Find odd one w.r.t. haplontic life cycle

Options

A. Ectocarpus
B. Ulothrix
C. Spirogyra
D. Chlamydomonas

Answer

To find the odd one out with respect to the haplontic life cycle, we will analyze each of the given options: Actocarpus, Eulothrix, Spirogyra, and Chlamydomonas.

### Step-by-Step Solution:

1. **Understanding Haplontic Life Cycle**:
- The haplontic life cycle is characterized by a dominant haploid stage, where the organism is primarily in the haploid form (n).
- In this cycle, the diploid stage (2n) is usually unicellular and occurs only briefly, typically as a zygote.

2. **Analyzing Each Option**:
- **Ectocarpus**:
- Ectocarpus exhibits a haplodeplontic life cycle, which means it has both haploid and diploid multicellular stages. The diploid stage is not unicellular, which is a key distinction.
- **Eulothrix**:
- Eulothrix follows the haplontic life cycle, where the dominant stage is haploid and the diploid stage is unicellular (the zygote).
- **Spirogyra**:
- Spirogyra also follows the haplontic life cycle, with a dominant haploid stage and a unicellular diploid zygote.
- **Chlamydomonas**:
- Chlamydomonas is another organism that exhibits a haplontic life cycle, characterized by a dominant haploid stage and a unicellular diploid zygote.

3. **Identifying the Odd One Out**:
- Since Ectocarpus is the only organism that does not follow the haplontic life cycle (it follows a haplodeplontic life cycle), it is the odd one out.

### Conclusion:
The odd one out with respect to the haplontic life cycle is **Ectocarpus**.

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