Interdependence and Interaction among Organisms, and between Organisms and the Environment

2.3

Interdependence and Interaction among Organisms, and between Organisms and the Environment

Habitat
- The natural surroundings or home of an organism.
Species
- A group of organisms that have common characteristics and can reproduce to breed offsprings
Population
- A group of organisms of the same species that live in the same habitat.
Community
- A few populations of different organisms live together in one habitat and have mutual interaction with one another.
Ecosystem
- A few communities that live together in one habitat and have mutual interaction with one another, including all the non-living components such as water, air and soil.
An ecosystem is said to be balanced if the living organisms and non-living components in the environment are in a state of harmony without any external interference.

Interaction between Organisms

Interaction between organisms comprises symbiosis, prey-predator and competition.

SYMBIOSIS

Symbiosis happens when two or more organisms of different species live closely together and interact with one another.
Symbiosis includes mutualism, commensalism and parasitism.

Mutualism

An interaction that benefits both organisms

Example: Lichens are algae and fungi that live together

Commensalism

The interaction between two organisms which only benefits one organism without harming or benefitting the other

Example: The remora fish (commensal) latches on the shark (host)

Parasitism

An interaction that benefits one organism and only and harms the other. The parasite gets benefit and host is harmed.

Example: Tapeworm(parasite) that lives in the human intestine(host)

PREY-PREDATOR

Involves one organism that eats another organism
Prey is the organism that is eaten by the predator
Predator is the organism that hunts another organism for food
Example : Lion(predator) and deer(prey)

COMPETITION

Competition happens when organisms in one habitat compete for a limited supply of basic needs such as light, space, water, food and mates

Biological Control

Biological control is a method that uses organisms that are natural predators or parasites to reduce the number of pests in an area.
Example: Owls are kept in palm oil plantations to control the population of rats

Factors that Influence Population Size in an Ecosystem

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Disease

Presence of predators

Source of food

Change of weather

Changes in the Ecosystem

Limited water supply
- Example: Drought season that will upset the paddy field ecosystem
Migration
- Example: The cattle egret migrates to Kuala Gula from September to April every year.
- As a result, the number of insects decreases as they are eaten by the egrets
Change in population size
- Example: The increase of pests causes the population of plants to decrease