Chief excretory matter in echinoderms

Options

A. (a) ammonia
B. (b) urea
C. (c) uric acid
D. (d) amino acid

Answer

### Step-by-Step Solution:

1. **Understanding Echinoderms**:
- Echinoderms are a group of exclusively marine animals that belong to the animal kingdom. Examples include starfish, sea urchins, and sea cucumbers.

2. **Excretory Organs**:
- Echinoderms have poorly developed excretory organs. In fact, they do not possess specialized excretory organs like kidneys that are found in many other animals.

3. **Excretion Process**:
- The excretion in echinoderms occurs primarily through the process of diffusion. This means that waste products are expelled directly through the body surface and gills into the surrounding water.

4. **Excretory Matter**:
- Being marine animals, echinoderms excrete ammonia as their chief excretory matter. Ammonia is a highly toxic substance, but because echinoderms are surrounded by water, they can afford to excrete it, as it requires a large amount of water to be safely removed from the body.

5. **Classification of Excretion**:
- Echinoderms are classified as ammonotelic animals because they primarily excrete ammonia. This is a common trait among many aquatic animals.

6. **Final Answer**:
- Therefore, the chief excretory matter in echinoderms is ammonia.