Sum total of all factors (biotic and abiotic), substances and conditions which influence organisms without becoming their constituent part, is called environment. All these factors are found integrated with in the limits of time and space.
Ecology deals with the various principles which govern the relationships between organisms and their environment.
Habitat is a specific place (locality) where an organism usually lives. It is a physical entity comprising the sum total of the abiotic factors to which a species or a group of species is exposed.
All the interacting organisms in an area together with the non living constituents of the environment form an ecosystem. This unit is capable of independent existence.
e.g. Forest , Pond and Lake (Natural ecosystems), Garden and crop fields (artificial ecosystem)
Biotic Components of an Ecosystem can be grouped in three categories:
All green plants and some photosynthetic bacteria which can be produce food by photosynthesis are grouped in this category. All other organisms depend upon the producers either directly or indirectly.
Organisms which consume the food produced, either directly from producers or indirectly by feeding on other consumers. Consumers can be classifieds variously as herbivores (primary consumers), carnivores, omnivores and parasites.
The microorganisms, comprising bacteria, fungi and actinomycetes, break-down the dead remains and waste products of the organisms are called decomposers. They provide simple inorganic substances to soil by their activities. This inorganic substances are available to plants for absorption.
Food Chains and Webs
A series of organisms taking part in feeding at various biotic levels forms a food chain. Each such level/step is called as trophic level (T).
Given flow chat can simply represent a food chain, where sun or detritus may function as sources of energy.
Here represents the energy.
In this way the energy trapped by producers flow as food energy from T1 to higher trophic levels. An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers. This is sometimes called as law of ecological tenth.
The loss of energy at each step is so great (about 90%) that very little usable energy remains available after four trophic levels. So food chains generally consists of only three or four steps.
The length and complexity of food chains vary greatly. Each organism is eaten by two or more other kinds of organisms which in turn are eaten by several other organisms. So instead of a straight line food chain, the relationship can be shown as a series of branching lines, called a food web. This provide more than one organisms at the same trophic level, hence help to maintain homeostasis in the ecosystem.
Some harmful chemicals which are non-biodegradable can also enter in bodies through food chain. e.g., DDT, BHC, Hg etc. This phenomenon is called as biomagnification. When they accumulate progressively at each trophic level, i.e. with the growing food chain. Major harm can be observed at top consumer level.
Ozone Layer and Its Depletion
Ozone gas is a deadly poison. This form at higher levels of atmosphere as a result of UV radiations acting on O2 molecule.
O2O + O
O + O2O3 (ozone)
In shields the surface of the earth against UV radiations from the sun, that otherwise is highly damaging to organisms, like it is known to cause skin cancer in humans. The amount of O3 in the atmosphere began to drop sharply in the 1980s. this decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
Biodiversity and Need of Conservation
Range of different species, genes and ecosystems in a given specific area is called Biodiversity. Its loss may lead to a loss of ecological stability, because all components of an ecosystem are interdependent.
To protect the wild life, the resources provided by nature need to be used in a sustainable manner. We can reduce pressure on the environment by sincerely applying the maxim of 'Reduce, Reuse and Recycle' in our lives. There have been many international initiatives to conserve the biodiversity, other hand local people are also participating.
There have been enough instances of traditional works for conservation, of forest biodiversity by local people. For example the case of Bishnoi community in Rajasthan, and of 'Chipko Movement' in Garhwal Himalayas.