21. What is ejected from a rhynchocoel? A) A proboscis, to capture prey B) Water

Question

21. What is ejected from a rhynchocoel? A) A proboscis, to capture prey B) Water, to use in filter feeding C) A proboscis, used to attach to a host animal. D) Ink, to deter predation. 22. What happens in echinoderms when their ampullae contract? A) Gonads are expelled. B) Tube feet expand. C) Waste product is expelled D) All of the above 23 What is the evolutionary origin of the crustacean mandible? A) It evolved from a tooth. B) It evolved from a gill slit C) It evolved from an appendage D) It evolved from a proboscis 24. 24 which of the following taxa is most abundant on earth (has most individuals)? A. Crustacea B.Rotifera C. Nematoda D.Insecta ost species)? Rotifera C. Nematoda D.Insecta

Explanation / Answer

21) B. 22)C The circulatory system consists of the rhynchocoel and peripheral vessels, while blood of other invertebrates is contained in the main body cavity. The fluid in the rhynchocoel moves substances to and from the proboscis, and functions as a fluid skeleton in everting the proboscis and in burrowing. 23). C 24)D 25)D

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