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Lecture VII. Biomes: Kinds Of Ecosystem. BiomEs.

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lecture vii

Lecture VII


Kinds Of Ecosystem

  • Biomesconsist of broadregional groups of relatedmanageableunitsalledecosystems.A biome is one of several immense terrestrialenvironments, a habitat characterizedthroughoutisextent by similar plants, animals,climate and soil types.
  • The world isdividedintomanageableunitscalled the ecosystems.Each biomes containsthousands of types of ecosystems. The ecosystemis the community of all the differentorganisms living in the area, alongwiththeirphysicalenvironment.
several major biomes
Several Major Biomes
  • Extensive tropical forest have major effects on the entirebiosphere. Scientist are concerned about the loss of tropical rainforestbecause of their global ecological importance and the rapid rate whichthey are beingdestroyed.


  • Desertsgenerallyoccur in semi-tropical and temperatureregionshavingrainfall of less about 20 cm a year.
there are two kinds of desert
There are TwoKinds of Desert

1.Cool Deserts - These are dominated by sagebrush, rabbitbrush and smallerperenial plants.



  • Rabbitbrush



Desertsoilislargerlyunprotected by vegetation. It issubject to severeerosionfromwind and occasionalrain. It has a thin top layer of decaying plant materialscalledhumus.


Grasslands are dominated by grasses, and a richarray of deep-prooted, beautifullyflowering non grasses species. They have a few treesbecause of inadequate and freuentgrassfirethatkillswoodyseedlings.



Forest are regionswheretreesgrow as a result of adequatetemperature and minimal precipitation of 75 centimeters or more.

  • Tropical Biomes

1. Tropical Rainforest – the forestwithhigh, fairly constant rainfall and temperaurethat permit trees to growthroughout the year. Annualrainfallmayexceed 400 cm. This is the biome with the highestspecisdiversity. The number of species in a given area may have almost 100 differentspecies per hectare.


2. Tropical seasonalforestisalsoknown as monsoonforest.Seasonalrainfallisconcentratedduring a certain part of the yearafterwhichfollows an increasinglypronounced dry season.


3. Tropical savannaconsist of grasslanddottedwithscatteredsmalltrees and shrubssuch as acacias. Somesavannas are entirelygrassland; otherscontainmanytrees.


4. Tropical thornwood, shrubland and tropical shrub. The proportion of treesdepends on the competitionbetweentrees and grasses for water. The oilis more fertile thanmost tropical rainforest, but the rainfalliserratic.

b temperate biomes
B. Temperate Biomes
  • The climate of temperateforestistypicallymoderate in terms of temperature. This forestoccurs in regions of abundantrainfall and containsbothdecidous and evergreentrees.
  • 1. Temperatedecidousforestoccurs in moderatelyhumid area whereprecipitationtakes place throughout the year but winter are cold, restricting plant growth to the summers. Most of the treeslosetheirleaves 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, stepein 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.

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.


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 biomes
Environmental Variables Affecting the Biomes
  • 1. 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.