Desert & Tundra

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2017-05-05 06:55:05
Compare Desert vs Tundra
DesertTundra
Distinct CharacteristicsA desert is a biome that receives no more than 25 centimeters (10 inches) of precipitation per year. Deserts are found in both temperate and tropical areas. The largest deserts are found at about 30° north or south latitude due to the dry air masses over these latitudes. Deserts also occur in rain shadows. A rain shadow is a dry region on the leeward side of a mountain range (see Lesson 16.1). Examples of rain shadow deserts include Death Valley and the Mojave Desert, both partly in California. The dry air in deserts leads to extreme temperature variations from day to night. Without water vapor in the air, there are no clouds to block sunlight during the day or hold in heat at night. Desert soil is usually very poor. They tend to be sandy or rocky and lack organic content. Because of the low precipitation, minerals are not leached out and may become too concentrated for plants to tolerate. Plant cover is very sparse, so most of the soil is exposed and easily eroded by wind. The occasional rain tends to be brief but heavy, causing runoff and more erosion. Most desert plants have evolved adaptations to the extreme dryness. For example: Many plants have special water-storing tissues in leaves, stems, or roots. Some plants have very long taproots that can reach down to the water table. Some plants have wide-spreading roots that can absorb water over a large area. Plants may have small, spiny leaves that help reduce water loss. Most desert animals have adaptations to the extreme heat and bright sunlight. For example: Many small animals stay underground in burrows during the day and come out only at night. Most animals that are active in daytime spend as much time as possible in the shade of rocks or plants. Some animals have very large ears or other appendages, which help them lose heat to the environment, keeping them cooler. Many animals are light in color, which helps them reflect sunlight and stay cooler.Tundra is an arctic biome where it is too cold for trees to grow. Outside of the polar ice caps, tundra has the coldest temperatures on Earth. There are two types of tundra: arctic tundra, which is also found in Antarctica, and alpine tundra, which is found only at high altitudes. Arctic tundra occurs north of the arctic circle and south of the antarctic circle. It covers much of Alaska and vast areas of northern Canada and Russia. It is also found along the northern coast of Antarctica. Alpine tundra occurs in mountains around the world at any latitude, but only above the tree line. The tree line is the edge of the zone at which trees are able to survive. Alpine tundra is found in the Rocky Mountains in the United States and in several other mountain ranges around the world. Both types of tundra receive very low precipitation, but little of it evaporates because of the cold. Arctic tundra has permafrost, which is soil that is frozen year-round. The top layer of soil thaws in the summer, but deeper layers do not. As a result, water cannot soak into the ground. This leaves the soil soggy and creates many bogs, lakes, and streams. Alpine tundra does not have permafrost, except at very high altitudes. Therefore, alpine tundra soil tends to be dry rather than soggy. Global warming poses a serious threat to Arctic tundra biomes because it is causing the permafrost to melt. When permafrost melts, it not only changes the tundra. It also releases large amounts of methane and carbon dioxide into the atmosphere. Both are greenhouse gases, which contribute to greater global warming. The most common vegetation in tundra is mosses and lichens. They can grow in very little soil and become dormant during the winter. Tundra is too cold for amphibians or reptiles, which cannot regulate their own body heat. Insects such as mosquitoes can survive the winter as pupae and are very numerous in summer. In addition, many species of birds and large herds of caribou migrate to arctic tundra each summer. However, few birds and mammals live there year-round. Those that remain have adapted to the extreme cold. Polar bears are an example. They have very thick fur to insulate them from the cold. In alpine tundra, animals must adapt to rugged terrain as well as to cold. Alpine animals include mountain goats, which not only have wool to keep them warm but are also sure-footed and agile.
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  • 2017-05-05 06:51:07
    2017-05-05 06:55:05
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