ZoologyLesson 4 of 7 in the course Invertebrates

Mollusks and Annelids: Body Plans, Diversity, and Development

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces the shared features of annelids and mollusks, then explores the basic molluscan body plan and life cycle.

Annelids and mollusks are bilaterally symmetrical, cephalized, triploblastic animals with a schizocoelous coelom. Many aquatic members of both groups develop a trochophore larva, a shared feature consistent with their evolutionary relationship. Their flexible body plans have contributed to great abundance and diversity.

All flashcards

What is a trochophore?
A larval form, common among many aquatic mollusks and annelids, that has bands of cilia around its body and an apical tuft of cilia.
What are the three main regions of the typical molluscan body?
The muscular foot, the visceral mass containing most internal organs, and the mantle covering the visceral mass.
What does the mantle do?
It covers the visceral mass, forms the mantle cavity, and in most mollusks secretes a protective shell.
What is the radula used for?
It is a toothed, tongue-like organ used by most mollusks to scrape or shred food before it enters the digestive tract.
How do many cephalopods differ developmentally from other aquatic mollusks?
They generally develop directly into juvenile versions of the adult rather than passing through a trochophore larval stage.

Quiz questions

  1. Which larval form is shared by many aquatic mollusks and annelids?Answer: The trochophore
  2. What is the main function of the molluscan mantle?Answer: It covers the visceral mass, forms the mantle cavity, and often secretes a shell.
  3. Which molluscan body region contains most internal organs?Answer: The visceral mass
  4. A mollusk scrapes algae from a surface with a toothed, tongue-like structure. What is it using?Answer: A radula
  5. Why is the mantle cavity especially important in adult mollusks?Answer: It is a major chamber that may house gills because the adult coelom is greatly reduced.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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