Two Marks Questions
1. What is metagenesis? Animals belonging to which phylum exhibit metagenesis?
A: Exhibit alternation of generations is called metagenesis. Cnidarians.
2. What do you call the locomotor structures of Nereis? Why is the nereis called a polychaeta?
A: Parapodia. Which bear many setae.
3. What are the respiratoy structures of Limulus and Palamnaeus respectively?
A: Limulus - book - gills, Palamnaeus - book - lungs.
4. Which arthropod, you have studied is called a living fossil? Name its respiratory organ.
A: Limulus - king crab, Respiratory organs - book gills.
5. What is the function of radula? Give the name of the group of molluscs which do not possess a radula.
A: The buccal cavity contains a file like rasping organ called radula. Radula is absent at Pelecypoda or Bivalvia.
6. What is Aristotle's lantern? Give one example of an animal possessing it.
A: A complex five jawed masticatory apparatus called Aristotle's lantern.
e.g.: Sea Urchin-Echinus.
Four Marks Questions
1. What are the salient features exhibited by Polychaeta?
A: Polychaeta: Poly - many, Chaetae - setae
* These are marine annelids, commonly called as 'bristle worms'. Some are freemoving and others burrowing or tubicolous. Head consists of as eyes, tentacles and palps. Parapodia which bear many setae helps in locomotion and respiration. Clitellum is absent. They are dioecious. Gonoducts are absent. Gametes are shed into the coelom and passed out through the nephridiopores. Fertilization is external, development includes a trochophore larva.
e.g.: Nereis (sandworm/ ragworm/ clam worm), Aphrodite (sea mouse), Arenicola (lugworm).
2. What are the chief characters of the crustaceans?
A: They are aquatic. Head and thorax fuse forming the cephalothorax. Exoskeleton is hardened by calcium carbonate. Cephalic region bears antennae. One pair or mandibules and two pairs of maxillae is present. Respiratory organs are gillls. Excretory organs are green glands/ antennary glands. Development is indirect and includes different larval forms.
e.g.: Palaemon (Freshwater prawn), Cancer (Crab), Balanus (Rock barncle), Astacus (Cray fish), Sacculina (Root headed barncle), Daphnia (Water flea).
