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By the end of the lesson, you should be able to;

define vegetation,

discuss factors influencing vegetation,

discuss the significance of vegetation

 

VEGETATION

Defination

Vegetation refers to all the plants that grow together in an area. It is made up of trees, shrubs, herbs and grasses.


The vegetation of an area can either be natural, secondary (derived) or planted.

Topographical factors

These are factors that relate to the nature of the land and include altitude, terrain, drainage and aspect.



Attitude

Attitude influences temperature and rainfall. Temperature decreases with increasing attitude, hence, higher lands are cool and low lands are warm. Some plants survive under cool temperatures while others only grow well in warm areas.Attitudinal decrease in temperature gives rise to successive vegetation zones in mountain slopes.


Terrain

Terrain refers to the physical appearance of an area. Gentle slopes are suitable for plant growth as they are well drained and have deep well formed soils. Steep rugged sloped are exposed to rapid soil erosion and mass wasting. This encourages growth of plants.

Drainage

Well drained areas support the growth of a larger variety of plants. While waterlogged areas have small variety of swamp plant species.



Aspect


Aspect refers to the direction of the slope in relation to sunshine and the rain-bearing winds. The slopes facing the sun are usually warmer and support a wide variety of plants then those facing away.This effect is more pronounced in the mid-latitudes where the north facing slopes have different formations and species form the south facing slopes.


Climatic Factors

These factors relate to the elements of climate and include temperature, precipitation, sunlight and wind.

Temperature

Temperature determines the rate at which plant processes of germination, flowering, ripening of fruits and shading of leaves takes place. Warm conditions facilitate rapid growth of plants while cold conditions slow down their growth. For instance plants of the same species grow faster in tropical areas than temperate areas.

Precipitation

Various forms of precipitation provide moisture which is necessary for plant life. The amount of rainfall received in an area determines the kind of plants that dominate that area. Regions that receive heavy and reliable rainfall have luxuriant vegetation e.g. areas with equatorial climate.


Areas that receive little and unreliable rainfall have scanty vegetation devoid of big trees e.g. the savannah climate.

Sunlight

Light is necessary for photosynthesis to take place in plants. Place that experience long hours of sunlight have large varieties of plants than those that receive less amounts of sunlight.

Wind

Wind influences vegetation both directly and indirectly. Hot dry winds cause drought and moist wind cause rainfall when they blow over a region. This in turn determines the type of vegetation that grows in the region. Warm dry winds increase the rate of transpiration.

Where strong winds are dominant plant growth is retarded and trees bend in the direction of the wind. If the strong winds blow consistently trees may not have branches on their wind ward side.

Edaphic and pedological factors

These are the factors that relate to the nature of the soil. They include soil organisms, soil air and soil texture and soil PH. Pedological factors refers to the soil forming processes such as leaching and the factors influencing the processes such as the parent rock material, climate and living organisms.

Inorganic minerals and organic matters are the major determinants of soil fertility. Soil with well balanced nutrients support large variety of plant while infertile soils have scanty vegetation.
The soil texture determines the ease of root penetration. Areas with deep soils support big trees while those with thin soils support mainly grasses and shrubs.
The PH of a soil effects the relative availability of minerals for plant growth. Some plants such as conifers grow well in moderate to high acidic soils while others such as grass do well in soils with low acidity.


Biological (Biotic) factors

These factors relate to the influence of human beings, animals and birds.

Human beings

People modify and destroy vegetation. Natural vegetation is cleared to give way to settlement, agriculture, transport routes, industrial centres and mines.

Bush fires have resulted in the extinction of some plant species while overgrazing have turned some grasslands into pure deserts. Rehabilitation of vegetation through afforestation and reafforestation has given rise to new types of plant species.

Animals and birds.

Many plants are dependant on animals and birds for seed dispersal and cross-pollination. A close relationship exists between the type of number of plants and those of the animals that can be supported directly or indirectly by them.

For instance a large population of elephants can destroy in wooded grassland turning the vegetation into an open grassland.


Bacteria and Insects

Bacteria and insects cause diseases which may result in certain species of plants dying.

.

Characteristics of major vegetation regions of the world
 
By the end of the session you should be able to identify and describe the characteristics of the major vegetation regions of the world.


Major world vegetation zones

The vegetation of an area has a direct relationship with the climatic conditions of that area. As such those areas that experience high amounts of rainfall have luxuriant vegetation.

Vegetation can be classified according to the types of vegetation. Thus the following categories.

Forests

Grasslands

Semi arid and arid

Mountain

Exercise
Use the photograph to describe the pampas using the following hints: (click on the correct answer)
A) Grass cover on the ground is ________________ Continuous/discontinuous
B) Trees in the pampas are _____________Scattered/ dense
C) The grass has a ______________ appearance.  Blade/ Feather like

 

FORESTS

A forest is a continuous growth of trees and undergrowths covering a large area of land. The trees are in most cases of different species.


Tropical rain forest

The rain forests are normally found in humid areas. The areas are hot and wet throughout the year.They are common within the tropic 5N and 7S of Capricorn.


Some trees have broad leaves others have small leaves.

Some trees have buttressed roots.
The trees form three distinct layers. Tall, medium and short.
There are also climbing plants known as lianas.


Mangrove forest


Mangroves are trees or forests that have the ability to grow in mud-flats. They do well in salty shallow waters between the high tide and low tide within the tropics. They have a unique root system which helps in breathing and supporting the plant.


Deciduous forest

Deciduous trees have broad leaves that they shed in autumn. They are basically hardwood and are found in the mid latitudes.


Summer season
During this season the leaves are very green.

Autumn season
During autumn, the leaves turn green, yellow, red, brown and finally fall off.

Winter season
During winter the trees have no leaves.

Spring season
In spring, the trees develop leaf buds and gradually grow bud leaves.
photograph


Mediterranean forests
These forests are evergreen and adopt themselves during hot and dry summers. Most of the trees are woodlands. This vegetation does well in warm temperate western margin climate.
The Mediterranean forest has cone shaped with needle like leaves while other deciduous have broad leaves.


Coniferous forest.

Such forests have little undergrowth and are evergreen. The trees have needlelike leaves. The leaves are of tough waxy skin, conical shape, flexible trunks, shallow root system.

These forests are called Taiga in Russia. They do well in high latitudes between 450N and 600N or mountain slope.

FORESTS

Tropical rain forest
A forest is a continuous growth of trees and undergrowths covering a large area of land. The trees are in most cases of different species.
The rain forests are normally found in humid areas. The areas are hot and wet throughout the year.
They are common within the tropic 5N and 7S of Capricorn.
Some trees have broad leaves others have small leaves.
Some trees have buttressed roots.
The trees form three distinct layers. Tall, medium and short.
There are also climbing plants known as lianas.
Have a photograph of tropical rain forest at a corner as the animation is giving on.
NB.

  1. All the trees must be green in color.
  2. The three different layers must be clearly shown.
  3. There should be very little undergrowth.

The diagram should look like this;
(Diagram)

Mangrove forest
Mangroves are trees or forests that have the ability to grow in mud-flats. They do well in salty shallow waters between the high tide and low tide within the tropics. They have a unique root system which helps in breathing and supporting the plant.
Animation
(Diagram)
Animation
Show the above plants during the low tide exposing the roots.
Show the plants during high tide.
The only thing to be seen is as if plants were floating. This should be done from above (during high tide).
Show a large area of mangrove trees along the shore.
Have a photograph of mangrove forests. (Inset)

Deciduous forest.
D
eciduous trees have broad leaves that they shed in autumn. They are basically hardwood and are found in the mid latitudes.

Summer season
Show a deciduous forest with broad green leaves everywhere. There should be no snow. During this season the leaves are very green.

Autumn season
Animation
Show the plants leaves turning from green, yellow, red, finally brown and then falling off.
During autumn, the leaves turn green, yellow, red, brown and finally fall off.

Winter season
Show the trees with no leaves at all and a little bit of snow.
During winter the trees have no leaves.

Spring season
Show the plants developing leaf buds and show them becoming broad leaves that are green again.
In spring, the trees develop leaf buds and gradually grow bud leaves.
photograph

Mediterranean forests
These forests are evergreen and adopt themselves during hot and dry summers. Most of the trees are woodlands. This vegetation does well in warm temperate western margin climate.
Animation
Show a landscape with different types of trees. Some are cone shaped and with needle like leaves (eg cypress). Deciduous plants ie plants have broad leaves.
The Mediterranean forest has cone shaped with needle like leaves while other deciduous have broad leaves.
(Diagram)
Let all the trees be green in color.
In the second animation show the stems become thick hence the plant or tree should have a thick bark.
Show undulating plateau where.
(Plateau)
And show the following trees growing on the plateau as indicated. They should form a forest.
Have a photograph of Mediterranean forests. (Inset)

coniferous forest
such forests have little undergrowth and are evergreen. The trees have needlelike leaves. The leaves are of tough waxy skin, conical shape, flexible trunks, shallow root system. These forests are called Taiga in Russia. They do well in high latitudes between 45N and 60N or mountain slope.

Animation

Exercise
Use the photograph to describe the pampas using the following hints: (click on the correct answer)
A) Grass cover on the ground is ________________ Continuous/discontinuous
B) Trees in the pampas are _____________Scattered/ dense
C) The grass has a ______________ appearance.  Blade/ Feather like

Exercise
Name two types of temperate grasslands

Match the following names with the area where they are found by dragging to the respective area.

      • Downs     South Africa
      • Veldt    Europe and Asia
      • Pampas    North America
      • Prairies     Australia
      • Steppe.     Argentina

Answers
Downs     Australia
Veldt       South Africa
Pampas    Argentina

Prairies    North America
   
Steppe.     Europe and Asia

 








GRASSLANDS


Tropical Grasslands


Tropical grasslands occur in areas which experienced a prolonged season of drought after which a reasonable period of rainfall allows growth of plants. The rain is, however, generally inadequate for tree growth and ranges between 500mm and 750mm annually.

Characteristics of tropical grasslands

Tropical grasslands are mainly covered with grass. The tallest is the elephant grass which can grow up to 5 meters.

Trees found in the grasslands are of medium height of about 10-15 meters. The trees are usually umbrella shaped and have small leaves and thorns to reduce transpiration. Some also have huge trunks and thick barks to store water.

 

Temperate Grasslands

They occur between 300-500 North and South of the equator. The temperate grasslands remain dormant till winter when the temperatures are low.They have different names according to their locality.

In South Africa, the grasslands are called the veldt.In the veldt, short red oat grass covers extensive areas uniformly. There are also very few trees.

In South America, the grasslands are mainly found in Argentina. Here, they are called the pampas. The grass occur together with xerophytic\drought resistant shrubs.


In Europe and Asia, the grasslands are called steppes. In some areas, the steppes are covered with flowering plants while in others trees grow among the grasses.

The desert steppe consists of coarse grass growing in tufts with many patches of bare ground.


In North America (USA) the grasslands are called the prairies. In the prairies, there is a continuous cover of short grass of up to 1 meter high which grows together. With some bulbous and leguminous plants.


Desert vegetation

It is divided into two namely; hot desert vegetation and Temperate and cold tundra desert vegetation.


Hot desert vegetation

These are drought resistant vegetation that has adapted themselves in hot and dry conditions. The vegetation is also referred to as xerophytes.

Succulent perennials.

These plants are leafless and have fibrous stems.

They have pines which protect them from browsing animals. They have shallow roots which enable them take moisture from the topsoil layer. The outer surface of the stem is hard and waxy e.g. cactus


The evergreen hard-leaved plants.

They are mostly shrubs. They have dense cell fluids and hard ever green, waxy leaf surfaces. Leaves are small and thorn like. They have long tap roots.

Short lived plants.

Most of the tuberous or bulbous seeds remain dormant over the dry season. They germinate and grow fast to maturity during the short rains period.

E.g. lilies and poppies

Drought resistant deciduous shrubs.

The leaves grow during moist periods and shed their leaves during the drought period shrubs.


Salt tolerant plants/halophytic.

They grow in areas of poor drainage where the soils are saline and alkaline. The plants store water in their fleshy leaves and stems.

They have such a high salt content that when transpiration exceeds the water intake, salt crystals are formed in the plants surface.

Temperate and cold desert

The vegetation is commonly found in the higher latitudes across the land masses of the northern hemisphere. Where there is little precipitation and frozen soils. The vegetation grows fast during the warmer days.

The vegetation forms a continuous cover. Where it grows there are shallow roots. Some of the examples are in lichen, mosses, marsh, marigold, willow and crowberry.



Mountain vegetation

On a mountain, the vegetation cover is influenced by altitude, aspect, slope, temperatures and availability of moisture.Different vegetation zones on a tropical mountain are shown in the illustration below:

TEMPERATE AND COLD VEGETATION/TUNDRA
The vegetation is commonly found in the higher latitudes across the land masses of the northern hemisphere. Where there is little precipitation and frozen soils. The vegetation grows fast during the warmer days. The vegetation forms a continuous cover. Where it grows there are shallow roots. Some of the examples are in lichen, mosses, marsh, marigold, willow and crowberry.
Provide split photographs of the following plants in the above text:


    • Lichens
    • Mosses
    • Willow
    • Crowberry
    • Marsh
    • Marigold

By the end of the session, you should be able to discuss the significance of vegetation

Significance of Vegatation

Vegetation helps to prevent soil erosion by bidding the soils together.

Plants roots bind the soil together preventing the soils from being easily washed away. Loose soils are easily washed away.
Plants also act as wind breakers thus preventing the soil from being blown away by strong winds that lift the soils. Plants leaves reduce the impact of rain which could otherwise loosen the soils particles.

The vegetation provides a natural habitat for wild animals the animals such as the herbivores carnivores reptiles birds and butter flies are some of the wildlife

Vegetation is used as a source of raw materials for various industries.

Soft wood are used for the manufacture of pulp and paper. They are also used in making of ply wood and veneers. For example there is pulp and paper manufacturing in Webuye They use soft wood such as pine and cypress.

Vegetation is a source of raw materials fo textile industries. For example , cotton, linen and sisal.

Latex from rubber trees is used in the manufacturing of tyres and shoe making

Vegetation products are sown to provide timber for building and construction

 

Vegetation uses carbon dioxide to make their food and release oxygen into the atmosphere. Thus vegetation purifies the air which is important for animals and human life

Vegetation takes up carbon dioxide from the air and releases oxygen.Vegetation balances the carbon since other organisms take oxygen and releases up carbon dioxide

Vegetation modifies the climate of a place. Specifically forests through evapotranspiration into the atmosphere. The water vapour ascends and cools to form clouds that fall as rain.

Vegetation is a source of herbal medicine. A variety of plants have medicinal value. Used to treat different ailments. For example Neem Tree.


Vegetation adds beauty to the environment.

See how beautiful the landscape A looks as opposed to landscape B.


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