Introduction

Environment, all of the external factors affecting an organism. These factors may be other biotic factors or abiotic factors, such as temperature, rainfall, day length, wind, and ocean currents. The interactions of organisms with biotic and abiotic factors form an ecosystem. Even minute changes in any one factor in an ecosystem can influence whether or not a particular plant or animal species will be successful in its environment. Organisms and their environment constantly interact, and both are changed by this interaction. Like all other living creatures, humans have clearly changed their environment, but they have done so generally on a grander scale than have all other species. Some of these human-induced changes-such as the destruction of the world’s tropical rain forests to create farms or grazing land for cattle-have led to altered climate patterns. In turn, altered climate patterns have changed the way animals and plants are distributed in different ecosystems.