Presence of gills in the tadpole of frog indicates that

Options

A. fishes were amphibious in the past
B. fishes evolved from frog like ancestors
C. frogs will have gills in future
D. frogs evolved from gilled ancestors.

Explanation

### Step-by-Step Solution:

1. **Understanding Gills in Tadpoles**:
- Gills are specialized respiratory structures found in aquatic organisms, primarily fish, that allow them to extract oxygen from water.
- In the case of tadpoles (the larval stage of frogs), they possess gills which they use for respiration while they are still in an aquatic environment.

2. **Respiration in Adult Frogs**:
- Adult frogs do not have gills; instead, they primarily use lungs for respiration when on land. They can also respire through their moist skin while in water, a process known as cutaneous respiration.

3. **Evolutionary Perspective**:
- The presence of gills in tadpoles can be understood through an evolutionary lens. Frogs, as amphibians, share a common ancestry with fish, which are the first vertebrates to have evolved in aquatic environments.
- This evolutionary relationship suggests that amphibians evolved from gilled ancestors (fish), which is why tadpoles retain gills during their early life stages.

4. **Theory of Recapitulation**:
- The theory of recapitulation, proposed by Ernst Haeckel, posits that the development of an organism (ontogeny) reflects its evolutionary history (phylogeny). This means that during their development, organisms may exhibit features that were present in their ancestors.
- In the case of frogs, the presence of gills in tadpoles reflects their evolutionary lineage from fish.

5. **Conclusion**:
- Therefore, the presence of gills in the tadpole of a frog indicates that frogs evolved from gilled ancestors, specifically fish. This evolutionary history is mirrored in the developmental stages of the frog.

### Final Answer:
The presence of gills in the tadpole of a frog indicates that frogs evolved from gilled ancestors.