Cladistics (5.4)

Question 1

Define cladistics

Answer 1

A branch of taxonomy that classifies organisms based on shared characteristics with a common ancestor.

Question 2

Define clade

Answer 2

A group of organisms that evolved from a common ancestor.

Question 3

Define cladograms

Answer 3

Tree diagrams that show the most probable sequence of divergence in clades. Each branch point (node) represents the formation of two new groups from a common ancestor.

Question 4

What does comparison of the base sequences of a common gene between two organisms show? (DNA analysis)

Answer 4

The differences between the base sequences demonstrate the degree of evolutionary divergence.

The more similar the base sequences of two species are, the more closely related the two species are expected to be. A greater number of differences suggests that it diverged into a new species a long time ago.

Question 5

What is the concept of the molecular clock?

Answer 5

Some genes may accumulate mutations at a relatively constant rate. If this rate of change is reliable, scientists can calculate the time of divergence by matching this with information from dated fossils.

Question 6

Define homologous traits

Answer 6

Features that have differing function but are structurally similar because of common ancestry. Eg. the pendactyl limb.

Question 7

Define analogous traits

Answer 7

Features that have a similar function but are structurally different. They do not share a common ancestor. i.e. they are superficially similar.

The result of convergent evolution.

Question 8

Define phylogeny

Answer 8

The history of the evolution of a species.