SecondaryCode 5090
Biology
52 topics and 300 objectives, each one something you should be able to do.
Written by Kindred in its own plain words. Your syllabus is still the official list, so check it for anything exact.
What this subject asks you to be able to do
1.1Cell structure and function6 objectives
- Examine animal cells and plant cells with a microscope, taking them from any suitable material that is available locally and preparing them with a temporary staining technique that is appropriate, such as iodine solution or methylene blue
- Draw diagrams to record what was seen in the animal and plant cells observed above
- Identify the ribosomes, mitochondria, nucleus, cytoplasm and cell membrane of an animal cell, working from diagrams, photomicrographs or electron micrographs
- Identify the ribosomes, mitochondria, chloroplasts, nucleus, sap vacuole, cytoplasm, cell membrane and cellulose cell wall of a plant cell, working from diagrams, photomicrographs or electron micrographs
- Describe a bacterial cell's structure, limited to: cell wall, cell membrane, cytoplasm, ribosomes, and circular deoxyribonucleic acid (DNA) together with plasmids
- Describe the functions performed by the structures named above across animal, plant and bacterial cells
1.2Specialised cells, tissues and organs3 objectives
- Understand that cells may take on specialised forms, and that each cell's structure is tied to the particular job it does, as shown through the examples taught in this course.
- Understand what the terms cell, tissue, organ, organ system and organism mean, using the examples taught in this course to illustrate them.
- Give the equation magnification = image size / actual size and use it
2.1Concept and use of a classification system4 objectives
- Understand that groups of organisms are formed by classification, using the features the organisms share
- Describe a species as a collection of organisms capable of reproduction that yields fertile offspring
- Describe the binomial system of naming species, which is agreed internationally and gives each organism a scientific name made of two parts that show its genus and species
- Construct and apply dichotomous keys built on features that can be identified
2.2Features of organisms6 objectives
- Give the key characteristics used to sort every organism into one of five kingdoms: Animal, Plant, Fungus, Prokaryote, Protoctist
- Name the principal characteristics used to assign organisms to subgroups of the animal kingdom, limited to: (a) the principal categories of vertebrates: mammals, birds, reptiles, amphibians, fish (b) the principal categories of arthropods: myriapods, insects, arachnids, crustaceans
- Give the key characteristics used to assign organisms to subgroups of the plant kingdom, limited to ferns and flowering plants (dicotyledons and monocotyledons)
- Classify organisms by drawing on the characteristics listed under 2.2.1, 2.2.2 and 2.2.3
- Give the principal characteristics of viruses, limited to a protein coat and genetic material
- Understand that viruses are able to replicate only inside living cells
3.1Diffusion and osmosis9 objectives
- Describe the function that water performs as a solvent within living things, in relation to digestion, excretion and transport
- Understand that diffusion and osmosis are powered by the kinetic energy that molecules and ions have as they move randomly
- Understand diffusion as the net movement of ions or molecules, driven by their random movement, from a place where they are more concentrated to one where they are less concentrated (i.e. down a concentration gradient)
- Investigate how diffusion is affected by various factors, limited to: distance, surface area, temperature and concentration gradient
- Understand that in osmosis, water molecules make a net movement through a partially permeable membrane, passing from an area with a higher water potential to one where the water potential is lower
- Know that plant support comes from water inside the cells exerting outward pressure on the cell wall
- Describe what osmosis does to plant and animal tissues, and explain why the water potential gradient and osmosis matter for water being taken up and lost
- Investigate and account for how plant tissues respond when placed in solutions of varying concentration, employing the vocabulary turgid, turgor pressure, plasmolysis and flaccid
- Investigate osmosis with the help of materials such as dialysis tubing
3.2Active transport2 objectives
- Understand active transport as molecules or ions being moved in or out of a cell across the cell membrane, from where they are less concentrated to where they are more concentrated (i.e. against a concentration gradient), with the energy for this released by respiration
- Account for the significance of active transport to the absorption of ions by root hair cells
4.1Biological molecules3 objectives
- List which chemical elements are found in each of these: (a) carbohydrates, (b) lipids, that is fats and oils, (c) proteins and (d) DNA
- State that big molecules are put together from smaller molecules, limited to: starch, cellulose and glycogen formed out of glucose; proteins formed out of amino acids; lipids formed out of fatty acids and glycerol; DNA formed out of nucleotides
- Describe, and carry out, the chemical test for each of: (a) starch, using iodine solution (b) glucose and maltose, using Benedict's solution (c) protein, using the biuret test (d) lipids, using the ethanol emulsion test
5.1Enzyme action4 objectives
- Describe a catalyst as a substance which speeds up a chemical reaction but is not itself changed by it
- Describe enzymes as proteins acting as biological catalysts, taking part in every metabolic reaction
- explain how an enzyme works, referring to the substrate, the active site, the enzyme-substrate complex and the product
- explain enzyme specificity by describing how the active site and the substrate must fit together in a complementary way (the 'lock and key' hypothesis)
5.2Effects of temperature and pH3 objectives
- Understand that it is possible to follow the progress of an enzyme-catalysed reaction by measuring how concentrated its reactants and products are
- Investigate the way temperature and pH change enzyme activity, and describe these effects
- Explain how changing temperature and pH alters enzyme activity, using kinetic energy, shape and fit, denaturation, and how frequently effective collisions take place
6.1Photosynthesis9 objectives
- Understand that photosynthesis is how plants use energy from light to make carbohydrates out of raw materials
- State that chloroplasts contain chlorophyll, a green pigment
- State that chlorophyll turns the energy of light into chemical energy, which goes towards making glucose and other carbohydrates.
- Outline how the carbohydrates produced by photosynthesis are later used and stored, limited to: (a) starch, acting as an energy store (b) cellulose, which builds cell walls (c) glucose, which respiration uses to supply energy (d) sucrose, which is transported through the plant
- Give the word equation for photosynthesis, together with its balanced chemical equation.
- Investigate how necessary chlorophyll, light and carbon dioxide are to photosynthesis, employing suitable controls
- Describe, and account for, how altering light intensity, carbon dioxide concentration and temperature affects the rate of photosynthesis.
- Investigate, with hydrogencarbonate indicator solution and aquatic plants kept under water, how changing light intensity, carbon dioxide concentration and temperature affects the rate of photosynthesis
- Identify and explain which limiting factor holds photosynthesis back under various environmental conditions
6.2Leaf structure2 objectives
- State that leaves are usually thin with a large surface area, and explain how each of these features is an adaptation for photosynthesis
- Identify and label, on diagrams or photomicrographs of a dicotyledonous leaf, the cuticle and the structures of its cells and tissues, and explain how each is adapted for photosynthesis and gas exchange, limited to: (a) the stomata with their guard cells (b) palisade and spongy mesophyll cells (c) the air spaces (d) vascular bundles, made of xylem and phloem (e) how the chloroplasts are distributed (f) the upper and the lower epidermis
6.3Mineral nutrition2 objectives
- Account for why nitrate ions are needed to build amino acids, which are required to produce proteins
- Account for why magnesium ions are necessary for chlorophyll formation
7.1Uptake and transport of water and ions3 objectives
- Relate how root hair cells are built to their function in the uptake of water and ions
- Outline the route water follows as it passes from root to stem to leaf, limited to: root hair cells, root cortex cells, xylem and mesophyll cells
- Investigate, by means of a suitable stain, the route water follows in a severed stem
7.2Transpiration and translocation9 objectives
- Describe transpiration as the process in which water vapour is lost from leaves
- Understand that water passes by evaporation from mesophyll cell surfaces into the air spaces, and then leaves the leaf as water vapour by diffusing out through the stomata
- Explain: (a) how wind speed, together with changes in temperature, humidity and light intensity, affects the rate of transpiration (b) the way in which wilting takes place
- Investigate how wind speed, light intensity and shifts in temperature alter the rate of transpiration
- Account for the process by which water rises through the xylem, describing it as a transpiration pull that lifts a column of water molecules, which stay joined by attractive forces between the molecules
- Outline translocation as the transport of sucrose and amino acids through the phloem, moving from sources (regions that make or release these substances) to sinks (regions that consume or store them)
- Identify where tissues lie when viewed in transverse section across non-woody dicotyledonous roots and stems, limited to: xylem, phloem and cortex
- Give the functions of xylem: conveying water and mineral ions, and providing support
- Relate the way xylem vessels are built to their function, limited to: (a) thick walls containing lignin (lignification need not be covered in detail) (b) no cell contents (c) cells linked end-to-end without any cross walls, forming a single long continuous tube
8.1Diet3 objectives
- Give the chief food sources of carbohydrates, lipids, proteins, vitamins (C and D only), mineral salts (calcium and iron only), fibre (roughage) and water, and outline why each one is important in the diet
- State the diseases caused by a lack of vitamin C (scurvy), vitamin D (rickets), calcium (rickets) and iron (anaemia), and outline the symptoms that each deficiency produces
- Understand what is meant by a balanced diet
8.2Human digestive system14 objectives
- Identify these main regions of the digestive system: the mouth, oesophagus, stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum and anus), together with the salivary glands, pancreas, liver and gall bladder
- Explain why digestion has to happen before most foods can be absorbed
- Describe physical digestion as food being split into smaller bits, a process without chemical change to its molecules
- Describe chemical digestion as the process of reducing big molecules to smaller ones
- State that physical digestion enlarges the surface area of food available to enzymes acting during chemical digestion
- Identify the classes of human tooth present, namely incisors, canines, premolars and molars
- Describe how human teeth are built, limited to: pulp, nerves, dentine, enamel and cement, and understand that each tooth is embedded in the gum
- Describe the functions of each category of human tooth during the physical digestion of food
- Describe the job of each main region of the digestive system, limited to: the mouth, which carries out ingestion and physical digestion and where amylase chemically digests starch; the salivary glands, which secrete saliva containing amylase; the stomach, which carries out physical digestion and the chemical digestion of protein by protease, and whose gastric secretions contain hydrochloric acid; the small intestine (duodenum and ileum), where starch is chemically digested by amylase, maltose by maltase, protein by protease and lipids by lipase; the liver, which produces bile and stores glycogen; the gall bladder, which stores bile; the pancreas, which releases an alkaline secretion containing amylase, protease and lipase; the ileum and colon, where absorption happens; and the rectum and anus, where egestion takes place
- Describe what amylase, maltase, protease and lipase do, giving the substrates and end-products of each, limited to: amylase – starch broken down to maltose; maltase – maltose broken down to glucose; protease (trypsin and pepsin) – protein broken down to amino acids; lipase – lipids broken down to fatty acids and glycerol
- Describe the function of the stomach's hydrochloric acid, which is to kill bacteria that have been ingested
- Understand that the various proteases in the stomach as well as the duodenum operate optimally at distinct pH levels
- Outline the function of bile in emulsifying fats so as to enlarge the surface area available for lipase to chemically digest fat into fatty acids and glycerol
- Describe peristalsis as circular and longitudinal muscles contracting in waves, pushing food along the digestive system
8.3Absorption and assimilation7 objectives
- State that the place where nutrients get absorbed is the small intestine
- Know that absorption, which uses diffusion, osmosis and active transport, means nutrients passing from the intestines into the cells that line the gut and then on into the bloodstream.
- Understand that assimilation means cells taking in nutrients from the blood and putting them to use.
- Describe how a villus is built and what capillaries and lacteals do within it.
- Explain why it matters that villi and microvilli increase the ileum's internal surface area
- Understand that both the small intestine and the colon absorb water from their lumen, but that the small intestine takes up most of it
- State that the hepatic portal vein's function is to be the main route into the liver for the molecules and ions absorbed in the ileum
9.1Human gas exchange9 objectives
- Describe the characteristics of human gas exchange surfaces, limited to: a large surface area, a thin surface, and a good supply of both blood and air
- State what percentage of atmospheric air each of its gases makes up
- Investigate how inspired air differs from expired air, and explain the differences
- Identify the larynx, trachea, lungs, bronchi, bronchioles, alveoli and accompanying capillaries when shown in drawings or photos
- Name the properties of the exchange surface found in the alveoli, and describe the part it plays in gas exchange
- Identify the diaphragm, the ribs and the internal and external intercostal muscles when shown in diagrams and images
- Explain how the ribs, internal and external intercostal muscles and diaphragm bring about changes in volume and pressure within the thorax, which drive air in and out of the lungs (breathing)
- Investigate how the rate and depth of breathing change with physical activity, and explain why
- Explain how mucus, goblet cells and ciliated cells help protect the gas exchange system against particles and pathogens
10.1Respiration3 objectives
- Describe respiration as the chemical reactions by which every living cell releases energy from glucose
- State what living organisms use energy for, including muscle contraction, protein synthesis, cell division, active transport, growth, carrying electrical impulses along neurones and keeping body temperature constant
- Investigate how temperature affects respiration in yeast, and describe the effect
10.2Aerobic respiration2 objectives
- Describe aerobic respiration as the process in which glucose is broken down with oxygen present, releasing energy in comparatively large quantities
- Give, for aerobic respiration, both the word equation and the balanced chemical equation.
10.3Anaerobic respiration5 objectives
- Describe anaerobic respiration as a process in which glucose is broken down without oxygen, releasing a relatively small quantity of energy.
- Give the word equation that sums up anaerobic respiration in humans
- Give the word equation that sums up anaerobic respiration in yeast
- Account for the accumulation of lactic acid in muscle tissue and the bloodstream during intense physical activity, which leads to Excess Post-exercise Oxygen Consumption (EPOC) or an 'oxygen debt'
- Outline how the oxygen debt is cleared after exercise, limited to: the heart rate staying fast so that blood carries lactic acid from the muscles to the liver; breathing staying deeper and faster so that the liver has oxygen to break down lactic acid
11.1Circulatory system3 objectives
- Describe the circulatory system as blood vessels forming a system, with a pump that moves the blood and valves that keep it flowing one way
- outline double circulation as an arrangement in which blood goes through the heart two times for every complete circuit
- Understand that a double circulation gives the lungs a circulation at low pressure and the body tissues a circulation at high pressure
11.2Heart8 objectives
- Identify the parts of a mammalian heart, limited to: the atria and the left and right ventricles, the septum, the muscular wall, the coronary arteries, and the atrioventricular and semilunar valves
- Explain how thick the muscular walls of the left ventricle and right ventricle are relative to each other, and how thick the atrial muscular walls are relative to the ventricular ones.
- Describe how the heart works by considering the contraction of the muscle in the atria and ventricles and what the valves do over the course of a single heartbeat.
- State that the heart pumps blood away along arteries and that blood returns to the heart via veins.
- State that heart activity can be tracked using an electrocardiogram (ECG), measuring the pulse rate, and listening to the sounds made as valves shut
- Investigate, and then explain, how physical activity affects heart rate.
- Describe coronary heart disease as the coronary arteries becoming blocked, and state what may increase someone's risk of it, including age, gender, genetic predisposition, diet, smoking, stress and a sedentary lifestyle
- Discuss the contribution that diet and exercise make to lowering the risk of coronary heart disease.
11.3Blood vessels3 objectives
- Name the chief blood vessels taking blood into and out of the heart, lungs, liver and kidneys, limited to: vena cava, aorta, pulmonary vein, pulmonary artery, hepatic artery, hepatic vein, hepatic portal vein, renal vein and renal artery
- Describe the structure of arteries, veins and capillaries, and identify them on diagrams and photomicrographs, limited to: how thick the wall is relative to the other vessels, what the wall is made of (muscle and elastic tissue), how wide the lumen is, and whether valves are present
- Explain the link between the structure of arteries, veins and capillaries and the pressure of the blood flowing through each
11.4Blood4 objectives
- Identify red and white blood cells (lymphocytes and phagocytes) by using a light microscope to look at prepared slides, and by examining diagrams and photomicrographs
- List the parts that make up blood, namely red blood cells, white blood cells, platelets and plasma
- Give the role of each blood component: red blood cells carry oxygen; white blood cells make antibodies through lymphocytes and ingest pathogens through phagocytes; platelets bring about clotting by changing soluble fibrinogen into insoluble fibrin, which stops blood loss and pathogen entry; plasma moves substances around the body, limited to: blood cells, ions, glucose, amino acids, hormones, carbon dioxide, urea, vitamins and plasma proteins
- Describe how substances move between the blood inside capillaries, tissue fluid and body cells
12.1Disease16 objectives
- Outline a pathogen as an organism that causes disease
- Describe a transmissible disease as one whose pathogen can spread from host to host
- Understand the ways a pathogen may be transmitted: by direct contact, including via blood or other body fluids; by indirect contact, including from contaminated food or surfaces; from animals; and from the air
- Outline the barriers that keep pathogens out of the human body, limited to: skin, hairs in the nose, mucus, stomach acid
- Understand how the mosquito acts as a vector that spreads disease
- Describe the malarial pathogen, using it to show what a parasite is, and explain how it is transmitted
- Describe how the mosquito that transmits malaria can be controlled, using what is known about its life cycle
- Explain that human immunodeficiency virus (HIV) belongs to the category of viral pathogens
- Outline the ways HIV gets transmitted
- Understand that an HIV infection can progress to Acquired Immune Deficiency Syndrome (AIDS)
- Outline the methods that can be used to control HIV
- Describe cholera as a bacterial disease, transmitted through water that is contaminated
- Explain why a clean water supply, hygienic preparation of food, good personal hygiene, waste disposal and sewage treatment matter in controlling cholera's spread (the stages of sewage treatment need not be detailed)
- Explain that the cholera bacterium releases a toxin which makes the small intestine secrete chloride ions, so that water moves into the gut by osmosis, leading to diarrhoea, dehydration and ions being lost from the blood
- Outline what happens when alcohol is consumed to excess: lowered self-control, acting as a depressant, impact on reaction times, damage to liver and social implications
- Describe the effects on health of tobacco smoke and of its major toxic components (carbon monoxide, nicotine and tar): a strong association between smoking and bronchitis, emphysema, lung cancer and heart disease, and an association between smoking in pregnancy and the baby having a reduced birth weight
12.2Antibiotics4 objectives
- Describe a drug as any substance which, after entering the body, changes or influences the chemical reactions going on inside it
- describe how antibiotics are used to treat bacterial infection
- state that bacteria are killed by antibiotics, though viruses are not affected by them
- Explain how using antibiotics only when they are essential can keep the development of antibiotic-resistant bacteria, including MRSA, to a minimum
12.3Immunity11 objectives
- Describe active immunity as protection against a pathogen through the body making its own antibodies
- State that every pathogen carries its own antigens, and that these have particular shapes
- Describe antibodies as proteins that attach to antigens, either destroying pathogens directly or tagging them so that phagocytes destroy them
- State that specific antibodies have shapes complementary to, and so fitting, the specific antigens they target
- Explain that people acquire active immunity following infection with a pathogen or through vaccination.
- Outline how vaccination works: weakened pathogens, or just their antigens, are administered, the antigens trigger lymphocytes to respond and make antibodies, and memory cells form to provide long-term immunity.
- Explain the part that vaccination plays in limiting the spread of transmissible diseases
- Explain that in passive immunity, antibodies obtained from another person give short-term defence against a pathogen, limited to: antibodies that cross the placenta and antibodies in breast milk
- Explain why breast-feeding matters for the build-up of passive immunity in infants
- State that passive immunity does not lead to the formation of memory cells
- Outline the effect of HIV on the immune system, limited to: a fall in lymphocyte numbers and in the ability to make antibodies, which leaves the immune system weaker
13.1Excretion3 objectives
- Describe excretion as organisms getting rid of toxic materials and of the waste products that metabolism makes
- State that the lungs excrete carbon dioxide, a waste product of respiration
- State that the liver makes urea, a toxic waste product, when excess amino acids are broken down
13.2Urinary system6 objectives
- Identify, on diagrams, the kidneys, ureters, bladder and urethra and give the job of each (the kidney's job should be stated plainly as taking urea and surplus salts and water out of the blood to make urine)
- Account for why excretion is needed, limited to the toxicity of urea
- Outline how a nephron and the blood vessels that serve it are built, limited to: glomerulus, Bowman's capsule, tubules, loop of Henle and collecting duct
- Outline what a nephron does, along with the blood vessels associated with it, limited to: the glomerulus filtering water, glucose, urea and ions out of the blood; the nephron reabsorbing into the blood all the glucose, most of the water and some of the ions; and the formation of urine, which contains urea, excess water and excess ions (these processes need not be described in detail)
- Describe the liver's contribution to the assimilation of amino acids, which it achieves by turning them into proteins
- Describe deamination, which happens in the liver, as removing the part of amino acids that contains nitrogen, so that urea is formed
14.1Mammalian nervous system10 objectives
- State that body functions are coordinated and regulated by the nervous system, which is made up of the brain, spinal cord and nerves
- Describe the mammalian nervous system as made up of the central nervous system (CNS), formed by the brain together with the spinal cord, and the peripheral nervous system (PNS), formed by the nerves outside the spinal cord and brain
- Identify on a diagram which neurones are sensory, which are relay and which are motor
- State that neurones transmit electrical impulses along their length
- Describe a simple reflex arc by tracing it from the receptor through the sensory neurone, relay neurone and motor neurone to the effector (muscles and glands)
- Describe a reflex action as an automatic response that happens rapidly when there is a stimulus
- Describe a synapse as the connection point where one neurone meets another
- Describe a synapse's structure, including the vesicles that contain neurotransmitter molecules, the synaptic gap and receptor proteins
- Describe the sequence of events at a synapse: an incoming impulse makes vesicles discharge neurotransmitter molecules into the synaptic gap; the molecules then diffuse to the far side and bind with receptor proteins there; as a result, a new impulse starts in the next neurone
- State that synapses make sure impulses pass in one direction only
14.2Mammalian sense organs5 objectives
- outline how sense organs are collections of receptor cells that react to particular stimuli: light, sound, touch, temperature and chemicals
- Identify, on a diagram, these parts of the eye, limited to: cornea, pupil, iris, lens, suspensory ligaments, ciliary muscles, retina, fovea, blind spot and optic nerve
- outline what each part of the eye does, limited to: cornea – refracts light; iris – regulates the amount of light passing into the pupil; lens – brings light to a focus on the retina; ciliary muscles and suspensory ligaments – alter the lens's shape; retina – holds light receptors, some responsive to different colours of light; fovea – has the highest concentration of light receptors; optic nerve – transmits impulses to the brain
- Explain how the pupil reflex responds to light intensity through the antagonistic action of the iris's radial and circular muscles
- Account for accommodation, which lets the eye see nearby and distant objects, by reference to contraction and relaxation of ciliary muscles, tension in suspensory ligaments, lens shape and light refraction
14.3Mammalian hormones4 objectives
- Describe a hormone as a chemical substance that is made by a gland and transported in the blood, and that alters the activity of a specific target organ or of several
- Identify, on a diagram, the hormone-producing endocrine glands, and state which hormone or hormones each gland releases, limited to: adrenaline from the adrenal glands; insulin and glucagon from the pancreas; follicle-stimulating hormone (FSH) and luteinising hormone (LH) from the pituitary gland; testosterone from the testes; oestrogen and progesterone from the ovaries
- Understand the role that adrenaline, a hormone made by the adrenal glands, plays in boosting the concentration of glucose in the blood and in speeding up heart rate, and give instances of circumstances in which these might arise.
- Compare nervous and hormonal control, limited to how quickly each acts and how long its effect lasts.
14.4Homeostasis2 objectives
- Describe homeostasis as keeping the internal environment constant
- Explain what is meant by control through negative feedback, referring to a set point
14.5Temperature control4 objectives
- Identify the following on a diagram showing skin: sweat glands, hairs and hair erector muscles, blood vessels, receptors, sensory neurones and fatty tissue
- Describe the function of insulation in keeping mammals' internal body temperature constant
- Describe what the hypothalamus and the skin's temperature receptors each do to keep mammals' internal body temperature constant
- Explain the part each of these processes plays in keeping a mammal's internal body temperature constant: shivering; sweating; the contraction of hair erector muscles; and vasodilation and vasoconstriction in the arterioles that supply capillaries at the skin surface
14.6Blood glucose control3 objectives
- Account for why the concentration of glucose in the blood must be regulated
- Describe how the liver and pancreas keep blood glucose concentration under control, along with the parts played by insulin and glucagon
- Describe the signs that point to Type 1 diabetes (limited to a raised blood glucose concentration and glucose present in urine) and how it is treated (by giving insulin)
15.1Coordination and response in plants4 objectives
- Describe gravitropism as a plant's growth response to gravity, with parts growing either towards it or away from it
- Describe phototropism as a plant's growth response to light, with parts growing either towards it or away from it
- Explain how auxin controls the growth of shoots, limited to: auxin is produced in the shoot tip; it spreads from the tip through the rest of the plant; light and gravity cause it to be distributed unequally; it stimulates cell elongation
- Investigate how shoots and roots show phototropism and gravitropism
16.1Nuclear division10 objectives
- Understand that DNA is found in chromosomes and carries genetic information as genes
- Describe a haploid nucleus as having its chromosomes in a single set
- Describe a diploid nucleus as having its chromosomes in two sets
- State that chromosomes in a diploid cell come in pairs, one pair of each type, and that human diploid cells have 23 such pairs
- Describe mitosis as a process of nuclear division that produces genetically identical cells, keeping the chromosome number unchanged (stage-by-stage detail is not required)
- Outline how mitosis contributes to growth, to asexual reproduction, to repairing damaged tissues and to replacing cells that are dying
- Describe stem cells as cells that are not yet specialised, which divide by mitosis to give daughter cells capable of specialising for specific functions
- State that meiosis takes part in making gametes
- Describe meiosis as a reduction division that halves the chromosome number, taking cells from diploid to haploid, and produces cells that are genetically different (the stages need not be detailed)
- Understand that cancers develop due to uncontrolled cell division
16.2Asexual and sexual reproduction4 objectives
- Describe asexual reproduction as a process in which one parent gives rise to offspring that are genetically identical to that parent
- Identify cases where organisms reproduce asexually
- Describe sexual reproduction as a process in which haploid nuclei merge, through fusion (fertilisation), to create a diploid zygote, and which yields offspring that differ genetically
- Discuss, for sexual and for asexual reproduction, the advantages and disadvantages of each
16.3Sexual reproduction in plants13 objectives
- Identify and draw the parts of a flower pollinated by insects: the sepals and petals, the stamens (filaments and anthers) and the carpels (ovaries, ovules, styles and stigmas)
- Identify and draw the stigmas and anthers in a flower that is pollinated by wind
- Relate how each part of a flower is built to the function it performs, limited to the parts listed in 16.3.1
- Compare flowers pollinated by wind with flowers pollinated by insects, in their structure and in their pollen
- Outline how pollination happens, and distinguish self-pollination from cross-pollination
- Discuss how self-pollination and cross-pollination could affect a population, considering variation, the ability to respond to environmental change and how far the population relies on pollinators
- Describe how the pollen tube grows, how it gets into the ovule and how fertilisation follows (endosperm production and developmental detail are not needed)
- Appreciate that, once fertilisation has taken place, ovules turn into seeds and the ovary becomes a fruit
- Investigate the parts of a seed and describe how it is built, limited to the testa and the embryo (radicle, plumule and cotyledons)
- Appreciate that dispersing seeds and fruits by wind and by animals helps plants to colonise new areas and to cut down competition
- Relate the features of fruits dispersed by animals, and of fruits dispersed by wind, to their functions
- Investigate which environmental conditions influence seed germination and state them, limited to: water, oxygen and a suitable temperature
- Describe how germination occurs, including the part played by enzymes
16.4Sexual reproduction in humans13 objectives
- Identify the testes, scrotum, sperm ducts, prostate gland, urethra and penis on diagrams showing the male reproductive system, and outline what each one does.
- Identify the ovaries, oviducts, uterus, cervix and vagina on diagrams showing the female reproductive system, and outline the role each one plays.
- Account for the way a sperm cell's structure links to its function, limited to: flagellum, mitochondria and enzymes in the acrosome.
- Explain how an egg cell is built to suit its function, limited to the stores of energy it holds and its jelly coat, which alters once fertilisation happens
- Describe fertilisation as two nuclei fusing: one from a sperm, the male gamete, and one from an egg cell, the female gamete
- Compare the size, structure, numbers and motility of male gametes with those of female gametes
- Outline the parts played by testosterone and oestrogen in forming and controlling secondary sexual characteristics at puberty
- Outline the menstrual cycle by looking at how an egg matures and is released, and how the uterine lining alters
- Account for the parts played by follicle-stimulating hormone (FSH), luteinising hormone (LH), oestrogen and progesterone in governing the menstrual cycle
- Describe how the zygote first develops, limited to its forming a ball of cells, the embryo, which then implants in the uterus lining
- State what the amniotic sac and amniotic fluid are each for
- Identify the placenta and umbilical cord on diagrams, and describe how they allow the fetus's blood and the mother's blood to exchange gases, dissolved nutrients and excretory products (structural details are not required)
- State that certain viruses are able to cross the placenta and impact the fetus
17.1Variation5 objectives
- describe variation as the way individuals within one species differ from each other
- understand that a spread of phenotypes lying between two extremes arises from continuous variation, including body length and body mass
- Understand that discontinuous variation produces a small number of distinct phenotypes with no intermediates, including ABO blood groups and the shape and colour of pea seeds
- understand that discontinuous variation is generally brought about by genes only, whereas continuous variation is produced by genes together with the environment
- Investigate examples of both continuous and discontinuous variation and describe them
17.2DNA5 objectives
- Describe the structure of a DNA molecule: (a) it is a double helix of two strands coiled round each other (b) each strand is a chain of nucleotides (c) every nucleotide has one base (A, T, C, G; full names are not required) (d) the strands are held together by bonds between pairs of bases (e) base pairing never varies: A always with T, and C always with G
- Define a gene as the section of a DNA molecule that holds the code for making a protein
- Explain that DNA governs what a cell does because it controls which proteins the cell makes, including enzymes
- State that the sequence of bases within a gene dictates the sequence of amino acids required to build a particular protein (detailed knowledge of the make-up of nucleotides is not required)
- Understand that alternative amino acid sequences result in protein molecules taking on different shapes
17.3Inheritance12 objectives
- Describe inheritance as genetic information being passed on from each generation to the one after it
- Define an allele as one of the alternative forms that a gene can take
- Understand what dominant, recessive, phenotype, genotype, homozygous and heterozygous mean, and use these terms
- Use genetic diagrams, including Punnett squares, to predict the offspring a monohybrid cross will give and calculate the phenotypic ratio among them, limited to ratios of 1:1 and 3:1
- Account for why observed ratios frequently diverge from expected ratios, particularly when few offspring are produced
- State that a pair of homozygous organisms sharing the same genotype, when mated together, will be pure-breeding
- Account for codominance with reference to how the ABO blood groups are inherited (phenotypes A, B, AB, O, gene alleles IA, IB and Io)
- Describe how sex is determined in humans by the XX and XY chromosomes
- Describe a gene mutation as a change to the base sequence in DNA that happens at random; sickle cell anaemia is one example
- Describe a chromosome mutation as any change to the chromosome number or to the structure of a chromosome; Down's syndrome, with 47 chromosomes instead of 46, is one example
- State that genetic variation within populations arises from mutation, meiosis, random mating and random fertilisation
- Understand that ionising radiation and certain chemicals raise the rate at which mutations take place
17.4Selection5 objectives
- Describe natural selection by referring to: the variation within populations; the large number of offspring produced; the struggle for survival, including the competition for resources; individuals better adapted to their environment than others going on to reproduce; and these individuals passing their alleles on to the next generation
- Describe how natural selection can cause a population's inherited features to evolve over time
- Outline the emergence of antibiotic-resistant bacterial strains, including MRSA, as a case of natural selection
- Describe artificial selection (selective breeding) by referring to: humans choosing plants or animals that have desirable features; crossing the chosen individuals to give the next generation; picking out the offspring that show the desirable features; and repeating this over many generations
- Outline the part played by artificial selection in creating plants and animals of economic value
18.1Biotechnology5 objectives
- account for the part yeast plays in making bread and ethanol
- appreciate that bacteria prove valuable across biotechnology and genetic modification, since they multiply quickly and can manufacture intricate molecules
- Discuss the reasons bacteria are useful in genetic modification and biotechnology, limited to: they contain plasmids, and growing and manipulating them raises no ethical concerns
- Describe how bacteria and fungi in fermenters can make useful products on a large scale, including which conditions must be controlled, limited to: temperature, pH, oxygen, nutrient supply and waste products
- Describe how enzymes are used in biological washing powders, how pectinase is used to produce fruit juice and how lactase is used to make lactose-free milk
18.2Genetic modification4 objectives
- Describe genetic modification as altering an organism's genetic material through the removal, alteration or insertion of single genes
- Understand that a gene coding for the manufacture of human insulin has been placed into the DNA of bacteria, to make insulin on a commercial scale
- Outline how genetic modification is applied to crop plants by inserting genes that give resistance to herbicides, give resistance to insect pests, or supply extra vitamins
- Discuss the possible benefits and hazards of genetic modification, limited to changing crop plants and bacteria
19.1Energy flow10 objectives
- Understand that most biological systems get their energy input mainly from the Sun
- Explain why the majority of living things cannot survive without photosynthesis
- Describe how energy moves along food chains and webs, including the energy arriving as light and the energy held within living organisms, and its final passage into the environment
- Construct simple food chains and interpret them
- Know what is meant by the terms producer, consumer, herbivore, carnivore and decomposer
- Describe a food web as a network formed by food chains that are linked together, and construct and interpret food webs
- Explain why energy is transferred inefficiently between trophic levels
- Account for why food chains rarely contain more than four trophic levels
- Account for why people gain more energy efficiency by eating crop plants directly than by eating livestock raised on those crop plants
- Construct pyramids of numbers, biomass and energy, then interpret them
19.2Nutrient cycles3 objectives
- Describe how carbon moves through the carbon cycle, limited to: feeding, photosynthesis, respiration, decomposition, combustion and the formation of fossil fuels
- Outline how the nitrogen cycle makes nitrogen available to plants and animals for building protein, limited to: nitrogen fixation by bacteria and by lightning; nitrification; plants absorbing nitrate ions; amino acids and protein being made; feeding and the digestion of proteins; the decomposition of plant and animal protein into ammonium ions; and denitrification
- Outline how fungi and bacteria contribute to decomposition
19.3Ecosystems and biodiversity6 objectives
- Describe a population as the members of a single species found together in one area at one time
- Outline a community as the entire collection of populations, each made up of a different species, found within an ecosystem
- Outline an ecosystem as a single unit made up of a community of organisms together with their environment, all interacting with one another.
- Outline biodiversity as the count of distinct species living within a given area
- Identify the factors that decide how quickly a population of an organism grows, and state them, limited to: food supply, competition, predation and disease
- Understand that as the human population grows, the world's resources are in ever greater demand
19.4Effects of humans on ecosystems3 objectives
- Outline why deforestation happens and describe what it leads to, limited to its effects on: biodiversity, extinction, flooding, soil loss and atmospheric carbon dioxide concentration
- Describe the effects people cause via: (a) over-harvesting plant and animal species (b) bringing a non-native species into an ecosystem
- Describe the damage done by: (a) water pollution from untreated sewage and fertilisers containing nitrogen, which leads to eutrophication, limited to: (i) more nitrate and other ions becoming available (ii) producers growing more (iii) more decomposition once producers die (iv) more aerobic respiration by decomposers (v) less dissolved oxygen (vi) the death of organisms that need dissolved oxygen in water (b) greenhouse gases (carbon dioxide and methane) polluting the air, which adds to global warming, with the effects this is likely to have (c) pollution caused by herbicides and insecticides (d) plastics that are not biodegradable left in the environment, in aquatic and terrestrial ecosystems alike
19.5Conservation4 objectives
- Discuss the reasons for conserving species, referring to: (a) maintaining biodiversity (b) reducing extinction (c) protecting environments that are vulnerable
- Explain how replanting, quotas, protected areas and education can help conserve forests
- Explain how monitoring, quotas, closed seasons, protected areas, controlled net types and mesh size, and education can help conserve fish stocks
- Describe a sustainable resource as one that is replaced at the same rate as it is taken from the environment, which means it is not used up
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