Other Land Areas

What areas are not easily classified into a major biome?

Some land areas do not fall neatly into one of the major biomes. Because they are not easily defined in terms of a typical community of plants and animals, mountain ranges and polar ice caps are not usually classified into biomes.

Mountain Ranges Mountain ranges exist on all continents and in many biomes. On mountains, conditions vary with elevation. From river valley to summit, temperature, precipitation, exposure to wind, and soil types all change, and so do organisms. If you climb the Rocky Mountains in Colorado, for example, you begin in a grassland. You then pass through pine woodland and then a forest of spruce and other conifers. Thickets of aspen and willow trees grow along streambeds in protected valleys. Higher up, soils are thin. Strong winds buffet open fields of wildflowers and stunted vegetation resembling tundra. Glaciers are found at the peaks of many ranges.

Polar Ice Caps Polar regions, like the one in Figure 4–19, border the tundra and are cold year-round. Plants are few, though some algae grow on snow and ice. Where rocks and ground are exposed seasonally, mosses and lichens may grow. Marine mammals, insects, and mites are the typical animals. In the north, where polar bears live, the Arctic Ocean is covered with sea ice, although more and more ice is melting each summer. In the south, the continent of Antarctica, inhabited by many species of penguins, is covered by ice nearly 5 kilometers thick in places.

FIGURE 4–19 Polar Ice Caps The polar ice caps do not fit neatly into a biome classification. At the poles, it is cold year-round, and land is usually covered with thick ice sheets.

4.4 Assessment

Review Key Concepts

1. 1. Review List the major biomes, and describe one characteristic of each.

   2. Explain How are biomes classified?

   3. Compare and Contrast Choose two very different biomes. For each biome, select a common plant and animal. Compare how the plants and animals have adaptated to their biomes.

2. 1. Review Why aren't mountain ranges or polar ice caps classified as biomes?

   2. Sequence Imagine that you are hiking up a mountain in the temperate forest biome. Describe how the plant life might change as you climb toward the summit.

Apply the Big idea

Interdependence in Nature

3. Choose one of the biomes discussed in this lesson. Then, sketch the biome. Include the biome's characteristic plant and animal life in your sketch. Add labels to identify the organisms, and write a caption describing the content of the sketch.

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