1. Name the three classes of Mollusks and give an example of each.
Gastropod- snail; bivalve – clam; cephalopod - octopus
2. How are jellies and sponges different from all other animals?
They both have only two cell layers: ectoderm and endoderm.
3. What are nematocysts? Describe how they are used. What phylum of animals uses them?
Nematocysts are stingers, used by Cnidarians, that are located in cnidocytes. They are used to paralyze prey for feeding.
4. Contrast the symmetry of jellies and sponges. Describe the advantage of the jellies’ symmetry with respect to feeding.
Jellies have radial symmetry and sponges are asymmetric. This allows the jellies to perceive stimuli on all sides because they are unable to actively hunt their own food.
5. Most animals have three cell layers. What are these three layers and what does each develop into?
Endoderm – digestive tract; mesoderm – muscles and most organs; ectoderm - skin
6. Describe why sponges are considered to be filter feeders. What cells are used in this process?
Sponges use their collar cells to create a current, pulling water into their cavity. Those collar cells then trap food particles, in effect, filtering them out of the water.
7. What major characteristic separates the roundworms from the flatworms?
Roundworms have a pseudocoelom and flatworms are acoelomates.
8. What is a coelom and why is it significant to the evolution of animals?
A coelom is a body cavity within the mesoderm that holds organs. This allows the animals to have more complex organs.
9. Which phylum of animals was the first to actually hunt for its prey? What major characteristic
evolved at this time to make this possible?
The flatworms, Platyhelminthes, were the first animals to actively hunt. They are able to do this because all of their sensory organs are located in a head region, a characteristic known as cephalization.
10. Which phylum was the first: a) to have three cell layers - Platyhelminthes d) to show cephalization- Platyhelminthes b) to have a true coelom- Mollusca c) to move as an adult -Cnidaria e) to have two openings - Nematoda f) to show segmentation - Annelida

11. Describe a symbiotic relationship that includes: a) a cnidarian, - algae living in coral b) a flatworm- tapeworm in a human c) a roundworm - heartworm in a dog
12. In what phylum of animals would you find an osculum? Porifera What is its function? The osculum is the main opening through which water leaves after the sponge filters the food out.
13. Compare protostomes to deuterostomes. Give an example of an animal that displays each of these
characteristics.
During development, the mouth forms before the anus in protostomes but in deuterostomes the anus forms before the mouth. A clam is a protostome and a bird is a deuterostome.
14. Why are Echinoderms considered to be more closely related to humans than insects?
Echinoderms and humans (vertebrates) are both deuterostomes where insects
(Arthropods) are protostomes.
15. What is the main characteristic that differentiates animals from: a) protozoans? Unicellular vs. multicellular b) plants? Heterotrophic vs. autotrophic
c) fungi? Cell wall vs. no cell wall, digest then ingest vs. ingest then digest
16. Why are flies considered to be insects but ticks are arachnids?
Flies, like all insects, have 6 legs and three body parts but ticks, like all arachnids, have
8 legs and two body parts.
17. Name the three main characteristics that define the arthropods.
Jointed legs, exoskeleton made of chitin, segmented bodies
18. Name the phylum, and class where appropriate, to which the following animals belong: a) coral Cnidarian e) sea urchin - Echinodermata b) tape worm – Platyhelminthes c) squid - Mollusca, cephalopod d) sponge Porifera f) millipede – Arthropoda, myriapod g) snail Mollusca, gastropod h) earthworm - Annelida
19. Describe three characteristics that all chordates share, whether they are vertebrates or not.
Tail at some point during development, pharyngeal slits (gills), notochord, nerve slit
20. Describe how the echinoderms move. What does the word echinoderm literally mean?
Echinoderms, “spiny skinned” animals, move using tube feet and a water vascular system. They move water around internal tubes to maneuver their suction cup-like tube feet.