IGCSE Biology June 2025 Exam Checklist

Part 1
1 Characteristics and classification of living organisms
1.1 Characteristics of Living Organisms
1. Describe movement as an action by an organism or part of an organism causing a change of position or place.
2. Understand respiration as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
3. Explain sensitivity as the ability to detect and respond to changes in the internal or external environment.
4. Define growth as a permanent increase in size and dry mass.
5. Describe reproduction as the processes that make more of the same kind of organism.
6. Understand excretion as the removal of the waste products of metabolism and substances in excess of requirements.
7. Explain nutrition as the taking in of materials for energy, growth, and development.
1.2 Concept and Uses of Classification Systems
1. State that organisms can be classified into groups by the features that they share.
2. Describe a species as a group of organisms that can reproduce to produce fertile offspring.
3. Describe the binomial system of naming species as an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species.
4. Construct and use dichotomous keys based on identifiable features.
5. Explain that classification systems aim to reflect evolutionary relationships.
6. Explain that the sequences of bases in DNA are used as a means of classification.
7. Explain that groups of organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor.
1.3 Features of Organisms
1. State the main features used to place animals and plants into the appropriate kingdoms.
2. State the main features used to place organisms into groups within the animal kingdom, limited to:
The main groups of vertebrates: mammals, birds, reptiles, amphibians, fish.
The main groups of arthropods: myriapods, insects, arachnids, crustaceans.
4. State the main features used to place all organisms into one of the five kingdoms: animal, plant, fungus, prokaryote, protoctist.
5. State the main features used to place organisms into groups within the plant kingdom, limited to ferns and flowering plants (dicotyledons and monocotyledons).
7. State the features of viruses, limited to a protein coat and genetic material.
2.1 Organisation of the Organism
Cell Structure
1. Describe and compare the structure of a plant cell with an animal cell, limited to: cell wall, cell membrane, nucleus, cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles.
2. Describe the structure of a bacterial cell, limited to: cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids.
3. Identify the cell structures listed in 2.1.1 and 2.1.2 in diagrams and images of plant, animal, and bacterial cells.
4. Describe the functions of the structures listed in 2.1.1 and 2.1.2 in plant, animal, and bacterial cells.
5. State that new cells are produced by division of existing cells.
6. State that specialised cells have specific functions, limited to:
▪ Ciliated cells – movement of mucus in the trachea and bronchi.
▪ Root hair cells – absorption.
▪ Palisade mesophyll cells – photosynthesis.
▪ Neurones – conduction of electrical impulses.
▪ Red blood cells – transport of oxygen.
▪ Sperm and egg cells (gametes) – reproduction.
7. Describe the meaning of the terms: cell, tissue, organ, organ system, and organism as illustrated by examples given in the syllabus.
2.2 Size of Specimens
1. State and use the formula: magnification = image size ÷ actual size.
2. Calculate magnification and size of biological specimens using millimetres as units.
3. Convert measurements between millimetres (mm) and micrometres (μm).
3 Movement into and out of Cells
Diffusion
1. Describe 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.
2. State that the energy for diffusion comes from the kinetic energy of random movement of molecules and ions.
3. State that some substances move into and out of cells by diffusion through the cell membrane.
4. Describe the importance of diffusion of gases and solutes in living organisms.
5. Investigate the factors that influence diffusion, limited to: surface area, temperature, concentration gradient, and distance.
Osmosis
1. Describe the role of water as a solvent in organisms with reference to digestion, excretion, and transport.
2. State that water diffuses through partially permeable membranes by osmosis.
3. State that water moves into and out of cells by osmosis through the cell membrane.
4. Investigate osmosis using materials such as dialysis tubing.
5. Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations.
6. State that plants are supported by the pressure of water inside the cells pressing outwards on the cell wall.
7. Describe 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.
8. Explain the effects on plant cells of immersing them in solutions of different concentrations by using the terms: turgid, turgor pressure, plasmolysis, flaccid.
9. Explain the importance of water potential and osmosis in the uptake and loss of water by organisms.
Active Transport
1. Describe 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.
2. Explain the importance of active transport as a process for movement of molecules or ions across membranes, including ion uptake by root hairs.
3. State that protein carriers move molecules or ions across a membrane during active transport.
4 Biological Molecules
Biological Molecules
1. List the chemical elements that make up carbohydrates, fats, proteins.
2. State that large molecules are made from smaller molecules, limited to:
▪ Starch, glycogen, and cellulose from glucose.
▪ Proteins from amino acids.
▪ Fats and oils from fatty acids and glycerol.
3. Describe the use of:
▪ Iodine solution test for starch.
▪ Benedict’s solution test for reducing sugars.
▪ Biuret test for proteins.
▪ Ethanol emulsion test for fats and oils.
▪ DCPIP test for vitamin C.
4. Describe the structure of a DNA molecule:
▪ Two strands coiled together to form a double helix.
▪ Each strand contains chemicals called bases.
▪ Bonds between pairs of bases hold the strands together.
▪ The bases always pair up in the same way: A with T, and C with G (full names are not required).
5 Enzymes
Enzymes
1. Describe a catalyst as a substance that increases the rate of a chemical reaction and is not changed by the reaction.
2. Describe enzymes as proteins that are involved in all metabolic reactions, where they function as biological catalysts.
3. Describe why enzymes are important in all living organisms in terms of a reaction rate necessary to sustain life.
4. Describe enzyme action with reference to the shape of the active site of an enzyme being complementary to its substrate and the formation of products.
5. Investigate and describe the effect of changes in temperature and pH on enzyme activity with reference to optimum temperature and denaturation.
6. Explain enzyme action with reference to: active site, enzyme-substrate complex, substrate, and product.
7. Explain the specificity of enzymes in terms of the complementary shape and fit of the active site with the substrate.
8. Explain the effect of changes in temperature on enzyme activity in terms of kinetic energy, shape and fit, frequency of effective collisions, and denaturation.
9. Explain the effect of changes in pH on enzyme activity in terms of shape and fit and denaturation.
6 Plant Nutrition
Photosynthesis
1. Describe photosynthesis as the process by which plants synthesize carbohydrates from raw materials using energy from light.
2. State the word equation for photosynthesis as: carbon dioxide + water → glucose + oxygen in the presence of light and chlorophyll.
3. State that chlorophyll is a green pigment that is found in chloroplasts.
4. State that chlorophyll transfers energy from light into energy in chemicals, for the synthesis of carbohydrates.
5. State the balanced chemical equation for photosynthesis as: 6CO2 + 6H2O → C6H12O6 + 6O2.
6. Outline the subsequent use and storage of the carbohydrates made in photosynthesis, limited to:
▪ Starch as an energy store.
▪ Cellulose to build cell walls.
▪ Glucose used in respiration to provide energy.
▪ Sucrose for transport in the phloem.
▪ Nectar to attract insects for pollination.
7. Explain the importance of:
▪ Nitrate ions for making amino acids.
▪ Magnesium ions for making chlorophyll.
8. Investigate the need for chlorophyll, light, and carbon dioxide for photosynthesis, using appropriate controls.
9. Investigate and describe the effects of varying light intensity, carbon dioxide concentration, and temperature on the rate of photosynthesis.
10. Investigate and describe the effect of light and dark conditions on gas exchange in an aquatic plant using hydrogencarbonate indicator solution.
Leaf Structure
1. State that most leaves have a large surface area and are thin, and explain how these features are adaptations for photosynthesis.
2. Identify 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.
3. Explain how the structures listed in 6.2.2 adapt leaves for photosynthesis.
4. Identify and explain the limiting factors of photosynthesis in different environmental conditions.
7 Human Nutrition
Diet
1. Describe what is meant by a balanced diet.
2. State the principal dietary sources and describe the importance of:
▪ Carbohydrates.
▪ Fats and oils.
▪ Proteins.
▪ Vitamins, limited to C and D.
▪ Mineral ions, limited to calcium and iron.
▪ Fibre (roughage).
▪ Water.
3. State the causes of scurvy and rickets.
Digestive System
1. Identify in diagrams and images the main organs of the digestive system, limited to:
▪ Alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum and ileum), and large intestine (colon, rectum, anus).
▪ Associated organs: salivary glands, pancreas, liver, and gall bladder.
2. Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to:
▪ Ingestion – the taking of substances, e.g., food and drink, into the body.
▪ Digestion – the breakdown of food.
▪ Absorption – the movement of nutrients from the intestines into the blood.
▪ Assimilation – uptake and use of nutrients by cells.
▪ Egestion – the removal of undigested food from the body as faeces.
Physical Digestion
1. Describe physical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules.
2. State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion.
3. Identify in diagrams and images the types of human teeth: incisors, canines, premolars, and molars.
4. Describe the structure of human teeth, limited to: enamel, dentine, pulp, nerves, blood vessels, and cement, and understand that teeth are embedded in bone and the gums.
5. Describe the functions of the types of human teeth in the physical digestion of food.
6. Describe the function of the stomach in physical digestion.
Chemical Digestion
1. Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules.
2. State the role of chemical digestion in producing small soluble molecules that can be absorbed.
3. Describe the functions of enzymes as follows:
▪ Amylase breaks down starch to simple reducing sugars.
▪ Proteases break down protein to amino acids.
▪ Lipase breaks down fats and oils to fatty acids and glycerol.
4. State where, in the digestive system, amylase, protease, and lipase are secreted and where they act.
5. Describe the functions of hydrochloric acid in gastric juice, limited to killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity.
6. Describe the digestion of starch in the digestive system:
▪ Amylase breaks down starch to maltose.
▪ Maltase breaks down maltose to glucose on the membranes of the epithelium lining the small intestine.
7. Describe the digestion of protein by proteases in the digestive system:
▪ Pepsin breaks down protein in the acidic conditions of the stomach.
▪ Trypsin breaks down protein in the alkaline conditions of the small intestine.
8. Explain that bile is an alkaline mixture that neutralizes the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action.
9. Outline the role of bile in emulsifying fats and oils to increase the surface area for chemical digestion.
Absorption
1. State that the small intestine is the region where nutrients are absorbed.
2. State that most water is absorbed from the small intestine but that some is also absorbed from the colon.
3. Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine.
4. Describe the structure of a villus.
5. Describe the roles of capillaries and lacteals in villi.

Part 1

1 Characteristics and classification of living organisms

1.1 Characteristics of Living Organisms

1.2 Concept and Uses of Classification Systems

1.3 Features of Organisms

2.1 Organisation of the Organism

Cell Structure

2.2 Size of Specimens

3 Movement into and out of Cells

Diffusion

Osmosis

Active Transport

4 Biological Molecules

Biological Molecules

5 Enzymes

Enzymes

6 Plant Nutrition

Photosynthesis

Leaf Structure

7 Human Nutrition

Diet

Digestive System

Physical Digestion

Chemical Digestion

Absorption