Interaction of organism in the environment

Interaction among living organisms

The relationship among organisms in the environment can be explained in the form of predation, competition and symbiosis.

Predation

This happens when one organism captures, kills and feeds on another in order to get nutrients. Example: cats eat mice and sharks eat fishes.

Competition

This is a relationship where organisms both need the same limited environment resources for survival. Examples: lions and leopards both hunt antelope and zebra. Hence lions and leopards are competitors. Organisms from the same places can also be competitors. Example: cows competing for grass.

Symbiosis

This is a relationship whereby there is a close association between organisms. This association could take various forms, such as mutualism, commensalism, neutralism, syn-necrosis, amensalism and parasitism.

Mutualism

This is the relationship in which two organisms benefit each other. Example: the rhizobium bacteria in the root nodules of legumes convert nitrogen into nitrates for use by the plant. The bacteria get protection and nutrients from the plants.

Commensalism

This is interaction that is beneficial to one organism and is neutral to the other organism. Example: when a bird builds a nest in a hole in a tree.

Parasitism

In this association one organism benefits while the other is harmed. Example: Plasmodium that causes malaria in human beings.

Food chains and food webs

Food chains and food webs show the flow of nutrients and energy among organisms in the environment.

1. Each organism in a food chain or food web represents a trophic level.
2. Trophic level is a position that an organism occupies in a food chain or food web.
3. Examples: producers like green plants, primary consumers like herbivores and secondary consumers like carnivores.

Producers

These are organisms that can manufacture their own food. Example: green plants and photosynthesis bacteria. This is the first trophic level.

1. Producers are eaten by primary consumers.
2. Primary consumers are mostly herbivores such as rabbits, cows, buffaloes, wild beasts, goats and sheep.
3. Primary consumers form the second trophic level.

Secondary consumers

These form the third trophic level.

1. They feed on primary consumers.
2. They are mostly carnivores such as domestic cats, dogs, hyenas, lions, leopards and wolves.
3. This level can be followed by tertiary consumers which feed on secondary consumer, then quaternary consumers feed on tertiary consumers.

Decomposers

These are organisms that decompose dead organic matter.

1. This is the final trophic level.
2. These organisms feed on dead matter and break it down, thereby facilitating recycling.
3. The two main decomposers are the saprophytic fungi and saprophytic bacteria.
4. The relationship between organisms at different trophic levels can be presented diagrammatically as follows.