Ans.
Fertilization involves fusion of sperm (male gamete) and egg cell (female gamete) to form zygote.
In aquatic animals, external fertilization takes place, during which both eggs and sperms are released into the water and their fusion takes place. The aquatic environment protects the eggs and sperms from drying out.
As their is no way or carrier to transfer sperms and eggs in Terri's trial environment, in those animals, fertilization is internal, in which sperms are inserted to the female body, where they fuse with egg cell.
Thus, the basis difference between marine and terrestrial organism is that marine organisms show external fertilization, while land animals show internal fertilizer.
