Answer:

The phylum Mollusca is a large, mainly marine group of invertebrates. Mollusks SHOW a VARIETY of MORPHOLOGIES.

Many mollusks secrete a calcareous shell for protection, but in other species, the shell is reduced or absent.

Mollusks are protostomes.

Explanation:

HomeScienceBiologyFlexBooksCK-12 BiologyCh182. Mollusks and Annelids

18.2 Mollusks and Annelids

Difficulty Level: Basic | Created by: CK-12

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Lesson Objectives

Describe invertebrates in the phylum Mollusca.

Summarize the characteristics of annelids.

Vocabulary

Annelida

deposit feeder

gills

heart

mantle

Mollusca

regeneration

Introduction

Mollusks are invertebrates such as the common snail. Most mollusks have shells. Annelids are worms such as the familiar earthworm. They have segmented BODIES. Annelids look like roundworms on the outside, but on the inside they are more like mollusks.

Mollusks

Have you ever been to the ocean or eaten seafood? If you have, then you probably have encountered members of the phylum Mollusca. Mollusks include snails, scallops, and squids, as shown in Figure below. There are more than 100,000 known species of mollusks. About 80 percent of mollusk species are GASTROPODS.

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