Question

Which of the following is a mollusca 1. Earthworm 2. Starfish 3. Snail 4. Hydra​

Answer 1

Answer:

3. snail

Explanation:

Mollusca

• This is the second largest animal phylum.
• Mollusca are terrestrial or aquatic (marine or fresh water) having an organ-system level of organisation.
• They are bilaterally symmetrical, triploblastic and coelomate animals.
• Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.
• The space between the hump and the mantle is called the mantle cavity in which feather like gills are present. They have respiratory and excretory functions.
• The anterior head region has sensory tentacles. The mouth contains a file-like rasping organ for feeding, called radula.  
• They are usually dioecious and oviparous with indirect development.
• Examples:

1. Pila (Apple snail),
2. Pinctada (Pearl oyster),
3. Sepia (Cuttlefish),
4. Loligo (Squid),
5. Octopus (Devil fish),
6. Aplysia (Sea-hare),
7. Dentalium (Tusk shell)
8. Chaetopleura (Chiton).