Co-ordinated Sciences (Double Award) — Biology

Science 0973 — specification explorer

All 230 specification statements from the official Cambridge International specification, as printed.

Paper/unit applicability has not been derived for this course yet — the statements below are the parsed specification, as printed.

1. Characteristics of living organisms

B1.1.1Describe the characteristics of living organisms by defining: (a). movement as an action by an organism or part of an organism causing a change of position or place (b). respiration as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism (c). sensitivity as the ability to detect and respond to changes in the internal or external environment (d). growth as a permanent increase in size and dry mass (e). reproduction as the processes that make more of the same kind of organism (f). excretion as the removal of waste products of metabolism and substances in excess of requirements (g). nutrition as the taking in of materials for energy, growth and development

2. Cells

1. Cell structure

B2.1.1Describe and compare the structure of a plant cell with an animal cell, limited to: cell wall, cell membrane, nucleus, cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles
B2.1.2Describe the structure of a bacterial cell, limited to: cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids
B2.1.3Identify the cell structures listed in 2.1.1 and 2.1.2 in diagrams and images of plant, animal and bacterial cells
B2.1.4Describe the functions of the structures listed in 2.1.1 and 2.1.2 in plant, animal and bacterial cells
B2.1.5State that new cells are produced by division of existing cells
B2.1.6State that specialised cells have specific functions, limited to: (a). ciliated cells – movement of mucus in the trachea and bronchi (b). root hair cells – absorption (c). palisade mesophyll cells – photosynthesis (d). neurones – conduction of electrical impulses (e). red blood cells – transport of oxygen (f). sperm and egg cells (gametes) – reproduction
B2.1.7Describe the meaning of the terms: cell, tissue, organ, organ system and organism as illustrated by examples given in the syllabus

2. Size of specimens

B2.2.1State and use the formula: image size magnification = actual size
B2.2.2Calculate magnification and size of biological specimens using millimetres as units
B2.2.3Convert measurements between millimetres (mm) and micrometres ( µ m)

3. Movement into and out of cells

1. Diffusion

B3.1.1Describe diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement
B3.1.2State that some substances move into and out of cells by diffusion through the cell membrane
B3.1.3Describe the importance of diffusion of gases and solutes in living organisms
B3.1.4Investigate the factors that influence diffusion, limited to: surface area, temperature, concentration gradient and distance

2. Osmosis

B3.2.1State that water diffuses through partially permeable membranes by osmosis
B3.2.2State that water moves into and out of cells by osmosis through the cell membrane
B3.2.3Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations
B3.2.4Describe 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
B3.2.5Explain the effects on plant cells of immersing them in solutions of different concentrations by using the terms: turgid, turgor pressure, plasmolysis, flaccid
B3.2.6Explain the importance of water potential and osmosis in the uptake and loss of water by organisms

3. Active transport

B3.3.1Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration
B3.3.2Explain the importance of active transport as a process for movement of molecules or ions across membranes, including ion uptake by root hairs

4. Biological molecules

1. Biological molecules

B4.1.1List the chemical elements that make up: carbohydrates, fats and proteins
B4.1.2State that large molecules are made from smaller molecules, limited to: (a). starch, glycogen and cellulose from glucose (b). proteins from amino acids (c). fats and oils from fatty acids and glycerol
B4.1.3Describe the use of: (a). iodine solution test for starch (b). Benedict’s solution test for reducing sugars (c). biuret test for proteins (d). ethanol emulsion test for fats and oils

5. Enzymes

1. Enzymes

B5.1.1Describe enzymes as proteins that are involved in all metabolic reactions, where they function as biological catalysts
B5.1.2Investigate and describe the effect of changes in temperature and pH on enzyme activity
B5.1.3Describe and explain enzyme action with reference to: the active site, enzyme–substrate complex, substrate and product
B5.1.4Describe and explain the specificity of enzymes in terms of the complementary shape and fit of the active site with the substrate
B5.1.5Explain the effect of changes in temperature on enzyme activity in terms of kinetic energy, shape and fit, frequency of effective collisions and denaturation
B5.1.6Explain the effect of changes in pH on enzyme activity in terms of shape and fit and denaturation

6. Plant nutrition

1. Photosynthesis

B6.1.1Describe photosynthesis as the process by which plants synthesise carbohydrates from raw materials using energy from light
B6.1.2State the word equation for photosynthesis as: carbon dioxide + water → glucose + oxygen in the presence of light and chlorophyll
B6.1.3State that chlorophyll is a green pigment that is found in chloroplasts
B6.1.4Investigate and understand the need for chlorophyll, light and carbon dioxide for photosynthesis
B6.1.5State the balanced symbol equation for photosynthesis as: 6CO + 6H O → C H O + 6O
B6.1.6State that chlorophyll transfers energy from light into energy in chemicals, for the synthesis of carbohydrates
B6.1.7Outline the subsequent use and storage of the carbohydrates made in photosynthesis: (a). starch as an energy store (b). cellulose to build cell walls (c). glucose used in respiration to provide energy (d). sucrose for transport in the phloem (e). nectar to attract insects for pollination
B6.1.8Explain the importance of: (a). nitrate ions for making amino acids (b). magnesium ions for making chlorophyll
B6.1.9Understand and describe the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis
B6.1.10Understand and describe the effect of light and dark conditions on gas exchange in an aquatic plant using hydrogencarbonate indicator solution

2. Leaf structure

B6.2.1State that most leaves have a large surface area and are thin, and explain how these features are adaptations for photosynthesis
B6.2.2Identify in diagrams and images the following 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
B6.2.3Explain how the structures listed in 6.2.2 adapt leaves for photosynthesis

7. Human nutrition

1. Diet

B7.1.1Describe what is meant by a balanced diet
B7.1.2State the principal dietary sources and describe the importance of: (a). carbohydrates (b). fats and oils (c). proteins (d). vitamins, limited to C and D (e). mineral ions, limited to calcium and iron (f). fibre (roughage) (g). water
B7.1.3State the causes of scurvy and rickets

2. Digestive system

B7.2.1Identify in diagrams and images the main organs of the digestive system, limited to: (a). alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum and anus) (b). associated organs: salivary glands, pancreas, liver and gall bladder
B7.2.2Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to: (a). ingestion – the taking of substances, e.g. food and drink, into the body (b). digestion – the breakdown of food (c). absorption – the movement of nutrients from the intestines into the blood (d). assimilation – uptake and use of nutrients by cells (e). egestion – the removal of undigested food from the body as faeces

3. Digestion

B7.3.1Describe physical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules
B7.3.2State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion
B7.3.3Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules
B7.3.4State the role of chemical digestion in producing small soluble molecules that can be absorbed
B7.3.5Describe the functions of enzymes as follows: (a). amylase breaks down starch to simple reducing sugars (b). proteases break down protein to amino acids (c). lipase breaks down fats and oils to fatty acids and glycerol
B7.3.6State where, in the digestive system, amylase, protease and lipase are secreted and where they act
B7.3.7Describe the functions of hydrochloric acid in gastric juice, limited to killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity of proteases in the stomach
B7.3.8Explain that bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action in the small intestine
B7.3.9Outline the role of bile in emulsifying fats and oils to increase the surface area for chemical digestion

8. Transport in plants

1. Xylem and phloem

B8.1.1State the functions of xylem and phloem: (a). xylem – transport of water and mineral ions, and support (b). phloem – transport of sucrose and amino acids
B8.1.2Identify in diagrams and images the position of xylem and phloem as seen in sections of roots, stems and leaves of non-woody dicotyledonous plants

2. Water uptake

B8.2.1Identify in diagrams and images root hair cells and state their functions
B8.2.2State that the large surface area of root hairs increases the uptake of water and mineral ions
B8.2.3Outline the pathway taken by water through root, stem and leaf as: root hair cells, root cortex cells, xylem, mesophyll cells

3. Transpiration

B8.3.1Describe transpiration as the loss of water vapour from leaves
B8.3.2State that water evaporates from the surfaces of the mesophyll cells into the air spaces and then diffuses out of the leaves through the stomata as water vapour
B8.3.3Investigate and describe the effects of variation of temperature and wind speed on transpiration rate
B8.3.4Explain the effects on the rate of transpiration of varying the following: temperature, wind speed and humidity
B8.3.5Explain how and why wilting occurs

4. Translocation

B8.4.1Describe translocation as the movement of sucrose and amino acids in phloem from sources to sinks
B8.4.2Describe: (a). sources as the parts of plants that release sucrose or amino acids (b). sinks as the parts of plants that use or store sucrose or amino acids

9. Transport in animals

1. Circulatory systems

B9.1.1Describe the circulatory system as a system of blood vessels with a pump and valves to ensure one-way flow of blood
B9.1.2Describe the single circulation of a fish
B9.1.3Describe the double circulation of a mammal
B9.1.4Explain the advantages of a double circulation

2. Heart

B9.2.1Identify in diagrams and images the structures of the mammalian heart, limited to: muscular wall, septum, left and right ventricles, left and right atria, one-way valves and coronary arteries
B9.2.2State that blood is pumped away from the heart in arteries and returns to the heart in veins
B9.2.3State that the activity of the heart may be monitored by: ECG (electrocardiogram), pulse rate and listening to sounds of valves closing
B9.2.4Investigate and describe the effect of physical activity on the heart rate
B9.2.5Describe coronary heart disease in terms of the blockage of coronary arteries and state the possible risk factors including: diet, lack of exercise, stress, smoking, genetic predisposition, age and sex Discuss the roles of diet and exercise in reducing the risk of coronary heart disease
B9.2.7Describe the functioning of the heart in terms of the contraction of muscles of the atria and ventricles and the action of the valves
B9.2.8Explain the effect of physical activity on the heart rate

3. Blood vessels

B9.3.1Describe the structure of arteries, veins and capillaries, limited to: relative thickness of wall, diameter of the lumen and the presence of valves in veins
B9.3.2State the functions of capillaries
B9.3.3Explain how the structure of arteries and veins is related to the pressure of the blood that they transport
B9.3.4Explain how the structure of capillaries is related to their functions
B9.3.5Identify in diagrams and images the main blood vessels to and from the: (a). heart, limited to: vena cava, aorta, pulmonary artery and pulmonary vein (b). lungs, limited to: pulmonary artery and pulmonary vein

4. Blood

B9.4.1List the components of blood as: red blood cells, white blood cells, platelets and plasma
B9.4.2Identify red and white blood cells in photomicrographs and diagrams
B9.4.3State the functions of the following components of blood: (a). red blood cells in transporting oxygen, including the role of haemoglobin (b). white blood cells in phagocytosis and antibody production (c). platelets in clotting (details are not required) (d). plasma in the transport of blood cells, ions, nutrients, urea, hormones and carbon dioxide
B9.4.4Identify lymphocytes and phagocytes in photomicrographs and diagrams
B9.4.5State the functions of: (a). lymphocytes – antibody production (b). phagocytes – engulfing pathogens by phagocytosis
B9.4.6State the roles of blood clotting as preventing blood loss and the entry of pathogens

10. Diseases and immunity

1. Diseases and immunity

B10.1.1Describe a pathogen as a disease-causing organism
B10.1.2Describe a transmissible disease as a disease in which the pathogen can be passed from one host to another
B10.1.3State that a pathogen is transmitted: (a). by direct contact, including through blood and other body fluids (b). indirectly, including from contaminated surfaces, food, animals and air
B10.1.4Describe the body defences against pathogens, limited to: skin, hairs in the nose, mucus, stomach acid and white blood cells
B10.1.5Explain the importance of the following in controlling the spread of disease: (a). a clean water supply (b). hygienic food preparation (c). good personal hygiene (d). waste disposal (e). sewage treatment (details of the stages of sewage treatment are not required)
B10.1.6State that vaccinations are available for some pathogens to help control the spread of diseases
B10.1.7State the features of viruses, limited to a protein coat and genetic material
B10.1.8Describe active immunity as defence against a pathogen by antibody production in the body
B10.1.9State that each pathogen has its own antigens, which have specific shapes
B10.1.10Describe antibodies as proteins that bind to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes
B10.1.11State that specific antibodies have complementary shapes which fit specific antigens
B10.1.12Explain that active immunity is gained after an infection by a pathogen or by vaccination
B10.1.13Outline the process of vaccination: (a). weakened pathogens or their antigens are put into the body (b). the antigens stimulate an immune response by lymphocytes which produce antibodies (c). memory cells are produced that give long-term immunity
B10.1.14Explain the role of vaccination in controlling the spread of diseases

11. Gas exchange in humans

1. Gas exchange in humans

B11.1.1Identify in diagrams and images the following parts of the breathing system: lungs, diaphragm, ribs, intercostal muscles, larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries
B11.1.2Investigate the differences in composition between inspired and expired air using limewater as a test for carbon dioxide
B11.1.3Describe the differences in composition between inspired and expired air, limited to: oxygen, carbon dioxide and water vapour
B11.1.4Investigate and describe the effects of physical activity on the rate and depth of breathing
B11.1.5Describe the features of gas exchange surfaces in humans, limited to: large surface area, thin surface, good blood supply and good ventilation with air
B11.1.6Explain the differences in composition between inspired and expired air
B11.1.7Explain the link between physical activity and the rate and depth of breathing in terms of: an increased carbon dioxide concentration in the blood, which is detected by the brain, leading to an increased rate and greater depth of breathing

12. Respiration

1. Respiration

B12.1.1State the uses of energy in living organisms, including: muscle contraction, protein synthesis, cell division, growth, the passage of nerve impulses and the maintenance of a constant body temperature
B12.1.2Describe aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
B12.1.3State the word equation for aerobic respiration as: glucose + oxygen → carbon dioxide + water
B12.1.4State the balanced symbol equation for aerobic respiration as: C H O + 6O → 6CO + 6H O
B12.1.5Describe anaerobic respiration as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
B12.1.6State that anaerobic respiration releases much less energy per glucose molecule than aerobic respiration
B12.1.7State the word equation for anaerobic respiration in muscles during vigorous exercise as: glucose → lactic acid
B12.1.8State that lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt
B12.1.9Outline how the oxygen debt is removed after exercise, limited to: (a). continuation of fast heart rate to transport lactic acid in the blood from the muscles to the liver (b). continuation of deeper and faster breathing to supply oxygen for aerobic respiration of lactic acid (c). aerobic respiration of lactic acid in the liver

13. Coordination and response

1. Coordination and response

B13.1.1State that electrical impulses travel along neurones
B13.1.2Describe the mammalian nervous system in terms of: (a). the central nervous system (CNS) consisting of the brain and spinal cord (b). the peripheral nervous system (PNS) consisting of the nerves outside of the brain and spinal cord
B13.1.3Describe the role of the nervous system as coordination and regulation of body functions
B13.1.4Identify in diagrams and images sensory, relay and motor neurones
B13.1.5Describe a simple reflex arc in terms of: receptor, sensory neurone, relay neurone, motor neurone and effector
B13.1.6Describe a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
B13.1.7Describe sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

2. Hormones

B13.2.1Describe a hormone as a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
B13.2.2Identify in diagrams and images specific endocrine glands and state the hormones they secrete, limited to: (a). adrenal glands and adrenaline (b). pancreas and insulin (c). testes and testosterone (d). ovaries and oestrogen
B13.2.3Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects, limited to: (a). increased breathing rate (b). increased heart rate (c). increased pupil diameter
B13.2.4State that glucagon is secreted by the pancreas

3. Homeostasis

B13.3.1Describe homeostasis as the maintenance of a constant internal environment
B13.3.2Explain the concept of homeostatic control by negative feedback with reference to a set point
B13.3.3Describe the control of blood glucose concentration by the liver and the roles of insulin and glucagon
B13.3.4Identify in diagrams and images of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue
B13.3.5Describe the maintenance of a constant internal body temperature in mammals in terms of: (a). insulation, sweating, shivering, the role of the brain (b). vasodilation and vasoconstriction of arterioles supplying skin surface capillaries

14. Drugs

1. Drugs

B14.1.1Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body
B14.1.2Describe the use of antibiotics for the treatment of bacterial infections
B14.1.3State that some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics
B14.1.4State that antibiotics kill bacteria but do not affect viruses
B14.1.5Explain how using antibiotics only when essential can limit the development of resistant bacteria such as MRSA

15. Reproduction

1. Asexual reproduction

B15.1.1Describe asexual reproduction as a process resulting in the production of genetically identical offspring from one parent
B15.1.2Identify examples of asexual reproduction in diagrams, images and information provided
B15.1.3Discuss the advantages and disadvantages of asexual reproduction to a population of a species in the wild

2. Sexual reproduction

B15.2.1Describe 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
B15.2.2Describe a species as a group of organisms that can reproduce to produce fertile offspring
B15.2.3State that nuclei of gametes are haploid and that the nucleus of a zygote is diploid
B15.2.4Discuss the advantages and disadvantages of sexual reproduction to a population of a species in the wild

3. Sexual reproduction in plants

B15.3.1Identify in diagrams and images and draw the following parts of an insect-pollinated flower: sepals, petals, stamens, filaments, anthers, carpels, style, stigma, ovary and ovules
B15.3.2State the functions of the structures listed in
B15.3.3Describe pollination as the transfer of pollen grains from an anther to a stigma
B15.3.4State that fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule
B15.3.5Describe the structural adaptations of insect- pollinated and wind-pollinated flowers
B15.3.6Investigate and describe the environmental conditions that affect germination of seeds, limited to the requirement for: water, oxygen and a suitable temperature
B15.3.7Identify in diagrams and images and describe the anthers and stigmas of a wind-pollinated flower

4. Sexual reproduction in humans

B15.4.1Identify on diagrams and state the functions of the following parts of the male reproductive system: testes, scrotum, sperm ducts, prostate gland, urethra and penis
B15.4.2Identify on diagrams and state the functions of the following parts of the female reproductive system: ovaries, oviducts, uterus, cervix and vagina
B15.4.3Describe fertilisation as the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell)
B15.4.4Describe the roles of testosterone and oestrogen in the development and regulation of secondary sexual characteristics during puberty
B15.4.5Describe the menstrual cycle in terms of changes in the ovaries and in the lining of the uterus (knowledge of sex hormones is not required)
B15.4.6Explain the adaptive features of sperm, limited to: flagellum, mitochondria and the presence of enzymes in the acrosome
B15.4.7Explain the adaptive features of egg cells, limited to: energy stores and the jelly coat that changes at fertilisation
B15.4.8Compare male and female gametes in terms of: size, structure, motility and numbers

5. Sexually transmitted infections

B15.5.1Describe a sexually transmitted infection (STI) as an infection that is transmitted through sexual contact
B15.5.2State that human immunodeficiency virus (HIV) is a pathogen that causes an STI
B15.5.3State that HIV infection may lead to AIDS
B15.5.4Describe the methods of transmission of HIV
B15.5.5Explain how the spread of STIs is controlled

16. Inheritance

1. Chromosomes and genes

B16.1.1State that chromosomes are made of DNA, which contains genetic information in the form of genes
B16.1.2Define a gene as a length of DNA that codes for a protein
B16.1.3Define an allele as an alternative form of a gene
B16.1.4Describe the inheritance of sex in humans with reference to XX and XY chromosomes
B16.1.5Describe a haploid nucleus as a nucleus containing a single set of chromosomes
B16.1.6Describe a diploid nucleus as a nucleus containing two sets of chromosomes
B16.1.7State that in a diploid cell, there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs

2. Cell division

B16.2.1Describe mitosis as nuclear division giving rise to genetically identical cells (details of the stages of mitosis are not required)
B16.2.2State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction
B16.2.3State that the exact replication of chromosomes occurs before mitosis
B16.2.4State that during mitosis, the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
B16.2.5State that meiosis is involved in the production of gametes
B16.2.6Describe meiosis as reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (details of the stages of meiosis are not required)

3. Monohybrid inheritance

B16.3.1Describe inheritance as the transmission of genetic information from generation to generation
B16.3.2Describe genotype as the genetic make-up of an organism and in terms of the alleles present
B16.3.3Describe phenotype as the observable features of an organism
B16.3.4Describe homozygous as having two identical alleles of a particular gene
B16.3.5State that two identical homozygous individuals that breed together will be pure- breeding
B16.3.6Describe heterozygous as having two different alleles of a particular gene
B16.3.7State that a heterozygous individual will not be pure-breeding
B16.3.8Describe a dominant allele as an allele that is expressed if it is present in the genotype
B16.3.9Describe a recessive allele as an allele that is only expressed when there is no dominant allele of the gene present in the genotype
B16.3.10Interpret pedigree diagrams for the inheritance of a given characteristic
B16.3.11Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1 : 1 and 3 : 1 ratios
B16.3.12Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

17. Variation and selection

1. Variation

B17.1.1Describe variation as differences between individuals of the same species
B17.1.2State that continuous variation results in a range of phenotypes between two extremes; examples include body length
B17.1.3State that discontinuous variation results in a limited number of phenotypes with no intermediates; examples include ABO blood groups
B17.1.4Describe mutation as a genetic change
B17.1.5State that mutation is the way in which new alleles are formed

2. Selection

B17.2.1Describe natural selection with reference to: (a). genetic variation within populations (b). production of many offspring (c). struggle for survival, including competition for resources (d). a greater chance of reproduction by individuals that are better adapted to the environment than others (e). these individuals passing on their alleles to the next generation
B17.2.2Describe selective breeding with reference to: (a). selection by humans of individuals with desirable features (b). crossing these individuals to produce the next generation (c). selection of offspring showing the desirable features
B17.2.3Outline 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
B17.2.4Describe the development of strains of antibiotic-resistant bacteria as an example of natural selection

18. Organisms and their environment

1. Energy flow

B18.1.1State that the Sun is the principal source of energy input to biological systems
B18.1.2Describe 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

2. Food chains and food webs

B18.2.1Describe a food chain as showing the transfer of energy from one organism to the next, beginning with a producer
B18.2.2Construct and interpret simple food chains
B18.2.3Describe a food web as a network of interconnected food chains and interpret food webs
B18.2.4Describe a producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
B18.2.5Describe a consumer as an organism that gets its energy by feeding on other organisms
B18.2.6State that consumers may be classed as primary, secondary and tertiary according to their position in a food chain
B18.2.7Describe a herbivore as an animal that gets its energy by eating plants
B18.2.8Describe a carnivore as an animal that gets its energy by eating other animals
B18.2.9Describe a decomposer as an organism that gets its energy from dead or waste organic material
B18.2.10Use food chains and food webs to describe the impact humans have through overharvesting of food species and through introducing foreign species to a habitat
B18.2.11Describe a trophic level as the position of an organism in a food chain and food web
B18.2.12Identify the following as the trophic levels in food webs and food chains: producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers
B18.2.13Explain why the transfer of energy from one trophic level to another is often not efficient
B18.2.14Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels
B18.2.15Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants

3. Carbon cycle

B18.3.1Describe the carbon cycle, limited to: photosynthesis, respiration, feeding, decomposition, formation of fossil fuels and combustion

19. Human influences on ecosystems

1. Habitat destruction

B19.1.1Describe an ecosystem as a unit containing the community of organisms and their environment, interacting together
B19.1.2Describe biodiversity as the number of different species that live in an area
B19.1.3Describe the reasons for habitat destruction, including: (a). increased area for housing, crop plant production and livestock production (b). extraction of natural resources (c). freshwater and marine pollution (a detailed description of eutrophication is not required)
B19.1.4State the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere
B19.1.5Explain the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere

2. Conservation

B19.2.1Explain why organisms become endangered or extinct, including: climate change, habitat destruction, hunting, overharvesting, pollution and introduced species
B19.2.2Describe how endangered species can be conserved, limited to: (a). monitoring and protecting species and habitats (b). education (c). captive breeding programmes (d). seed banks Chemistry