Environment is defined as the total surrounding or medium of any organism in a given area. This include the physical surroundings, climatic factors and other living organisms in that surrounding.


The earth as an environment is grouped into four spheres:

  1. Lithosphere: The solid portion of the environment which contains rocks, sand, soil, minerals etc.
  2. Hydrosphere: This is the liquid portion of the environment like rivers, lakes and oceans.

iii.        Atmosphere: This is the gaseous portion of the environment where gases like oxygen, nitrogen, carbon-dioxide, ozone are found.

  1. Biosphere: This is the portion of the environment where plants and animals are found.

These four spheres of the environment are interrelated and interdependent on each other.


  1. What is an environment?
  2. State the components of the environment.


Ecosystem: An ecosystem is defined as the community of plants and animals living together in harmony and interacting with their physical environment.

In other word, an ecosystem can be defined as the relationship that exists between living things and their non-living environment.

Components of  Ecosystem

The ecosystem is made up of two main components.  These are:

(a)        Abiotic (non-living) component: These are the components like soil, water, gases, sunlight etc in the environment.

(b)        Biotic component: This is the living component of the ecosystem.  It includes plants and animals.

Biotic components can be grouped into three:

(1)        Autotrophs: These are also called the producers.  They include the green plants which manufacture their own food through a process known as photosynthesis.

(2)        Heterotrophs: These are called primary and secondary consumers.  These organisms cannot manufacture their own food but depend directly or indirectly on plants for their food e.g. man, parasites, saprophytes.

(3)        Decomposers: These are micro – organisms that decompose dead organic matter in order to release nutrients required by producers to prepare their food e.g. Fungi and bacteria.


Interdependence is used to describe the relationship between the components of the ecosystem.  This is because components in an ecosystem depend on one another and they cannot exist in isolation.  A state of inter-dependence within the ecosystem is best achieved where the components are undisturbed.

Inter-dependence in an ecosystem exist in three ways:

(1)        Interdependence within Abiotic components e.g. The weathering of rock to form soil or the evaporation of water to form cloud etc.

(2)        Interdependence within Biotic components e.g. Animals depend on plants for food or the exchange of oxygen and carbondioxide by plants and animals.

(3)        Interdependence between the biotic and abiotic components e.g. plants depend on soil for support and nutrients, Autotrophs convert sunlight to energy, water and carbon dioxide during photosynthesis to produce food etc.


  1. Define an ecosystem.
  2. State the components of an ecosystem.
  3. Explain the interdependence within an ecosystem.


Environmental balance refers to the ways of recycling matter and the flow of energy within an ecosystem in order to ensure continuous supply or availability of energy.

Environmental balance is achieved through the following processes:

(i)         Hydrological (water) Cycle

(ii)        Carbon Cycle

(iii)       Nitrogen Cycle

(iv)       Mineral or Nutrient Cycle

(v)        Food Chain and Food Web.


  1. What does the word ‘Interdependence’ mean?
  2. What is environmental balance and how is it achieved?
  3. What is an environment?
  4. State the spheres of the environment.
  5. Explain the lithosphere.


  1. The liquid portion of the earth is called ________ (a) Hydrosphere  (b) Biosphere  (c) Atmosphere
  1. Animals, man and parasites are grouped as ______(a) Decomposers (b) Heterotrophs  (c) Autotrophs
  1. The relationship between organisms and its physical environment is called ______   (a) Environment                (b) Ecosystem     (c) Community
  1. The best example of autotrophs are ________ (a) Animals  (b) Man     (c) plants
  2. One of these is not a way an environmental balance is achieved (a) Food chain  (b) Water cycle (c) Sand cycle


  1. What is an ecosystem?
  2. Mention four importance of the environment.

See also


PLATEAUX: Types of Plateau, Tectonic Plateaux, Volcanic or Lava Plateau, Dissected Plateau

MOUNTAINS: Fold Mountains, Block Mountains, Volcanic Muntain & Residual Mountain



Leave a Comment

Your email address will not be published. Required fields are marked *

Get Fully Funded Scholarships

Free Visa, Free Scholarship Abroad

           Click Here to Apply