NCEA Level 2 Biology key terms

The variety of living things, measured as the number of different species, the range of genetic variation within each species, and the variety of ecosystems they form.

A group of organisms that can interbreed and produce fertile offspring under natural conditions, and which is reproductively isolated from other such groups.

All the individuals of one species living in the same area at the same time, which can potentially interbreed with one another.

All the populations of different species living and interacting together in a particular area at a particular time.

A community of interacting organisms together with the non-living parts of their environment, such as soil, water, light and temperature, functioning as a unit.

The particular physical place where an organism lives, described by features such as vegetation type, moisture, shelter and food supply.

The role a species plays in its community, including what it eats, where it lives, when it is active, and how it interacts with other species.

A living influence on an organism, such as predators, competitors, parasites, disease organisms, or the availability of food and mates.

A non-living physical or chemical influence on organisms, such as light intensity, temperature, water availability, soil pH, salinity or oxygen concentration.

The maximum population size of a species that a given environment can support indefinitely, given the food, space and other resources available.

Any resource or condition that is in shortest supply and therefore restricts the growth, distribution or abundance of a population.

The range of values of an environmental factor, such as temperature, within which a species can survive and reproduce; outside it the species cannot persist.

A graph of population size over time, typically showing a lag phase, an exponential growth phase, and a plateau where the population stabilises at carrying capacity.

Population increase in which the number of individuals multiplies by a roughly constant factor each generation, producing a rapidly steepening curve while resources remain plentiful.

An interaction in which one organism, the predator, kills and eats another organism, the prey, influencing both populations, often in cyclical ways.

An interaction in which organisms require the same limited resource, such as light, food, space or mates, and both are harmed by the shortage.

Competition between individuals of different species for the same limited resource, which can lead to competitive exclusion or to resource partitioning.

The division of a shared resource, such as food or space, among species so that each uses a different part, reducing competition and allowing coexistence.

An inherited feature of a structure, behaviour or physiology that improves an organism's chance of surviving and reproducing in its particular environment.

The process by which individuals with inherited traits better suited to their environment survive and reproduce more successfully, so those traits become more common in later generations.

An environmental factor, such as a predator, disease or climate condition, that reduces the survival or reproduction of some individuals more than others.

Differences in the alleles carried by individuals in a population, arising from mutation, sexual reproduction and recombination, and providing the raw material for natural selection.

The total collection of alleles present in a population at a given time, whose frequencies can change over generations through selection, drift, mutation and migration.

A condition in which members of different groups cannot interbreed successfully, for example because of different breeding times, behaviours or habitats, or because offspring are infertile.

The formation of a new species, typically when separated populations accumulate enough genetic differences that they can no longer interbreed to produce fertile offspring.

One of the alternative versions of a gene that can occupy the same position on a chromosome and produce different forms of a trait.

The particular combination of alleles an organism carries for a gene or set of genes, written as symbols such as AA, Aa or aa.

The observable characteristics of an organism, resulting from its genotype interacting with the environment, such as flower colour or blood type.

Describing an organism that carries two identical alleles for a particular gene, for example AA or aa.

Describing an organism that carries two different alleles for a particular gene, for example Aa.

The relationship in which one allele masks the expression of another in a heterozygote; a dominant allele is expressed, while a recessive allele is only expressed when homozygous.

An allele whose effect on the phenotype is hidden when a dominant allele is present, and which is only expressed in individuals carrying two copies.

A grid diagram used to predict the possible genotypes and their proportions among offspring from a cross between two parents of known genotype.

A breeding cross in which the inheritance of a single gene with two alleles is followed, typically giving a 3:1 phenotype ratio from two heterozygotes.

A cross between an individual of unknown genotype and a homozygous recessive individual, used to reveal whether the unknown carries a dominant or recessive allele.

A family tree diagram using symbols to show how a trait is inherited across generations, allowing the inference of genotypes and modes of inheritance.

A permanent change in the DNA base sequence of a gene or chromosome, which may alter the protein produced and is the ultimate source of new alleles.

A type of cell division that halves the chromosome number to produce gametes, generating genetic variation through independent assortment and crossing over.

A reproductive cell, such as a sperm, egg or pollen grain, containing half the normal chromosome number and able to fuse with another gamete at fertilisation.

The exchange of corresponding sections of DNA between homologous chromosomes during meiosis, producing new combinations of alleles on a chromosome.

The fusion of a male and a female gamete to form a zygote, restoring the full chromosome number and combining alleles from two parents.