Question

7 match the class with the correct organism or characteristic. fasciola hepatica a. class turbellaria dugesia b. class cestoda parasitic flukes c. class trematoda tapeworms free - living, carnivorous, aquatic flatworms oral and ventral suckers present; oral sucker used for feeding body consists of segment - like proglottids 8 the cuticles of flukes and tapeworms are highly resistant to enzyme action. why is this feature an important evolutionary modification for endoparasites? 9 why does the tapeworm lack a mouth, well - developed sensory structures, and a digestive system? 10 briefly describe the life cycle of the sheep liver fluke, fasciola hepatica. 11 based on your observations of planaria behaviors, predict how a planaria may react to each of the following stimuli, and indicate which sensory structure would be responsible for the response. a. a bright, sunny day b. a dead earthworm at the bottom of the lake c. a small minnow nibbling at the flatworms tail

Explanation:

1. Fasciola hepatica - c. Class Trematoda (it is a parasitic fluke). Dugesia - a. Class Turbellaria (free - living flatworm). Parasitic flukes - c. Class Trematoda. Tapeworms - b. Class Cestoda. Free - living, carnivorous, aquatic flatworms - a. Class Turbellaria. Oral and ventral suckers present; oral sucker used for feeding - c. Class Trematoda. Body consists of segment - like proglottids - b. Class Cestoda.
2. Endoparasites live inside the host's body where they are exposed to various digestive enzymes. A highly resistant cuticle protects them from being digested by the host's enzymes, allowing them to survive and thrive within the host environment.
3. Tapeworms live in the host's digestive tract where nutrients are already digested. They absorb nutrients directly through their body surface, so they don't need a mouth or a digestive system. Since they are in a relatively stable environment inside the host, well - developed sensory structures are not necessary for survival.
4. The life cycle of Fasciola hepatica starts when eggs are passed in the feces of an infected host. The eggs hatch into miracidia which infect a snail intermediate host. Inside the snail, they develop into sporocysts, rediae, and then cercariae. The cercariae are released from the snail and encyst on vegetation as metacercariae. When a definitive host (such as a sheep) ingests the vegetation with metacercariae, the metacercariae excyst in the host's intestine and migrate to the liver, where they mature into adult flukes.
5. a. A planaria may move away from the bright, sunny day. The eyespots (photoreceptors) are responsible for detecting light and the planaria will seek a darker, more suitable environment.

b. A planaria may move towards the dead earthworm. Chemoreceptors on its body surface will detect the chemical signals released by the decaying earthworm, guiding it to a potential food source.
c. A planaria may contract or try to escape. Mechanoreceptors on its body will detect the physical contact of the minnow nibbling at its tail and trigger a defensive or escape response.

Answer:

1. Fasciola hepatica - c. Class Trematoda

Dugesia - a. Class Turbellaria
Parasitic flukes - c. Class Trematoda
Tapeworms - b. Class Cestoda
Free - living, carnivorous, aquatic flatworms - a. Class Turbellaria
Oral and ventral suckers present; oral sucker used for feeding - c. Class Trematoda
Body consists of segment - like proglottids - b. Class Cestoda

1. Protects from host's digestive enzymes for survival inside host.
2. Absorbs nutrients directly from host's digested food, stable internal environment doesn't require such structures.
3. Eggs in feces, hatch into miracidia, infect snail, develop into sporocysts, rediae, cercariae, encyst on vegetation as metacercariae, ingested by definitive host, mature in liver.
4. a. Move away, eyespots.

b. Move towards, chemoreceptors.
c. Contract/escape, mechanoreceptors.