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The Terrestrial environment


									The Terrestrial
    Soils, soils, soils
• Discuss the formation of soils
• Compare different soil types
• Relate soil fertility to physical & chemical
  properties of soil.
• Discuss soil erosion and its preventative
• Compare farming methods
• Discuss food chains & food webs found in
  the terrestrial environment

• Describe the oxygen, carbon, nitrogen &
  water cycles.
             Soil formation
• Soil formation begins with weathering.

• This is the process by which rocks are
  broken up into small particles over long
  periods of time.

• There are various ways in which
  weathering may occur.
• Physical weathering is caused by changes in
  temperature and water pressure.

• Chemical weathering is caused by rainwater in
  cracks of rock dissolving away some of the

• Biological weathering is caused by growth of
  roots through rocks.
Components of soil
          Soil components
These include:
• Humus
• Mineral particles
• Rock particles
• Air
• Water
• Living organisms
                      *Discuss the functions of each
               Soil types
• Clay soils have mainly clay particles with
  small air spaces.

• Sandy soils have mainly sand particles
  with large air spaces.

• Loam soils are a mixture of sand & clay
  particles with medium size air particles.
           Size of particles
• The size of the particles affects the
  following physical characteristics of the
1) Air content
2) Water-holding capacity
                   Soil fertility
•    Soil fertility is determined by

1)   Particle size
2)   Mineral content
3)   Organic content
4)   pH

     Nb. Soil which possesses the conditions
     needed for optimum plant growth of a plant are
     fertile with respect to that plant.
             Soil Erosion
• Erosion is a natural process, whereby the
  topsoil is removed by action of wind and
• It has been increased dramatically by
  human land use, especially industrial
  agriculture, deforestation, and urban
        Causes of soil erosion
•   Careless farming methods
•   Deforestation
•   Overgrazing
•   Over cropping
•   Loss of soil structure
         Reducing soil erosion
•   Contour ploughing
•   Terracing
•   Planting trees
•   Strip cropping

              *Please check text for various farming techniques
       Feeding relationships
• An ecosystem is a system formed by the
  interaction of a community of organisms
  with their physical environment.

• Forests, deserts, grasslands & savannas
  have their own terrestrial ecosystems.
       Feeding relationships
• All organisms interact with each other and
  their surroundings within an ecosystem.

• One of these main interactions involve the
  various feeding relationships.
       Feeding relationships
• A food chain shows the feeding sequence
  of organisms in an ecosystem.

• The 1st member is called the producer. It
  is a plant, and it produces its own food.

• All of the other members of the food chain
  are called the consumers. These acquire
  their food otherwise.
               Food chain
• A food chain always starts with the
• The arrows shows the direction of energy
  from consumption.

• The consumers follow thereafter and are
  classified primary, secondary, tertiary etc.
Consumers can be:
*Herbivores: feed only on plant material
*Carnivores: feed only other animals
*Omnivores: feed on both plants & animals
*Decomposers: feed on dead organic matter

Can you give examples of these?
               Food web
• A food web is a network of inter-related
  food chains.
• If the number of one organism in a food
  web changes, it can affect the numbers of
  all the others.
The natural
The Carbon cycle
The Nitrogen cycle
The water cycle

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