Natural Selection Darwin compiled his notes from his voyage and came to the following conclusion. – Traits are inherited from the parents – Traits can.

Natural Selection• Darwin compiled his notes from his voyage and came

to the following conclusion.– Traits are inherited from the parents – Traits can be selected for through selective breeding

• Confirmed in domestic animals in what became known as artificial selection – Selected traits based on human desire and not the natural environment

Natural Selection causes Evolution• Darwin stated in the absence

of artificial selection, Nature provides the selective pressure to drive evolution– Natural selection is driven by

competition among members of a community for resources

Survival of the Fittest• According to Malthus’s calculations, the

world would quickly run out of resources if the birth rate or organisms wasn’t tied to competition.– Each species struggles to find its niche

• Creates a struggle for existence (inter species competition)

– Fitness is tied to reproductive success• The organism that can out compete individuals

within its species and those outside their species will leave the most offspring

Descent with Modification• Infers that ALL organisms

that are similar are related by a common ancestor– Changes were the result of

natural selection• Intra-species selection• Inter-species selection• Availability of resources• Presence of resources• Catastrophes

– Changes are gradual and take a long time• Inferred based on the gradual

changes to our planet• Verified using the fossil

record

Other Evidence of Natural Selection

• Homologous structures– Similar structure but different function within different

species• Provides evidence of common ancestor

Other Evidence of Natural Selection

• Vestigial Organs– Evidence of similarity of structure but with loss of function

• Provides evidence of relatedness

Other Evidence of Natural Selection

• Similar Embryonic stages (development)

Summation of Darwin’s Theory• Individuals differ due to heritable traits• Organisms produce more offspring than are supposed to survive

– Creates competition• Each type of organism will seek to exploit its advantages in a

community• The species that we see today are here because they could best

exploit their niche