Phylum Coelentrata l Animal kingdom Notes and MCQs

Class 11 CBSE Notes: Phylum Coelenterata (Cnidaria)

Table of Contents

Introduction Key Features of Phylum Coelenterata Body Forms: Polyp and Medusa Examples of Cnidarians Frequently Asked Questions (FAQs) Multiple Choice Questions (MCQs)

Introduction

Phylum Coelenterata,is the second phylum of invertebrates of kingdom animalia. First phylum is Phylum Porifera.

Key Features of Phylum Coelenterata

Phylum Coelenterata, also known as Cnidaria, includes aquatic, mostly marine animals that can be either sessile or free-swimming. These animals exhibit radial symmetry. The name Cnidaria is derived from cnidoblasts or cnidocytes, which contain stinging capsules or nematocysts. These structures are present on the tentacles and the body and are used for anchorage, defense, and prey capture. Cnidarians exhibit tissue-level organization and are diploblastic.

Cnidarians have a central gastro-vascular cavity with a single opening, the mouth, located on the hypostome. Digestion in cnidarians is both extracellular and intracellular. Some cnidarians, such as corals, have a skeleton composed of calcium carbonate.

Body Forms: Polyp and Medusa

Cnidarians exhibit two basic body forms: polyp and medusa. The polyp form is sessile and cylindrical, as seen in organisms like Hydra and Adamsia. The medusa form is umbrella-shaped and free-swimming, like Aurelia (jellyfish). Some cnidarians exhibit alternation of generations (Metagenesis), where polyps produce medusae asexually, and medusae produce polyps sexually, as seen in Obelia.

Examples of Cnidarians

• Physalia (Portuguese man-of-war)
• Adamsia (Sea anemone)
• Pennatula (Sea-pen)
• Gorgonia (Sea-fan)
• Meandrina (Brain coral)

Frequently Asked Questions (FAQs)

What are Cnidoblasts?

Cnidoblasts are specialized cells in cnidarians that contain stinging capsules called nematocysts. They are used for anchorage, defense, and capturing prey.

What is the function of the gastro-vascular cavity in cnidarians?

The gastro-vascular cavity in cnidarians serves as the primary site for digestion and distribution of nutrients. It has a single opening that serves as both mouth and anus.

What is Metagenesis in cnidarians?

Metagenesis is the alternation of generations in cnidarians where the asexual polyp form produces medusae, and the medusa form produces polyps sexually.

What is the difference between polyp and medusa forms?

Polyp is a sessile and cylindrical form of cnidarians, while medusa is an umbrella-shaped and free-swimming form.

What is the role of calcium carbonate in corals?

In corals, calcium carbonate forms the skeleton, providing structure and protection.

Multiple Choice Questions (MCQs)

1. What type of symmetry do cnidarians exhibit?
   1. Bilateral symmetry
   2. Radial symmetry
   3. Asymmetry
   4. None of the above

   Answer: b) Radial symmetry

2. What is the primary function of cnidoblasts in cnidarians?
   1. Reproduction
   2. Digestion
   3. Stinging and capturing prey
   4. Respiration

   Answer: c) Stinging and capturing prey

3. Which of the following is an example of a polyp form?
   1. Hydra
   2. Jellyfish
   3. Sea anemone
   4. Both a and c

   Answer: d) Both a and c

4. In what form does Metagenesis occur in cnidarians?
   1. Polyp to polyp
   2. Medusa to medusa
   3. Polyp to medusa and vice versa
   4. None of the above

   Answer: c) Polyp to medusa and vice versa

5. What type of skeleton do corals have?
   1. Calcium phosphate
   2. Chitin
   3. Calcium carbonate
   4. Silica

   Answer: c) Calcium carbonate

6. Which cnidarian is also known as the Portuguese man-of-war?
   1. Physalia
   2. Adamsia
   3. Pennatula
   4. Gorgonia

   Answer: a) Physalia

7. What is the mode of reproduction in medusae during Metagenesis?
   1. Sexual
   2. Asexual
   3. Budding
   4. Fragmentation

   Answer: a) Sexual

8. What is the main component of the skeleton in sea-fans?
   1. Chitin
   2. Calcium carbonate
   3. Silica
   4. Protein

   Answer: b) Calcium carbonate

9. Which cnidarian exhibits a free-swimming medusa form?
   1. Hydra
   2. Adamsia
   3. Aurelia
   4. Meandrina

   Answer: c) Aurelia

10. What type of digestive process is exhibited by cnidarians?
    1. Extracellular
    2. Intracellular
    3. Both extracellular and intracellular
    4. None of the above

    Answer: c) Both extracellular and intracellular

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