What is the advantage of the countercurrent gas exchange in the case of some molluscs? Why is it not present in all representatives

14. Nematode Life Cycle Matching: Match each of the descriptions below with the correct nematode worm species (A-D). Note that some descriptions may not apply to any of the 4 species (in which case just write “none") and some descriptions may apply to multiple worms species (in which case write the letters of all applicable species). (A) Dirofilaria (heartworms) (B) Dracunculus (Guinea worm) (C) Ascaris (D) Hookworms 1. Life cycle includes only a single host 2. The infective stage is a free-living larva that can enter the skin directly 3. On target to become the first parasite-caused human disease to be eradicated 4. Has an arthropod intermediate host 5. Traditional treatment involves winding the female worm around a matchstick 6. Infections can be prevented by not defecating on soill improving sanitation of soil 7. Female lays eggs around the anus of the host 8. Produce microfilaria that circulate in the blood 9. Has multiple larval stages and a snail intermediate host 10. Migrate…

Which of the following terms apply to the body cavity of Molluscs (except Cephalopods)? Choose all that apply. O hemocoel with a coelom persistent blastocoel O pseudocoelom/hemocoel acoelom

2. Describe, compare and contrast movements in the major annelid groups: surface crawling in polychaetes, burrowing in oligochaetes, and "inch- worming" in hirudineans. Be sure to address: means of attaching to substrate, muscles employed, and the role of parapodia, setae, and the coelom.

1.What are the characteristics of the Mollusca? Be precise.

7. Define "heterochrony". Explain how heterochrony may have been involved in the evolution of (or transitions between) 1) pteropod gastropods, 2) the byssal threads of mussels, 3) ascidians and larvaceans and 4) between ascidians and vertebrates.