B2.6

Þ    New species can arise from existing species if a group becomes isolated from the rest.

Þ    Genetic variation occurs through natural selection in each population. The alleles that control the characteristics which help the organism to survive are selected. The organisms with these alleles will survive and breed.

Þ    If the environment, competitors, food supply and predator are different for each population they will evolve differently.

Þ    Speciation has occurred when the two populations can no longer successfully interbreed.

They can be formed:

Þ    From the hard parts of animals that don’t decay easily (bones, teeth, shells, claws)

Þ    From parts of organisms that haven’t decayed as conditions for decay are absent, oxygen, water, warmth, etc.

Þ    From parts of the organism that are replaced by other materials (i.e. minerals) as they decay

Þ    From preserved traces of organisms i.e. footprints, burrows + rootlet traces