1. 26.1 Invertebrate Evolution and Diversity
Miss Grant
Kaimuki Christian School

2. Origins of Invertebrates
About 3 billion years after the first prokaryotic cells evolved, organisms remained single-celled
Scientists think multicellular eukaryotes evolved from choanoflagellates (single-celled eukaryotes that typically live in colonies)
Oldest evidence of multicellular life: 600 million year old fossils (eggs, embryos, trace fossils)
Evidence shows the first animals began evolving long before the Cambrian Explosion

3. Ediacaran Fauna
Ediacara Hills of Australia: where some of the most important fossils explaining early animal life came from
2 major Cambrian Fossil sites: Chengjiang, China and the Burgess Shale of Canada
Fossils show that over million years animals evolved complex body plans
Cambrian animals evolved shells, skeletons, and other hard body parts
Why do you think we have more fossils from the Cambrian era than the pre-Cambrian era?

4. Invertebrate Diversity
Most abundant animals on Earth
Live in nearly every ecosystem
Present in nearly every food web

5. Non-chordate Invertebrates
The cladogram shows the proposed evolutionary relationships among major groups of modern invertebrates
Indicates sequence in which characteristics evolved

6. Types of Invertebrates
Porifera- sponges
Cnidarians- jellyfish sea fans, sea anemones, hydras, corals
Arthropoda- spiders, centipedes, insects, crustaceans
Nematoda- nematodes (round worms)

7. Types of Invertebrates (Cont.)
Platyhelminthes- flatworms
Annelida- annelids (earthworms, parasites, leeches)
Mollusca- snails, slugs, clams, squid, octopi
Echinodermata- sea stars, sea urchins, sand dollars