This stunning bird is a peacock. Do you know why he is spreading out his big, colorful tail feathers like a fan? He is trying to attract a female for mating. Both the feathers and the behavior evolved because they increase the chances that males of the species will reproduce and pass their genes to the next generation. Many other vertebrates have similar behaviors for attracting mates. Even fish display some remarkably sophisticated mating behaviors.
Fish and birds are both vertebrates. Vertebrates are a diverse and fascinating group of animals. In many ways, they are very different from the invertebrates described in previous chapters. Elaborate mating behaviors are just one way they differ. This chapter describes many other differences between vertebrates and invertebrates. It also describes in detail the classes of vertebrates from fish to birds.