Ecosystem - Nutrients and Energy Flow - TopperLearning

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Ecosystem - Nutrients and Energy Flow

Ecosystem

An ecosystem is a self-contained area composed of different kinds of organisms which interact with

each other as well as with the physical conditions such as sunlight, air, water, soil and climatic factors

prevailing in the area.

Components of an Ecosystem

An ecosystem consists of two main components:

o Biotic components

o Abiotic components

Types of ecosystems

Natural ecosystem

Aquatic ecosystem

Freshwater ecosystem

Lentic ecosystem

Lotic ecosystem

Marine ecosystem

Pond ecosystem

Terrestrial ecosystem

Forest ecosystem

Desert ecosystem

Grassland ecosystem

Tundra ecosystem

Artificial ecosystem



Biotic Components of an Ecosystem

The biotic components are the living components of an ecosystem. These include animals, plants

and microorganisms. They constitute the food-obtaining steps or trophic levels of the ecosystem.

TROPHIC LEVELS DESCRIPTION

Trophic level I (Green plants)

They are the starting point of the nourishment chain

for all life forms in the ecosystem.

They produce food through the process of

photosynthesis.

They are regarded as self-food producers or

autotrophs.

These include trees, bushes and grasses.

Trophic level II (Plant-eating

animals/herbivores)

They directly eat plants or their products such as

leaves, grains, fruits, grasses, seeds and flowers as

their food or suck plant sap from their leaves or

stems.

They are also known as primary consumers.

These include animals such as deer, rabbits, rats,

pigeons, parrots, grasshoppers, bees etc.

Biotic components

Producers

Herbivores

Carnivores

Large carnivores

Parasites

Decomposers



Trophic level III (Flesh-eating

animals/carnivores)

They capture their prey and eat it.

They are also known as secondary consumers.

These include tigers, wolves, snakes, lizards,

certain birds etc.

Trophic level IV (High Order Flesh-

eating animals/large carnivores)

They capture smaller carnivores and eat them.

They are also known as tertiary consumers.

These include peacock, eagle etc.

Parasites

These organisms cannot live independently.

They live inside or on the body surface of another

organism, called the host, and obtain their food or

nourishment from the host.

Worms which live in the guts of animals and fleas

which live on the skin of animals such as dogs are

examples of parasites.

Decomposers

They live on dead and decaying plant and animal

bodies.

They breakdown the complex organic compounds

present in these dead organisms into simpler

substances.

They are also known as microconsumers or

detritivores.

These include certain bacteria and fungi, vultures,

kites, crows, some insects etc.



Abiotic Components of an Ecosystem

The abiotic components are non-living components of an ecosystem. These include sunlight, air,

water and soil, and climatic factors such as wind, temperature, rainfall and light.

Abiotic components

Sunlight

Air

WaterTemperature

Soil



Sunlight

The energy obtained from sunlight is essential for the production of food by photosynthesis.

Air

Oxygen from the air is essential to animals for respiration.

Carbon dioxide is useful to plants for photosynthesis.

Air serves as a medium for the flight of birds, insects etc.

Air is an agent for the dispersal of seeds, fruits, flowers, pollen etc.

Water

Water is used by plants and animals for drinking and various other purposes.

Water is the chief constituent of protoplasm in cells.

It is required for various biochemical reactions which occur in organisms.

It helps to transport nutrients and excretory products in organisms.

Temperature

Temperature affects the distribution of living organisms in the environment.

It affects the enzymatic activities in organisms.

Hot, mild or cold temperature influences the kind of body functions of plants and animals

living in such areas.

Most plants and animals survive between 10°C and 40°C.

Soil

Soil provides the substratum for the growth of plants.

It contains water and mineral nutrients such as sodium and potassium required by plants.

Soil also provides a dwelling place for burrowing animals such as rats, snakes and

earthworms which even swallow the mud containing dead organic matter.

In deserts, soil provides support to plants such as prickly pear and date palms.

Even water bodies have some soil at the bottom which is required by organisms living there.

Food Chain

The sequential process of eating and being eaten is called a food chain.

All food chains begin with green plants or the producers. So, the plants or the producers constitute the

first trophic level. Example: Grass

The herbivores or primary consumers which feed on plants constitute the second trophic level.

Example: Grasshopper

The herbivores are next fed upon by the carnivores or secondary consumers. They constitute the third

trophic level. Example: Snake

Finally, the large carnivores, also called the top carnivores or tertiary consumers form the fourth

trophic level. Example: Hawk

The large carnivores die and form the feed of the decomposers. The decomposers feed on these dead

animals and plants. Example: Fungi

There is transfer of food from one organism to the other forming a chain.

A food chain represents unidirectional transfer of energy.



Examples of Short Food Chains

Rice → Man (Two steps)

Grass → Rabbit → Fox (Three steps)

Maize → Goat → Man (Three steps)

Examples of Long Food Chains

Grass → Grasshopper → Lizard → Crow (Four steps)

Algae → Protozoa → Small fish → Large fish (Four steps)

Green plant → Grasshopper → Frog → Snake → Eagle (Five steps)

Top carnivores (Fourth trophic

level)

Carnivores

(Third trophic level)

Herbivores

(Second trophic level)

Producers

(First trophic level)



Energy Flow in a Food Chain

In a food chain, along with food, transfer of energy also occurs from one trophic level to the other. The

flow of energy which occurs along a food chain is called energy flow.

All living organisms in an ecosystem require energy for carrying out various life processes such as

breathing, growth and movement. This energy supports various activities of the living world.

All the energy used by living organisms is obtained from the Sun. Solar energy enters the living

components through the autotrophs or green plants, where it gets converted into chemical energy.

However, only 1% of the total energy is actually captured by green plants.

The food energy produced by plants is partially used by them for their growth and development. A

major part of it is lost as heat energy.

The plants are then eaten by primary consumers, the herbivores, and the energy stored in plants is

transferred to these organisms. A part of the energy is used by herbivores for activities such as

digestion, growth and reproduction. Again, most of the energy is lost to the environment in the form of

heat.

When herbivores are consumed by carnivores, a part of the energy is used by the carnivores for their

metabolic activities and growth, while most of it is released as heat energy.

The amount of energy gradually declines as one moves up to each higher trophic level, because at

each level, energy is lost in the form of heat.

Due to the loss of energy at each step, food chains consist of only three to four trophic levels. If there

are many levels, then animals at the end of the food chain will not have enough food and energy to

survive. The solar energy converted by the autotrophs into food energy cannot be reconverted into

solar energy, and the energy which passes from the herbivores to the carnivores can never go back to

the herbivores. The energy lost as heat cannot be returned to the plants and reused during

photosynthesis. Therefore, the flow of energy through a food chain is always unidirectional.

Significance of Food Chain

In all types of food chains, one organism becomes the food of the other organism. As a result, a

situation of eating and being eaten exists. This maintains a check on the population and a balance in

the ecosystem.

Energy in the form of food is continuously transferred between different food chains. This helps to

maintain the equilibrium in an ecosystem.

Food chains help us to understand the interaction and the interdependence of different organisms in

an area.

The loss of energy in food chains and the transfer of energy from one trophic level

to the other can be explained by the Ten Percent Law which states that:

Only 10% of the energy entering a particular trophic level of organisms is available

for transfer to the next higher trophic level.



Food Web

Similar kinds of organisms may occur in more than one food chain. They eat more than one type of

food to satisfy their requirements. A plant of a particular species can serve as food for a variety of

herbivores.

No food chain can operate in isolation. Individual food chains are interconnected in a complex way.

A network of interconnecting food chains in a natural community of different organisms is called a

food web.

Example of Food Web

Consider six food chains which are interconnected to form a food web. The food web begins with

plants and ends with the top carnivore, the vulture.

In the first food chain, the plants are eaten by the grasshopper, and the grasshopper, in turn, is eaten

by the vulture.

Plants → Grasshopper → Vulture

In the second food chain, the plants are eaten by the rabbit. The rabbit is then consumed by the

vulture.

Plants → Rabbit → Vulture

In the third food chain, the plants are eaten by the rat. The rat is then eaten by the vulture.

Plants → Rat → Vulture

In the fourth food chain, the plants are eaten by the rat, the rat is eaten by the snake, and the snake, in

turn, is eaten by the vulture.

Plants → Rat → Snake → Vulture

In the fifth food chain, the plants are eaten by the grasshopper, and the grasshopper, in turn, is eaten

by the frog. The frog is eaten by the snake, and the snake is consumed by the vulture.

Plants → Grasshopper → Frog → Snake → Vulture

Finally, in the sixth food chain, the plants are eaten by small birds which in turn are eaten by the

vulture.

Plants → Small birds → Vulture



Significance of Food Web

Food webs permit alternative foods.

They ensure a better chance of survival of an organism if any of its food sources is scarce.

Food Pyramid

A graphical representation of various trophic levels of a food chain in an ecosystem is called an

ecological pyramid or a food pyramid.

Ecological pyramids are of three types:

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

•Pyramid of numbers

•A pyramid of numbers is constructed on the basis of thenumber of individuals which occupy a particular trophic level ina given area at a given time.

•A large number of shrubs and grasses provide food and energyto the deer in grasslands. They are the producers and form thebase of the pyramid.

•As we move higher, there are deer and few lions. However,their number is less as compared to that of grasses andshrubs.

•The lions or the top carnivores are at the top of the pyramidand are found in fewer numbers.

•Pyramid of biomass

•A pyramid of biomass is a graphical representation of biomassor organic matter present per unit area in different trophiclevels.

• In the example of the grassland ecosystem, the biomass ofproducers is the highest of all trophic levels of the ecosystem.The biomass keeps on decreasing as one proceeds from onetrophic level to the next, forming an upright pyramid.

•Pyramid of energy

•A pyramid of energy is a graphical representation of energyflow within an ecosystem.

•The solar energy trapped by producers is converted into foodenergy. This trapped energy flows through the food chain, fromthe producers to the top carnivores. As energy flows, itdecreases with each trophic level, forming an upright pyramid.



Significance of Food Pyramid

The trophic levels in a food chain can be explained by a food pyramid.

The ecological pyramids help us to understand the structure, functional diversity and energy

conversion efficiency of ecosystems.

The flow of materials in an ecosystem is cyclic, but the flow of energy is unidirectional as the

energy lost as heat cannot be reused by plants during photosynthesis.

Ecosystem - Nutrients and Energy Flow - TopperLearning

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