Monday, December 10, 2007

Concept 26.5

Q1: How does the division of function differ for single-celled and multicellular organisms?

A1: A single-celled organism must carry out all of the functions required to stay alive. Most multicellular organisms have many types of specialized cells, and life functions are divided among specific cell types.

Q2: In what way is “Cambrian explosion” a good description of the early part of the fossil record of animal history? What is meant by the metaphor of a “long fuse” for the Cambrian explosion?

A2: Fossils of most major animal phyla appear suddenly in the first 20 million years of the Cambrian period. Molecular clocks suggest that many animal phyla originated much earlier.

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