Which of the following refers to alternation of generation or Metagenesis

Options

A. the presence of different morphic forms
B. alternation of generation between asexual and sexual phases of an organism
C. occurrence of a drastic change in form during post-embryonic development
D. the presence of a segmented body and parthenogenetic mode of reproduction

Explanation

To answer the question regarding which of the following refers to alternation of generation or metagenesis, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Metagenesis**:
- Metagenesis, also known as alternation of generations, is a biological process where an organism alternates between two different forms, typically asexual and sexual forms. This is commonly observed in certain phyla, particularly in Cnidaria (e.g., jellyfish and corals).

2. **Identifying Relevant Organisms**:
- Members of the phylum Cnidaria exhibit metagenesis. They have two distinct body forms: the polyp and the medusa. The polyp is typically a sessile form, while the medusa is free-swimming.

3. **Analyzing the Options**:
- **Option 1**: Presence of different morphic forms.
- This statement is true but does not fully capture the essence of metagenesis.
- **Option 2**: Alternation of generation between the asexual and sexual phase of an organism.
- This statement accurately describes metagenesis, as it highlights the alternation between asexual (polyp) and sexual (medusa) forms.
- **Option 3**: Occurrence of a drastic change in form during post-embryonic development.
- This statement is incorrect as it does not specifically relate to the concept of metagenesis.
- **Option 4**: Presence of a segmented body and parthenogenetic mode of reproduction.
- This statement is also incorrect as it pertains to other organisms, such as certain insects, and does not relate to metagenesis.

4. **Conclusion**:
- Based on the analysis, the correct answer is **Option 2**: "Alternation of generation between the asexual and sexual phase of an organism."