1. Chapter 33 Invertebrates

2. Lack a backbone Account for 95% of all known animal species. All but one of the 35 animal phyla.

3. Porifera Sponges are sedentary suspension feeders. They pass water through their pores and extract food. They are sessile.

5. Radial Symmetry Cnidarians are invertebrates such as jellyfish, corals, and hydras. Many inverts have radial symmetry.

6. Bilateral Symmetry Most animals are bilaterally symmetrical, and have triploblastic development. Platyhelminthes flatworms

7. Rotifera Tiny animals inhabiting fresh water, marine, and damp soil. Unique because many of them reproduce via parthenogenesis.

8. Parthogenesis Females produce offspring from unfertilized eggs.

9. Parthogenesis Some species of rotifers produce two types of eggs. One develops into a female, the other into a short-lived male. The male survives long enough to produce sperm that fertilize the eggs.

10. Parthogenesis Some rotifers produce females. These females lay more unfertilized eggs that develop into more females.

11. Mollusca Have a muscular foot. A visceral mass containing internal organs. A mantle, a tissue that secretes a shell.

12. Annelida Segmented worms.

13. Arthropoda 2/3’s of all known species. They have a hard exoskeleton and jointed appendages.

14. Echinoderms and Chordata Echinoderms are spiny skinned animals such as sea stars and sea urchins. Chordata are the subphyla of invertebrates that contain a notochord but no vertebra.