Birds have hollow bones due to the fact thay need to be as light as possible for their wings to generate enough lift for them to fly
Answer:
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.
63 in water 100/g KNO3 Potassium nitrate
