8.3 3.1.4 ecosystems  (Page 2/6)

Air / gases

• The movement of air is called wind.
• Wind affects many things in the ecosystem ie speeds up evaporation, assist in pollination of plants and the dispersal of their seeds.
• Air is composed of 78% Nitrogen, 21% Oxygen, 4% Carbon dioxide and water vapour.
  • Oxygen – used in cellular respiration and combustion and is returned to the environment by the process of photosynthesis.
  • Carbon dioxide – is a product of cellular respiration and decayed organic matter. It is removed from the atmosphere by plants during the process ofphotosynthesis.
  • Nitrogen – is needed by all living organisms for the synthesis of proteins.
  • Water vapour - the amount of water vapour found in the air remains constant on average, however, it can vary greatly from one place to another. Some parts ofthe Earth are prone to high humidity levels, why other locations have very dry air. Much of what we consider weather is caused by water vapour. The clouds inthe sky are largely made up of it, and it is the condensation of this vapour into droplets that creates rain and snow.

Edaphic factors:

Soil structure

• Humus content is the decomposed remains of dead organic matter. It gives
• the topsoil its dark colour. It supplies plants with nutrients and helps the soil
• absorb (retain) water. Soils rich in humus are fertile soils.
• Texture of soil is determined by the size of the soil particles.

Soil properties

• How acid or alkaline a soil is, can be measured by the pH scale .
• pH is a measure of the acidity or alkalinity of a solution.
• The pH scale ranges from 0 to 14. Neutral solutions have a pH value of 7 . Acid solutions have a pH value of less than 7 and alkaline solutions greater than 7 .
• Litmus paper or universal indicator can be used to determine whether a solution is acid or alkaline.

Physiographic factors:

Aspect

• Refers to the position of an area in relation to the sun or wind or wave action.
• It is the direction that the slope faces ie North, South, East, West .
• In Southern Hemisphere -
  • North facing habitats receive:
    • more solar radiation than a South facing one.
    • are warmer and drier
    • greater variety of animals
  • South facing habitats are:
    • cooler
    • have a higher water capacity
    • plant growth is luxurious

Slope

• Also referred to as the gradient which represents the steepness of a slope.
• Affects the rate of water run-off
  • Ie Steep slope – encourages fast run-off of water and causes soil erosion. Soils tend to be shallow and infertile and plant growth is reduced. Plants are small and few animals present
• Gentle slope – favours slower flow of surface water, reduces erosion, and increases availability of water to plants.

Altitude

• Is the height of the land above sea level.
• At high altitudes :
  • the temperature is lower ,
  • the wind speed is greater,
  • and the rainfall less and more likely to get snow.
  • Less plant and animal species found
  • Plants more stunted than at lower elevations.

Biotic components

Living organisms in an ecosystem are usually grouped according to how they obtain food.

• Autotrophs that make their own food are known as producers, while
• Heterotrophs that eat other organisms, living or dead, are known as consumers.
• The producers include land and aquatic plants, algae and microscopic phytoplankton in the ocean.
• They all make their own food by using chemicals and energy sources from their environment.