Short summary
Scientific words are useful because they let people be precise, but they can also slow readers down. This glossary keeps the language simple and gives short examples so the terms feel practical rather than intimidating.
Key terms
Adaptation: a heritable trait that helps organisms survive or reproduce in a certain environment. Example: Fur color that makes an animal harder for predators to see can be an adaptation.
Allele: one version of a gene. Example: A population may have different alleles linked to different flower colors.
Ancestor: an earlier organism or population from which later groups descended. Example: Humans and chimpanzees share ancestors in the distant past.
Common ancestry: the idea that different species can trace back to shared ancestors. Example: Similar DNA in related species supports common ancestry.
DNA: the molecule that carries inherited biological information. Example: Mutations are changes in DNA.
Evolution: change in the inherited traits of a population over generations. Example: A resistant form of bacteria becoming more common is evolution.
Fossil: preserved remains or traces of past life. Example: Bones, footprints, and shells can all become fossils under the right conditions.
Gene: a stretch of DNA that helps carry instructions for growth, structure, or function. Example: Genes help influence traits such as blood proteins or eye development.
Genetic drift: change in a population caused by chance, especially in small groups. Example: After a disaster, some genetic variants may become rare simply because the survivors were a random sample.
Inherited trait: a trait that can be passed from parents to offspring. Example: Coat color in many animals has an inherited component.
Mutation: a change in DNA. Example: A single DNA letter change is one kind of mutation.
Natural selection: when inherited traits linked to better survival or reproduction become more common over time. Example: Better-camouflaged individuals may leave more offspring in a predator-rich environment.
Population: a group of the same species living in the same place at the same time. Example: All the frogs of one species in a wetland can form a population.
Species: a group whose members can usually reproduce with one another and have fertile offspring. Example: Different dog breeds are still part of one species.
Speciation: the formation of new species. Example: Separated populations can become different enough over time to count as separate species.
Theory, scientific: a broad explanation supported by many observations and tests. Example: Evolution is a scientific theory, not a casual guess.
Transitional fossil: a fossil showing a mix of traits that helps connect older and later groups. Example: Some fossils show both fish-like and land-related traits.
Variation: differences among individuals in a population. Example: Members of a bird population may vary in beak size, color, or song.
How to use this page
If you get stuck on a word in another article, come back here for a quick reset. Then return to the full article for the larger explanation.