The basis of this similarity is the biogenetic law. Hence the similarity between tadpoles and fish follows.
Similar signs include:
Chorda, as the foundation of the skeleton;
Breathing with gills;
The device of the circulatory system.
This similarity is visible only in the early stages of development. In the future, observing the development of the tadpole, we see the metamorphoses occurring with it, which are inherent in amphibians.
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