The World of Animals

I. Life evolved in the oceans

• A. Least stressful environment

• B. Moderating temperature• C. Closest to osmotic

properties• D. Buoyancy not a problem• E. Gametes can be released

with no problem• F. Abundant food

II. Parazoa-Sponges (Porifera)A. Introduction

• 1. do not possess true tissues• 2. cell layers are loose associations• 3. if you take a sponge and pass it through a screen-it can reassemble• 4. layers are dependent upon one another-but not as dependent as

higher levels• 5. very sessile organisms• 6. lack muscles, nerves-individual cells can react to the environment

B. Body Plan• 1. epidermis with porocytes• 2. mesohyl with amoebocytes• 3. Inner cell layer with choanocytes

4. Endoskeleton of spicules

• a. some spicules are calcium carbonate

• b. some spicules are proteinaceous

• c. found in mesohyl• d. can be used to

classify sponge

5. Choanocytes power the sponge

• a. 275 gallons needed to produce three ounces of new sponge

• b. Flagella creates water currents

• c. Microvilli filter water as it comes through

6. Osculum and spongocoel

C. Reproduction of sponge

• 1. asexual fragmentation• 2. production of gemmules• 3. sexual reproduction-

hermaphroditic

III. Cnidarians or Coelenterates

A. Basic body plan

• 1. diploblastic• 2. gastrovascular

cavity• 3. radial symmetry• 4. tentacles• 5. cnidoblasts• 6. mesoglea• 7. two basic forms-

polyp and medusa

Polyp or medusa?

B. Cnidocyte

C. Classes• 1. Hydrozoa– a. Alternate– B. Poly most predominant

Examples of hydrozoans

Hydrozoans

Hydra videos

• http://www.schooltube.com/video/8b4ca7db15144b83b7c6/Hydra

2. Scyphozoa• a. Medusa stage is prevalent• b. jellyfish

3. Anthozoa-sea anemones and corals

Other anthzoans