EvidenceFor

Evolution

Homologous Structures:

Similar features that indicate a common ancestor.

Example:

Click here for a link to Winging It: Fish with Fingers PBS video clip

Homologous Structures (cont.):

Analogous Structures:Features that are similar in appearance or function, but do NOT indicate close ancestry.

Vestigial Structures:

Features with no apparent purpose which may have been useful to an

ancestor.

Click here for link to: Whale evolution

Similarities in early embryonic stages may also indicate common ancestry…

***The evidence for similarities in embryo development has now been shown to have been fabricated: The researcher lied about his results…

The more closely related organisms are, the more similar their DNA.

Using DNA to determine evolutionary relationships…

Molecular Clocks:•Single genes evolve (mutate) at a relatively constant rate.•“The longer the time since the organisms diverged [became separate species], the greater the number of differences in the nucleotide sequences.”•The changes in a gene can then be used to calculate dates of divergence.

Convergent EvolutionWhen the environment “selects” similar features even though the ancestors are quite different. (Similar to analogous structures.)

Porpoise (mammal) Shark (fish)

Patterns of Evolution…

Divergent EvolutionWhen different habitats cause related populations to become dissimilar.

http://userwww.sfsu.edu/~biol240/labs/lab_01variation/media/darwinsfinches.gif

Artificial Selectiondeliberately selecting certain characteristics for breeding purposes, in order to produce species that are useful to us for agriculture, food production or transport.

Coevolution

When closely associated species evolve to work together.

Acacia ants and Acacia trees