Content Outline for Teaching - Potosi School District - Home

17
Section 2
Content Outline
for Teaching
Invertebrate Animals
Sponges, Cnidarians, Flatworms, and Roundworms
Underlined words and
phrases are to be filled
in by students on the
Note-taking Worksheet.
A. Sponges—don’t move to find food since adults are sessile or stuck in one place
1. Filter feeders—filter food out of water that flows through body
a. Pores let water into central cavity.
b. Flagella keep water moving through sponge.
2. Soft sponge bodies are protected by sharp spicules or rubbery spongin.
3. Sponges reproduce sexually and asexually.
a. In asexual reproduction a new sponge grows from pieces of an old sponge.
b. Most sexually reproducing sponges are hermaphrodites,producing both
eggs and sperm.
B. Cnidarians—have tentacles and hollow bodies
1. Two body shapes
a. Polyp cnidarians are usually sessile and have vase-shaped bodies.
b. A medusa body is free-swimming and bell-shaped.
2. Cnidarians reproduce both sexually and asexually.
a. Polyp forms reproduce asexually by budding.
b. Some polyps also reproduce sexually by releasing sperm or eggs.
c. Medusa forms have a two-stage life cycle in which they reproduce both sexually
and asexually.
C. Flatworms—search for their food
1. Have long, flattened bodies with organs and systems
2. Most are parasites living off or in a host.
3. Tapeworms—a type of flatworm
a. Lack a digestive system and absorb nutrients from the host’s intestines
b. Tapeworms reproduce sexually.
Invertebrate Animals 54