ZoologyLesson 2 of 2 in the course Marine animals

Cnidarian Biology: Body Plans, Physiology, Life Cycles, and Ecology

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

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Summary

Cnidarians are aquatic invertebrates that include jellyfish, corals, sea anemones, hydroids, and tiny parasites. This lesson introduces the phylum and explains its characteristic body plans and basic layers.

The phylum Cnidaria contains more than 11,000 known species, living mainly in marine environments, although some live in freshwater. Its name comes from the Greek knídē, meaning “nettle,” a reference to the stinging cells characteristic of the group.

All flashcards

Cnidocyte
A specialized cnidarian cell containing an ejectable structure used in prey capture, defense, or other functions.
Spirocyst
A cnidocyte type that entangles targets with sticky threads and does not inject venom.
Rhopalium
A sensory structure that can detect stimuli such as light, pressure, and chemical changes.
Planula
A ciliated cnidarian larva that swims or crawls before settling.
Mesoglea
The non-living, jelly-like material between a cnidarian’s ectoderm and gastroderm.

Quiz questions

  1. What does strobilation by a scyphozoan polyp produce?Answer: Stacked sections that develop into juvenile medusae.
  2. How do cnidarians generally exchange oxygen and carbon dioxide?Answer: By diffusion across thin body layers to and from the surrounding water.
  3. How does bell movement contribute to swimming in many medusae?Answer: Bell contraction expels water, and mesoglea recoil helps draw water back in.
  4. What do coral hosts commonly gain from symbiotic zooxanthellae?Answer: Organic nutrients produced through photosynthesis.
  5. What information can a cnidarian statocyst help detect?Answer: Balance and acceleration using internal mineral grains.

Based on the Wikipedia article Cnidaria, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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