations of tissues, and organ systems working together to form organisms.
• 3.2Describe the digestive system as an organ system in which several organs work together to digest and absorb food.
• 3.3Describe enzymes as biological catalysts that catalyse specific reactions because of the shape of their active site, and use the lock-and-key model to explain enzyme action.
• 3.4Relate enzyme activity to temperature and pH changes: higher temperature raises the rate up to an optimum, then the enzyme denatures; each enzyme has an optimum pH, and extremes denature the active site.
• 3.5Recall the sites of production and the action of amylase, proteases and lipases: carbohydrases break down carbohydrates to simple sugars (amylase breaks down starch); proteases break down proteins to amino acids; lipases break down lipids to glycerol and fatty acids.
• 3.6Describe how the products of digestion are used to build new carbohydrates, lipids and proteins, and how some glucose is used in respiration.
• 3.7Describe bile as made in the liver and stored in the gall bladder: it is alkaline to neutralise stomach hydrochloric acid, and it emulsifies fat into small droplets, increasing surface area — so the alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• 3.8Carry out the food-tests required practical: use Benedict’s solution for sugars, iodine for starch and Biuret reagent for protein, describing positive results for each.
• 3.9Carry out the amylase required practical: investigate the effect of pH on the rate of amylase reaction using continuous sampling with iodine every 30 seconds, controlling temperature with a water bath.
• 3.10Carry out rate calculations for enzyme reactions, including rate = 1 ÷ time taken.

FoundationEvery student

• 4.1Describe the human circulatory system as a double circulatory system: the right ventricle pumps blood to the lungs where gas exchange takes place, and the left ventricle pumps blood around the rest of the body.
• 4.2Describe the structure and function of the heart, including the four chambers and the major vessels associated with it: aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
• 4.3Describe how the natural resting heart rate is controlled by a group of cells in the right atrium that act as a pacemaker, and that artificial pacemakers are electrical devices used to correct irregular heart rhythms.
• 4.4Explain how the structures of arteries, veins and capillaries relate to their functions.
• 4.5Use simple compound measures such as rate and carry out rate calculations for blood flow.
• 4.6Describe blood as a tissue consisting of plasma, in which red blood cells, white blood cells and platelets are suspended, and explain how each component is adapted to its function.
• 4.7Describe coronary heart disease: layers of fatty material build up inside the coronary arteries, narrowing them, reducing blood flow and resulting in a lack of oxygen for the heart muscle.
• 4.8Evaluate the treatment of cardiovascular disease by drugs (statins), mechanical devices (stents, artificial hearts, replacement biological or mechanical valves) or transplant (donor hearts), weighing benefits against risks.

FoundationEvery student

• 5.1Describe health as the state of physical and mental well-being, and diseases — both communicable and non-communicable — as major causes of ill health; other factors including diet, stress and life situations affect both physical and mental health.
• 5.2Describe how different types of disease may interact: immune-system defects raise the risk of infectious diseases; viruses living in cells can trigger cancers; immune reactions to pathogens can trigger allergies such as skin rashes and asthma; severe physical ill health can lead to depression and other mental illness.
• 5.3Describe risk factors as aspects of a person’s lifestyle, or substances in the body or environment, that are linked to an increased rate of a disease; explain that a causal mechanism has been proven for some risk factors but not for others.
• 5.4Explain the effects of diet, smoking and exercise on cardiovascular disease; obesity as a risk factor for type 2 diabetes; alcohol on the liver and brain function; smoking on lung disease and lung cancer; smoking and alcohol on unborn babies; and carcinogens, including ionising radiation, as risk factors in cancer.
• 5.5Discuss the human and financial cost of non-communicable diseases to an individual, a local community, a nation and globally.
• 5.6Translate disease-incidence information between graphical and numerical forms; construct and interpret frequency tables, bar charts and histograms; use scatter diagrams to identify correlations between two variables; and understand the principles of sampling as applied to epidemiological data.
• 5.7Describe cancer as the result of changes in cells that lead to uncontrolled growth and division; describe benign tumours as growths contained in one area, usually within a membrane, that do not invade other parts of the body.
• 5.8Describe malignant tumour cells as cancers: they invade neighbouring tissues and spread through the blood to form secondary tumours elsewhere in the body; and describe lifestyle and genetic risk factors for various types of cancer.

FoundationEvery student

• 6.1Explain how the structures of plant tissues are related to their functions, including epidermal tissues, palisade mesophyll, spongy mesophyll, xylem and phloem, and meristem tissue at the growing tips of shoots and roots.
• 6.2Describe the leaf as a plant organ, limited to the epidermis, palisade and spongy mesophyll, xylem and phloem, and guard cells surrounding stomata.
• 6.3Explain how the structures of root hair cells are adapted to their functions — a large surface area, thin walls and many mitochondria for absorbing water and mineral ions.
• 6.4Explain how the structures of xylem and phloem are adapted to their functions: hollow lignified xylem tubes carrying water and mineral ions upwards in the transpiration stream, and elongated phloem cells with sieve plates carrying dissolved sugars up and down in translocation.
• 6.5Describe the processes of transpiration and translocation, including the structure and function of stomata and guard cells.
• 6.6Explain the effects of changing temperature, humidity, air movement and light intensity on the rate of transpiration.
• 6.7Measure and calculate the rate of transpiration by water uptake, using simple compound measures, and process stomata-count data to find arithmetic means and understand sampling.
• 6.8Translate information between graphical and numerical form, and extract and interpret information from graphs, charts and tables about transpiration rates.

FoundationEvery student

• 7.1Explain that communicable diseases are caused by microorganisms called pathogens, which may be viruses, bacteria, protists or fungi; pathogens reproduce inside a host and may damage cells or release toxins; diseases can be spread by direct contact, water, air (droplets) or vectors.
• 7.2Describe measles as a viral disease spread by droplets, causing fever and a red skin rash, which can be fatal if complications such as a lung or brain infection develop.
• 7.3Describe HIV as a virus spread by sexual contact or exchange of body fluids such as blood, which initially causes a flu-like illness; describe how antiretroviral drugs stop the virus replicating, and how, if untreated, the virus attacks immune cells so the body cannot cope with other infections or cancers.
• 7.4Describe tobacco mosaic virus (TMV) as a widespread plant pathogen that gives a mosaic discolouration pattern on leaves, damaging chloroplasts so photosynthesis slows and growth is stunted.
• 7.5Describe salmonella as bacteria spread through food prepared in unhygienic conditions or eaten undercooked, secreting toxins that cause fever, abdominal cramps, vomiting and diarrhoea; in the UK poultry are vaccinated against salmonella to control its spread.
• 7.6Describe gonorrhoea as a sexually transmitted bacterial disease with symptoms of a thick yellow or green discharge and pain on urinating, once easily treated with penicillin but with resistant strains now common, so it is treated with other antibiotics and prevented with barrier contraception.
• 7.7Describe malaria as a disease caused by a protist parasite carried by mosquito vectors; the protist infects the blood and causes recurring episodes of fever, which can be fatal; spread is reduced by preventing mosquitoes breeding and using insecticide-treated nets, while antimalarial drugs treat or help prevent infection.
• 7.8Describe rose black spot as a fungal disease of rose leaves with purple or black spots that turn yellow and drop early, reducing photosynthesis and growth; it spreads by spores carried in wind or water and is treated with fungicides and by removing and destroying affected leaves.
• 7.9Describe the body’s nonspecific defence systems: the skin as a physical barrier producing antimicrobial secretions, the nose trapping particles and pathogens in mucus and hairs, the trachea and bronchi secreting mucus that cilia waft upwards, and stomach acid killing pathogens swallowed with food.
• 7.10Explain how the immune system responds to a pathogen that has entered the body: phagocytes engulf and digest pathogens, lymphocytes produce antibodies that bind to specific antigens on the pathogen surface and antitoxins that neutralise toxins, and memory lymphocytes give immunity to future infection.
• 7.11Explain how vaccination introduces small quantities of dead or inactive forms of a pathogen so the immune system produces antibodies and memory cells, giving protection against future infection; explain how widespread vaccination makes a population immune and helps prevent epidemics.
• 7.12Evaluate the advantages and disadvantages of vaccination: large-scale protection against epidemics and the disappearance of diseases in many countries, set against the fact that vaccines do not always give immunity and can occasionally cause mild side effects or very rarely harm.
• 7.13Explain that antibiotics such as penicillin cure bacterial infections by killing or preventing the growth of the bacteria without damaging body cells, that specific antibiotics treat specific bacteria, and that antibiotics cannot kill viruses because viruses reproduce inside cells.
• 7.14Explain how the emergence of strains resistant to antibiotics, such as MRSA, is a consequence of natural selection, and how the problem is reduced by doctors prescribing antibiotics only when needed and patients completing their course.
• 7.15Describe that painkillers and other medicines treat the symptoms of disease but do not kill pathogens, that some medicines relieve symptoms while antibiotics remedy infections.
• 7.16Describe the discovery and development of drugs: traditionally extracted from plants and microbes, for example digitalis from foxgloves, aspirin from willow and penicillin from the Penicillium mould discovered by Fleming; modern drugs are synthesised by chemists but many still start from a plant compound.
• 7.17Describe preclinical testing on cells, tissues and live animals for efficacy, toxicity and dosage, and clinical testing on healthy volunteers and then patients at low doses, with placebo controls, blind or double-blind trials and peer review before results are published.

FoundationEvery student

• 8.1Explain that monoclonal antibodies are antibodies produced from a single clone of cells, all binding to one specific antigen; describe how they are produced by fusing mouse lymphocytes that make the desired antibody with tumour cells to form hybridoma cells, which both divide rapidly and produce the antibody; hybridomas are grown in bulk and the monoclonal antibodies are collected and purified.Biology only
• 8.2Describe uses of monoclonal antibodies: in pregnancy tests, where HCG hormone in urine binds to antibodies on the test strip; in diagnosis, where monoclonal antibodies bind to particular pathogens or blood-clot proteins in blood samples; and in treatment, where they are attached to radioactive substances, toxic drugs or chemicals that kill cancer cells, delivering the treatment to specific cell types without harming other cells.Biology only
• 8.3Evaluate the advantages and disadvantages of monoclonal antibodies: the specificity means healthy cells should be unaffected, unlike standard chemotherapy or radiotherapy; however they create more side effects than were expected, are expensive to develop, and are suitable for treating fewer types of cancer than scientists first hoped.Biology only
• 8.4Describe how plant diseases are detected and identified: from signs and symptoms such as stunted growth, spots on leaves, areas of decay, growths, malformed stems or leaves, discolouration and the presence of visible pests; identification uses garden-centre manuals and websites, laboratory testing of samples, or testing kits containing monoclonal antibodies.Biology only
• 8.5Describe the physical, chemical and mechanical plant defences: cellulose cell walls, tough waxy cuticles and bark as physical barriers; antibacterial chemicals and poisons that deter herbivores as chemical defences; and mechanisms such as thorns, hairs, leaves that droop or curl when touched, and leaves that mimic insect shapes or eggs to frighten or confuse pests.Biology only
• 8.6Describe the required practical of culturing microorganisms: make an agar plate with a culture medium containing carbohydrate, minerals, vitamins and sometimes nitrogen; sterilise inoculating loops in a flame before and after transferring microorganisms; seal and incubate the plate; in school laboratories incubate at about 25 °C to reduce the risk of growing harmful pathogens, while industry uses higher temperatures and cultures known microorganisms safely.Biology only
• 8.7Calculate the cross-sectional areas of bacterial colonies or of clear inhibition zones around antibiotic discs on agar plates, using πr² with the radius taken from the measured diameter.Biology only

FoundationEvery student

• 9.1Describe photosynthesis as an endothermic reaction in which energy from the environment is transferred from light to chlorophyll in the chloroplasts, converting carbon dioxide and water into glucose and oxygen.
• 9.2Describe the rate of photosynthesis as affected by light intensity, the concentration of carbon dioxide, and temperature; explain how each can act as a limiting factor, and interpret graphs showing rate against each factor.
• 9.4Describe the required practical investigating the effect of light intensity on the rate of photosynthesis using an aquatic plant such as pondweed, measuring oxygen production (for example by counting bubbles or collecting gas), and how the results show the law of limiting factors.
• 9.5Explain the uses of glucose produced by photosynthesis: respiration to transfer energy; converted into insoluble starch for storage; used to produce fat or oil for storage; used to produce cellulose to strengthen cell walls; and combined with nitrate ions absorbed from the soil to produce amino acids for protein synthesis.
• 9.6Explain how the rate of photosynthesis is directly proportional to light intensity below the limiting threshold and how temperature affects the rate, including the fall at high temperatures as enzymes denature.
• 9.7Evaluate the benefits and costs of managing the environment in commercial greenhouses: lighting, heating and carbon dioxide enrichment raise photosynthesis and yields, but each carries a cost that must be weighed against the extra crop value.

HigherHigher tier only

• 9.3(Higher) Describe and apply the inverse square law: light intensity is inversely proportional to the square of the distance from the source, so light intensity ∝ 1/d², and doubling the distance quarters the intensity.

FoundationEvery student

• 10.1Describe respiration in cells as the process of transferring energy from the breakdown of glucose, continuing constantly in all living cells; describe it as an exothermic reaction that transfers energy to the environment.
• 10.2Describe aerobic respiration as glucose + oxygen → carbon dioxide + water, taking place continuously inside the mitochondria of cells, and explain that the energy transferred is used to power the chemical reactions in cells that build larger molecules.
• 10.3Explain the body’s responses to exercise: the heart rate, breathing rate and breath volume increase during exercise so that the blood supplies the muscles with more glucose and more oxygenated blood, while muscles store glycogen that is converted back to glucose for respiration.
• 10.4Describe anaerobic respiration in muscles as the breakdown of glucose without oxygen, producing lactic acid; explain why much less energy is transferred per glucose molecule than in aerobic respiration, and why hard exercise leads to oxygen debt.
• 10.6Describe anaerobic respiration in plant and yeast cells as glucose → ethanol + carbon dioxide, and explain the economic importance of anaerobic respiration in yeasts for bread-making (carbon dioxide raises the dough) and brewing (ethanol).
• 10.7Describe metabolism as the sum of all the reactions in a cell or in the body, and give examples of reactions powered by the energy transferred by respiration: conversion of glucose to starch, glycogen and cellulose; forming lipids from glycerol and fatty acids; using glucose and nitrate ions to form amino acids; breaking down excess protein to urea for excretion.

HigherHigher tier only

• 10.5(Higher) Explain how, after exercise, breathing rate stays high until the oxygen debt is repaid: blood transports lactic acid to the liver, where extra oxygen oxidises it to carbon dioxide and water.

FoundationEvery student

• 11.1Explain that homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimal conditions for function, in response to internal and external changes; give examples such as blood glucose concentration, body temperature and water levels.
• 11.2Describe how automatic control systems keep conditions steady: receptors detect a stimulus, coordination centres (brain, spinal cord, pancreas) receive and process the information, and effectors (muscles or glands) bring about a response; explain negative feedback as a loop in which a change triggers a response that reverses the change.
• 11.3Describe the structure and function of the nervous system: the brain and spinal cord form the central nervous system (CNS), which coordinates the response; neurones carry electrical impulses; receptors detect stimuli such as light, sound, chemicals, temperature and touch.
• 11.4Describe the reflex arc: stimulus → receptor → sensory neurone → coordination centre (in the CNS) → motor neurone → effector (muscle or gland); explain that reflexes are fast, automatic responses that do not involve the conscious part of the brain, protecting the body from harm.
• 11.5Describe the structure of a reflex arc at the synapse: chemicals called neurotransmitters transfer the impulse across the tiny gap between neurones; they diffuse across and bind to receptor molecules on the next neurone, continuing the impulse.
• 11.6Describe the required practical measuring reaction time with the ruler-drop method: a ruler is dropped without warning and caught as fast as possible; the distance it falls gives a measure of reaction time; compare results with caffeine, with dominant versus non-dominant hand, or measure reaction time with a computer.

FoundationEvery student

• 12.1Describe the brain as part of the central nervous system with three key regions: the cerebral cortex, responsible for consciousness, intelligence, memory and language; the cerebellum, responsible for muscle coordination and balance; and the medulla, which controls unconscious activities such as breathing and heart rate.Biology only
• 12.2Describe how the brain and spinal cord are protected: the skull encases the brain, the vertebral column encases the spinal cord, and membranes (with protective fluid between them) cushion both.Biology only
• 12.3Explain why investigating and treating the brain is difficult and why progress is slow: the brain is complex and delicate, it is enclosed in the skull and hard to access, and studying it has relied on patients with brain damage, electrical stimulation of brain tissue and MRI scanning methods, each with limits and risks.Biology only
• 12.4Describe the structure and function of the eye: the sclera is the tough white outer coat; the transparent cornea refracts light as it enters; the iris controls the size of the pupil; the lens focuses light onto the retina; the retina contains light receptors; and the optic nerve carries impulses to the brain.Biology only
• 12.5Describe accommodation: to focus on distant objects the ciliary muscles relax, the suspensory ligaments are pulled tight and the lens is pulled thin, so light is refracted less; to focus on near objects the ciliary muscles contract, the suspensory ligaments slacken and the lens becomes thicker, so light is refracted more strongly.Biology only
• 12.6Describe common defects of the eye and how they are corrected: myopia (short sight), where distant objects are focused in front of the retina and corrected with a diverging (concave) lens; and hyperopia (long sight), where near objects are focused behind the retina and corrected with a converging (convex) lens; hard contact lenses, laser surgery to change the cornea shape, and replacement lenses as treatments.Biology only
• 12.7Explain how body temperature is controlled: the thermoregulatory centre in the brain monitors and controls core temperature, with receptors in the skin sending information about skin temperature; if too hot, vasodilation and sweating increase heat loss (sweat evaporates, transferring energy); if too cold, vasoconstriction, sweating stops, hairs are raised to trap an insulating layer and shivering (respiration) increases heat production.Biology only

FoundationEvery student

• 13.1Describe the principles of hormonal coordination: the endocrine glands secrete hormones directly into the bloodstream, and the blood carries them to a target organ where they bring about a response.
• 13.2Describe the pituitary gland in the brain as a “master gland” which secretes several hormones into the blood in response to body conditions, and these hormones in turn act on other glands to stimulate the release of other hormones and bring about effects.
• 13.3Compare hormonal and nervous coordination: nerves act fast, carry electrical impulses along neurones to specific effectors, and have short-lived effects; hormones act more slowly, travel in the blood, act on wider areas and have longer-lasting effects.
• 13.4Explain how blood glucose concentration is monitored and controlled by the pancreas: the pancreas produces the hormone insulin, which lowers blood glucose by causing it to move from the blood into cells and be stored as glycogen in the liver and muscles; the pancreas also produces glucagon, which raises blood glucose by causing glycogen to be converted back to glucose and released; the two form a negative feedback system.
• 13.5Describe Type 1 diabetes as a disorder in which the pancreas fails to produce sufficient insulin, characterised by uncontrolled high blood glucose levels, and explain its treatment with insulin therapy (injections before meals), limiting intake of simple carbohydrates and regular exercise; untreated Type 1 diabetes can cause death.
• 13.6Describe Type 2 diabetes as a disorder in which the body cells no longer respond to insulin produced by the pancreas, explain that obesity is a risk factor, and describe treatment with a carbohydrate-controlled diet and an exercise programme.
• 13.7Evaluate the correlation between obesity (measured with body mass index, BMI = mass ÷ height²) and Type 2 diabetes, interpreting data on rates of the disease.
• 13.8Describe that water and ion content of the body must be kept within narrow limits, and that excess water, ions and urea are removed from the body in urine produced by the kidneys.
• 13.9(Biology only) Describe how the kidneys filter the blood: sugar, dissolved ions and water are filtered out of the blood and then all of the sugar, and as much water and ions as the body needs, are reabsorbed; excess water, ions and urea are removed in the urine.Biology only
• 13.10(Biology only) Explain how the water content of the body is regulated by the hormone ADH: receptors in the brain detect the water concentration of the blood, the pituitary gland releases ADH, and ADH increases the permeability of the kidney tubules so more water is reabsorbed; this is negative feedback.Biology only
• 13.11(Biology only) Evaluate the treatment of kidney failure by dialysis compared with kidney transplant: dialysis removes urea and excess ions and water by filtering the blood through a machine several times a week for life, while a transplant is a long-term cure but requires a matching donor, major surgery and lifelong immunosuppressant drugs to prevent rejection.Biology only

FoundationEvery student

• 14.1Describe the roles of hormones in human reproduction, including the hormones testosterone, produced by the testes and responsible for sperm production and male secondary sexual characteristics, and oestrogen and progesterone, produced by the ovaries and involved in the menstrual cycle and female secondary sexual characteristics.
• 14.2Describe the menstrual cycle as a roughly 28-day cycle in which the uterus lining builds up, an egg is released (ovulation) at about day 14, and — if the egg is not fertilised — the lining breaks down (menstruation).
• 14.3Describe the hormones involved in the menstrual cycle: FSH from the pituitary causes a follicle to mature and stimulates oestrogen production; LH from the pituitary stimulates the release of the egg; oestrogen from the ovaries repairs the uterus lining and stimulates LH release; progesterone maintains the uterus lining and inhibits FSH and LH release.
• 14.5Explain the use of hormones in contraception: oral contraceptives containing oestrogen and progesterone inhibit FSH release so no eggs mature; slow-release methods (implants, injections, patches) deliver progesterone over months; and evaluate the benefits and risks, including possible side effects.
• 14.6Describe non-hormonal methods of contraception: barrier methods such as condoms and diaphragms, intrauterine devices (IUDs), spermicides, abstinence, and surgical sterilisation.
• 14.7Describe the use of hormones in modern reproductive technology: FSH and LH as “fertility drugs” to stimulate egg maturation and release, and in vitro fertilisation (IVF), in which eggs are collected, fertilised in the laboratory with sperm, and the resulting embryos implanted in the uterus.
• 14.8Evaluate IVF: it has allowed many couples to have children, but success rates are low, treatment is physically and emotionally stressful, hormone side effects occur, and multiple births carry risks; ethical issues include the fate of unused embryos.
• 14.9(Biology only) Describe the effects of plant hormones: auxins control cell elongation near the shoot tips and are involved in phototropisms and gravitropisms, and are used as weedkillers and rooting powders and to control dormancy; gibberellins stimulate seed germination, flowering and fruit production; ethene controls cell division and ripening, and is used in the food industry to ripen fruit.Biology only
• 14.10(Biology only) Describe the required practical investigating the effect of light or gravity on the growth of seedlings, using seedlings grown in different conditions and measuring their shoot growth, and explain the results in terms of auxin distribution.Biology only

HigherHigher tier only

• 14.4(Higher) Explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle, including the feedback effects of oestrogen (low levels inhibit FSH; high levels stimulate LH) and progesterone (inhibits FSH and LH).

FoundationEvery student

• 15.1Describe sexual reproduction as involving the fusion of male and female gametes, producing genetic variation in offspring; describe asexual reproduction as involving one parent and no gamete fusion, producing genetically identical offspring (clones).
• 15.2Describe meiosis as the type of cell division that produces gametes: the genetic information is copied, the cell divides twice to form four gametes, each with a single set of chromosomes; gametes join at fertilisation to restore the body’s chromosome number.
• 15.3Explain the advantages and disadvantages of sexual and asexual reproduction: sexual reproduction produces variation, giving resilience to change but requiring two parents and being slower; asexual reproduction is fast and needs only one parent but produces no variation, so a whole population can be wiped out by one disease or change; give examples such as the malaria parasite and fungi, and plants that reproduce both ways.
• 15.4Describe DNA as a polymer made up of two strands coiled into a double helix, with nucleotides consisting of a common sugar and phosphate group joined to one of four different bases (A, C, G and T); describe complementary base pairing, in which A always pairs with T and C always pairs with G.
• 15.5Describe a gene as a section of DNA that codes for a particular sequence of amino acids, put together to make a specific protein; describe the genome as the entire genetic material of an organism.
• 15.7Describe mutations as rare, random changes to genetic material that occur continuously; explain that mutations arise spontaneously and can occur in both coding and non-coding DNA, and that most have no effect on the phenotype; some influence phenotype by changing the protein — for example an enzyme’s active site — altering its activity.

HigherHigher tier only

• 15.6(Higher) Explain how DNA codes for proteins: each gene codes for a sequence of amino acids; the DNA base sequence determines the amino acid sequence; proteins are synthesised on ribosomes in the cell cytoplasm, using a template molecule carried from the DNA in the nucleus, because DNA cannot leave the nucleus.

FoundationEvery student

• 16.1Describe that in sexual reproduction offspring inherit a combination of genes from both parents, producing variation; describe alleles as different versions of the same gene, with individuals carrying two alleles for each gene — one from each parent.
• 16.2Describe the inheritance of a dominant allele, which is expressed even when only one copy is present, and a recessive allele, which is expressed only when both alleles are recessive; define genotype as the combination of alleles and phenotype as the observable characteristics.
• 16.3Explain how genetic diagrams and Punnett squares predict the results of crosses: the possible allele combinations of offspring and the probability of each phenotype, including monohybrid crosses between homozygous and heterozygous parents.
• 16.4Use family trees (pedigrees) to identify whether a characteristic is controlled by dominant or recessive alleles, and to predict probabilities for future children.
• 16.5Describe sex determination: ordinary body cells have 23 pairs of chromosomes, of which one pair are the sex chromosomes — XX in females and XY in males; a Punnett square shows offspring have an equal 50% probability of being male or female.
• 16.6Describe polydactyly as an inherited disorder caused by a dominant allele (extra fingers or toes), which can therefore be inherited if just one parent carries the allele, and cystic fibrosis as a disorder of cell membranes caused by a recessive allele, which must be inherited from both parents; parents can be carriers without having the disorder.
• 16.7Describe embryo screening as a way of detecting inherited disorders and evaluate the economic, social and ethical issues it raises, alongside the decisions faced by families who receive screening results.
• 16.8Describe Mendel’s work: in the mid-19th century he carried out inheritance experiments with pea plants, showing that characteristics are inherited in discrete units; his work was recognised long afterwards, once chromosomes and genes were observed and understood.
• 16.9Describe variation as arising from mutations and from the recombination of genes during sexual reproduction; explain that the phenotype results from the interaction of genotype and environment, giving examples such as height, body mass and hair colour.

FoundationEvery student

• 17.1Describe evolution as a change in the inherited characteristics of a population over time, through the process of natural selection: mutations and genetic variants arise; organisms with characteristics better suited to the environment are more likely to survive and reproduce, passing their alleles on; over many generations the useful variant becomes common.
• 17.2Describe Darwin’s theory of evolution by natural selection: his observations that organisms produce more offspring than survive, that there is variation, and that traits are suited to their place; his conclusion that better-adapted organisms survive, breed and pass on their characteristics, and that all species have evolved from common ancestors; explain that the theory was gradually accepted because it was supported by evidence and because later work on genetics explained the mechanism.
• 17.3Explain antibiotic resistance as an example of evolution by natural selection: random mutations make some bacteria resistant; antibiotics kill the non-resistant bacteria, so the resistant ones survive, reproduce and spread; explain how this supports Darwin’s theory and how the rise of resistant strains is reduced.
• 17.4Describe selective breeding (artificial selection) as choosing parents with the best characteristics and breeding them over many generations to produce improved crops and domestic animals; explain the advantages (better yields, disease-resistant crops) and disadvantages (reduced genetic variation, health problems such as inherited defects in some breeds).
• 17.5Describe genetic engineering as modifying an organism’s genome to introduce desirable characteristics: enzymes are used to cut out a gene and transfer it from one organism’s genome into another; bacteria have been engineered to produce human insulin; genetically modified (GM) crops include ones resistant to insects or herbicides or with improved nutritional value.
• 17.6Discuss the benefits and concerns of genetic engineering: benefits include increased food production and improved nutrition; concerns include that transferred genes may spread to wild populations, effects on food chains and populations of wild organisms, and unknown effects of eating GM crops.
• 17.7(Biology only) Describe cloning methods: tissue culture (using small groups of cells from a plant to grow identical plants), cuttings (a simple, traditional cloning method), embryo transplants (splitting animal embryos to clone prize animals), and adult cell cloning (as with Dolly the sheep, transferring a body-cell nucleus into an empty egg); discuss the benefits and risks of cloning.Biology only
• 17.8(Biology only) Describe the theories of evolution: Darwin’s theory of natural selection, which is accepted because it explains so much evidence; and Lamarck’s earlier idea that characteristics acquired during life are inherited — now discredited because acquired changes do not alter genes.Biology only
• 17.10(Biology only) Describe the work of Alfred Wallace, who independently proposed natural selection and prompted Darwin to publish; his work on warning colouration in animals contributed to the theory.Biology only
• 17.11Describe classification: organisms were traditionally classified by characteristics and structure; today genome sequencing and other evidence refine the groupings; the Linnaean system orders organisms from kingdom, phylum, class, order, family, genus to species, with binomial naming (genus plus species, e.g. *Homo sapiens*); the three-domain system (Archaea, Bacteria, Eukaryota) divides all life using new evidence; evolutionary trees show how species are related.

HigherHigher tier only

• 17.9(Higher, Biology only) Explain speciation: populations become isolated (for example by a geographical barrier), genetic variation and natural selection act differently in the isolated groups, and genetic drift changes allele frequencies; eventually the populations are so different that they can no longer breed successfully — new species.Biology only

FoundationEvery student

• 18.1Describe a community as all the organisms living in a habitat, and an ecosystem as the interaction of that community with the non-living (abiotic) parts of the environment; describe abiotic factors (light, temperature, water, pollutants) and biotic factors (food availability, competitors, pathogens) that affect communities.
• 18.2Describe levels of organisation: producers make glucose by photosynthesis; primary consumers eat producers; secondary consumers eat primary consumers; tertiary consumers eat secondary consumers; predators and prey are part of these chains, and their populations rise and fall in linked cycles.
• 18.3Describe the required practical of measuring populations using quadrats: place quadrats randomly, count organisms in each, calculate the mean per quadrat, and scale up to estimate the population of the whole area; transects measure how distribution changes across a habitat.
• 18.4Describe organisms’ adaptations to their environments as structural, behavioural or functional, including extremophile organisms that live in extreme conditions, and explain how adaptations make organisms better suited to survive and reproduce.
• 18.5(Biology only) Describe the role of decomposers in breaking down dead material and waste, returning nutrients to the environment; describe the decay required practical (measuring the rate of decay of fresh milk by pH change) and explain how temperature, water and oxygen availability affect decay; describe anaerobic decay producing biogas.Biology only
• 18.6Describe the water cycle (evaporation, condensation, precipitation returning water to the land and sea) and the carbon cycle (photosynthesis removing carbon dioxide, respiration, combustion and decay returning it), and explain the importance of these cycles in returning materials to the environment.
• 18.7Describe biodiversity as the variety of organisms in an area; explain the human impacts that reduce it (land use, deforestation, peat bog destruction, pollution) and the programmes that maintain it (breeding programmes, habitat protection, hedgerows, recycling rather than landfill).
• 18.8(Biology only) Describe food security as having enough food to feed a population, explain the biological factors threatening it (rising human population, new pests and pathogens, environmental change, costs of agricultural inputs, conflicts), and describe farming techniques that improve efficiency, including factory farming, fertilisers and GM crops.Biology only

HigherHigher tier only

• 18.9(Higher, Biology only) Explain that biomass is transferred between trophic levels inefficiently, and calculate the efficiency of biomass transfers as (biomass transferred ÷ biomass intake) × 100, explaining the losses to respiration, movement, uneaten parts and waste.Biology only