6.3.1-2 - Theory of Evolution & Speciation

Outline the theory of evolution by natural selection.

• Individuals of a species show a wide range of variation for characteristic.

• Those with the characteristics most suited to the environment will survive breed most sucessfully.

• The desirable characteristic that has enables the individuals to survive are passed onto their offspring.

Why was Darwin’s theory of evolution not accepted initially?

• Most people believed in creationism.

• Insufficient evidence to prove the theory.

• The mechanism of variation and inheritance was not known at the time.

What was Jean-Baptiste Lamarck’s theory of inheritance?

That changes during the lifetime of an organism can be inherited.

What is speciation?

The formation of a new species, when two populations become so varied that they cannot interbreed to produce fertile offspring.

What is the definition of a species?

A group of organisms with similar characteristics which are able to interbreed to produce fertile offspring.

Outline the process of speciation through geographic isolation.

• Two populations of the same species are separated geographically.

• Geographic isolation prevents interbreeding and mixing of genes between the populations.

• Due to different selection pressures, different mutations occur producing different phenotypes in each population.

• Over time, the two populations may evolve so that they aren’t able to interbreed.

Why is genetic variation important in speciation?

Genetic variation produces phenotypic variation, some of which are better suited to the environment and are selected for.