Endoskeleton of echinoderms is made of
(a) Silica
(b) Lime
(c) Chitin
(d) Cartilage

Options

A. Silica
B. Lime
C. Chitin
D. Cartilage.

Answer

To determine what the endoskeleton of echinoderms is made of, we will analyze the options provided in the question step by step.

### Step 1: Understand the Definition of Endoskeleton
The endoskeleton is an internal skeleton that provides support and structure to an organism. In echinoderms, this structure is located beneath the epidermis.

**Hint:** Remember that the endoskeleton is internal and is different from an exoskeleton, which is external.

### Step 2: Identify the Phylum
Echinoderms belong to the phylum Echinodermata, which includes organisms such as starfish, sea urchins, and sea cucumbers.

**Hint:** Knowing the classification of echinoderms can help you understand their biological features.

### Step 3: Analyze the Options
Now, let's look at the options provided:

- (a) Silica: This is a compound often found in the structure of some organisms, but not in echinoderms.

- (b) Lime: This is another name for calcium carbonate, which is known to form the endoskeleton in echinoderms.

- (c) Chitin: This is a component of the exoskeleton in arthropods, not echinoderms.

- (d) Cartilage: This is a flexible connective tissue found in vertebrates, but not in echinoderms.

**Hint:** Focus on which materials are commonly associated with the structure of echinoderms.

### Step 4: Conclusion
Based on the analysis, the correct answer is (b) Lime, as the endoskeleton of echinoderms is primarily made of calcium carbonate, which is also referred to as lime.

**Final Answer:** (b) Lime