Lecture VII

Biomes:Kinds Of

Ecosystem

BiomEs Biomes consist of broad regional groups of

related manageable units alled ecosystems.A biome is one of several immense terrestrial environments, a habitat characterized throughout is extent by similar plants, animals,climate and soil types.

The world is divided into manageable units called the ecosystems.Each biomes contains thousands of types of ecosystems. The ecosystem is the community of all the different organisms living in the area, along with their physical environment.

Several Major BiomesExtensive tropical forest have major effects on the

entire biosphere. Scientist are concerned about the loss of tropical rain forest because of their global ecological importance and the rapid rate which they are being destroyed.

Deserts Deserts generally occur in semi-tropical and

temperature regions having rainfall of less about 20 cm a year.

There are Two Kinds of Desert1.Cool Deserts - These are dominated by

sagebrush, rabbitbrush and smaller perenial plants.

Sagebrush Rabbitbrush

2.Hot Deserts – these are dominated by creosote, cacti, acacias, agave, and yucca.

Creosote Cacti

Yucca Agave

Desert soil is largerly unprotected by vegetation. It is subject to severe erosion from wind and occasional rain. It has a thin top layer of decaying plant materials called humus.

grassland Grasslands are dominated by grasses, and a rich array of deep-prooted, beautifully flowering non grasses species. They have a few trees because of inadequate and freuent grass fire that kills woody seedlings.

Forest Forest are regions where trees grow as a

result of adequate temperature and minimal precipitation of 75 centimeters or more.

A.Tropical Biomes1. Tropical Rainforest – the forest with high, fairly

constant rainfall and temperaure that permit trees to grow throughout the year. Annual rainfall may exceed 400 cm. This is the biome with the highest specis diversity. The number of species in a given area may have almost 100 different species per hectare.

2. Tropical seasonal forest is also known as monsoon forest. Seasonal rainfall is concentrated during a certain part of the year after which follows an increasingly pronounced dry season.

3. Tropical savanna consist of grassland dotted with scattered small trees and shrubs such as acacias. Some savannas are entirely grassland; others contain many trees.

4. Tropical thornwood, shrubland and tropical shrub. The proportion

of trees depends on the competition between trees and grasses for water. The oil is more fertile than most tropical rainforest, but the rainfall is erratic.

B. Temperate Biomes The climate of temperate forest is typically

moderate in terms of temperature. This forest occurs in regions of abundant rainfall and contains both decidous and evergreen trees.

1. Temperate decidous forest occurs in moderately humid area where precipitation takes place throughout the year but winter are cold, restricting plant growth to the summers. Most of the trees lose their leaves in autumn.

2. Temperate evergreen forest occurs where condition favors conifers or broad-leave evergreen over decidous trees. I has poor soil condition, frequent droughts and forest fires. The temperate evergreen plants include ponderosa and pine trees. These forest are found in Eastern Asia, Southern Chile, New zealand and Australia.

3. Temperate rainforest occurs in cold climate near the sea with abundant winter rainfall and summer clouds or frogs.

4. Temperate woodland ocurrs where the climate is too dry to support a forest yet provides sufficient moisture to support trees as well as grasses. Dominant trees are conifers, evergreen, flowering trees, or decidous trees.

5. Temperate shrubland is represented by the Chapparal communities that occurs in all five regions of the world having fairly dry climate with little or no summer rain. Most shrubs have leathery leaves.

6. Temperate grassland is also known variably as prairie in north America, stepe in Asia, pampas in South America, and veldt in Souh Africa. The grasslands are natural ranges for grazing animals, but they must be treated with care or hey degrade into shrubland.

Taiga The term “taiga” comes from the russian word

meaning “primeval forest”. It is also known as boreal forest. It is dominated by conifers that can survive extreme cold in winter. The trees in taiga are further apart than in he forest and enough sunlight penetrates the forest floor to support an extensive ground cover for the shrubs. Most taiga precipitations are snow.

Tundra The tundra is a treeless biome that occurs far north

in the Arctic regions where winters are too dry and cold to permit the growth of trees.

Environmental Variables Affecting the Biomes1. Sunlight- sunlight powers the photosynthesis

that supplies energy to nearly all life on earth. 2. Temperature- organisms can survive within a

specific, limited range of temperature.3. Water and dissolve salts- precise balance of

water, dissolved salts, and organic molecules in the body fluids of organisms must be maintained to keep the cells alive.

4. Oxygen- The concentration of available oxygen can be an important limiting factor in a variety of environment.

5. Metabolic Waste- all organisms produce metabolic waste products. Plants release oxygen by day, give off carbon dioxide by night, and discard leaves and stems on a seasonal basis.

6. Nutrients- distribution of nutrients is important in determining where organisms can grow and where they cannot. The more nutrients available in a given area, the more living things can succesfully survive.