for all defence aspirants what is ecosystem? Its constituents

for all defence aspirants what is ecosystem? Its constituents




An Ecosystem Can Be Visualised As A Functional Unit Of Nature, where living organism(producers, unit consumers and decomposers)interact among them-selves and also with the surroundings physical the ecosystem, biotic and abiotic components are linked together through nutrient cycles and energy flows.

An ecosystem can be any size but usually encompasses specific and limited species’e.g : aquatic ecosystem.

Everything that lives in an ecosystem is dependent on the other species and elements that are also part of that ecological community. If one part of an ecosystem is damaged or disappears it has an impact on everything else.

Environment- can be almost everything or a small region.

Habitat- area where an organism lives.

Biosphere-the region on earth that supports life

Ecosystem- producers, consumers, decomposers and their relationships (tiny environment) .it is the functional unit of the environment.



Physical factors-temperature ,humidity , light , atmospheric condition

Inorganic substances- water , oxygen , carbon dioxide , nitrogen

Organic substances- proteins , carbohydrates , lipids


Producers (green plants)

Consumers (animals)

Decomposers ( microorganism)

Effect of abiotic components on terrestrial primary producers-plants


extremely high intensity favors root growth which results in increased transpiration, short stem ,smaller thicker leaves.

On the other hand low intensity of light retards growth .flowering and fruiting.

When the intensity of light is less than the minimum the plants cease to grow due to accumulation of co2 and finally die.

Out of 7 colours in the visible part of spectrum, only red and blue are effective in photosynthesis.

Plant growth in blue light are small red-light results in elongation of cells resulting in etiolated plants.


Frost results in freezing the soil moisture. The plants growing in such soil, get exposed to direct sun light in the morning, they are killed due to increased transpiration when their roots are unable to supply moisture. This is the main reason for innumerable death of sal seedlings.

As a result of frost, water in the intercellular spaces of the plant gets frozen into ice which withdraws water from the interior of the cells. This results in increasing concentration of salts and dehydration of cells. Thus, coagulation and precipitation od the cell colloid results in death of plant. Also .frost leads to formation of canker (a destructive fungal disease.)


Snow acts as blanket prevents further drop in temperature and protects seedlings from excessive cold and frost.

Accumulation of snow on tree parts can break the branches or even uproot the tree.

Snow shortens the period of vegetative growth.


High temperature results in death of plant due to coagulation of protoplasmic proteins (some bacteria can survive high temperature because of their protoplasmic proteins that don’t coagulate at normally high temperature.

High temperature disturbs the balance between respiration and photosynthesis thereby causing depletion of food resulting in greater susceptibility to fungal and bacterial attacks.

It also results in desiccation (extreme drying) of plant tissues and depletion of moisture).


Structural adaptation

An organism’s environment shapes its appearance through structural adaptations.

Desert foxes evolved to have large ears for heat radiation while arctic foxes evolved to small ears for retaining body heat; similarly white polar bears evolved to blend into ice.

Physiological adaptation

They consist of things like more efficient kidneys for desert animals like kangaroo rats; compounds that prevent blood coagulation in mosquito saliva physiological adaptations usually don’t appear from the outside.

Behavioural adaptation

These affect how an organism acts or behaves. For example, bears hibernate to escape cold; certain snails (e.g otala lacteal) insects ( lady beetle),crustaceans (land crabs) ,amphibian’s (frogs) aestivate to avoid damage from high temperatures and the risk of desiccation.

Cultural adaptation

Human beings employ cultural adaptation as a subset of behavioural adaptations .e.g,people who live in any given environment learn ways of raising the food they need and also coping with nay particular given climate.

Types of adaptation


Variation are induced by changes in genetic makeup due to addition or deletion of certain genes.

Mutations change in climate, geographical barriers etc. Induce variations over a period of time.

Species are generally composed of a number of distinct population which freely interbreed even though they appears to be different in appearance(e.g American man and Chinese woman can interbreed. They are sub species under homo sapiens).

Adaptive radiation

In evolutionary biology, adaptive radiation is a process in which organism diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges ,or opens new environmental niches.


Speciation is the process by which new species are formed and evolution is the mechanism by which speciation is brought about.

The most common way a population undergoes speciation is by geographic isolation(allopatric speciation is brought about.

After a long period of time ,the sub populations become very different and get isolated, reproductively i.e they no longer interbreed.

Later even when the barrier is removed the sub-populations are unable to interbreed and thus subsequently the sub-populations become two different species.


Mutation (a change in genetic material that results from an error in replication of DNA ) causes new genes to arise in a population.

Further, in a sexually reproducing population ,meiosis and fertilization produce new combination of genes every generation ,which is termed recombination.

Thus, members of the same species show, variation and are not exactly identical. Variations are heritable.


Evolution is the change which gives rise to new happens in order to make the organism better suit to the present environment.

Climate change, competition adaptability ,need, changing environment etc. evolution leads to speciation or formation of new species.

A valid theory of evolution was propounded by Charles Darwin and Alfred Wallace in 1859.this theory has been extended in the light of progress in genetics and is known as neo- Darwinism.


The primary reason for these extinctions is environmental change or biological competition.

Extinction may take place due to catastrophic natural phenomena such as tsunami, volcanoes etc.

In recent time, human activities such as deportation ,over exploitation ,environmental pollution and environmental change are other factors responsible for extinction.




Er. HartaJ is one of the main Instructors and a part of the team At NCA. He himself has cleared the SSB process thrice, but as per his grandfather's Late Lt. Col H.S.Dhaliwal Wish he is continuing teaching and making officers. Been associated with New Careers Academy for the last 8 years, he also has been succefull in making Second and Third Generation Of officers. Once Taught by his Grandfather and Father Capt. Dhaliwal. He is know all across with students for the way he teaches and he is more of a role model for them .