Which of the following is NOT one of the two tissue layers of a cnidarian? A. outer epidermis B. mesoderm that forms into all body systems C. inner layer lining the gastrovascular cavity

Modern sponges produce microscopic spicules (right) to deter predation but, as the earliest animals, they existed before any predators evolved; how might biologists interpret this observation?   A. Spicules were probably absent in the earliest sponges and evolved later as predation began. B. Spicules performed other tasks in early sponges, possibly structural support, and were later modified for defense. C. Spicules were present in some sponge species and absent in others; predation became a selection pressure that eliminated some species entirely. D. All of the above are valid hypotheses.

Can have both a medusa stage and a polyp stage (both in water) 1. Echinodermata2. Platyhelminthes3. Annelida4. Porifera5. Chordata6. Arthropoda7. Nematods8. Cnidaria9. Mollusca

Which of the following in sponges form the outermost epithelium-like layer that is in contact with the external, aquatic environment? a. Pinacocytes and choanocytes b. Pinacocytes only c. Choanocytes and collencytes d. Pinacocytes and collencytes e. Choanocytes only  f. Collencytes only

The gastrovascular cavity of cnidarians has two openings, one serves as mouth and the other serves as anus.   True   False   The body wall of cnidarians has epidermis, gastrodermis and mesoglea.   True   False   Some cnidarians only have a polyp stage.   True   False

You are trying to identify a living organism which you are observing closely.  Which one of the following would convince you that the organism is acoelomate?     It responds to food by moving toward it.     It is triploblastic.     It has bilateral symmetry.     It possesses sensory structures at its anterior end.     Muscular activity of its digestive system distorts the body wall.   The flatworms have     a true coelom     a pseudocoelom     radial symmetry     tissues derived from the three basic germ layers (i.e. they are triploblastic) need help with both questions for my HW please thank you!

Most anatomists consider bats more specialized than moles; but what important differences can you see between the mole's forelimbs and that of humans? Why is the front limb of the mole so specialized?

8. What is the difference between an open and a closed circulatory system? 9. What is a radula? What is it used for? 10. Define regeneration. 11. Identify distinguishing traits of most arthropods. 12. What is molting? Why does it occur? 13. Name three arthropod head appendages and state their functions. 14. Describe two structures that allow arthropods to breathe air.