plants
An apple grows on a tree and has little seeds inside.
Fruits like apples contain seeds because seeds are how plants make new plants, carrying everything needed to grow into a fresh tree or plant of the same kind. The sweet, juicy fruit around the seeds exists partly to attract animals, who eat the fruit and later drop or spread the seeds somewhere new.
Fruit has nothing to do with staying cold, and seeds don't make fruit taste sour — flavor comes from sugars and acids in the fruit's flesh, which is a completely separate matter from the seeds' actual job of growing new plants.
When an animal eats a fruit and later passes the seeds in its droppings far from the parent tree, that seed often gets a helpful boost of natural fertilizer right where it lands.
plants
What group of living things do mushrooms really belong to?Why do many trees drop their leaves in autumn?What was special about the little plant nicknamed the Woolly Devil?What kind of plant is famous for being one of the fastest growing plants on Earth?Why do plants really need bees to visit their flowers?What do roots drink from the soil?Which part of a plant usually grows first from a seed?How do dandelion seeds usually travel to new places?Where does cotton for our clothes come from?What is this rare, gigantic, terrible-smelling flower called?What can those rings inside a tree trunk tell us?Which part of the carrot plant do we eat?Quration — Quration Kids