Cambrian Explosion Reading

Cambrian Explosion

A period approximately 540 million years ago when most major animal groups, or phyla, appeared in the fossil record over a relatively short geological time frame

What was the first theory for the Cambrian Explosion?

Oxygen: The sudden appearance of oxygen in the atmosphere and ocean removed barriers to evolution. We can now have larger, more complex forms of life with oxygen

What was wrong with the oxygen theory?

It explained the timing but not the mechanism. How did oxygen explain the sudden burst of diversity at this time?

What was the second theory for the Cambrian Explosion?

Carnivory: Once animals start hunting other animals, this kickstarts the evolutionary arms race. Predators evolve better ways to catch things and prey evolve better defenses. This cycle drives evolution and causes further diversification of life forms

What was wrong with the carnivory theory?

It explains the mechanism, but it doesn’t explain the timing

Why were oxygen minimum zones important?

Oxygen minimum zones showed that the number of carnivorous taxa is much lower in suboxic conditions. Solidified that oxygen is needed to sustain carnivory

Why does low oxygen suppress carnivory?

Predation involves intense burst of activity. Chasing, capturing, and fighting prey takes a lot of energy and oxygen which creates a lot of oxygen debt that you can’t pay back. It’s not only hard but rather physiologically impossible - there’s not enough oxygen in the ocean. All these processes, including digesting prey, takes energy and oxygen which can’t be sustained by the environment

What are the steps of the Cambrian Explosion?

1) Oxygen Rises

2) Debt Payable

3) New Strategy

4) Arms Race

5) Explosion