Suppose you traveled back in time and located the first animals to have evolved feathers. You found that these animals were tree
-dwelling ectotherms, able to run quickly but unable to fly. You also noticed that only males had feathers. Which hypothesis of feather evolution would these data most support? Feathers initially evolved in a role associated with ________.
Feathers initially evolved in a role associated with sexual selection.
Explanation:
In species where only males had feathers, these feathers can be considered to have evolved into a role associated with sexual selection. This is because in these species, males used their feathers as a sexual attraction for females, in this case, females chose the males that had more attractive feathers to mate and generate new individuals for the species. An example of this can be seen in the peacock, where the tail with lush feathers is only present in males and is intended to sexually attract females.
The food trickles from the crop into the bird's stomach (proventriculus or gizzard) where digestive enzymes are added to the mix and physical grinding of the food occurs. The gizzard is why chickens do not need teeth.
