The presence of gill slits, in the embryos of all vertebrates, supports the theory of

Options

A. metaorphosis
B. biogenesis
C. organic evolution
D. recapitulation.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which theory is supported by the presence of gill slits in the embryos of all vertebrates. We need to identify the relevant evolutionary theory that explains this phenomenon.

2. **Recognizing Evolutionary Concepts**: Evolution is an ongoing process that leads to gradual changes in life forms over time. The presence of similar structures in different organisms can indicate a common ancestry.

3. **Introducing Ernst Haeckel**: Ernst Haeckel proposed the biogenetic law, also known as the theory of recapitulation. This theory suggests that the development of an organism (ontogeny) reflects its evolutionary history (phylogeny).

4. **Explaining Gill Slits**: Gill slits are a feature found in the embryos of all vertebrates, including humans, even though they are not present in adults. This similarity in embryonic development suggests a shared evolutionary ancestor among vertebrates.

5. **Connecting Ontogeny and Phylogeny**: According to Haeckel's theory, the embryonic development of vertebrates shows early similarities, indicating that these organisms share a common lineage. The presence of gill slits in embryos is an example of how ontogeny (development) can reflect phylogeny (evolutionary history).

6. **Conclusion**: Therefore, the presence of gill slits in the embryos of all vertebrates supports the theory of recapitulation, or the biogenetic law, which states that "ontogeny repeats phylogeny."

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