Cnidarians Lecture Review

Flashcards covering the characteristics, feeding, reproduction, diversity, and ecological importance of Cnidarians, based on the provided lecture notes.

What phylum do jellyfish and sea anemones belong to?

Cnidaria

What is the approximate number of species in the phylum Cnidaria, and where are most found?

About 10,000 species, mostly marine

What are two key characteristics of the cnidarian body structure?

One body opening, most have two layers of cells, and they exhibit radial symmetry.

Which specialized cells on cnidarian tentacles are used for stinging?

Cnidocytes

What is the capsule within a cnidocyte that contains poison and barbs?

A nematocyst

How do nematocysts function?

They work like tiny harpoons, discharging a coiled tube containing poison and barbs in response to touch or chemical stimuli.

Describe the feeding and digestion process in cnidarians.

Cnidarians capture prey with nematocysts, bring it to the single mouth/anus opening, digest it in the gastrovascular cavity with enzymes, and expel undigested materials through the same opening.

What type of nervous system do cnidarians possess to conduct impulses?

Cnidarians possess a nerve net, which is a decentralized network of nerves found throughout the body. This system allows for the conduction of impulses in multiple directions and facilitates responses to stimuli, such as contracting body parts or tentacles. Unlike more complex animals, cnidarians do not have a centralized brain or ganglion.

What are the two main body forms exhibited by cnidarians?

Polyp and medusa

Describe the polyp body form.

It is tube-shaped with a mouth surrounded by tentacles.

Describe the medusa body form.

It is umbrella-shaped with tentacles hanging down.

Which class of cnidarians has a dominant medusa body form and floats near the ocean surface?

Jellyfishes

Which classes of cnidarians have a dominant polyp stage?

Sea anemones and corals

Which classes of cnidarians have both stage?

Hydroids

List two ecological importances of cnidarians.

They are involved in mutualism, provide habitat for fishes, and offer recreational pleasure (coral reefs) and potential medical uses for humans.