Biology » Variation and evolution

Variation and evolution

Key Words

Species - class of plants or animals whose members have the same main characteristics and are able to breed with each other.

Variation - differences in within-species eg. In humans, hair colour or eye colour etc.

Genetic Variation - caused by different genes from the parents.

Environmental variation - differences caused by the conditions that organisms live and grow in.

Mutations - random changes in an organism's DNA. These can sometimes be inherited.

Charles Darwin - came up with the Theory of Evolution:

All of today's species have evolved from simple life forms that first started to develop over three billion years ago.

Phenotypic variation - wide variation in a species characteristics.

'Survival of the fittest' - organisms that are more likely to survive because of their suitable characteristics for the environment they live in.

Speciation - populations of the same species change enough to become reproductively isolated.

Reproductively isolated - species can't interbreed to produce fertile offspring.

Extinction - when no individuals of a species remain.

Fossils - remains of plants and animals found in rocks. They can be formed in three ways:

  • Gradual replacement - the remains replaced by minerals while buried. Fossil is distinct inside the rock.
  • Casts and impressions - soft remains decay leaving a cast or impression.
  • Preservation - no decay takes place it's preserved in amber, glaciers or peat bogs.

Classification - organising living organisms into groups.

Linnaean system - created by Carl Linnaeus, it groups living things according to their characteristics and the structures that make them up.


Also see Reproduction, Genetics