Evidence from Fossils Sequence fossils appear matches the sequence they would evolve Age of fossils determined from age of rock Bac t., algae, fungi, worms, land vetebrates Bony fish, amphibians, reptiles, birds, placental mammals Plants before animals, land plants before land animals, flowering plants before insects Many sequences link existing organisms to ancestors

Evidence from selective breeding Large differences between modern livestock and wild species Variation between domesticated breeds Humans selectively breed animals for specific traits that they consider useful. This process is called artificial selection Artificial selection causes large changes in a short period of time. Selection causes evolution

Analogous Structures Structures that have different origins but become similar because they perform the same or a similar function. Result of Convergent evolution. Wings of birds and butterflies Tail fins of whales and fishes Unrelated species evolved similar features out of necessity

Evidence of Homologous structures Structures that look different and may form a different function, but have a “unity of type.” Forelimbs of human, mole, horse, porpoise, and bat Same bones in same positions. All share common ancestor that had a pentadactyl limb. Limbs have become different because they perform different functions. Adaptive Radiation

Vestigial Structures Reduced structures that show no particular function Developing teeth in whale embryos when adult whales have no teeth Small pelvis and thigh bone in whales and some snakes Appendix in humans. Structures that no longer have a function and are eventually being lost by evolution

Pentadactyl Limb Bone StructureForelimbHindlimb Single bone in the proximal partHumerusFemur Two bones in the distal partRadius and ulnaTibia and fibula Group of wrist/ankle bonesCarpalsTarsals Series of bones in each of 5 digitsMetacarpals and phalangesMetatarsals and phalanges

Speciation Populations of a species become separated so they cannot interbreed. Natural selection acts differently on each of the two populations Species evolve in different ways. Characteristics gradually diverge and become recognizably different Species no longer capable of interbreeding Often occurs if species become geographically isolated

Charles Darwin Young naturalist explored the Galapagos Islands located off the western coast of South AmericaGalapagos Noticed on the islands numerous different organisms Finches: differences in the size and shape of their beaks

Evidence from Patterns of Variation Divergence is gradual Organisms present at different stages of divergence Red Grouse of Brittain and Willow Ptarmigan of Norway Sometimes classified as same species, sometimes not. Darwins Finches

Populations will gradually diverge over time and it is natural to see continuous variation across a geographical range. The Red Grouse and the Willow Ptarmigan where at one time classified as two separate species. The current scientific consensus is that they are both members of the same species (Lagopus lagopus) The greater the geographical separation and the longer the populations have been separated the greater the divergence.

Industrial Melanism Melanistic- dark varieties of typically light-colored insects Melanistic varieties more common in polluted, industrial areas In unpolluted areas, light colored insects are better camouflaged. In polluted areas, dark colored insects are better camouflaged. Example of evolution by natural selection