Lecture 9 - Extinctions and Radiations

Question 1

What is the Cambrian Explosion?

Answer 1

It was an extensive radiation that occurred 535-525 million years ago. Many present-day animal phyla and large, hard-bodied animals and predators first appeared.

Question 2

What is the Burgess shale?

Answer 2

It is a fossil bed with many strange animals from the Cambrian era.

Question 3

What qualifies as a mass extinction?

Answer 3

A mass extinction is caused by a change in global temperature and more than half of marine species become extinct. It shows the decimation of hard-bodied animals that live in shallow areas.

Question 4

What is an adaptive radiation?

Answer 4

A period of evolutionary change where organisms form many new species whose adaptions allow them to fill different ecological roles.

Question 5

What are 4 mechanisms for adaptive radiations?

Answer 5

1. Changes in the environment
2. Availability of new habitat
3. New innovations in morphology, development, or behavior
4. New species interactions

Question 6

What are 4 causes of the Cambrian explosion?

Answer 6

1. Rise in oxygen levels
2. Receding glaciers
3. Appearance of diverse body plans
4. Emergence of predators

Question 7

How is coevolution like an “arms race”?

Answer 7

Two interacting species reciprocally evolve to maintain a relationship leading to genetic diversity within each population.