Structural Evidence of Evolution

1. Structural Evidence of Evolution • Distinguish between homologous and analogous structures. Which is best used as supportive evidence of recent common ancestry? • What are vestigial structures? How are they evidence of common ancestry?

5. Evidence of Evolution: Fossils

6. Evidence: Molecular Biology Why do we compare amino acid sequence instead of DNA base sequence?

7. Apply Darwin’s Theory: An orange grower discovered most of his trees were covered with infested mites. He sprayed the trees with an insecticide that killed 99% of the mites. Five weeks later, the trees were infested again, so he re-sprayed using the same amount of the insecticide used initially. This time, only half the mites were killed. Apply Darwin’s theory of natural selection to account for this observation.

8. Apply Darwin’s Theory: Over a period of several thousand years deer mice found in the desert evolved a pale coat that helped it to evade predators. Deer mice are widespread across North America, but they usually have dark coat, so that they can blend into dark soils and stay hidden from owls How does Darwin’s theory of natural selection account for this change?

9. Apply Darwin’s Theory: The ancestor of the modern panda was a meat-eating hunter. It’s paws were adapted for running and catching prey, not for fine movement. The modern panda appears to have a “thumb”, which is actually a small bone on the panda’s wrist and not an extra digit. How would Lamarck account for the evolution of this “thumb”? How would Darwin? How does Darwin’s theory of natural selection account for this change?

10. Sample 5pt Response There was probably a shortage of prey so the panda’s were struggling to get food. (1pt) Some of them had a mutation that resulted in a wrist bone growing into a thumb-like appendage. This variation between them and the rest (1pts) of the panda population enabled them to grab bamboo. The “thumb” was therefore an adaptation because it provided them with the advantage(1pt) of expanding their potential food supply. Having the adaptation increases fitness so those pandas with it are surviving and reproducing more. They will pass their genes for the adaptation during reproduction leading to an increase in alleles for the “thumb”(1pt) in the panda population. Over many generations, as a result of natural selection, more and more descendants of these pandas will have the adaptation, leading to a modification in the species. (1pt)