A Walk Through Time

The One And The Many

1200 Million Years Ago

The explosive growth of the fossil record of algae and other organisms moves some paleobiologists to dub this the Big Bang period of eukaryotes, beings made of cells with nuclei.

Over all Earth, protoctists form communities with bacteria as well as with other protoctists. Manic mixing and matching of organisms occurs.

In "colonial" protoctists, a few cells break off from the individual body and regenerate the entire organism. This is not possible for most multicellular protoctists, whose cells, like ours, differentiate (specialize).

Top: The white blobs are freeloading red algae living on photosynthesizing other red algae. The white blob actually sends its nuclei into the red photosynthesizer. It then directs the transfer of photosynthetic products back "home." (Photograph by Lynda Goff)

Bottom: A filamentous alga, coated with bacteria, supports the base of a tuliplike ciliate that grabs even tinier organisms out of the water through multiple feeding tubes. (Photograph by John Sieburth)

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