Food for Thought 17. Contrast the digestive systems of free-living and parasitic
ID: 218241 • Letter: F
Question
Food for Thought 17. Contrast the digestive systems of free-living and parasitic flatworms. 18. Explain the relationship between the tremendous numbers of eggs produced by fukes and ta and the complexity of their life cycles 19. The relatively simple animals Hydra and Dugesiz can regenerate lost body part, but humansgenerall an- not. Discuss this in terms of tissue differentiation and the comparative levels of structural complexity of these organisms 20. Search the World Wide Web for sites that include references to flatworms or rotifers. List two addresses and briefly describe their contents. http:// http:// 372 EXERCISE 18Explanation / Answer
Answer-17)
Flatworms of the class Turbellaria are said to be independent free living flatworms. The digestive cavity is absent in some turbellarians but most of them possess a blind digestive cavity which are simple and unbranched chambers. The turbellarians are carnivores and feed on small invertebrates. The pharynx function as an ingestive organ. The pharyngeal glands secret enzymes that break down food into simpler forms which is then passed into the pharynx. The food is broken into intracellular vessicles and hence the digestion is completed.
Tapeworm or the parasitic tapeworm possess neither a mouth nor a digestive tract. They derive the nourishment from the host intestine. They bath in the pre-digested fluids of there host and hence absorb nutrients directly into there body. Hooks and suckers help attach them to the host.