EVOLUTION means change over time.


Organisms are CLASSIFIED as plant, animal or micro-organism using the similarities and differences in their characteristics.

Classification can show how organisms are related by evolution or by how they live (ecological relationship).

The evidence for evolution suggests that all living species have evolved from simple life forms that first developed over 3 billion years ago.

Models of evolutionary relationships

EVOLUTIONARY TREES are models of the relationships between organisms.


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Theories of evolution

There have been many different theories about how evolution happens.

('s theory

Darwin's theory states that evolution happens through NATURAL SELECTION.

Natural selection works on inherited characteristics (caused by GENES).

Relatively rapid evolution will occur if:

  • a new form of a gene occurs due to MUTATION
  • there is a large change in the environment
  • Individuals in a species vary in their characteristics - some of these variations are caused by genes
  • Some variations are better suited to the environment than others
  • Individuals with the better-suited variations are more likely to breed successfully and pass on genes for the better-suited variations
  • the next generation will contain more individuals with the genes for better-suited variations
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