Ecology : Study / Science of Biosphere

Ecology: Concepts & Facts

  • The term Ecology is the combination of two Greek words, Oikos (='house/habitat/dwelling place) and Logos (= the study /science of). Thus, Ecology is the study/science of the biosphere (dwelling place of organism)
  • Ecology is defined as the study of the relationships of organism to one another and to their physical environment. Ecology is also called Bioecology, Bionomics or Environmental biology.

  • There is some controversy about the person who coined the term 'ecology'. Some scholars think that it was H. Reiter who introduced the term 'Oekologie (= ecology) in 1868; but most of the scholars think that it was German scientist Ernst Hackel (1834-1919) who coined the term Oekologie(= ecology) and put the firsprecise definition and explanation in the year 1869.

American biologist E.P. Odum (1913-2002) wrote in his popular textbook 'Fundamentals of Ecology': "The word 'oekologie' was first proposed by the Ernst Hackel in 1869. Hackel defined ecology as 'the study of the natural environment including the relations of organism to one another and to their surroundings'."

  • Ernst Hackel (1834-1919) is known as the father of Ecology (classical period). [According to some scholars. German naturalist Alexander Von Humboldt (176% 1859) as the father of ecology (classical period)]
    E.P. Odum (1913-2002) is known as the father of Modern Ecology (Modern Period).
    Ramdeo Misra
    (1908-98) is revered as the father of Indian Ecology.
  • Note: In science, the period from the Beginning to 19th century (i.e, the Beginning-19th century) is considered as 'Classical Period' and the period from 20thcentruryto Till Date (i.e. 1901-Till Date) as 'Modem Period'.
  • Like other fields of learning, the development in thefield of ecology has been gradual. Ecology has progressed from Natural History and Biogeography to Ecosystem Ecology. In the last quarter of the 20th century, (i.e 1975-2000), Global Ecologv with an emphasis on biodiversity climate change and ecological sustainability has been emerged. Global Ecology is a subfield of ecology and it treats ecology at a global scale.

Levels of Ecological Organisation (Ecological Hierarchy)

  • Levels of Ecological Organisation or Ecological Hierarchy provide a convenient but a holistic approach to understand ecology which is very complex in nature. It is represented in triangular form in diagram below. In ecology, levels of ecological/biospherical organization range from organism to ecosphere/biosphere. It is also called Ecological/ Biospherical Hierarchy (Hierarchy means an arrangement into a graded series). Levels of Ecological organisation i.e. Ecological Hierarchy, seven transcending processes or functions are depicted as vertical components in desscending order.

Levels of Ecological Organisation (Ecological Hierarchy)


  1. In Biology, there are 11 levels of organisation: Cell -- Tissue -- Organ -- Organ system -- Organism -- Population -- Community -- Ecosystem -- Landscape -- Biome -- Biosphere.

The elementary 4 levels (Cell--Tissue--Organ--Organ system) of Biological levels of organisation are not included in Ecology. So, there are only 7 levels of organisation in Ecology.

  1. Cell is the basic unit to study in Biology, where as organism is the basic unit to study in Ecology.
  2. There are 3 key levels of Ecological organisation: Organism, Ecosystem & Ecosphere/ Biosphere. If we understand these 3 terms (or levels) properly, then the rest 4 terms (or levels) shall be easily comprehensible to us.
  3. The Level 1 to Level 3 (organism to community) and the level 4 to level 7 (Ecosystem to Ecosphere/ Biosphere) are loosely synonym to one another; they are almost similar in traits (characteristics), but differ in size and extension. Hence, we can say, organism is the reduced & compressed form of community and community' is the enlarged & extended form of organism. Similary, Ecosystem is the reduced & contracted form of Biosphere and Biosphere is the enlarged & extended form of Ecosystem. This is the reason that Biosphere is called a 'giant ecosystem'.
  4. Biosphere is synonym of Ecosphere. With name 'biosphere' someone may confuse that it is concerned only to biotic/living environment, but it is not so. It is concerned with both biotic / living environment and physical/non-living environment. Similary, with name 'ecosphere', don't confuse that it is concerned only to physical environment, but it is concerned with physical environment as well as biotic environment.

Subnote: Keep these concepts well in mind. Don't take general meaning of these terms, but specific meaning whenever you tackle the questions of Ecology.

The levels of ecological organisation

1. Organism:

Organism is the basic and smallest unit to study in ecology. Organism means any individual living being/thing, whether of plant or animal. Thus, any living structure (plant, animal, bacterium or fungus) capable of growth and reproduction is called organism.

(Note: Virus is not included in constituent parts of organism because they are incapable of autonomous metabolism, growth or reproduction). Organism is an assemblage of organ systems. Similar organism having the potential for interbreeding and producing fertile off-spring constitute what we call species For example : a rose, an elephant etc.

2. Population

The term population, originally coined to denote a group of people, is broadened to include groups of individuals of any kind of organism. Hence population is a group of individuals of a plant or animal species in habiting in a given area. For example all individuals of roses in a area, all individuals of elephants in a area etc.

3. Community:

The term community is a combination of French word Commune (= a group of people) and noun suffix - ity (= state, condition). Community (sometimes designated as Biotic community) is an assemblage of all the populations occupying in a given area. For example: all population of roses in a area, all population of elephants in a area etc.

4. Ecosystem:

Ecosystem is the acronym of Ecological system. The system means a set of things that work together. The biological community and the physical environment function together as an ecological system or ecosystem. It is a fundamental functional unit of ecology, because it includes both biotic (living) and abiotic (non-living) environments, For example: Forest, grassland, desert, marine, lake, river, pond; crop field, park, spacecraft, swimming pool, well, aquarium etc.

Ecosystem is not only a middle level but also a very important level of ecological hierarchy. So the structure and functioning of ecosystem shall be discussed in detail in 'Biosphere: A Giant Ecosystem'.

5. Landscape:

The term landscape, originally referring to a painting and explained as 'an expanse of scenery seen by the eye as one view'. In ecology, landscape is defined as a heterogenous area composed of a cluster of interacting ecosystem that are repeated in a similar manner throughout. For example: a watershed etc.

6. Biome:

The term biome is a combination of Greek word bios (= life) and noun suffix - (o) ma (= mass, growth). A biome is a large regional unit characterised by a major vegetation type and associated fauna found in a specific climate zone.

For example:

(a) Terrestrial (land-related) Biomes— Equatorial (0°-15° of globe) evergreen forest biome, Tropical (12°-25°) rainforest biome, Temperate (45°-661/2°) deciduous forest biome etc.

(b) Aquatic (water-related) BiomesMarine (Salty-water) biomes like ocean, sea etc, Freshwater biomes like Lentic (standing water): lakes and ponds, & Lotic (running water) : rivers and streams & Wetlands : marshes and swamp forests (like mangrove forest).

7. Ecosphere / Biosphere:

The largest and most nearly self-sufficient ecological/biological system is designated as the Ecosphere/Biosphere. Ecosphere /Biosphere includes all the living organisms interacting with physical environment as a whole to maintain a self-adjusting, loosely controlled pulsating state.

Note: A simple formula to remember levels of ecological organisation (Ecological hierarchy):

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