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Relationships of organisms with one another and the environment

(Credits to Mustafa Asif)


Ecology is the study of the relationships between living organisms and the natural environment

Consists of

  • biotic: concerning living things which an organism comes into contact with

  • abiotic: includes light, water, oxygen, temperature, salinity and pH of water or soil

Some terms

  • Habitat: a place where an organism lives

  • Population: a group of individuals of the same species

  • Niche: the role played or position occupied by an organism in the habitat

  • Community: consists of populations of plants and animals living together and interacting with one another under the same environmental conditions

  • Producers: green plants that can manufacture food materials by photosynthesis

  • Consumers: obtain their energy from the organisms on which they feed

  • Decomposers: break down organic matter, feeding on some of the remains and releasing the rest

Food chain and Food web

  • Food chain:

    • a series of organisms through which energy is transferred in material form constitutes a food chain

    • A food chain is usually short because of the loss of much energy to the environment at each level

  • A food web consists of two or more food chains interlinked together

Carbon cycle

  • The carbon cycle consists of processes by which carbon dioxide is removed and restored to the atmosphere


  • Parasitism is an association between 2 organisms such that one organism (the parasite) lives on or in the body of another organism (the host)

  • The parasite usually does some harm to its host


  • The malaria parasite requires 2 hosts (man and anopheles mosquito) to complete its life cycle

    • It is transmitted from an infected person to a healthy person by the female Anopheles mosquito (the vector)