In some algae, the two gametes are so similar in appearance that is not possible to categorise them into male and female gametes. These gametes are called

Options

A. Isogametes
B. Heterogametes
C. Homogametes
D. Both (1) and (3)

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a specific type of gametes found in some algae that are indistinguishable from each other in terms of appearance, making it impossible to categorize them as male or female.

2. **Identifying Gamete Types**: In the context of reproduction, gametes can be classified into two main types based on their morphology:
- **Isogametes**: These are gametes that are similar in size, shape, and appearance. They cannot be easily differentiated into male and female.
- **Heterogametes**: These are gametes that are morphologically distinct, allowing for clear categorization into male and female.

3. **Focusing on Algae**: The question specifically refers to algae, where the gametes are similar. This indicates that we are dealing with isogametes.

4. **Conclusion**: The gametes in some algae that are so similar in appearance that they cannot be categorized into male and female are called **isogametes**. They may also be referred to as **homogametes**.

5. **Final Answer**: The correct answer is **isogametes** (or **homogametes**), as both terms are used to describe these indistinguishable gametes.