Around the globe, plants and animals have evolved adaptive strategies that are specific to the conditions in their environment. These conditions might include intense heat and solar radiation or a lack of direct sunlight, a lot of precipitation or very little, many predators or just a few, and countless others. Organisms have adapted over many generations and over thousands or millions of years in ways that help them exploit available resources and withstand shortages and other negative environmental pressures.

Take cacti, for example. Over thousands of generations, these plants have adapted to the extremes of the desert environment. They have spines that provide protection and shade, wax that makes their surfaces less porous, and stomata, the pores through which they take in carbon dioxide, that open at night and close tightly during the heat of the day. All of these adaptations enable cacti to conserve water, a precious commodity in a region that receives less than 25 centimeters of rainfall each year.

In general, adaptations to one type of environment don't serve well in other environments. A cactus plant transplanted to a rainforest, for example, would undoubtedly die from a lack of sunlight and from an inability to defend itself against the fungi and bacteria common in rainforest soils.

This is not to say, however, that organisms adapted to one location cannot survive in other locations. There are many examples of plants and animals adapted to a particular environment on one continent -- a grassland, for example -- surviving quite well when moved to a similar environment on another continent