Basic concepts; Levels of organization. Inter-
relationships between the living world and the
environment, the components and dynamism,
N. Sannigrahi, Associate Professor
Department of Botany
Nistarini College, Purulia (W.B) India
• Nature and diversity-the awesome source of pleasure and
scientific exploration since the onset of human consciousness.
The two components of nature, organisms and their
environments are not only much complex and dynamic but
also interdependent and mutually reactive and interrelated.
Ecology, a synthetic science deals with the various principles
which explore the relationships between the organisms and the
environment. Ecology, the vast encyclopedic biological
subject started its journey since the time immemorial but
etymologically it is comprising of two Greek words- Oikos
meaning home or dwelling space and logos means the study
of. Kormondy (1969) first tried to give the credit to Henry
David Thoreau in 1853 for this terminology. But German
biologist, Ernst Haeckel has been consensually agreed to be
the first proponents of this terminology.
• Ecology basically echoes the interaction between organisms
• All living organisms and their environments are mutually
reactive bit animal population, flora and vegetation are
independent through environment and are mutually reactive.
• Environment being dynamic works as a sieve selecting
organisms for growth from so many forms and one or other
factors become critical at critical stages of life cycle of the
• Every species puts its effort to maintain its uniformity and
structure, function, reproduction by preservations its own
genetic pool , however, species is also plastic and reacts to the
environment to get itself adjustment-somatic plasticity, the
ecads or by the recognition of their genes during sexual
• The environment not only influences the life of an organisms
but organisms too also modify the environment by the dint of
their growth , dispersal, reproduction, death and decay. The
dynamic environment and the organisms make the unique
ways for the development of the differe3nt kind of organisms
through succession. The process continues until the climax is
• By means of coactions and reaction. The plants and animals
related to each other by biomes and under climatic conditions,
more than one communities develop, some may reach to the
cli8max stage whereas the other experiences different
succession stages .
• Thus an interdependence along with freedom lies side by side
in the interaction between organisms and the environment to
make it dynamic.
• 1. Biotic and abiotic components build up the structural and
functional aspects of ecosystems.
• Discrete biological units consists of population, communities
including biomes and each population occupies a specific
niche-a unique functional position with respect to other
organisms with which it interacts
• Varying degree of interactions present that enables
competition, either at population or communities level,
• Energetics of ecosystem maintaining 10% law of energy
• Mineral recycling accounts of biogeochemical cycles like
Nitrogen, carbon, sulpher etc,
• Successful growth is governed by law of limiting factor
• Both the structural and functional aspects of ecology, Tansely
(1935) emphasized the role of environment , with the various factors
interacting with each other in his comprehensive term ecosystem
which involves all the living and non-living factors working with
synchroziation.with the new concept of modern ecology, following
are the basic concepts in the modern light of ecology.
• 1. When the biotic and abiotic components are considerted as the
structural and functional units of the ecosystems, discrete biological
units consist of population and communities, including biomes are
• 2. The natural interaction either positive or negative determine along
with abiotic parameters , the degree of success a particular
population has within a given habitat.
• The unidirectional energy flow involved the energetics of
• 3. The biogeochemical cycles frequently regulate the rate of
movement of cycling of chemicals for sustainable supply of
nutrients in the ecosystem.
• 4. The minimal and maximal levels of tolerance for ecological
factors are governed by the law of limiting factors,
• 5. Under natural conditions, the different kind of population
undergo succession. Ecosystems undergo an orderly process of
change with time, passing from a less complex to more complex
state. This process not only involves changes in species composition
but also changes in physical environment of a community to a
stabilized state known as climax.
• 7. Then come the probabilities of disruption and exploitation of
ecosphere. Species diversity of an ecosystem is reduced either by
man made or natural condition. Whether managed or natural-
disturbances caused a serious concern in the ecosystem.
SUB-DIVISIONS OF ECOLOGY
• BASED ON TAXONOMIC AFFINITIES: Plant Ecology &
• BASED ON HABITAT
• Whether freshwater, marine, estuarine, grassland, forests etc, it
is termed as Habitat ecology,
• BASED ON LEVELS OF ORGANISATION
• Autecology- Ecology of individuals at a given time together
with the influence of environment upon it,
• Synecology- Ecological interactions among the multiple
groups of organisms like plants, animals, microbes together to
create a more complex situations exist to build up a
community. This again subdivided under the following
headings-Population ecology, Community ecology, Biome
ecology, Ecosystem ecology etc.
LEVELS OF ORGANISATION
• Species make the basic unit of study in ecology. At each level,
the biological unit has a specific structure and function. At this
level, the form, physiology, behavior, distribution and
adaptations in relation to the environmental conditions are
studied. The organisms of the similar type have the potential
for interbreeding, and produce fertile offspring, which are
called species. The organism performs all the life processes
independently. However, parts of organism cannot exist
independently of one another. An organism is fully adapted to
its environment. It has a definite life span including definite
series of stages like birth, hatching, growth, maturity,
senescence, aging and death. Competition, mutualism and
predation are various types of interaction between organisms.
LEVELS OF ORGANISATION
• The levels of organizations in ecology follow the basic pattern:
• In ecology, a population is a group of individuals of the same
species, inhabiting the same area, and functioning as a unit of
biotic community. The interaction between populations is
generally studied. These interactions may be a predator and its
prey, or a parasite with its host. Competition, mutualism,
commensalism, parasitism, and predation are various types of
• Biotic community organization results from interdependence
and interactions amongst population of different species in a
habitat. This is an assemblage of populations of plants,
animals, bacteria and fungi that live in an area and interact
with each other.
LEVELS OF ORGANISATION
• A biotic community is a higher ecological category next to
population. These are three types of biotic community, they
are: animals, plants and decomposers (i.e., bacteria and fungi).
A biotic community has a distinct species composition and
• The ecosystems are parts of nature where living organisms
interact amongst themselves and with their physical
environment. An ecosystem in composed of a biotic
community, integrated with its physical environment through
the exchange of energy and recycling of the nutrients. The
term ecosystem was coined by Sir Arthur Tansley in 1935. An
ecosystem has two basic components:
• (i) Abiotic (non-living), and (ii) Biotic (living organisms).
FACTORS OF ENVIRONMENT
• Abiotic components comprise inorganic materials, such as
carbon, nitrogen, oxygen, CO2, water etc., while biotic
components include producers, consumers and decomposers.
• Landscape: A landscape is a unit of land with a natural
boundary having a mosaic of patches, which generally
represent different ecosystems.
• Biome: This is a large regional unit characterized by a major
vegetation type and associated fauna found in a specific
climate zone. The biome includes all associated developing
and modified communities occurring within the same climatic
region, e.g., forest biomes, grassland and savanna biomes,
desert biome, etc.
• On a global scale, all the earth’s terrestrial biomes and aquatic
systems constitute the biosphere.
FACTORS OF ENVIRONMENT
• Biosphere: The entire inhabited part of the earth and its
atmosphere including the living components is called the
• (i) The hydrosphere which includes all the water components,
• (ii) The lithosphere comprises the solid components of the
earth’s crust, and (iii) The atmosphere formed of the gaseous
envelope of the earth. The biosphere consists of the lower
atmosphere, the land and the oceans, rivers and lakes, where
living beings are found.
• Thus, the different factors of the environment plays a very
crucial role in this regard to build up the structural and
functional organizations in the environment as well as a
tendency to recycle and replenish in order to maintain a
dynamic equilibrium of the surroundings.
INTER-RELATIONSHIPS BETWEEN THE
LIVING WORLD AND THE ENVIRONMENT
• Environment is a complex of so many attributes like light,
temperature, soil, water etc that surrounds an organism. Any
external force, substance or condition that surrounds and
affects the life of an organism in any way becomes the factor
of the environment- environmental factors, ecological factors
are either biotic or abiotic factors. Ecological factors may be
• 1. Direct factors- Light, temperature, humidity of air, soil air,
soil water, soil nutrients etc.
• 2. Indirect factors-include soil structure, soil organisms,
altitude, wind, slope etc.
• Generally four categories of factors are included-
• 1. Climatic or aerial factors- Light, temperature, rainfall,
Humidity of air, Atmosphere
• 2. Topographic factors- altitude, direction of mountain chains,
valleys, Steepness and exposure of slopes,
• 3. Edaphic factors- These deal with the formation of soil, its
physical and chemical properties and details of the related
• 4. Biotic factors- these are all kinds of interactions between
the different forms of life like plants, animals and
• All these factors play a very crucial role for the sustainable
environmental complex to make the avenue of the formation
of life and its gradual changes corresponding to the changes of
BIOTIC AND ABIOTIC INTERACTIONS
• The effects of environment on the life of an organisms is the
interaction of the ecological factors .In the normal conditions,
at the same time, the life of an organism is effected by the sum
of all the ecological factors- the environment- not by the
individual factors. All the factors are interrtelated.But
variations in one effect may have strong effect upon the
organisms. The law of the limiting factors govern the guiding
principles of the life of an organisms as well as the different
metabolism of the counterparts of the environment.
Increasingly the intensity of light affect the rate of the
photosynthesis along with the increase of the temperature.
Since various ecological factors affect the life of an organism
in a holistic manner, it becomes difficult to understand the
mechanism of the nature of influence of individual factor.
BIOTIC AND ABIOTIC INTERACTIONS
• To understand the mechanism of environmental influence, it
thus becomes essential study the effect the each factor
separately and this is to considered as analytical approach. Let
us give some examples in this regard.
• 1. Light directly or indirectly effects the plants life on
chlorophyll production, heating action, effect on transpiration
rate, stomata movement, distribution of plants along with the
overall vegetative and reproductive development of plants life.
• 2. Temperature effects on plants and animals life on
metabolism, reproduction, growth and development, on
crossing over, sex-ratio, coloration and morphology. Animals
may be either endothermic, exothermic leading to a gross
• 3. Rainfall effects on hydrological cycle
BIOTIC AND ABIOTIC INTERACTIONS
• 4. Topographic factors like mountain chains, direction of
mountains and valleys, steepness of slope and it exposure have
strong effect upon organisms.
• 5.Soil- Mineral matter, organic matter, soil water, soil
atmosphere, biological systems etc are some of the factors of
soil that have strong effect upon the plants and animals of the
• In addition to the aforesaid issues, there are other number of
factors that have strong synergistic or antagonistic effect upon
the counterparts of the different components of the biotic and
abiotic constituents of the system. Thus, the living world and
the abiotic constituents play a very important relationship to
maintain a dynamic equilibrium of the environment since the
onset of life in the blue planet.
• Because ecosystems consist of living things that can change, it
makes sense that the ecosystem itself can change over time.
For example, if a certain population experiences a significant
transformation, it will affect the entire ecosystem.
Since the inception of life on the blue planet followed the
different physical, chemical and biological changes, the
environment has taken the present shape enriched with the
diversity of life forms. Any ecosystem if experiences any kind
of changes affect the gross. Take for the example of
disappearance of one consumer, it will effect upon the other
consumers in the successive levels. The ecological pyramid of
energy, number and biomass are interrelated to upon one
another. Nature always tries to maintain a sustainable and
replanishable system to maintain a dynamic equilibrium as
earth is a close system as far as matter but an open system as
far as energy.
THANKS FOR YOUR PLEASURE
• Images for Google
• Different websites
• Ecology & Environment- P.D.Sharma
• Concepts of Ecology-Kormondy
• Ecology &Environmental Biology-Saha
• Disclaimer: This presentation has been developed as free
knowledge sources without any financial interest of the