Q1: Living in the ocean surrounded by water, most marine mollusks have which type of reproduction? (pick one)
a. External fertilization
b. Internal fertilization
c. Self- fertilization
Ans) External fertilization
The term Mollusca was coined by the Johnstonus in 1650. Mollusca are a diverse group of organisms belongs to the invertebrates and they occupy both terrestrial and aquatic habitats, most of the aquatic mollusks are marine but snails & Bivalves are live in fresh water. Phylogenetically they are closely related to the annelids and they are coelomate with bilateral symmetry and show the spiral cleavage. The body of Mollusca consists of foot visceral mass & mantle. Mollusca is classified into Aplacophora, Polyplacophora (Chitons), Monoplacophora (Gastroverms), Gastropoda, Bivalvia, Cephalopoda. Among all Polyplacophora also called Chitons & are exclusively marine mollusks show bilateral symmetry. Separate sexes are observed, show external fertilization. They have trochophore larva during their developmental stage.
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