AQA GCSE Combined Science: Trilogy glossary
77 key terms from the AQA GCSE Combined Science: Trilogy notes, A to Z. Each definition links to the note that teaches it.
A
- Active transport
- Moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.Revise it: Active transport
- Adaptation
- A feature that enables an organism to survive in the conditions in which it normally lives.Revise it: Adaptations
- Aerobic respiration
- Respiration that uses oxygen.Revise it: Aerobic and anaerobic respiration
- AIDS
- Late stage HIV infection, when the immune system is so badly damaged that it cannot deal with other infections or cancers.Revise it: Viral diseases
- Allele
- A different form of the same gene.Revise it: Genetic inheritance
- Anaerobic respiration
- Respiration without oxygen.Revise it: Aerobic and anaerobic respiration
- Asexual reproduction
- Reproduction with only one parent, no fusion of gametes and no mixing of genetic information. Offspring are genetically identical clones. Only mitosis is involved.Revise it: Sexual and asexual reproduction
B
- Binomial system
- Naming organisms using their genus and species, for example Homo sapiens. The genus has a capital letter; the species does not.Revise it: The Linnaean system and binomial names
- Biodiversity
- The variety of all the different species of organisms on Earth, or within an ecosystem.Revise it: Biodiversity
- Biotic factor
- A living factor that can affect a community.Revise it: Biotic factors
C
- Cancer
- The result of changes in cells that lead to uncontrolled growth and division.Revise it: Cancer
- Carcinogen
- A substance or radiation that can cause cancer. Ionising radiation is one example.Revise it: Risk factors and causes
- Causal mechanism
- An explanation of how a risk factor causes a disease. It has been proven for some risk factors but not others.Revise it: Risk factors and causes
- Cell
- The basic building block of all living organisms.Revise it: Cells, tissues, organs and organ systems
- Cell differentiation
- The process by which cells acquire different sub-cellular structures to carry out a particular function, becoming specialised.Revise it: Cell differentiation
- Chromosome
- A structure in the nucleus that contains DNA.Revise it: DNA and the genome
- CNS
- The central nervous system: the brain and spinal cord. It coordinates the response of effectors.Revise it: Structure and function of the nervous system
D
- Diffusion
- The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.Revise it: Diffusion
- Dominant
- An allele that is always expressed, even if only one copy is present.Revise it: Genetic inheritance
- Dose
- The amount of drug to give so that it works without causing harm.Revise it: Discovery and development of drugs
- Double circulatory system
- Blood passes through the heart twice per circuit: once to the lungs and once around the rest of the body.Revise it: The heart and the double circulatory system
E
- Ecosystem
- The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.Revise it: Communities
- Effector
- A muscle or gland that brings about a response which restores optimum levels.Revise it: What homeostasis is
- Efficacy
- How well the drug works to treat the condition.Revise it: Discovery and development of drugs
- Endocrine system
- Glands that secrete hormones directly into the bloodstream. The blood carries them to a target organ.Revise it: The human endocrine system
- Eukaryotic cells
- Cells with genetic material enclosed in a nucleus, plus a cell membrane and cytoplasm. Plant and animal cells are eukaryotic.Revise it: Eukaryotes and prokaryotes
- Evolution
- A change in the inherited characteristics of a population over time through a process of natural selection, which may result in the formation of a new species.Revise it: Evolution
- Evolutionary tree
- A method showing how scientists believe organisms are related, using classification data for living organisms and fossil data for extinct ones.Revise it: The Linnaean system and binomial names
- Extinction
- When there are no remaining individuals of a species still alive. Factors include new predators, diseases or competitors, environmental change, or a single catastrophic event.Revise it: Extinction
- Extremophile
- An organism that lives in an environment that is very extreme, such as at high temperature, pressure or salt concentration. Bacteria living in deep sea vents are extremophiles.Revise it: Adaptations
F
- Fermentation
- Anaerobic respiration in yeast cells.Revise it: Aerobic and anaerobic respiration
- Fertility drug Higher tier
- It contains FSH and LH, given to a woman. She may then become pregnant in the normal way.Revise it: The use of hormones to treat infertility
G
- Gamete
- A sex cell (sperm, egg or pollen) that has a single set of chromosomes.Revise it: Genetic inheritance
- Gene
- A small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein.Revise it: DNA and the genome
- Genetic engineering
- A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.Revise it: Genetic engineering
- Genome
- The entire genetic material of an organism.Revise it: DNA and the genome
- Genotype
- The alleles present for a characteristic.Revise it: Genetic inheritance
H
- Health
- The state of physical and mental well-being. Disease, diet, stress and life situations can all affect health.Revise it: Health and disease
- Heterozygous
- Having two alleles that are different for a trait.Revise it: Genetic inheritance
- Homeostasis
- The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.Revise it: What homeostasis is
- Homozygous
- Having two alleles that are the same for a trait.Revise it: Genetic inheritance
- Human sex chromosomes
- Females XX, males XY. Humans have 23 pairs of chromosomes; 22 pairs control characteristics only.Revise it: Sex determination
I
- Interdependence
- Within a community each species depends on other species for food, shelter, pollination, seed dispersal and so on. If one species is removed it can affect the whole community.Revise it: Communities
L
- Limiting factor
- The factor in shortest supply, which stops the rate from increasing even if other factors are increased.Revise it: Factors that affect the rate of photosynthesis
M
- Magnification
- How many times larger the image is than the real object.Revise it: Microscopy
- Mean
- The total of all the values divided by the number of values.Revise it: Sampling: distribution and abundance
- Median
- The middle value when the values are in order. With an even number of values, it is halfway between the two middle values.Revise it: Sampling: distribution and abundance
- Meristem tissue
- Tissue in plants whose stem cells can differentiate into any type of plant cell, throughout the life of the plant.Revise it: Stem cells
- Metabolism
- The sum of all the reactions in a cell or the body.Revise it: Metabolism
- Mode
- The value that occurs most often.Revise it: Sampling: distribution and abundance
- Muscle fatigue
- After long periods of vigorous activity, muscles stop contracting efficiently.Revise it: Response to exercise
N
- Negative feedback Higher tier
- A change is reversed to bring the level back to normal. Thyroxine levels are controlled this way.Revise it: Adrenaline, thyroxine and negative feedback
O
- Organ
- An aggregation of tissues performing specific functions.Revise it: Cells, tissues, organs and organ systems
- Organ system
- Organs are organised into organ systems, which work together to form organisms.Revise it: Cells, tissues, organs and organ systems
- Osmosis
- The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.Revise it: Osmosis
- Oxygen debt Higher tier
- The extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.Revise it: Response to exercise
P
- Pathogen
- A microorganism that causes infectious disease.Revise it: Communicable (infectious) diseases
- Phagocytosis
- A white blood cell engulfs a pathogen and digests it.Revise it: Human defence systems
- Phenotype
- How the characteristic is expressed, such as black fur.Revise it: Genetic inheritance
- Preclinical testing
- Testing in a laboratory using cells, tissues and live animals.Revise it: Discovery and development of drugs
- Producers
- Organisms that make their own glucose by photosynthesis, usually green plants or algae. All food chains begin with one.Revise it: Producers, consumers and food chains
- Prokaryotic cells
- Bacterial cells. Much smaller than eukaryotic cells, with cytoplasm and a cell membrane surrounded by a cell wall. Genetic material is not enclosed in a nucleus.Revise it: Eukaryotes and prokaryotes
R
- Recessive
- An allele that is only expressed if two copies are present (so no dominant allele is present).Revise it: Genetic inheritance
- Resolving power
- The ability to distinguish between two points that are close together as separate points. Higher resolving power gives a sharper, more detailed image.Revise it: Microscopy
- Risk factor
- Something linked to an increased rate of a disease, such as an aspect of lifestyle or a substance in the body or environment.Revise it: Risk factors and causes
S
- Selective breeding
- The process by which humans breed plants and animals for particular genetic characteristics. It is also called artificial selection.Revise it: Selective breeding
- Stable community
- A community where all the species and environmental factors are in balance so that population sizes remain fairly constant.Revise it: Communities
- Standard form
- A number between 1 and 10 multiplied by a power of ten, for example 3 × 10⁻⁴.Revise it: Eukaryotes and prokaryotes
- Stem cell
- An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.Revise it: Stem cells
- Stent
- A device used to keep the coronary arteries open.Revise it: Coronary heart disease
T
- Therapeutic cloning
- An embryo is produced with the same genes as the patient, so stem cells from it are not rejected by the patient's body.Revise it: Stem cells
- Tissue
- A group of cells with a similar structure and function.Revise it: Cells, tissues, organs and organ systems
- Toxicity
- How harmful the drug is to cells and the body.Revise it: Discovery and development of drugs
- Toxin
- A poison produced by bacteria that damages tissues and makes us feel ill.Revise it: Communicable (infectious) diseases
- Translocation
- The movement of dissolved sugars through phloem from the leaves to the rest of the plant. Phloem is tubes of elongated cells with pores in the end walls.Revise it: Roots, xylem and phloem
- Transpiration
- The loss of water vapour from the leaves. Water moves up the xylem, evaporates from leaf cells and diffuses out through the stomata.Revise it: Roots, xylem and phloem
V
- Vector
- An organism that carries a pathogen from one host to another. For malaria the vector is the mosquito.Revise it: Protist diseases
Test yourself on these terms with the AQA GCSE Combined Science: Trilogy flashcards, or tick them off on the specification checklist.