Bell Ringer: 1.Define Adaptation 2.Define Natural Selection 3.Define Fitness 4.What will eventually happen to a species that is not “fit” for it’s environment? 5.“Secretariat” was an example of what? 6.What is another name for “Survival of the Fittest?”

Homologous Structures and Speciation

Joke of the Day:

Homologous Structures Structures in different species that are similar because of common ancestry.

TurtleAlligatorBirdMammals Typical primitive fish Homologous Structures

Humerus Ulna Radius Wrist Homologous Structures are of the same basic structure but used differently in the adult organism.

Homologous Structures Activity

Speciation

The origin of new species in evolution. –Example: Darwin’s Galapagos Finches The Theory…… The 13 species of Darwin's finches descended from an ancestral pair of South American finches that landed there accidentally over 100,000 years ago? This pair found an area free of predators and probably adapted to the various unfilled niches.

Speciation Flow Chart Founders Arrive Process A population arrives in a new place How It Leads to Speciation Populations are separated by a geographic barrier and do not share a gene pool. Populations evolve new traits in response to natural selection in their environments. Populations reproduce only within their own group, leading to the development of new species. Species evolve in a way that reduces competition between them Geographic isolation Changes in the gene pool (adaptations) Reproductive isolation Ecological competition

Homologous Structure Activity and Beak of the Finch Activity