Lecture 8: Evolutionary Trends in Animals (Chs. 32-33)

1. Structure, nutrition, and life history define animals

2. The animal kingdom probably evolved from a colonial, flagellated protist

3. The remodeling of phylogenetic trees illustrates the process of scientific inquiry

4. The traditional phylogenetic tree of animals is based mainly on grades in body “plans”

5. Molecular systematists are moving some branches around on the phylogenetic tree of animals

6. Most animal phyla originated in a relatively brief span of geological time

7. “Evo-devo” may clarify our understanding of the Cambrian diversification

8. More than a million extant species of animals are known, and at least as many more will probably be identified by future biologists. Arthropods dominate diversity (especially Coleoptera)

9. Animals are grouped into about 35 phyla.

10. Animals inhabit nearly all environment on Earth, but most phyla consist mainly of aquatic species.

11. Most live in the seas, where the first animals probably arose.

12. Terrestrial habitats pose special problems for animals. Only the vertebrates and arthropods have great diversity.

13. Our sense of animal diversity is biased in favor of vertebrates, the animals with backbones, which are well represented in terrestrial environments. But, vertebrates are just one subphylum within the phylum Chordata, less than 5% of all animal species.

14. Most of the animals inhabiting a tidepool, a coral reef, or the rocks on a stream bottom are invertebrates, the animals without backbones.

Phylums:

1. Phylum Porifera: Sponges are sessile with porous bodies and choanocytes
2. Phylum Cnidaria: Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes
3. Phylum Ctenophora: Comb jellies possess rows of ciliary plates and adhesive colloblasts
4. Phylum Platyhelminthes: Flatworms are acoelomates with gastrovascular cavities
5. Phylum Rotifera: Rotifers are pseudocoelomates with jaws, crowns of cilia, and complete digestive tracts
6. The lophophorate phyla: Bryozoans, phoronids, and brachiopods are coelomates with ciliated tentacles around their mouth
7. Phylum Nemertea: Proboscis worms are names for their prey-capturing apparatus
8. Phylum Mollusca: Mollusks have a muscular foot, a visceral mass, and a mantle
9. Phylum Annelida: Annelids are segmented worms
10. Phylum Nematoda: Roundworms are nonsegmented pseudocoelomates covered with tough cuticles
11. Arthropods are segmented coelomates with exoskeletons and jointed appendages.
12. Phylum Echinodermata: Echinoderms have a water vascular system and secondary radial symmetry
13. Phylum Chordata: The chordates include two invertebrate subphyla and all vertebrates.