1. In some molluses, the free-swimming larva is a trochophore while in others, i
ID: 207042 • Letter: 1
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1. In some molluses, the free-swimming larva is a trochophore while in others, it ls a velliger with the beginnings of a foot, shel and mantle. What is the relationship of these molluscan juvenile stages? A. A veliger is found strictly in terrestrial molluscs 8. The trochophore is considered ancestral and the veliger is a derived larval stage C. The two larval for D. The veliger is ancestral and the trochophor E. Only the cephalopods have the veliger stage: all other molluses have a trochophore stage rms represent two early and distinct branches of molluscs e is a derived larval stage 2. Which of the following is not a class of the phylum Platyhelminthes? A. Cestoda B. Trematoda C. Nemertea D. Turbellaria 3. Which of the following is NOT a correct description of cnidarian nervous tissues? A. Hydrozoan medusae have ring nerves 8. Scyphozoan medusae have marginal sense organs C. The nerve net synapses with both the nematocysts and the epitheliomuscular cells o. Scyphozoa have both a fast conducting and a slow conducting system to coordinate movements E. Cnidaria are the first animals to develop a central nervous system 4. Cephalization should be most likely in animals A. radial B. parasitic C. motile predatory D. sessile filter-feeding E. sessile animals buried in sand 5. A syncytial tegument is the synapomorphy (unique shared derived feature) of A. Class Turbellaria B. Class Trematoda C. Class Monogenea D. Class Cestoda E. Groups b, c and d together 6. The parasite stages that one might find inside the digestive cavity and gonads of a snail probably belong to the Class: A. Monogenea B. Cestoda C. Trematoda D. Hirudinea E. Turbellaria 7. What is (are) the function(s) of the cnidarian medusa during the life cycle? A. dispersal B. reproduction C. claiming territory for the clone D. a& b E. b&c;Explanation / Answer
Q 1) In some molluscs , the free swimming larvae is trochophore while in others , it is a veliger with the begining of a foot , shell and mantle . What is the relationship of these Molluscan juvenile stages?
Answer- B - The Trochophore larvae is considered ancestral and the velliger is a derived larval stage.
Explanation:- Veliger is a sea snail, it is the characteristic larvae of gastropods, veliger develops from trochophore larvae, trochophore is an ancestral form of larvae .
Q2) Which of the following is not a class of Phylum-Platyhelminthes.
Answer- c- Nemertea.
Explanation:- Phylum platyhelminthes is classified into four classes they are i) Turbelleria(Planarians) ii) Monogenea( ectoparasites) iii) Trematoda (Flukes) iv) Cestoda (Tapeworm). Among these classes Turbelleria is the non-parasitic class of animal, and other three groups belong to parasitic group.
Q3)Whic of the following is not a correct description of cnidarian nervous system?
Answer- E - Cnidarians are the first animals to develop a central nervous system.
Explanation:- Cnidarians have a simple nervous system , that is they have a diffuse nerve net, cnidarians also possess radial cemetry, central nerovus sytem is a characteristic feature of bilateral animals .
Q 4) Cephalization should be most likely in ___ animals?
Answer- e - sessile animals burried in land.
Explanation- Brachiopods are the examples of sessile animals burried in land , they show cephalization, cephalization is development of a control center or brain.
Q 5) A syncytial tegumen is the synapomorphy (unique shared derived feature ) of ___.
Answer:- E- Group B,C,D together.
Explanation:- In Trematoda, Monogenea and Cestoidea there is a syncytial, non-ciliated body covering, called tegument.It is a unique shared derived feature of these three classes.
Q)6) The parasitic stage that one might find inside the digestive cavity and gonads of a snail probably belong to class-
Answer:- C- Trematoda.
Explanation- The trematode parasite has a complex life cycle, it requires two host to reproduce i) snails and ii) water fowls. The parasite produces encysted metacercariae larvae it develops into adult stage in snail, it comes out from snail by its faces. When waterfowl ingests it it produces eggs inside waterfowl, when waterfowl passes the eggs in its faces. Snails get exposed upon ingesting the eggs. Trematode eggs hatch in the snail gut, and the parasite penetrates the snail tissues to develop in the gonads .
Q7) What are the functions of cnidarian medusae during the life cycle?
Answer- D - A& B
Explanation- polyp is the asexual stage and the medusa is the sexual stage of cnidarians , both help in reproduction. Polyp, by budding, gives rise to medusae, medusae either detach themselves and swim away or remain permanently attached to the polyp. The medusae produces new polyps by sexual reproduction. A medusa produces eggs or sperm, they are shed into the water, when an egg gets fertilized, it develops into a swimming larva.
Medusae helps in reproduction as well as in disperse the species in sea due to its motility.
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