Pine trees are in a group of plants called Gymnosperms. This means "naked seed." That is because, unlike a flowering plant, the seeds of pine trees are not inside a protective, fleshy fruit. Think of how an apple protects its seeds inside its fleshy body. A gymnosperm does not have that.
A pine tree's seeds are not inside a fruit, like an apple but out in the air attached to a pinecone. When the pollen from a male pine cone floats on the wind and reaches a female pinecone, it fertilizes cone so seeds can grow, When the seeds are ready the pine tree will drop the cone to the forest floor.
An animal, like a squirrel, will take the pinecone apart to eat the seeds. Many will fall to the ground. Some may have a chance to sprout and grow. If just one of those seeds grow into a pine tree, the parent tree has been successful raising young!
The cycle begins over again!
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