Chapter 33 Invertebrates Invertebrates Lack a backbone Account

Chapter 33 Invertebrates

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

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

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

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

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

Parthogenesis • Females produce offspring from unfertilized eggs.

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.

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

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

Annelida • Segmented worms.

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

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.