The Biosphere• The biosphere is the region within which all living things are found on Earth.• It is the narrow belt around the Earth extending from
Biomes• The biosphere encompasses all living things on Earth.• It comprises a number of aquatic and terrestrial biomes.• Biomes are the largest geographically based biotic communities that can be conveniently recognized.• Biomes within the same category have specific, characteristic features.
Terrestrial Biomes• Terrestrial biomes are recognized for all the major climatic regions of the world and are classified on the basis of their predominant vegetation type.• The same biome may occur in widely separated regions.
Predicting Biome DistributionFigure :Biomes most likely to occur in the absence of human disturbance or other disruptions, according to average annual temperature and precipitation.
•Biomes most likely to occur in the absence of humandisturbance or other disruptions, according to average annualtemperature and precipitation. Polar Arctic region Latitudinal regions Subarctic region Temperate region Tropical region Equatorial Annual precipitation (mm)
•Biomes most likely to occur in the absence of humandisturbance or other disruptions, according to average annualtemperature and precipitation.
What is a Desert ?Definition of the desert Botanist Scientists of soil Scientists of the climate Geologists Summary of the previous definitions:
Definition of the desert• Every body defines the desert on the basis of his understanding and capabilities.• In fact, the definition of desert is not easy as it seems due to the difference of the correct scientific concept, even among scientists with different specialties.
Botanists :• The Botanist sees that the characteristics of the vegetation cover are the specific standard in the definition of the desert.• He sees that desert plants are located in scattered and limited manner and the shrubs are short, far, and with low percentage and that these plants have morphological, anatomical and physiological characteristics that enable them to survive droughts and high temperatures.
Scientists of soil• The scientist of soil interests in soil types, the degree of permeability, its color, its geological history and the surface sediments that form the soil.
Scientists of the climate • They are interested in the movement of the masses of dry air and the amount of rainfall and other climatic factors, they put equations that connect between the amount of annual rainfall and water loss which results by evaporation factors to give a coefficient that indicates the severity of drought, so that represents the relativities between the available water resources and aspects of the water loss to determine the status of drought or moisture, since the amount of annual rainfall alone can not be relied upon to determine this case without taking into account the degree of evaporation.
Geologists• Geologists look to the lower strata and the date of their formation in addition to the components of the surface sediments.
• However, it could be concluded that deserts are the areas where: - - Water resources, much less than the ability of evaporation agents for drying. - Lack of rain and lack of regularity and intensity of evaporation. - Extreme disparity in temperature between night and day, summer and winter. - Their soil is characterized by low organic matter which in turn affects the vegetation cover, so vegetation become scattered and with rare trees.
So ,What is a Desert ?A desert is a landscape or region that receivesan extremely low amount of precipitation, lessthan enough to support growth of most plants.Deserts can also be described as areas wheremore water is lost by Evaporation than falls asprecipitation.