Lecture 8: Evidence for Evolution

Question 1

What are the predictions we can make based on Darwin’s theory of evolution?

Answer 1

1. There should be variation among individuals within a species, and the variation should be heritable.
2. There should be evidence of Natural Selection (differential survival and reproduction) within populations
3. If there has been common descent, then molecules should indicate life has a shared history (molecular homologies)
4. The anatomy and structure of organisms should indicate they shared a common ancestor
5. There should be evidence of transitional forms in the fossil record
6. There should be evidence of extinction

Question 2

List similarities that are overwhelming evidence that many molecular features are shared due to common ancestry

Answer 2

• The Central dogma is followed in all living things
• Process of making proteins and RNA is very similar in all living things
• All cell have cell membrane that are primarly composed of lipid bilayers
• The same 20 amino acids are used for proteins
• The DNA code for protein synthesis is basically unchanged among living species
• The basic biochemical pathways are retained in all cells
• The great diversity of chemicals in living organisms are based on relatively small number of building blocks found in all organisms

Question 3

What is a vestigial trait?

What vestigial structures do humans have?

Answer 3

Structures that are reduced or incompletely developed but clearly show similarity to functiongin structures in closely related species.

Basically useless structures that show common ancestry but we have them.

Coccyx (tailbone), appendix, wisdom teeth

Question 4

What is a transitional feature in a fossil?

Answer 4

A transitional feature is a trait in a fossil species that is intermediate between those of ancestral and derived species (older and younger).

Question 5

How is the Archaeopteryx respresentiative of a transitional fossil?

Answer 5

1. Archaeopteryx fossils have a few characteristics of modern birds that most dionsaurs did not have
2. Archaeopteryx fossils display many traits in common with dinosaurs

Because they contain features of birds and dinosaurs, it is an organism that represents the transition from birds to dinosaurs

Question 6

What are the 2 kinds of extinction?

Answer 6

Background-level extinction (smaller) and mass extinction events

Question 7

What are the 3 most recent mass extinction events?

Answer 7

1. End-cretaceous extinction; 65 million years ago
2. Late triassic extinction; 205 mililon years ago
3. End-Permian Extinction (mother of all extinctions); 250 million years ago

89-96% of all species at the time of end-permian extinction went extinct