Variation and evolution
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.
Links for Learning
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Revision Science: Evolution & Extinction
Live Science: Darwin's Theory of Evolution
Revision World: Variation & Mutation
Bitesize: Evidence for evolution - rock fossils
Bitesize: Linnaean system of classification
Bitesize: Classification of animals