Physiology and Reproduction in Mollusca MCQ - Practice Questions with Answers

Digestion in Mollusca:

• A complete digestive system is present with a distinct mouth and anus. 
• They can be carnivores, herbivores, filter-feeders, detritivores, or parasites. 
• The herbivorous molluscs have a rasping organ called radula.

Respiration in Mollusca:

• The gills called ctenidia present in the mantle cavity serve as breathing organs for aquatic molluscs. 
• The terrestrial molluscs use the space of mantle cavity for the diffusion of gases. 
• The under surface of the mantle cavity is provided with blood vessels that take in oxygen and give out carbon dioxide. 
• Some terrestrial molluscs also have lungs.

Circulatory System in Mollusca:

• There is a dorsally located heart within pericardial space and blood vessels. 
• The slow moving molluscs have open circulatory system while the fast moving molluscs have closed circulatory system.

Nervous System and Sense Organs in Mollusca:

• The nervous system is represented by three pairs of ganglia - cerebral, visceral and pedal. Octopus has a well-developed brain that allows development of memory.
• They have sense organs for touch, smell and balance. 
• Osphradium in Pila is a chemoreceptor.

Reproduction and Development:

• Molluscs are dioecious animals, i.e., the male and female sex organs are present in different individuals. They are usually oviparous. The development is indirect and the following larval stages are involved:
• Trochophore
• Veliger