Organism and population One Shot
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The term ecology was coined and described by – - E.Haeckel
Father of ecology – - Reiter
Father of Indian Ecology- – Prof. Ram Deo Misra
First of all term ecology was employed – - Warming
for study of plant by
Branches of Ecology – It is based on organisation level
1. Autecology – Study of the relation of a single species with its environment is known as autecology
2. Synecology – Study of the relation of the group of different species with their environment is known as
synecology.
ORGANISM
An organism is the smallest unit of ecological hierarchy and basic unit of ecological study.
It may be small/large, unicellular/multicellular.
Fixed life span and organized life cycle (birth to death)
Ecology at the organismic level is essentially physiological ecology
POPULATION
A group of Individuals (members) of same species living at one place (specific geographical area) constitute a
population.
w Local Population or demes (Sub groups of population) – Population of organism inhabiting a
particular area.
eg. Homosapiens inhabiting hills, plains
w Sister population – Different population of same species of organisms which are found in different
places are known as sister population.
SPECIES
Definition - Species is a basic unit of classification, defined as the group of living organisms similar in
structure,function and behaviour and produced by similar parents, have common gene pool, can inter breed
under natural conditions and reproductively isolated from other group of organism.
SOME TERMS RELATED TO SPECIES :
Endemic Species or Endemism :
A species which is found only in a particular area is known as endemic species.
e.g. Meta sequoia is found only in valley of China, Kangaroo in Australia
Key-stone Species :
The species which have great influence on the community's characteristics relative to their low
abundance or biomass are called key-stone species. The activities of key-stone species determine the
structure of the community.
e.g. Lion in forest, Kangaroo rat in desert, fig tree in tropical forest.
Critical Link Species :
The species which establishes an essential link with other species to help the latter in some vital
activity is called link species.
e.g. Mycorrhizal fungi, many insect species which works as pollinators of flowers.
COMMUNITY
Groups of organisms of different species that live in common area, which are interrelated and interdependent.
It is a natural aggregation of plants and animals in the same environment.
Biotic Community = Animal community + Plant community + Microbial community
Characteristics of a community –
1. Species Diversity –
There are different types of population (species) found in community, this is called species diversity. It
depends on size of the area, type of area, type of soil , altitude, climate.
2. Dominance –
The highest number of organism of a species present in community, is called as the dominant species.
Whole community is known by the name of that particular dominant species.
e.g. Prosopis in Aravali hills, Pinus in Himalaya
3. Stratification –
The different growth form (trees, shrubs, under shrubs, herbs) determines the structure of a plant
community. Stratification is based on mode of arrangement of various growth forms
Statification in Lake
In deep lake, zonation or stratification may be according to the need of light. There are three types of zone diffrenetiate in a deep lake
Littoral Zone – This zone is found at bank of lake where very shallow water or marshy land is present. Rooted vegetation is found in this zone.
Limnetic zone – This is the zone of lake water, where light reaches in sufficient amount to entire
surface area. It means this is not too deep. In this region different types of floating plants (phytoplanktons),
suspended and submerged plants are present
Profundal zone – It is very deep area of the lake where light does not reach up to the bottom. Only
heterotrophs are present in this zone
Stratification in forest –
The clear stratification (vertical arrangement) in various growth forms of plants according to the need of
light in any dense forest.
Surface dewellers - Herbs - Under shrubs - Shrubs - Trees
Note : The clear stratification is found in tropical rain forest. So it is known as multistoried forest.
SUCCESSION
Development of plant community on barren area is called ecological succession or Biotic succession. The
replacement of existing community by new ones, in an orderly sequence in barren area with time due to
change in environmental conditions. Biotic communities are never stable. They are changing more or
less over period and space, due to presence of different types of climatic & environmental conditions. So a
continuous interaction is going on between the community and environment till state of stability.
Term for community in succession :-
Pioneer community – The first community to inhabit an area is called Pioneer community
Climax community – The last and stable community in an area is called climax community. This is more
stable. Usually mesophytes are present in climax community.
An important characteristic of all communities is that composition and structure constantly change in response
to the changing environmental conditions. This change is orderly and sequential, parallel with the changes
in the physical environment.These changes lead finally to a community that is in near equilibrium with the
environment and that is called a Climax Community
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