Scheda di revisione: Biology Coordination and Inheritance

📋 Course Outline

1. Cells and Cell Organisation
2. Classification of Organisms
3. Movement Across Cell Membranes
4. Biological Molecules and Enzymes
5. Photosynthesis and Leaf Adaptations
6. Transport in Plants
7. Human Nutrition and Gas Exchange
8. Mammalian Coordination and Homeostasis
9. Plant Responses and Tropisms
10. Cell Division and Reproduction
11. Human and Plant Sexual Reproduction
12. Inheritance and Natural Selection
13. Biotechnology and Genetic Modification
14. Ecology and Practical Assessment
15. Entries and Exam Administration
16. Language and Accessibility Arrangements
17. Grades and Assessment Outcomes
18. Syllabus Changes and Accessibility

📅 Key Dates

1. December 2024Version 2 made a minor typographical change to the metric units on page 38 and clarified that Paper 02 lasts 1 hour 45 minutes
2. January 2025Version 3 amended the list of command words on page 41
3. December 2025Version 4 of the syllabus was published and contains no significant changes affecting teaching

📖 1. Cells and Cell Organisation

🔑 Key Concepts & Definitions

• Bacterial cell : Contains ribosomes, circular DNA, plasmids, cytoplasm, a cell membrane and a cell wall.
• Specialised cell : A cell whose structure is related to its specific function.

★ Must-know

📌 Animal cells contain ribosomes, mitochondria, a nucleus, cytoplasm and a cell membrane, whereas plant cells also contain chloroplasts, a sap vacuole and a cellulose cell wall.

📐 Formula — Magnification is calculated as $\text{magnification} = \frac{\text{image size}}{\text{actual size}}$.

Further detail

• Animal and plant cells can be examined under a microscope using a temporary stain such as methylene blue or iodine solution, and observations can be represented with labelled diagrams.

📌 A cell is the basic unit, a tissue is a group of similar cells, an organ is a group of tissues, an organ system is a group of organs, and an organism is an individual living thing.

📖 2. Classification of Organisms

🔑 Key Concepts & Definitions

• Species : A group of organisms that can reproduce to produce fertile offspring.
• Binomial system : An internationally agreed naming system in which an organism’s scientific name has two parts showing its genus and species.
• Virus : Consists of a protein coat and genetic material and can replicate only inside living cells.

★ Must-know

• A dichotomous key identifies organisms by directing the user through successive choices based on identifiable features.

• The five kingdoms are:

  • Animal
  • Plant
  • Fungus
  • Prokaryote
  • Protoctist

Further detail

• The specified animal groups are:
  • mammals
  • birds
  • reptiles
  • amphibians
  • fish
  • myriapods
  • insects
  • arachnids
  • crustaceans

📖 3. Movement Across Cell Membranes

🔑 Key Concepts & Definitions

• Diffusion : The net movement of molecules or ions from a region of higher concentration to a region of lower concentration as a result of random movement.
• Osmosis : The net movement of water molecules from higher water potential to lower water potential through a partially permeable membrane.
• Active transport : Moves molecules or ions through a cell membrane from lower concentration to higher concentration using energy released during respiration.

★ Must-know

• Osmosis can make plant tissues turgid, flaccid or plasmolysed when they are immersed in solutions of different concentrations.

Further detail

• Factors influencing diffusion include:
  • surface area
  • temperature
  • concentration gradient
  • distance

💡 Memory Hook

Diffusion and osmosis move down a gradient, whereas active transport moves against it.

📖 4. Biological Molecules and Enzymes

🔑 Key Concepts & Definitions

• Enzyme : A protein that functions as a biological catalyst and is involved in metabolic reactions.

★ Must-know

• Carbohydrates contain carbon, hydrogen and oxygen; lipids contain carbon, hydrogen and oxygen; proteins contain carbon, hydrogen, oxygen and nitrogen; and DNA contains carbon, hydrogen, oxygen, nitrogen and phosphorus.

• Large molecules are formed from:

  • glucose into starch, cellulose and glycogen
  • amino acids into proteins
  • fatty acids and glycerol into lipids
  • nucleotides into DNA

• The required food tests are:

  • iodine solution for starch
  • Benedict’s solution for glucose and maltose
  • biuret test for protein
  • ethanol emulsion test for lipids

• During enzyme action, a substrate fits the active site to form an enzyme-substrate complex, after which products are formed and released.

Further detail

📌 Enzyme specificity results from the complementary shape and fit between a substrate and an enzyme’s active site, as described by the lock-and-key hypothesis.

📖 5. Photosynthesis and Leaf Adaptations

🔑 Key Concepts & Definitions

• Photosynthesis : The process by which plants make carbohydrates from raw materials using energy from light.

★ Must-know

• Chlorophyll is a green pigment in chloroplasts that transfers light energy into chemical energy for forming glucose and other carbohydrates.

📐 Formula — The balanced chemical equation for photosynthesis is $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$ in the presence of light and chlorophyll.

• The rate of photosynthesis is affected by light intensity, carbon dioxide concentration and temperature, with the limiting factor being the environmental factor in shortest supply.

Further detail

• Carbohydrates made in photosynthesis are used as:

  • starch for energy storage
  • cellulose for cell walls
  • glucose for respiration
  • sucrose for transport through the plant

• Nitrate ions are needed to make amino acids for protein production, and magnesium ions are needed to make chlorophyll.

💡 Memory Hook

Light energy captured by chlorophyll causes glucose formation, which supports storage, respiration, transport and cell-wall construction.

📖 6. Transport in Plants

🔑 Key Concepts & Definitions

• Transpiration : The loss of water vapour from leaves.
• Translocation : The movement of sucrose and amino acids in phloem from sources that produce or release them to sinks that use or store them.

📝 Essential Points

• Water follows this pathway:

  • root hair cells
  • root cortex cells
  • xylem
  • mesophyll cells

• Water evaporates from mesophyll-cell surfaces into air spaces and then diffuses out of the leaf through stomata as water vapour.

• Water moves upwards in xylem through transpiration pull, which draws up a continuous column of water held together by attraction between water molecules.

• Xylem vessels transport water and mineral ions and provide support; their vessels have thick lignified walls, no cell contents, and cells joined end-to-end without cross walls.

💡 Memory Hook

Root hair cells → cortex → xylem → mesophyll.

📖 7. Human Nutrition and Gas Exchange

🔑 Key Concepts & Definitions

• Balanced diet : Supplies the principal dietary components in appropriate amounts for health.
• Alveolar exchange surface : Has a large area, a thin surface, and a good blood and air supply for gas exchange.

★ Must-know

📌 Physical digestion breaks food into smaller pieces without chemical change, whereas chemical digestion breaks large molecules into small molecules.

• The main digestive regions are:

  • mouth
  • salivary glands
  • oesophagus
  • stomach
  • small intestine
  • pancreas
  • liver
  • gall bladder
  • large intestine
  • rectum and anus

• The main digestive enzymes act as follows: amylase breaks down starch to maltose, maltase breaks down maltose to glucose, protease breaks down protein to amino acids, lipase breaks down lipids to fatty acids and glycerol

• The ribs, intercostal muscles and diaphragm produce changes in thoracic volume and pressure that move air into and out of the lungs.

Further detail

• Vitamin C deficiency causes scurvy, vitamin D or calcium deficiency causes rickets, and iron deficiency causes anaemia.

📖 8. Mammalian Coordination and Homeostasis

🔑 Key Concepts & Definitions

• Nervous system : consisting of the brain, spinal cord and nerves, coordinates and regulates body functions
• Synapse : a junction between two neurones containing vesicles with neurotransmitter molecules, a synaptic gap and receptor proteins
• Hormone : a chemical substance produced by a gland and carried by the blood that alters the activity of one or more specific target organs
• Homeostasis : the maintenance of a constant internal environment through control by negative feedback around a set point

📝 Essential Points

📌 The central nervous system consists of the brain and spinal cord, whereas the peripheral nervous system consists of nerves outside the brain and spinal cord.

• 🔄 A simple reflex arc follows this sequence:

  1. receptor
  2. sensory neurone
  3. relay neurone
  4. motor neurone
  5. effector

• 🔄 Events at a synapse occur in this order: an impulse stimulates neurotransmitter release from vesicles, neurotransmitters diffuse across the synaptic gap, neurotransmitters bind to receptor proteins, an impulse is stimulated in the next neurone

📌 Nervous control acts rapidly and has a short-lived effect, whereas hormonal control acts more slowly and has a longer-lasting effect.

💡 Memory Hook

Nervous control is fast and short-lived, whereas hormonal control is slower and longer-lasting.

📖 9. Plant Responses and Tropisms

📝 Essential Points

📌 Gravitropism is a plant growth response towards or away from gravity, whereas phototropism is a plant growth response towards or away from light.

• 🔄 Auxin controls shoot growth through this sequence: auxin is made in the shoot tip, auxin spreads through the plant, auxin becomes unequally distributed in response to light and gravity, auxin stimulates cell elongation

💡 Memory Hook

Unequal auxin distribution → unequal cell elongation → phototropic or gravitropic growth.

📖 10. Cell Division and Reproduction

🔑 Key Concepts & Definitions

• Mitosis : nuclear division that produces genetically identical cells while maintaining the chromosome number
• Meiosis : a reduction division involved in producing gametes, halving the chromosome number from diploid to haploid and producing genetically different cells

★ Must-know

• Mitosis is involved in:
  • growth
  • repair of damaged tissues
  • replacement of dying cells
  • asexual reproduction

📌 A haploid nucleus contains one set of chromosomes, whereas a diploid nucleus contains two sets; human diploid cells contain 23 pairs of chromosomes.

Further detail

• Stem cells are unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions.

• Cancers form as a result of uncontrolled cell division.

💡 Memory Hook

Mitosis maintains chromosome number and produces identical cells, whereas meiosis halves chromosome number and produces different cells.

📖 11. Human and Plant Sexual Reproduction

★ Must-know

📌 Asexual reproduction produces genetically identical offspring from one parent, whereas sexual reproduction involves fusion of haploid nuclei to form a diploid zygote and produces genetically different offspring.

• In flowering plants, pollination is followed by pollen tube growth into the ovule, fertilisation, and development of ovules into seeds and the ovary into a fruit.

• Seed germination requires:

  • suitable temperature
  • water
  • oxygen

📌 The sperm cell has a flagellum, mitochondria and enzymes in the acrosome related to fertilisation, whereas the egg cell has energy stores and a jelly coat that changes at fertilisation.

• During the menstrual cycle, an egg develops and is released while the lining of the uterus changes under the roles of FSH, LH, oestrogen and progesterone.

• The placenta and umbilical cord exchange dissolved nutrients, gases and excretory products between the blood of the mother and the blood of the fetus.

Further detail

📌 Insect-pollinated and wind-pollinated flowers differ in flower structure and pollen features, and these features are related to their methods of pollen transfer.

• Seed and fruit dispersal by wind and animals helps plants colonise new areas and reduces competition.

💡 Memory Hook

Pollination → pollen tube growth → fertilisation → seed and fruit formation.

📖 12. Inheritance and Natural Selection

🔑 Key Concepts & Definitions

• Variation : differences between individuals of the same species
• Gene : a length of DNA that codes for a protein

★ Must-know

📌 Continuous variation produces a range of phenotypes between two extremes, whereas discontinuous variation produces a limited number of phenotypes with no intermediates.

• Discontinuous variation is usually caused by genes only, whereas continuous variation is caused by genes and the environment.

• DNA consists of two coiled strands forming a double helix; each strand contains nucleotides, whose bases pair consistently as A with T and C with G.

• The sequence of bases in a gene determines the sequence of amino acids in a protein, and different amino-acid sequences give proteins different shapes.

• Natural selection occurs when variation, production of many offspring and competition for resources result in better-adapted individuals reproducing and passing their alleles to the next generation.

Further detail

• 🔄 Artificial selection involves: selection of organisms with desirable features, crossing selected organisms, selection of offspring with desirable features, repetition over many generations

💡 Memory Hook

Continuous variation has intermediates, whereas discontinuous variation has distinct phenotypes.

📖 13. Biotechnology and Genetic Modification

🔑 Key Concepts & Definitions

• Genetic modification : changing an organism’s genetic material by removing, changing or inserting individual genes

★ Must-know

• The gene controlling human insulin production has been inserted into bacterial DNA for commercial insulin production.

• Bacteria are useful because they: reproduce rapidly, make complex molecules, have plasmids, present no ethical concerns over their manipulation and growth

• Fermenters control:

  • temperature
  • pH
  • oxygen
  • nutrient supply
  • waste products

Further detail

• Genetic modification in crop plants can insert genes for herbicide resistance, insect-pest resistance or additional vitamins.

💡 Memory Hook

Identify a useful gene → insert it into DNA → reproduce modified cells → produce the desired product.

📖 14. Ecology and Practical Assessment

🔑 Key Concepts & Definitions

• Ecosystem : a unit containing the community of organisms and their environment interacting together
• Sustainable resource : produced as rapidly as it is removed from the environment, so that it does not run out

★ Must-know

• Energy enters most biological systems from the Sun, passes through food chains and webs, and is eventually transferred to the environment; transfer between trophic levels is inefficient.

• Eutrophication follows increased nitrate availability, increased producer growth, increased decomposition, increased aerobic respiration by decomposers, reduced dissolved oxygen and death of organisms requiring dissolved oxygen.

• Deforestation can cause: reduced biodiversity, increased extinction, loss of soil, increased flooding, increased atmospheric carbon dioxide concentration

📌 In an experiment, the independent variable is changed by the scientist, whereas the dependent variable is observed or measured in response.

Further detail

• The carbon cycle includes:
  • photosynthesis
  • respiration
  • feeding
  • decomposition
  • formation of fossil fuels
  • combustion

📌 In graphs, the independent variable is normally plotted on the x-axis and the dependent variable on the y-axis, with axes labelled by quantity and unit.

📌 Measurements should reflect instrument precision, include appropriate units, and be recorded systematically in tables with quantity and unit in the column headings.

• A best-fit line should be a single thin smooth line or curve with roughly even scatter on either side, while clearly anomalous points are ignored.

📖 15. Entries and Exam Administration

🔑 Key Concepts & Definitions

• Administrative zones : geographical areas to which Cambridge schools are allocated, with each zone using a specific examination timetable

★ Must-know

• Exams officers submit entries to Cambridge International, working with candidates to select the correct number of candidates and syllabus components using the Cambridge Guide to Making Entries.

Further detail

• The exceptions are: Cambridge IGCSE Biology (0610), Cambridge IGCSE (9–1) Biology (0970), Cambridge IGCSE Combined Science (0653), Cambridge IGCSE Co-ordinated Sciences (Double Award) (0654), Cambridge IGCSE (9–1) Co-ordinated Sciences (Double Award) (0973), Cambridge O Level Combined Science (5129), syllabuses with the same title at the same level

📌 Candidates can retake the whole qualification as many times as they want to.

💡 Memory Hook

Entries → zones → components → retakes

📖 16. Language and Accessibility Arrangements

🔑 Key Concepts & Definitions

• Access arrangements : including modified papers, are the principal way Cambridge International makes reasonable adjustments for candidates with special educational needs, disability, illness or injury

★ Must-know

• This syllabus and its related assessment materials are available in English only.

📌 Requested access arrangements must be supported by evidence of the candidate’s barrier to assessment and should reflect the candidate’s normal way of working at school.

Further detail

📌 Cambridge International approves an access arrangement only when it is a reasonable adjustment, involves reasonable cost and timeframe, and does not affect assessment security and integrity.

💡 Memory Hook

Accessibility arrangements remove barriers, whereas assessment security preserves exam integrity.

📖 17. Grades and Assessment Outcomes

🔑 Key Concepts & Definitions

• Ungraded : “Ungraded” means that a candidate’s performance did not meet the standard required for grade E, and it appears on the statement of results but not on the certificate.

★ Must-know

• Cambridge O Level grades range from A* as the highest grade to E as the lowest grade.

📌 Assessment at Cambridge O Level measures learning and achievement against the syllabus knowledge, understanding and skills, and indicates likely future success in a course or career.

Further detail

• The letters Q (PENDING) and X (NO RESULT) may appear on a statement of results in specific circumstances, but neither letter appears on the certificate.

📖 18. Syllabus Changes and Accessibility

📝 Essential Points

• The only change in version 4 was an updated weblink on page 42.

📌 Textbooks endorsed for the syllabus examination from 2023 remain suitable for use with this syllabus.

📊 Synthesis Tables

Mitosis and Meiosis

Feature	Mitosis	Meiosis
Chromosome number	Maintained	Halved from diploid to haploid
Genetic outcome	Genetically identical cells	Genetically different cells
Role	Growth, repair and asexual reproduction	Production of gametes

Continuous and Discontinuous Variation

Feature	Continuous	Discontinuous
Phenotypes	Range between extremes	Limited number with no intermediates
Causes	Genes and environment	Usually genes only
Examples	Body length and body mass	ABO blood groups, pea seed shape and pea seed colour