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Biology 17.3 Major Biological Communities

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1 Biology 17.3 Major Biological Communities
Major Biological Communities: Biomes

2 Climate’s effect on where species live
If we were to drive across the country we would notice that the plants and animals, the variety of species, changes as we move from zone to zone, climate to climate. Plants and animals from one climate will not live in another climate zone. Climate refers to the prevailing weather conditions in any given area. Climate map of North America Showing plant hardiness zones

3 Temperature and Moisture
The two most important elements of a climate are temperature and moisture. Temperature : Most organisms are adapted to live within a particular range of temperatures and will not thrive if temperatures are colder or warmer. Every living organism has a range of temperatures it can live within. Moisture: All organisms require water. On land, water is sometimes scarce, so patterns of rainfall often determine an areas life forms. The moisture-holding ability of air increases when it is warmed and decreases when it is cooled.

4 Biological Communities: Biomes
If we look at all the world’s biological communities we notice a trend. Similar communities exist in different world areas that have similar climates and geographies. A major biological community that occurs over a large area is called a biome. The Earth is a biosphere and is broken up into biomes. A biome’s structure and appearance are the similar no matter where in the world it is geographically located. All desert biomes are similar for example. World biome map

5 Biomes of the world While there are different ways of classifying biomes, the classification system we will examine uses 7 of the most widely distributed biomes. Tropical rain forests Savanna Taiga Tundra Desert Temperate grassland Temperate forest

6 Biomes of the World Many factors such as soil type or wind play important roles in where biomes occur. The two most important factors that determine a biome are temperature and precipitation. The chart at right shows the relationships between cold-warm and wet-dry locations and the biomes that they produce. The 11 biomes shown are in response to the climate combinations of temperature and precipitation (rain) available.

7 Terrestrial Biomes: tropical rain forests
Tropical rain forests receive an average of as much as 450 cm (180 inches) of rain per year, with little difference in amount of rain from season to season. The richest biome in terms of the number of species is the tropical rainforest. Tropical rainforest may contain half the world’s species, more than 2 million.

8 Terrestrial Biomes: tropical rain forests
Tropical rainforest have a high productivity even though they often exist on infertile soil. Most of the nutrients in a rainforest are held within the plants, not the soil.

9 Terrestrial Biomes: Savannas
The world’s great dry grasslands, savannas, are found in the tropical areas that have relatively low precipitation (little rain) or prolonged annual dry seasons. Annual rainfall is generally 90 to 150 cm (35 to 60 inches) in savannas. There is a wider range of temperatures throughout the year than in a tropical rain forest, and there is a seasonal drought where little or no rain falls.

10 Terrestrial Biomes: Savannas
These factors have led to an open landscape with widely spaced trees. Many of the animals are active only during the rainy season. Huge herds of grazing animals are found on the savannas of East Africa.

11 Terrestrial Biomes: Taiga
Cold wet climates promote the growth of coniferous trees and forests. A great ring of coniferous trees, primarily spruce and fir, extends across vast areas of Eurasia and North America. This biome, one of the largest on Earth, is called by it’s Russian name, taiga.

12 Terrestrial Biomes: Taiga
Winters in the taiga are long and cold, and most of the precipitation falls during the summer. Many large mammals, including herbivores such as elk, moose and deer and carnivores such as bears, lynx, and wolverine live in the taiga.

13 Biomes: Tundra Tundra:
Between the taiga and the permanent ice cap that surrounds the North Pole, lies the open boggy biome we call the tundra. Tundra biome covers approximately one fifth of the entire Earth’s surface. Annual precipitation in the tundra is very low, usually less than 25 cm (10 inches) and water is unavailable most of the year as it is frozen. The permafrost, or permanent ice, usually exists within 1 meter of the surface. Foxes, owls, lemmings and caribou are among the inhabitants.

14 Biomes: Deserts Deserts:
In deserts, less than 25 cm (10 inches) or precipitation falls annually. The scarcity of water is the overriding factor influencing most biological processes within a desert biome. In desert regions, vegetation is very sparse.

15 Biomes: Deserts Deserts:
Deserts are most extensive in the interiors of continents. Less than 5 % of North America is open desert. The amount of water that can fall in a particular place in a desert can vary greatly, both during a given year and during successive years.

16 Biomes: Temperate Grasslands
Moderate climates half-way between the equator and the poles promote the growth of rich temperate grasslands called prairies. Temperate grasslands once covered much of the interior of North America. Such grasslands are often highly productive when converted to agricultural use. Buffalo on a prairie

17 Biomes: Temperate Grasslands
The roots of prairie grasses characteristically penetrate far into the soil, which tends to be deep and fertile. Herds of grazing animals often populate grasslands. North America was once covered with huge herds of buffalo that covered the plains. Buffalo on a prairie

18 Biomes: Temperate Deciduous Forests
Relatively mild climates and plentiful rain promote the growth of temperate deciduous forests. Temperate deciduous forests (deciduous trees shed their leaves in the fall) grow in areas with relatively warm summers, cold winters and annual precipitation of from 75 to 250 cm (30 to 100 inches) of rain each year.

19 Biomes: Temperate Deciduous Forests
Temperate deciduous forests cover much of the eastern United States and are home to deer, beavers, raccoons, and other familiar animals. The trees in these forests include hardwoods such as oak, hickory and beech.

20 Biomes: temperate evergreen forests
In other temperate areas, drier weather and different soil conditions favor the growth of evergreen forests. Large portions of the southeastern and southwest United States have temperate evergreen forests; extensive areas where pine forests are predominant over deciduous forests.

21 Biomes: chaparral Where conditions are even drier, temperate forests give way to areas of dry shrubs such as in the chaparral areas of coastal California and in the Mediterranean. The chaparral is a shrub association dominated by buckbrush and white-leaf manzanita. Patches of chaparral occur as the dominant vegetation, or as an understory beneath the savanna or woodland. Plants found in this habitat must be able to live in hot, dry conditions on shallow soils. You will see mostly bushes or shrubs with woody, round, waxy leaves that prevent loss of water. This area supports large bird populations by providing good food sources and many great places to live.


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