Earth Floor: Adaptation

Environments Change
All of the environments on Earth change over time. Some changes are caused by the slow movement of the continents (plate tectonics) and take millions of years. For example, right now southern California has a warm and dry climate, but the part of southern California west of the San Andreas fault is being carried northward by the movement of the Pacific plate. In ten million years, that part of California will move a thousand kilometers (600 miles) to the north and become cold and wet.

Other changes are caused by variations in Earth's climate and take thousands of years. For example, 12,000 years ago the area around the Great Lakes was very cold and covered by huge sheets of ice a kilometer thick. Today, that same area is warm and covered by forests, farms, and cities.

Image of a building being built. Some changes are caused by people, and these usually occur in relatively short periods of time. For example, a forest or field can be changed into a farm, or a housing tract, or concrete streets and buildings in just a few months or a few years. By building a dam, a valley floor can be changed into a lake bottom in just a few years. Photo © 2000-www.arttoday.com

Every time a physical environment is changed, all the plants and animals in that environment must adapt to the changes or become extinct. Slow changes give living things time to adapt by the process of evolution over many generations. Fast changes usually don't give living things time to adapt, so they must either move elsewhere or become extinct.