The sequence of events in geographic speciation is most likely to be
Genetic divergence $\rightarrow$ geographic barrier $\rightarrow$ reproductive isolation
Geographic barrier $\rightarrow$ genetic divergence $\rightarrow$ reproductive isolation
Reproductive isolation $\rightarrow$ genetic divergence $\rightarrow$ geographic barrier
geographic barrier $\rightarrow$ reproductive isolation $\rightarrow$ Genetic divergence
Correct order is.
The viruses contain
Gill clefts and notochord appear in the embryonic development of all vertebrates from fishes to mammals. This supports the theory of