WACE ATAR Biology key terms

The variety of living things in a given area, measured as variation within species, between species, and across ecosystems, and shaped by both evolutionary history and current environmental conditions.

A simple count of how many different species live in a defined area, without weighting for how common or rare each species is.

The proportion each species contributes to the total number of individuals in a community, showing evenness of distribution rather than just presence or absence.

A functioning unit made up of all living organisms in an area interacting with each other and with the non-living components such as light, water, soil and temperature.

Any living influence on an organism, including predators, competitors, parasites, disease organisms, mutualistic partners and food availability.

A non-living environmental influence such as temperature, light intensity, pH, salinity, moisture or mineral availability that affects survival and distribution of organisms.

The position an organism occupies in a feeding sequence, starting with producers and moving through primary, secondary and tertiary consumers to decomposers.

An autotroph that builds organic molecules from inorganic raw materials using an energy source such as sunlight or chemical reactions, forming the base of every food chain.

A heterotroph that obtains energy and matter by eating other organisms, classified as primary, secondary or tertiary depending on how far it sits from the producer.

An organism such as a bacterium or fungus that breaks down dead organic matter and returns nutrients to the soil or water for reuse by producers.

A diagram linking several interconnected food chains to show the many feeding pathways in a community, revealing indirect effects of removing or adding a species.

A species whose influence on community structure is far greater than its abundance suggests, so its removal triggers major shifts across many other populations.

An interaction in which organisms require the same limited resource, reducing the fitness of at least one party; it may occur within a species or between different species.

The full set of resources, conditions and interactions a species uses and experiences in a community, including its role and its tolerance limits.

The division of a limiting resource among species so that each uses a different portion, reducing direct competition and allowing coexistence in the same habitat.

An interaction in which one organism captures and consumes another, shaping prey populations and often driving selection for defensive traits on both sides.

A close, prolonged association between organisms of different species, covering mutualism, commensalism and parasitism depending on the benefit and harm involved.

A symbiotic relationship in which both partners gain a fitness benefit, such as pollinators receiving nectar while transferring pollen for the plant.

A symbiotic relationship in which one organism lives in or on a host, gaining nutrients while harming the host's growth, survival or reproduction.

An inherited feature that improves an organism's chance of surviving and reproducing in its environment, arising through natural selection over generations.

The span of an environmental variable within which an organism can survive and function, with performance declining toward the upper and lower limits.

The movement of elements such as carbon, nitrogen and phosphorus between living organisms and the physical environment, driven largely by decomposition and uptake by producers.

A group of individuals of the same species living in the same area at the same time and capable of interbreeding.

The maximum population size an environment can sustain indefinitely given the resources available, often shown as the plateau of a logistic growth curve.

Using resources and ecosystems at a rate that meets present needs without reducing the ability of future generations to meet theirs.

A sampling frame of known area placed at random positions to estimate population density, percentage cover or species richness in a habitat.

A line or belt laid across a habitat along which organisms are recorded, used to reveal how species distribution changes with an environmental gradient.

The extent to which a measurement or experiment actually tests the intended variable and supports the conclusion drawn, rather than being distorted by other factors.

The consistency of repeated measurements, improved by taking multiple readings, using adequate sample sizes and reducing observer bias.

A factor held constant across treatment groups so that any observed change can be attributed to the independent variable rather than to a confounding influence.

A testable, falsifiable statement predicting a relationship between variables, framed so that data can either support or contradict it.

The principle that all living things are made of one or more cells, that the cell is the basic unit of life, and that new cells arise from existing cells.

A cell lacking a membrane-bound nucleus and membrane-bound organelles, with circular DNA in a nucleoid region, as found in bacteria and archaea.

A cell containing a membrane-bound nucleus and other membrane-bound organelles such as mitochondria and chloroplasts, found in protists, fungi, plants and animals.

A double-membraned organelle where aerobic respiration generates most of the cell's ATP, containing its own small circular genome inherited maternally in humans.

A plant-cell organelle containing chlorophyll and thylakoid membranes where photosynthesis converts light energy into chemical energy stored in glucose.

The theory that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by a host cell, supported by their own DNA and double membranes.

Nuclear division producing two genetically identical daughter nuclei, used for growth, repair and asexual reproduction in eukaryotic organisms.

Two successive nuclear divisions producing four haploid cells with recombined chromosomes, forming gametes and generating genetic variation.

Exchange of corresponding segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis, creating new allele combinations.

The random orientation of homologous chromosome pairs at metaphase I, so alleles of different genes are distributed to gametes independently of one another.

One of the alternative versions of a gene at a given locus, which may differ in nucleotide sequence and produce different phenotypes.

The particular combination of alleles an organism carries for a gene or set of genes, written as pairs of letters such as homozygous or heterozygous states.

The observable characteristics of an organism, resulting from its genotype interacting with environmental influences during development.

The total set of alleles present in a population, whose frequencies change over time through selection, mutation, gene flow and genetic drift.

Random change in allele frequencies between generations, most pronounced in small populations, independent of any fitness advantage.

The process by which individuals with inherited traits better suited to their environment survive and reproduce more, increasing those alleles in later generations.

A permanent change in DNA sequence, ranging from a single base substitution to large chromosomal rearrangements, and the ultimate source of new alleles.

The formation of new species when populations become reproductively isolated and diverge genetically over time until they can no longer interbreed.

Any barrier preventing members of different populations from interbreeding successfully, such as temporal, behavioural, geographic or genetic incompatibility.

A branching diagram showing hypothesised evolutionary relationships among organisms, with branch points representing common ancestors and branch lengths or nodes indicating divergence.

A simplified representation of a real system used to explain observations and make predictions, valuable but limited by the assumptions built into it.

Independent scrutiny of research by experts in the field before publication, checking methods, analysis and interpretation for quality and credibility.

Moral principles guiding what research is acceptable, including informed consent, humane treatment of animals, honesty in reporting and minimising environmental harm.

The branch of ethics applied to biological and medical decisions, weighing benefits against harms for individuals, populations and ecosystems when applying new technology.