Cnidarians

Overview

Cnidarians are a diverse group of invertebrate animals found in marine environments. They are characterized by their radial symmetry and specialized stinging cells called cnidocytes, which they use for capturing prey and defense.

Anatomy

Cnidarians have a simple body plan that consists of a central body cavity surrounded by tentacles. The body cavity is called the gastrovascular cavity, which serves both as a stomach for digestion and a means of circulating nutrients and gases.

Reproduction

Cnidarians can reproduce both sexually and asexually. They typically have a polyp stage, where they are attached to a substrate, and a medusa stage, where they are free-swimming. These different stages allow for a varied reproductive strategy.

Types of Cnidarians

• Jellyfish: Free-swimming medusae with trailing tentacles.
• Corals: Colonial polyps that secrete calcium carbonate to form reefs.
• Sea Anemones: Solitary polyps that resemble flowers and are often found attached to rocks or other substrates.
• Hydrozoans: Diverse group that includes both solitary and colonial forms, such as the Portuguese man o' war.

Ecological Importance

Cnidarians play a crucial role in marine ecosystems. Coral reefs, in particular, provide habitat for a wide variety of marine organisms and help protect coastlines from erosion.

Study Guide

Here are some key points to remember when studying cnidarians:

1. What are the defining characteristics of cnidarians?
2. Describe the anatomy of a typical cnidarian.
3. Compare and contrast the different reproductive strategies of cnidarians.
4. Identify and describe the various types of cnidarians, including examples of each.
5. Explain the ecological importance of cnidarians in marine environments.

[Cnidarians] Related Worksheets and Study Guides:

• Sponges, Cnidarians and WormsScience • Sixth Grade
• Invertebrates - Animals without BackbonesScience • Fourth Grade
• Mollusks, Arthropods and EchinodermsScience • Sixth Grade