Ova Development in Oviparous Animals
In the oviparous animals (all birds, most fishes, amphibians and reptiles) the ova develop protective layers and pass through the oviduct to the outside of the body. They are fertilized by male sperm either inside the female body (as in birds), or outside (as in many fishes). After fertilization, an embryo develops, nourished by nutrients contained in the egg. It then hatches from the egg, outside the mother's body. See egg (biology) for a discussion of eggs of oviparous animals.
The egg cell's cytoplasm and mitochondria (and chloroplasts in plants) are the sole means the egg is able to reproduce by mitosis and eventually form a blastocyst after fertilization.
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