ZoologyLesson 3 of 5 in the course Diversity of Animals

Body Plans and Physiology of Flatworms, Nematodes, and Arthropods

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

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Summary

Flatworms show how a simple body plan can support both free-living and parasitic ways of life. This lesson covers their structure, basic physiological processes, and traditional major groups.

Flatworms belong to phylum Platyhelminthes. They are triploblastic, meaning their embryos develop three germ layers: ectoderm, mesoderm, and endoderm. They are also bilaterally symmetrical: a lengthwise division can separate the body into matching right and left sides. Bilateral symmetry is associated with cephalization, the concentration of nervous tissue and sensory organs at the front end, which encounters the environment first.

All flashcards

How do flame cells help flatworms?
Their beating cilia move waste-containing fluid through excretory tubules.
What is a nematode cuticle?
A tough, flexible, chitin-containing external covering that supports and protects the body.
What is ecdysis?
The periodic shedding and replacement of an external cuticle.
What is the hemocoel in arthropods?
The body cavity where circulating fluid bathes internal organs.
What are proglottids?
Repeated tapeworm body units that contain reproductive structures.

Quiz questions

  1. Which feature makes the nematode digestive system complete?Answer: It has separate mouth and anus openings.
  2. How do longitudinal muscles help nematodes move?Answer: They produce side-to-side bends that travel along the body.
  3. How do insects and myriapods commonly exchange gases?Answer: Branching tracheae connect to the outside through spiracles.
  4. Where do the three pairs of legs attach in hexapods?Answer: They attach to the thorax.
  5. What happens in an arthropod open circulatory system?Answer: Circulating fluid leaves vessels and bathes organs in the hemocoel.

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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