ZoologyLesson 1 of 1 in the course Diversity of Animals

Echinoderm Body Plans and Chordate Developmental Features

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

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Summary

The phylum Echinodermata takes its name from Greek words meaning spiny skin. It includes sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, sea lilies, and feather stars. Echinoderms are exclusively marine and include about 7,000 described living species.

Adult echinoderms typically have pentaradial symmetry: their body parts are arranged in five sections around a central axis. Their larvae, in contrast, have bilateral symmetry, with distinct left and right sides. This difference reflects a change in body organization during development.

All flashcards

What is pentaradial symmetry?
A body arrangement in which parts are organized in five sections around a central axis.
What are ossicles in echinoderms?
Small calcareous plates that make up the endoskeleton.
What four features characterize chordates at some developmental stage?
A notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.
What happens to the notochord in vertebrates after birth?
It is replaced by the vertebral column.
How do tunicate larvae differ from most adult tunicates in chordate features?
Larvae possess all four features; adults usually retain pharyngeal slits while the other three disappear.

Quiz questions

  1. Which four structures characterize chordates at some stage of development?Answer: Notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail
  2. What happens to the embryonic notochord in vertebrates after birth?Answer: It is replaced by the vertebral column.
  3. Which chordate feature do most adult tunicates retain after metamorphosis?Answer: Pharyngeal slits
  4. How do adult lancelets differ from most adult tunicates in their chordate features?Answer: Lancelets retain all four features; tunicates usually retain only pharyngeal slits.
  5. How can a sea star begin digesting prey such as a clam?Answer: It turns one stomach outward through its mouth and digests the prey externally.

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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