Most reptiles and all birds are , meaning that their young develop in fertilized eggs laid outside the mother's body. in contrast, most mammals are , meaning that their young develop inside the mother's body.

Most reptiles and all birds are oviparous, meaning that their young develop in fertilized eggs laid outside the mother's body. In contrast, most mammals are viviparous, meaning that their young develop inside the mother's body.

The main difference between these two groups is that oviparous animals do not undergo any embryonic development inside the mother whereas viviparous do.

Maybe haha

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.