The Tundra Biome
The tundra is found across northern Alaska, Canada, and Siberia. This biome has long cold winters and short cool summers. The Arctic tundra has low precipitation (less than 10 inches per year) and dry winds. These conditions make the Arctic tundra a desert-like climate.One unique characteristic of the Arctic tundra is permafrost--ground that is permanently frozen. Because the permafrost has no cracks or pores, nothing can penetrate it--neither plant roots nor water. The surface layer above the permafrost thaws each summer. This layer is called the active layer. Thickness of the active layer depends on its location in the tundra. The more northerly the location, the thinner the active layer is.Curiously, during the summer Arctic tundra is characterized by lots of surface water. When snow melts, the water percolates through the active layer but is unable to penetrate the permafrost. Since the water has nowhere to go, the active layer becomes saturated and pools of water form on the surface. Another characteristic of the Arctic tundra is the limited amount of sunlight it receives due to the position of the Sun in the sky. Depending on the latitude, the Sun can remain below the horizon for up to 2 months, leaving the Arctic tundra in darkness. Although the sun remains in the sky 24 hours a day during the summer, it stays close to the horizon and provides only low intensity sunlight.
Animals
Not many kinds of animals live year-round in the tundra. Most birds and mammals only use the tundra as a summer home. Mammals that do live year-round in the tundra include the muskox, Arctic wolf, and brown bear; and each has its own way of adapting to the extreme climatic conditions. Animals need to find ways to stay warm and to provide nourishment for themselves in order to survive the long, cold, winter months.
Animal adaptations
Migration and hibernation are examples of behavioral adaptations used by animals in the Arctic tundra. The fact that many animals do not live year-round in the tundra means they leave or migrate for a length of time to warmer climates.Hibernation is a combination of behavioral and physical adaptations. For example, during the summer the brown bear's behavior is to eat just about anything it can find; then it hibernates, or sleeps, during the winter. The bear's physical adaptation allows the food eaten during the summer to be stored as a layer of fat underneath its skin. The layer of fat insulates the bear from the cold. While in hibernation the fat is slowly converted into energy that maintains life.A physical adaptation used by the Musk Ox is the growth of two layers of fur--one short and the other long. Air is trapped in the short layer of fur and is warmed by body heat. The warmed air, trapped close to the body, acts as insulation from the cold. The layer of long fur protects the Musk Ox from the wind and water. In addition to thick layers of fur, the Musk Ox relies on another physical adaptation to help it survive. The hooves of the Musk Ox are large and hard. During the winter months, this adaptation allows the Musk Ox to break the ice and drink the water underneath.
Plants
Plants need warmth and sunlight to grow and reproduce. In the Arctic tundra, warmth and sunlight are in short supply, even in the summer. The ground is frequently covered with snow until June, and the Sun is always low in the sky.Only plants with shallow root systems grow in the Arctic tundra because the permafrost prevents plants from sending their roots down past the active layer of soil. The active layer of soil is free from ice for only 50 to 90 days.Arctic plants have a very short growing season. However, in spite of the severe conditions and the short growing season, there are approximately 1,700 kinds of plants that live in the Arctic tundra. Some of the plants that live in the Arctic tundra include mosses, lichens, low-growing shrubs, and grasses--but no trees. In fact, "tundra" is a Finnish words which means "treeless".
Plant Adaptations
Growing close together and low to the ground are some of the adaptations that plants use to survive. This growing pattern helps the plant resist the effects of cold temperatures and reduce the damage caused by the impact of tiny particles of ice and snow that are driven by the dry winds.Plants also have adapted to the Arctic tundra by developing the ability to grow under a layer of snow, to carry out photosynthesis in extremely cold temperatures, and for flowering plants, to produce flowers quickly once summer begins. A small leaf structure is another physical adaptation that helps plants survive. Plants lose water through their leaf surface. By producing small leaves the plant is more able to retain the moisture it has stored.
Activity:
Click on the link below. Watch the Movie, and then Complete the Quiz!
http://magma.nationalgeographic.com/ngexplorer/0211/quickflicks/