The Terrestrial environment Soils, soils, soils
The terrestrial environment
Objectives • Discuss the formation of soils • Compare different soil types • Relate soil fertility to physical & chemical properties of soil. • Discuss soil erosion and its preventative methods • Compare farming methods
Objectives • 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.
Weathering • 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 substances. • Biological weathering is caused by growth of roots through rocks.
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 soil: 1) Air content 2) Water-holding capacity 3)Drainage
Soil fertility • Soil fertility is determined by • Particle size • Mineral content • Organic content • 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 water. • It has been increased dramatically by human land use, especially industrial agriculture, deforestation, and urban sprawl.
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 producer. 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.