Why Do Some Trees Lose Their Leaves While Others Don't?

Some trees, like maples and oaks, lose their leaves in the fall because they need to save energy during winter. Their leaves are like blankets, they help keep the tree warm in summer, but when it gets cold, it's easier for them to let go of those leaves and start fresh in spring. Other trees, like pines and firs, keep their leaves all year round because they're used to the cold and don't need to let go of their blankets.