As a result of natural selection , comparable ecosystems have developed in these separated areas. Scientists call these major ecosystem types biomes . The map in Figure 9k-1 describes the geographical locations of the eight major biomes of the world. Because of its scale, this map ignores the many community variations that are present within each biome category. Distribution of the Earth's eight major terrestrial biomes.
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Physical Geography of the Global Environment. John Wiley, New York. Most of the classified biomes are identified by the dominant plants found in their communities. For example, grasslands are dominated by a variety of annual and perennial species of grass , while deserts are occupied by plant species that require very little water for survival or by plants that have specific adaptations to conserve or acquire water. The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation.