Evolution vocabulary
Use technical vocabulary for evolution and natural selection: adaptation, evolution, natural selection, extinct, extinction, fossil record, species, common ancestor, mutation, variation, and explain the mechanism of natural selection using these terms in the correct sequence
What a learner can do afterwards
- Use 'adaptation' correctly to describe a feature that helps an organism survive in its environment
- Explain natural selection using 'variation', 'selection pressure', and 'reproduction' correctly in sequence
- Use 'extinct' and 'extinction' correctly and distinguish them from 'endangered'
1 · Read
Every living thing belongs to a species: a group that can breed together, like all giraffes or all housecats. Within a species, individuals are not identical. This is called variation. A giraffe with a slightly longer neck than others in its group is an example of variation. Variation can come from a mutation, a random change in genes passed from parents to young.
When a feature helps an organism survive and reproduce in its environment, we call it an adaptation. A polar bear's thick white fur is an adaptation: it keeps the bear warm and hides it in the snow. Adaptations build up over many generations. If every member of a species dies out, the species is extinct. An endangered species still has a few members left.
Giraffe ancestors had necks of different lengths, and that was variation. When food near the ground grew scarce, that shortage acted as a selection pressure. Giraffes with longer necks could reach higher leaves, so they were more likely to survive and reproduce. Their calves inherited the longer-neck trait. Repeated over many generations, this process is natural selection, and it is one way evolution happens. Fossils in rock show how life changed, and shared bones point to a common ancestor.
If every member of a species dies out, the species is extinct, and that event is called extinction. Don't confuse this with endangered: an endangered species has very few members left, but it has not disappeared yet.
Scientists study the fossil record: traces and remains of past life preserved in rock. It helps them trace species back to a common ancestor, an earlier species that two or more living species evolved from. Evolution is the word for how species change across generations.
Variation creates differences, selection pressure decides who survives and reproduces, and repeated over generations that is evolution, while species that cannot keep up may become extinct.
Rewritten readings were written for this dataset.
More to read
Glossary of Evolution Words
Here are some important words scientists use when they talk about evolution.
Adaptation: a feature or change in a living thing that helps it, and its offspring, survive better in its environment. A polar bear's thick fur is an adaptation to the cold.
Common ancestor: an ancestor shared by two or more species that came later. Humans and chimpanzees share a common ancestor that lived long ago.
Natural selection: the way evolution happens. Living things with helpful traits that can be passed down tend to survive and have more offspring, so those helpful traits become more common over many generations.
Species: a group of living things that are so similar they can have offspring together.
Extinct: when every member of a species has died and that species is gone forever, like the dinosaurs.
Fossil record: all the fossils scientists have found. It is like a giant photo album that shows how life has changed over millions of years.
How inherited traits become more common
Natural selection involves variation, inheritance and differences in survival and reproduction. These are connected conditions, not three events that must happen in order.
Variation means individuals differ. Beetles may be green or brown; finches may have larger or smaller beaks.
Some differences are inherited: offspring receive genes from their parents. A mutation is a change in genetic material that may produce a new difference.
Living things often produce more offspring than available food can support, creating competition. Traits suited to the environment can help individuals survive and leave more offspring. Their inherited traits can then spread.
Across generations, these traits may become more common in a population. Changes in inherited traits over generations are evolution. A species unable to cope with environmental change may disappear entirely, which is extinction.
Evidence and explanations for evolution
Evolution is change in the inherited traits of populations across generations. People proposed that species could change before Darwin. He explained a mechanism for such change: natural selection.
An adaptation is an inherited feature that helps survival or reproduction in a particular environment. Natural selection can spread adaptations; wanting a feature does not create it. A giraffe cannot gain a longer neck by deliberately stretching. For example, inherited differences in neck length could help some giraffes reach more leaves and leave more offspring, making longer necks more common.
Fossils reveal past species and changes through time. Anatomy also provides evidence. Human arms, cats' front legs and bats' wings share a basic bone pattern, suggesting common ancestry.
Evolution does not have a goal of producing more advanced organisms. Whether a trait helps depends on the environment.
Four ways populations evolve
Members of one species living in the same area form a population. Its inherited traits can change in frequency over generations through four main mechanisms.
Natural selection can spread inherited traits that help individuals survive and reproduce.
Mutations are changes in genetic material that happen without regard to what an organism needs. They create new genetic variants. Their effects may be neutral, harmful or helpful. Mutation is the original source of new genetic variants.
Genetic drift changes variant frequencies by chance. A storm, for example, might leave survivors with a different mix of inherited traits.
Gene flow transfers genetic variants between populations when organisms, or their reproductive cells, move. Wind carrying pollen between flower fields is an example.
Natural selection consistently favours traits suited to the environment. The other mechanisms may improve that fit by chance, but do not reliably do so.
Inherited differences give selection something to act on
Individuals vary. Among rabbits, some have thicker coats, faster running speeds or better sight.
For natural selection to change inherited traits across generations, the relevant differences must be heritable: passed through genes. Muscle a rabbit develops through exercise is not itself inherited. Genes affecting leg strength, however, can pass to its offspring.
Mutations are changes in genes that happen without regard to what an organism needs. They create new genetic variants. When parents reproduce, their genes are also combined in different ways, producing inherited differences among offspring.
Without inherited variation, selection cannot favour one inherited trait over another. Identical inherited traits do not guarantee identical outcomes, because chance also affects survival.
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