Why do animals need sunlight and water?

Reptiles need sun to warm up and function. Due to them being cold-blooded, they cannot create their own body heat, and rely on the sun for warmth.

Other animals such as various herbivores rely on the sun to help plants grow, in turn they eat the plants which provide them food.

Carnivores need the sun to provide food for the herbivores, which the carnivores eat.