Answer:
This is called the recapitulation theory or bio genetic law.
Step-by-step explanation:
E. Haeckel postulated the biogenetic law or theory of recapitulation. This theory said that the stages of embryological development in different animals are similar. It has seen the developmental stages of animals similar to their ancestors. The multicellular organisms develop from a single-celled zygote. This proves all animals evolved from a single ancestor. This ancestor had a simple cellular organisation. Then the zygote, by mitotic cell division becomes a multicellular fetus. For example, the early embryos of vertebrates like fish, salamander, bird, and man are similar. The tadpole larva of frog resembles a fish. The higher animals embryonic development stages are similar to many lower animals.