Why do some trees have needles instead of broad, flat leaves?

Conifers, or cone-bearing trees, evolved to have needles that retain more water and seeds that could hang out until there was enough moisture to take root. It may not seem like it, but needles are leaves. They do the same job that broad leaves do—capture sunlight, “inhale” carbon dioxide, and “exhale” oxygen—providing the tree with food and air for us to breath. Instead of shedding every fall, though, needles can last three or four years!