There are a wide variety of animals on earth today, that occupy many different types of ecosystems. Mammals, reptiles, amphibians, and birds inhabit just about all land masses. When you examine some of these, however, you can see remnants of their ancient ancestors.

As in the past, today’s animals must be able to adapt to changes in ecosystems. Ecosystems are constantly changing, and what may be found on earth in a thousand years will likely be much different than now. These changes may be caused by a combination of environmental and human factors. Environmental factors may include changes in climate or soils. Human factors may involve changing habitat or the atmosphere. This does not mean that changes caused by humans will always be bad. Those who have knowledge of how ecosystems work, and make wise decisions from that knowledge, may actually make things better for both humans and animals.