Fertilization - Internal and External

Syngamy - what is more commonly called fertilization - is the fusion of two haploid gametes to produce a single diploid zygote, and depending on exactly where in the environment this fusion takes place, it is classified into two types. In external fertilization, the male and female gametes fuse outside the female's body, typically in a surrounding water medium; this is the pattern seen in sponges, fishes and amphibians, all of which release their gametes into water where fertilization then occurs. In internal fertilization, by contrast, the male and female gametes fuse within the female's own body; this is the pattern seen in reptiles, birds (aves) and mammals, where the male gamete is delivered directly into the female's reproductive tract before fusion takes place. …