Gill cells and notochord appear in the embryonic development of all vertebrates from fishes to mammals. This supports the theory of

Options

A. Recapitulation
B. Metamorphosis
C. Biogenesis
D. Abiogenesis

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question states that gill cells and notochord appear during the embryonic development of all vertebrates, from fishes to mammals. We need to identify which theory this observation supports.

2. **Identifying the Theories**: The options provided are:
- Recapitulation
- Metamorphosis
- Biogenesis
- Abiogenesis

3. **Analyzing the Theories**:
- **Recapitulation Theory**: Proposed by Ernst Haeckel, this theory suggests that the development of an individual organism (ontogeny) follows the stages of evolution (phylogeny) of its species. In other words, the embryonic development of an organism reflects the evolutionary history of its ancestors.
- **Metamorphosis**: This refers to the transformation of an organism from one stage to another, typically seen in insects and amphibians (e.g., tadpole to frog). It does not relate to embryonic development across species.
- **Biogenesis**: This is the principle that living organisms arise from pre-existing living organisms. It does not pertain to embryonic development or evolutionary stages.
- **Abiogenesis**: This refers to the origin of life from non-living matter, which is unrelated to the development of vertebrates.

4. **Connecting the Dots**: Since gill cells and notochord are features that appear during the embryonic development of all vertebrates, this supports the idea that these organisms share a common ancestor and that their embryonic development reflects their evolutionary history.

5. **Conclusion**: The presence of gill cells and notochord in embryonic development supports the **Recapitulation Theory** (also known as the Biogenetic Law).

**Final Answer**: Recapitulation Theory.

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