IGCSE Biology Common Past Paper Review

Vocabulary practice flashcards covering fundamental IGCSE Biology definitions and core concepts from Vasumitra Gajbhiye's past paper revision guide.

Species

A group of organisms that can reproduce to produce fertile offspring.

Sensitivity

The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

Growth

A permanent increase in size, length, mass, or volume, as well as an increase in cell number.

Organ

A structure made up of a group of tissues working together to perform a specific function or functions.

Sense organ

Groups of receptor cells responding to specific stimuli.

Prokaryote

A single-celled organism characterized by cytoplasm, a cell membrane, a peptidoglycan (murein) cell wall, a circular loop of naked DNA, smaller ribosomes, and no true nucleus or membrane-bound organelles.

Protoctista

A group of organisms possessing cells with a true nucleus, nuclear membrane, linear chromosomes, and internal membrane-bound organelles.

Nucleus

An organelle that stores chromosomes, genes, and DNA, controls cellular reactions and growth, and provides instructions for protein synthesis.

Cell membrane

A cellular barrier that encloses cell contents and controls the movement of substances into and out of the cell.

Tissue

A group of cells with similar structures working together to perform a shared function.

Wilting

A state in plants caused by water loss down a water potential gradient via osmosis, resulting in a loss of turgor pressure against cell walls.

Plasmolysis

The shrinking of the cytoplasm and vacuole away from the cell wall when a plant cell loses water in a hypertonic solution and becomes flaccid.

Active transport

The movement of substances against a concentration gradient across a membrane using protein carriers or pumps and requiring energy.

Hydrogencarbonate indicator

An indicator solution used to detect $CO_2$ concentration; it is yellow at the highest $CO_2$ levels, orange at higher levels, red at atmospheric levels, magenta at low levels, and purple at the lowest levels.

Catalyst

A substance that increases the rate of a chemical reaction without being changed or consumed during the reaction.

Enzyme-substrate complex

The intermediate formed when a substrate collides with and binds to the complementary active site of an enzyme.

Gravitropism

A plant growth response to gravity, ensuring roots grow downward to absorb water and minerals and shoots grow upward to access light.

Palisade mesophyll

A layer of columnar, vertically packed cells near the upper leaf surface containing abundant chloroplasts to maximize light absorption for photosynthesis.

Translocation

The movement of sucrose and amino acids through the phloem from a source (region of production) to a sink (region of storage, respiration, or growth).

Bile

A fluid that emulsifies fat globules into smaller droplets to increase the surface area for lipase action and neutralises stomach acid to optimize intestinal pH.

Sickle-cell anaemia

A genetic blood disorder caused by a base substitution mutation in the haemoglobin gene, resulting in abnormal haemoglobin and rigid, sickle-shaped red blood cells.

Double circulation

A circulatory system where blood flows through the heart twice for every complete circuit, consisting of pulmonary circulation to the lungs and systemic circulation to the body.

Lymphatic system

A system of vessels and nodes that drains tissue fluid back to the bloodstream, provides immunity via lymphocytes, and absorbs fats via lacteals.

Chemical digestion

The breakdown of large, insoluble molecules into small, soluble molecules through enzymatic action.

Mechanical digestion

The physical breakdown of food into smaller pieces by teeth and muscle action without chemical modification, increasing the surface area for enzymes.

Assimilation

The movement of digested food molecules into cells where they become integrated as part of the cells.

Lacteal

A lymphatic capillary located within an intestinal villus that absorbs and transports digested fats, fatty acids, and glycerol.

Transpiration

The evaporation of water from the surfaces of mesophyll cells followed by the diffusion of water vapour through the stomata into the atmosphere.

Xylem vessels

Hollow, continuous tubes composed of dead, lignified cells lacking end walls, adapted to transport water and dissolved minerals under tension and provide structural support.

Auxin

A plant hormone synthesized in shoot tips that moves away from light to stimulate cell elongation on the shaded side of the stem.

Coronary heart disease (CHD)

A condition caused by the build-up of fatty deposits in the coronary arteries, restricting blood flow and reducing oxygen supply to the cardiac muscle.

Antibody

A specific protective protein produced by lymphocytes that binds to complementary antigens on pathogens to mark or destroy them.

Transmissible disease

A disease caused by a pathogen that can be passed from one host to another.

Active immunity

Long-term defence against pathogens stimulated by exposure to foreign antigens, resulting in antibody and memory cell production.

Passive immunity

Short-term protection against pathogens acquired through antibodies from an external source without an active immune response or memory cell formation.

Goblet cell

A specialized epithelial cell that produces and secretes mucus to trap dust particles and pathogens in the respiratory tract.

Synapse

A junction between two neurones where nerve impulses are transmitted via the diffusion of chemical neurotransmitters across the synaptic cleft.

Hormone

A chemical substance produced by an endocrine gland, transported in the blood plasma, that alters the activity of specific target organs or tissues.

Insulin

A hormone secreted by the pancreas that lowers blood glucose concentration by stimulating liver and muscle cells to absorb glucose and convert it into glycogen.

Excretion

The removal from organisms of toxic substances, waste products of metabolism, and substances in excess of requirements.

Deamination

The metabolic process in the liver that removes the nitrogen-containing amino group from excess amino acids to form urea.

Glomerulus

A tight cluster of blood capillaries in the kidney cortex responsible for the ultrafiltration of blood under high pressure.

Self-pollination

The transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant.

Cross-pollination

The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.

Asexual reproduction

A reproductive process involving one parent that produces genetically identical offspring via mitosis without the fusion of gametes.

Meiosis

A reduction nuclear division that halves the chromosome number from diploid to haploid, producing genetically varied gametes.

Follicle-stimulating hormone (FSH)

A pituitary hormone that stimulates follicle growth, egg maturation in the ovary, and oestrogen secretion.

Luteinising hormone (LH)

A pituitary hormone that surges to trigger ovulation and stimulates the remaining follicle (corpus luteum) to produce progesterone.

Co-dominance

A condition in which both alleles for a gene are expressed in the phenotype of a heterozygote, producing an intermediate or distinct characteristic.

Allele

An alternative version or form of a gene.

Sex-linked characteristic

A characteristic determined by a gene located on a sex chromosome ($X$ or $Y$), making it more common in one sex.

Phenotype

The observable physical and physiological features of an organism.

Adaptive feature

An inherited characteristic resulting from natural selection that increases an organism's fitness and chances of survival and reproduction in its environment.

Eutrophication

An aquatic environmental event where nutrient enrichment causes algal blooms, blocking light and causing plant death, aerobic bacterial decomposition, and severe oxygen depletion.

Producer

An autotrophic organism that synthesizes its own organic nutrients using light energy from the Sun through photosynthesis.

Fitness

The probability that an organism will survive and reproduce in the environment in which it is found.

Population

A group of individuals of the same species living in the same geographic area at the same time.

Discontinuous variation

Variation that results in distinct, non-overlapping phenotypic categories with no intermediates, controlled entirely by genes and unaffected by the environment.

Xerophytes

Plants adapted to survive in dry habitats with limited water supply through traits such as sunken stomata, thick cuticles, rolled leaves, and extensive root systems.

Hydrophytes

Aquatic plants adapted to live submerged or floating in water, featuring large air spaces for buoyancy, reduced root and xylem systems, and stomata on upper leaf surfaces.

Ecosystem

A biological unit containing a community of organisms and their abiotic environment interacting together.

Sustainable development

Development that provides for the needs of an increasing human population without causing harm to natural ecosystems and habitats.