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Evolution and Diversity
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Lecture 9
2/25/98
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| | Last week, we began looking at some of the biologic principles necessary to understand the history of life. |
| | On Monday we looked at a film that detailed the diversity of life and how it was produced. |
| | Todays, lecture will expand on that theme, and look at the evolution of diversity in animals. |
| | Evolution of animals resulted from increasingly complex cellular interactions and advances in body plans. |
| | These advances opened up new opportunities for animals in by allowing them to exploit into new environments. |
| | New opportunities allowed further evolution of new forms. |
| From Protista to Porifera |
| | Protista are single-celled "animals" |
| | Porifera are colonial organisms |
| | cellular level of organization |
| | Cnidarians and Ctenophores |
| | tissue level of organization |
| | a simple sack forms the gut |
| | Cnidarians show two modes of existence |
| Planula to flatworms (playhelminthes) |
| | Playhelminthes contain a third layer of tissue |
| | development of a head end (cephalization) |
| Development of the coelom |
| | provides support for the organism |
| | provides method for circulation |
| | Coelom formed independently in two groups |
| | Coelom-like structures formed in other groups (pseudocoelomates) |
| | Coelom allowed expansion into new environments and life styles |
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