Importance of interaction between living organisms and the environment to maintain a

balance ecosystem1. An organisms cannot exist by itself. It needs to interact with other

organisms to maintain a balanced ecosystem.2. Living organisms interact among themselves in order to obtain food and

protection.3. Interaction can exist between:

• Animals and animals• Animals and plants• Plants and plants

4. Interaction between living organisms in an ecosystem will:• Create equilibrium in the environment• Control the size of a population in a community.

5. The types of interactions are • Predator-prey• Competition• Symbiosis

a) Predator-prey• This interaction controls the populations of predator and

prey.• The animals that hunts other animals for food is called

Predators, while the hunted animals are Prey.• Characteristics of predators and prey:

Predators Prey

Example : Tigers , Eagle Example : Horses , rabbit

Size : Bigger Size : Smaller

Food : Carnivores Food : Herbivores

Teeth/Jaws : Sharp , strong Run : Fast

Eyes : Sharp Colour : Blend with surrounding

Vision : Stereoscopic Vision : Monocular

Legs/Muscles : Strong Live : In groups or herds.

b) Competition• An interaction among organisms competing for the same basic

need.• Animals compete for food, space and mate. While the plants

compete for space, sunlight, water and mineral salts.• Controls the size of population and the stability of ecosystem.• It has 2 types of competition :

Intra-species competition - between organisms of same species. For example , cat

competing for a mate. Inter-species competition - between organisms of different species. For example ,

tiger and lions competing for food.

c) Symbiosis• An interaction between different organisms live in close

relationship.• One organisms always benefits while other organisms may

benefits, harmed or not affected.• Three types of symbiosis:

Mutualism - Benefits both organisms (symbiont). Commensalism - Benefits one organisms(commensal) while another organisms is

not affected (host). Parasitism - Benefits one organisms (paresite) while other organisms is

harmed(host). - Entoparasite. Its live outside the body of host. - Endoparasite. Its live inside the body of host.

Importance of photosynthesis-respiration in maintaining a balanced ecosystem

• Stable ecosystem is very important for survival of communities.• Stable ecosystem is dependent on :

Concentration of oxygen in the air Concentration of carbon dioxide in the air

• Photosynthesis and respiration are the processes that maintain the concentration of oxygen and carbon dioxide.• Living thing absorb oxygen and releases carbon dioxide during respiration.• Green plants absorb carbon dioxide and releases oxygen during photosynthesis.• Photosynthesis and respiration are balances one another in an ecosystem.