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  1. Living Things (Habitat) | Week 1, 2 & 3
    8 Topics
    1 Quiz
  2. Living Things (Uniqueness of Man) | Week 4
    9 Topics
    1 Quiz
  3. Growth and Development | Week 5 & 6
    4 Topics
    1 Quiz
  4. Chemicals | Week 7 & 8
    4 Topics
    1 Quiz
  5. Work, Energy & Power | Week 9
    4 Topics
    1 Quiz

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What is an Ecosystem?

Ecosystem is a community of living organisms, in conjunction with non-living thing components, interacting as a system.

Various kinds of feeding relationships exist between organisms in a community. These feeding relationships or interactions may be harmful, beneficial, or neutral to each of the organisms in a community.

They are:

1. Parasitism.

2. Mutualism.

3. Saprophytism.

4. Commensalism.

5. Predation.

1. Parasitism:

This is an association or relationship in which one organism, called the parasite, lives in, or on, another organism called the host, where nourishment is derived. In this case, the parasite is gaining and the host is losing. Examples include man and tapeworm, man and roundworm, tapeworm and pig, ticks and cattle, fleas and birds, lice and man, etc.

ticks and cattle

2. Mutualism/Symbiosis:

This is an association between two organisms in which both of them benefit, each member is called a symbiont. Examples are algae and fungi (lichen), flowering plants and insects, cattle and tick birds, and bacteria in the root of plants.

Let us take a look at the symbiotic relationship between the water buffalo and oxpecker. Large mammals like the water buffalo are prone to ticks, which feed on their blood and can spread diseases and cause anaemia. Luckily for the water buffalo, the oxpecker feeds on ticks.

By eating the ticks from the hide of the water buffalo, the oxpecker gets a free meal, and the water buffalo gets cleaned of parasites.

water bufallo and tick birds

3. Saprophytism:

This is a feeding association between living organisms (saprophytes) and dead remains of once-living organisms. Examples of saprophytes include fungi, for example, mushrooms and mould, as well as bacteria. Saprophytes also help in the decay of organisms.

Saprophytic feeding:
Mushroom is a Saprophyte that grows on dead organic matter, such as fallen leaves, plant roots, and dead wood.

4. Commensalism:

This is the association between two organisms where one partner (the commensal) benefits while the other (the host) is unaffected. Examples include remora (shark sucker) and the shark, ferns (epiphyte) on trunks of palm trees.

The remoras use a type of built-in suction to stick to a shark’s skin and hitch a ride. When the shark makes a kill, the remora eats the scraps. The shark does not attack the remora. The remora benefits greatly from this commensal relationship, by getting a free meal and protection.

shark and remora
The remoras swim very close to the sharks, feeding off scraps of food dropped by the shark.

5. Predation:

This is the kind of association in which an organism, called a predator, hunts and kills another one, called prey, for food. Examples of predators and prey include cats and rats, lions and antelopes, leopards and impalas, etc.

cat and rat
Cat preying on a rat.


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