Our world is overflowing with the diversity of life. Imagine that you are taking a leisurely walk through a wooded park. Oak and maple trees cast dancing shadows under the noonday sun. Birds and butterflies dart through the air and a squirrel scampers noisily up a tree trunk. In a typical woodland area, you will be surrounded by dozens of types of trees and plants, filled with even more types of birds. Insects will be crawling on the ground, climbing in the foliage, and flying through the air. Even in the middle of the city, you can find a huge selection of different plants—some carefully tended and some stealthily avoiding the gardener—filled with a variety of birds and insects, all scraping out a living between the houses and concrete.