| Answer Key Mollusks, Worms, Arthropods, Echinoderms | |
| 1. Explain the difference between the three types of mollusks and give an example for each. | |
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Answer: Univalves have only one shell, like the snail. Bivalves have two shells, such as the giant clam. Finally, some mollusks do not have a shell like the squid and slug.
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| 2. Look for and find three mollusks that contain shells that you have collected at the beach or seen in a store or museum. Were you surprised at the animal that lived in those shells? Why or why not? | |
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Answer: Students should list three types of shelled mollusks and describe where they found those shells. They should describe their thoughts about the mollusks that lived within those shells.
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| 3. Describe how the cephalopod is different from other mollusks. | |
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Answer: The cephalopods lack shells (for the most part) and have advanced brain systems (compared to most other mollusks that have little brain systems). Cephalopods also have amorphous bodies and can move around very quickly.
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| 4. In the video clip with the squid jetting itself forward, which way has the squid gone? You may need to watch the video a few times; the action is very rapid. Describe how the squid has accomplished this. | |
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Answer: The squid actually moves to the left, leaving a cloud of ink in its wake. The squid takes in water through its mantle which then traps the water and then contracts to blow out a forceful jet-like explosion of water, which then propels the squid forward.
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| 5. What makes the planarian so unique? | |
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Answer: They can regenerate their heads and tails. A sliced body part (even the head) will re-grow into two separate parts.
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| 6. What makes the leech so unique? | |
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Answer: The leech (there are over 600 species) are parasitic blood-suckers.
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| 7. What types of worms are leeches most similar too? | |
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Answer: Leeches are actually annelids with segmented bodies and are “cousins” to earthworms.
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| 8. Describe how a leech can help a patient in surgery. | |
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Answer: Leeches suck excess blood away from the patient, preventing build-up of blood, which clots. The leech saliva actually serves as a blood thinner which helps encourage the flow of blood from the patient.
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| 9. Describe the main difference between an earthworm’s circulatory system and your own. | |
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Answer: The earthworm does not have a heart. Instead, it has a set of aortic arches that act as the heart. Extending from the arches is a dorsal and ventral blood vessel that carries blood to the extremities of the body.
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| 10. Why should we not call the sea star the popular term, “star fish”? | |
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Answer: Sea stars are not fish at all. They are invertebrates and lack gills and fins. They use their water vascular system for structural support and their tube feet for locomotion.
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| 11. Provide a step-by-step description of how a sea star capture and eats its prey. | |
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Answer: The sea star uses its tube feet to move towards and then climb onto the prey, usually some sort of non-moving bivalve. The muscular sea star uses its tube feet to suction onto the shells and then pull them apart. The sea star then inserts its sac-like stomach into the mollusk, secreting digestive enzymes that rapidly break down the mollusks soft interior. The food is sucked back into the sea star along with its stomach.
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| 12. Describe some escape mechanisms. | |
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Answer: Movement away from the predator, secretion of chemicals and body fluids, catching the current, and extension of spines are all methods animals may use to escape from a predator.
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