* Internal fertilization: This is the most common type in animals and occurs within the female's body.
* Mammals: Fertilization occurs in the oviduct, specifically in the fallopian tube.
* Birds, reptiles, and most fish: Fertilization occurs within the oviduct as well.
* External fertilization: This type occurs outside the female's body, typically in aquatic environments.
* Fish, amphibians, and some invertebrates: The female releases eggs into the water, and the male releases sperm over them. Fertilization occurs externally.
Key points:
* In both internal and external fertilization, the sperm must reach the egg for fertilization to occur.
* Fertilization is the moment when the sperm and egg nuclei fuse, forming a zygote, the first cell of a new individual.
* The zygote then undergoes cell division and development, eventually forming a new organism.