15. Our Environment

• What are the components of an eco-system?

  Biotic and abiotic factors
• All interacting organisms in an area together with the non-living constituents of an environment form an ecosystem.
• What are the two types of ecosystems?

  Natural ecosystems and man made or artificial ecosystems
• Organisms can be classified as: Producers, Consumers and Decomposers
• What are producers?

  Producers (autotrophs) are organisms that synthesise food.

  For example; plants and certain bacteria
• Consumers are organisms that consume food produced by the produces directly or indirectly. Consumers are categorised into herbivores, carnivores, omnivores and parasites
• Decomposers break down dead remains and wastes. They break down complex organic substances into simple inorganic substances.

  example: bacteria and fungi
• If the decomposers are not present natural replenishment of the soil will not take place.
• What percentage of solar energy is trapped and utilised by plants in a food chain?

  1%
• Name the group of chemical confidence that damaged the ozone layer.

  CFCs
• A series of organisms feeding on one another at various biotic levels from a food chain
• What is a trophic level?

  Each step or level of the food chain forms a tropical level
• The autotrophs or producers are at the first trophic level.
• Autotrophs or producers fix up the solar energy and make it available for heterotrophs or the other consumers.
• The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level.
• An average of 10% of the food eaten by an organism is turned into its own body and made available for the next level of consumers.
• Food chains generally contain only 3-4 steps. This is because the energy available for the next level of consumers is very little.