We have considered the two modes of reproduction observed across all living organisms. In this section, we narrow our focus to vertebrates: fish, amphibians, reptiles, birds, and mammals. Interestingly, even among vertebrates, there are many different reproductive strategies. Understanding these strategies not only gives us a picture of how these organisms reproduce but also sheds light on how they live and behave.

How vertebrates reproduce is also intimately connected to the transition of vertebrates from water to land 400 to 375 million years ago. Moving from an aquatic environment to a terrestrial one involved many adaptations. Among these were changes in the way that reproduction took place, so it is helpful to consider reproductive strategies in an evolutionary context.