Chapter 8 Dynamic Ecosystem




  • The ecosystem refers to a system in which organisms live as communities related in an inseparable way to their environments.
  • It may be a pond or a forest, a fresh water lake, but in every case the nature of the environment and the changes in it have an influence on every aspect of the lives of the organisms that inhabit it. These organisms in their turn exercise some control over the nature of the conditions (referring to the abiotic components) in which they live.
  • An ecosystem is made up of all living things and environmental factors with the energy flow and transformation that occurs within it.
  • All the ecosystems ultimately merge and combine to form the biosphere (ecosphere).
  • The ecosystem is made up of four main components.
  • There are
(a) the non-living or abiotic components including pH, temperature, light intensity, humidity, topography and the microclimate.
(b) the producer component of the living organisms, the autotrophs chiefly the green plants.

(c) the consumer element, mostly animals.
(d) the decomposers, the fungi and bacteria.
  • All the organisms in an ecosystem and in a particular community are linked together by a number of food chains.
  • Some examples of such chains are
(a) Green plants —> aphids —> ladybird —> insectivorous bird —> hawk.
(b) Marine alga —> Copepod —> small fish —> large fish —> man.
(c) Green plants —> rabbit —> fox
(d) Green plants —> caterpillar —> bird —> eagle
(e) Grass —> grasshopper —> frog —> snake.
  • The food chains above begin with the producer-the green
  • A pyramid of numbers can be constructed with the base occupied by a large number of organisms and the top by a few.
  • In any ecosystem the vast number of individual food chains are always interconnected to form complex food web.
  • Interaction between biotic components include the following
(a) Symbiosis - interaction between two specific organisms that exist for a long period of time.
(i) Commensalism
(ii) Parasitism
(iii) Mutualism
(b) Saprophytism - where the saprophyte gets its food from dead, decaying matters of plants and animals.
(c) Predator - prey interaction involves two organism where one, the prey becomes food to another, the predator.
  • The interaction between biotic components in relation to competition include
(a) Intraspecific competition - competition between individuals of the same species.
(b) Interspecific competition - competition between individuals of different species.
  • Habitat refers to the specific area where an organism lives.
  • For example they inhabit such habitats as the pond, the lake or the sea.
  • Ecological niche refers to the physical space occupied by an organism and the role played by this organism in its community.
  • Population refers to a group of organism of the same species occupying the same habitat or area.
  • A community is a natural group of organisms made up of different population of plants and animals that interact with each other in a specific area.
  • Colonisation is a process whereby an organism successfully conquers a new area or habitat. The species of organism that successfully inhabits this new area is known as the pioneer.
  • The process by which the pioneer species is gradually replaced in a sequence is known as succession.
  • The climax community refers to the culmination of the succession process in a vegetation of a stable community consisting of life forms of the highest kind which the habitat is capable of supporting.
  • In Malaysia the climax community is the tropical rain forest.
  • The distribution of organisms in a community can be studied by using certain techniques.
  • (a) Quadrat sampling
  • (b) The catch - mark - release and recapture technique.
  • Biodiversity refers to the variety of species of plants and animals (flora and fauna) that exist in our ecosystems.
  • Classification of organisms involves grouping organisms with specific similar characteristics together.
  • For example, the 5 Kingdoms of organisms are as follows.
(a) Procaryotae (bacteria) (b) Protista (protozoa)
(c) Fungi (yeast)
(d) Plantae (fern)
(e) Animals (cow)
  • Hierarchy in the classification of organisms from kingdom to species is as follows:
  • Kingdom —> Phylum —> Class —> Order —> Family —> Genus —> Species
  • Microorganisms refer to minute sized organisms that cannot be observed by the naked eye.
  • They can be divided into five groups:
  • protozoa, fungus, alga, bacteria and virus.
  • The abiotic factors which influence the activities of the microorganisms include nutrients. moisture, temperature, pH and light intensity.
  • The role of useful microorganisms can be seen in the following:
(a) Decomposition
(b) Increasing soil fertility (c) Nitrogen cycle
(d) Waste disposal

(e) Alimentary canal of termite (Digestion of food)
(f) Digestive system in human beings.
  • Harmful microorganisms cause diseases and spoilage of food and substances.
  • Microorganisms that cause diseases are known as pathogens.
  • Pathogens can cause diseases by the following methods
(a) by contaminating food and drinks (cholera)
(b) through air (pneumonia)

(c) through sex (AIDS)
(d) through the wound in the skin (tetanus)
(e) by a vector (malaria)
  • The methods for controlling pathogen
- use of antibiotics, vaccines, antiseptics and disinfectants.
  • Microorganisms are useful in biotechnology for example
(a) in the production of antibiotics and vacccines (b) cleaning of oil spills
(c) waste treatment

(d) food processing
(e) production of bioplastic


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