how many members have a rigid cell wall made of an inner layer of cellulose and outer layer of pectose ?
Chara , Fucus, Porphyra, Ectocarpus, Gelidium, Spirogyra, Sargassum, Volvox, Laminaria, Dictyota

Options

A. Three
B. Five
C. Six
D. Two

Answer

To determine how many members have a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose, we need to identify which of the given organisms are classified as green algae. The organisms listed are: Chara, Fucus, Porphyra, Ectocarpus, Gelidium, Spirogyra, Sargassum, Volvox, Laminaria, and Dictyota.

### Step-by-Step Solution:

1. **Identify the Types of Algae**:
- First, we need to categorize the listed organisms into their respective types of algae: green, brown, or red.

2. **List the Organisms**:
- **Green Algae**: Chara, Spirogyra, Volvox
- **Brown Algae**: Fucus, Ectocarpus, Laminaria, Sargassum, Dictyota
- **Red Algae**: Porphyra, Gelidium

3. **Focus on Green Algae**:
- From the list, we see that the green algae are Chara, Spirogyra, and Volvox.

4. **Check Cell Wall Composition**:
- Green algae typically have a rigid cell wall composed of an inner layer of cellulose and an outer layer of pectose.

5. **Count the Green Algae**:
- The green algae identified are:
- Chara
- Spirogyra
- Volvox
- Therefore, there are **3 members** that have a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose.

### Final Answer:
The number of members with a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose is **3**.