Worksheet, Annelids, Mollusks, FlatwormsSupplemental InstructionIowa State University

Leader: Delaney R.Course: Biol 211

Instructor: Dr. StewartDate: 9-19-2017

1. Make a list of annelid characteristics.

Worms with body segments. Oligochaetes (earthworms) – decomposers while leeches are secondary consumers (carnivores, ectoparasites) Hydrostatic skeleton; move by muscle contraction. Has a CNS. Asexual (fragmentation) or sexual (monecious)

2. Give 2 reasons why annelids are important in ecosystems.

Inhabit soil and sediment of many types within aquatic and terrestrial ecosystems. They are detritivores and prey, they are important in energy/nutrient flow pathways.

3. What is the importance of annelids to human welfare?

Ecosystem services – oligochaetes enhance soil fertility by consuming organic matter and excreting nutrients and by increasing soil porosity

4. Make a list of mollusk characteristics.

Body plan – mantle and foot. Primary consumers (herbivores, gastropods, bivalves) secondary consumers (carnivores, cephalopods) Hydrostatic skeleton; move using muscular foot, or jet propulsion or tentacles derived from foot. Asexual (parthogenesis in few species) Sexual (monecious or dioecious) – internal (mostly) or external fertilization; eggs hatch into larvae or juveniles resembling small adults.

5. Give 2 reasons why mollusks are important in ecosystems.

Inhabit many aquatic and terrestrial environments. Important in energy/nutrient flow pathways as primary consumers; gastropods consume plants or benthic algae, bivalves filter-feed on phytoplankton

6. What is the importance of mollusks to human welfare?

Economically important as food and nutrition for us as food. Gastropods are hosts for flatworms ex. Schistosoma that cause human disease.

7. Make a list of Platyhelminthes characteristics.

Body plan – flat (usually non-segmented) worms. Secondary consumers (endoparasites, cestodes, trematodes) decomposers or secondary consumers (carnivores, turbellarians)

Hydrostatic skeleton. Asexual- turbellarians (often) by fragmentation. Sexual (monecious or dioecious) – some have complex life cycles (Schistosoma)

8. Give 2 reasons why flatworms are important in ecosystems.

Restricted to aquatic ecosystems or endoparasitic lifestyle. Endoparasitic flatworms can regulate host population sizes.

9. What is the importance of flatworms to human welfare?

Diseases from flatworms effect human health and economies. Cestodes acquired by eating raw or undercooked meat. Schistosomiasis is caused by a trematode.

10. What type of embryos do annelids, mollusks, and flatworms have?

Triploblastic

11. Which of the following are decomposers as well as prey for other animals? (Which makes them very important in the energy and nutrient flow pathways of soil food webs.) A. Trematodes (flukes) B. Oligochaetes C. LeechesD. Cestodes (tapeworms)

12. Review Schistosoma life cycle. How would you accurately describe the life cycle?

Schistosoma eggs hatch into larvae which infect a gastropod. They then undergo metamorphosis into another larval stage and leave the gastropod, penetrate human skin, mature in the human liver and reproduce in the intestine, and produce eggs that are released in human feces.

13. What can humans become infected with from eating undercooked meat?

Cestodes (tapeworms)

14. Recall the frog in the jar that Dr. Stewart showed in lecture. What type of endoparasite caused the hind limb deformities of the frog?

Trematode (fluke)

15. Give an example of an ecosystem service performed by an animal discussed in this lecture?

Oligochaetes increasing soil fertility and plant production by increasing water infiltration and oxygen levels.

16. T or F? The high surface area relative to body volume in flatworms is an adaptation (maximize movement of nutrients and other materials across body wall.)

True

17. Review structure of a tapeworm.

18. Review importance of flatworms in ecosystems (frog deformities.)

19. Review Schistosoma reproduction.

20. Review Schistosoma infecton.

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