Lecture 22, slide 104.3 --- Astronomy 183 --- Spring 2009

The first eukaryotes

It is also worth pointing out that oxygen in the atmosphere is generally poisonous to anaerobic organisms.

So the rise of atmospheric oxygen had two results:

(1) it killed off many existing organisms;

(2) it allowed some of the remaining organisms to launch respiration and, soon after, multicellular growth; and

(3) the respiring organisms had much more powerful engines under the hood because they were burning oxygen.

There was an explosion of multicellular development that corresponded with the rise of atmospheric oxygen. The oldest eukaryotic fossils are around 2 billion years old. Remember: this explosion of diverse eukaryotes was enabled by the rise in oxygen.

Question: Is this explosion of multicellular development a natural consequence of the development of life (especially photosynthetic organisms)? We will talk about this more later this week and next week: Is life, and is multicellular or higher life, an unavoidable consequence of life arising, or is it an unusual phenomenon?

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