Which of the following are not red algae ?

Options

A. Gracilaria, Gelidium
B. Ectocarpus, Dictyota
C. Porphyra, Gracilaria
D. Polysiphonia, Porphyra,

Answer

To determine which of the following are not red algae, we will analyze the given options based on their classification.

### Step-by-Step Solution:

1. **Identify the Types of Algae:**
- Algae are classified into three main groups based on their pigments:
- **Chlorophyceae** - Green algae
- **Pheophyceae** - Brown algae
- **Rhodophyceae** - Red algae

2. **Understand the Characteristics of Red Algae:**
- Red algae belong to the class **Rhodophyceae**.
- They contain the pigment **phycoerythrin**, which gives them their red color.
- The stored food in red algae is **fluoridine starch**.

3. **Examine the Given Options:**
- The options provided are:
- **Option 1:** Gracilaria, Gelidium
- **Option 2:** Ectocarpus, Dictyota
- **Option 3:** Porphyra, Gracilaria
- **Option 4:** Polysiphonia, Porphyra

4. **Identify Examples of Red Algae:**
- **Gracilaria**, **Gelidium**, **Porphyra**, and **Polysiphonia** are all examples of red algae (Rhodophyceae).
- **Ectocarpus** and **Dictyota** are examples of brown algae (Pheophyceae).

5. **Determine the Correct Answer:**
- From the analysis, **Option 2: Ectocarpus and Dictyota** are not red algae. Therefore, the correct answer is **Option 2**.

### Final Answer:
**The organisms that are not red algae are Ectocarpus and Dictyota (Option 2).**

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