Ecosystem: Class 12 Biology NCERT Chapter 14

Key Features of NCERT Material for Class 12 Biology Chapter 14 – Ecosystem                

In the previous chapter: Organisms and population, we will study population, it’s attributes, growth and other important terms related to it. In this chapter we will learn, Why is earth the main planet with life on it? We have oceanic living things, earthly living things, and aeronautical life frames as well. How is earth the main planet to have ‘An Ecosystem’ on it? Be that as it may, what is the environment and for what reason is it essential to find out about it? What might occur on the off chance that one of the biological systems vanishes? Let us concentrate more on it beneath. 

A mind-boggling connection between all the living and nonliving things (plants, creatures, life forms, sun, water, atmosphere etc)interact with one another is known as ‘An Ecosystem’. Biological systems are the establishment of ‘Biosphere’ and keep up the characteristic equalization of the earth.

For instance, how about we make the connection between sheep and lion in the biological system; for its endurance, the lion eats the sheep. What’s more, every relationship like this affects different animals and plants living in a similar area.

Subsequently, if the lion eats more sheep, it affects the plants as well; they start to prosper; since there aren’t numerous sheep to eat the plants.

Every life form in the biological system assumes a significant job, so whenever an ‘unfamiliar’ factor is placed in the environment, it represents a significant danger to the biological system. This happens in light of the fact that the unfamiliar factor can disfigure the characteristic parity of the biological system and mischief it conceivably.

This unfamiliar factor could be anything extending from rising temperature to the tidal wave. The unfamiliar factor as well as man-made can likewise demolish the biological system.

Quick revision notes

A biological system is the utilitarian unit of nature where living life forms communicate among themselves and furthermore with the environmental factors physical condition.

Environment Structure and Functions

Environment: There are two fundamental classes of a biological system, to be specific the earthly and the amphibian.

Earthly biological system – timberland, meadow, desert and so forth.

Amphibian biological system – lakes, lake, stream estuary and so on.

The biotic and abiotic variables of biological system work in an incorporated way for a stream of energy inside the parts of the environment. Communication of biotic and abiotic parts brings about a physical structure that is a trademark for each sort of environment. The vertical dissemination of various species possessing various levels is called stratification. For model, trees involve top vertical layers or layer of a woodland, bushes the second and spices and grasses possess the base layers.

The parts of the biological system that are viewed as a utilitarian unit are

(I) Productivity

(ii) Decomposition

(iii) Energy stream

(iv) Nutrient cycling.

  • Productivity-Primary creation is characterized as the measure of biomass or natural issue delivered per unit area over a timespan by plants during photosynthesis. It is communicated regarding weight (g – 2 ) or energy (kcal m–2 ). The pace of biomass creation is called efficiency. It is communicated as far as g – 2 yr – 1 or (kcal m–2 ) yr – 1. It very well may be separated into net essential efficiency (GPP) and net essential profitability (NPP). GPP of an environment is the pace of creation of natural issue during photosynthesis and NPP is the rest of the biomass after breath (R).



It is the accessible biomass for utilization to heterotrophs. Auxiliary profitability is characterized as the pace of arrangement of the new natural issue by shoppers.

Deterioration breakdown of the complex natural issue into inorganic substances like carbon dioxide, water and nutrients is called disintegration. Dead plants stay like leaves, bark, blossoms and dead survives from creatures establish debris. Disintegration includes following advances discontinuity, filtering, catabolism, humification and mineralization.

Discontinuity of Detritus:

Detritivores feed on waste — breakdown — builds the surface area of debris particles for microbial activity.


Soluble inorganic nutrients break up in the water – – permeate through the dirt — evacuated because of draining activity.


Decomposers (microorganisms, parasites) discharge chemicals — decay garbage — less difficult inorganic mixes.


Simplified garbage—changed over to humus

– Humus is a Dark, Amorphous substance.

– Highly impervious to Microbial Action

– Undergoes Decomposition Slowly.

– The reservoir of nutrients (because of colloidal nature)

  1. Mineralisation: Humus is corrupted – discharges inorganic substances

( CO2, H2O and so forth) and nutrients (Ca2+, Mg2+, K+ and so on)

Components influencing the pace of Decomposition:

  1. Compound structure – deterioration rate will be moderate when rubbish is wealthy in lignin and chitin and rate increments when the debris is wealthy in nitrogen and water solvent substances like sugars.
  2. Climatic conditions – warm and soggy condition favour disintegration and low temperature and anaerobiosis repress deterioration.

Energy Flow-

All living beings are needed for their food on makers, straightforwardly or in a roundabout way. There is a unidirectional progression of energy from the sun to makers and afterwards to buyers. Photosynthetically dynamic radiation (PAR) is answerable for amalgamation of food by plants. Creatures acquire their food from plants, so they are called purchasers. The way toward eating and being eaten is called a food chain in which energy stream from makers to buyers. In Grazing food chain (GFC)-

Energy flow

The waste food chain starts (DFC) starts with a dead natural issue. It is comprised of decomposers which are heterotrophic living beings (growths and microscopic organisms). These are otherwise called saprotrophs (appro: to break down). Decomposers emit stomach related catalysts that breakdown dead and waste materials into basic, inorganic materials, which are along these lines consumed by them. Natural interconnection of food chain shapes the food web. 

grazing and detritus food chain

In view of the wellspring of food, life form possesses a particular spot in the food chain that is known as a trophic level. 

Examples of producer and consumer

Every tropic level has a specific mass of living material at the specific time called a standing yield. It is estimated as the biomass of living being or number in a unit area.

The quantity of trophic levels in the brushing food chain is restricted as the exchange of energy adheres to 10 per cent law that is just 10 per cent of the energy is moved to each trophic level from the lower trophic level. In GFC, following trophic levels are conceivable maker, herbivore, essential flesh-eater, an optional meat eater. 

Natural Pyramids

consumer-producer pyramid

The natural pyramid is the graphical portrayal of a biological boundary (number, biomass, energy) arrangement savvy in different trophic degrees of a food chain with makers at the base and herbivores in the centre and carnivores at the top levels. It very well may be upstanding, modified, or shaft formed. 

Three basic biological pyramids are

a) Pyramids of number-utilizes the number of people per unit area at different trophic levels with the maker at the base and different buyers at progressively more significant levels. It is commonly upstanding.

A pyramid of the number if there should arise an occurrence of a major tree is commonly rearranged on the grounds that the number of creepy crawlies benefiting from that tree by and large surpasses in number.

b) Pyramids of biomass-speak to the biomass in different trophic levels. A pyramid of mass is upstanding aside from in amphibian food chain including fleeting tiny fish.

A pyramid of biomass in the ocean is commonly modified in light of the fact that biomass of fishes, for the most part, surpasses that of phytoplankton.

c) Pyramids of energy-that give a realistic portrayal of the measure of energy caught by various trophic levels per unit area. Pyramid of energy is consistently upstanding, can never be rearranged, in light of the fact that when energy streams from a specific trophic level to the following trophic level, some energy is constantly lost as warmth at each progression e.g in taking care of, processing, digestion and breath.

sunlight- consumer pyramid

Natural Succession

The progressive and genuinely unsurprising change in species organization of a given area is called natural succession. During succession, a few animal groups colonize an area and their populace turns out to be more various while the populace of different species decrease and even vanish.

  • Orderly and consecutive change that prompts a network that is close to balance is called the peak network.
  • The whole grouping of networks that progressively changes in a given area is called sere and individual momentary networks are named seral stage or seral networks.

Ecological Succession: Primary succession, Secondary Succession

  • Primary succession begins where no life form is there. For instance, uncovered rocks, cooled well of lava and so on. Auxiliary succession happens in the area where the living life forms have lost because of specific areas like woods fire. Seismic tremor and so forth.

Succession of Plants

Based on the nature of the environment, a succession of plants can be gathered as-

 Hydra succession happens in the wetter area and the successional arrangement progress from hydric to the mesic conditions.

differentiation between successions

 Xerarch succession happens in dry areas and arrangement progress from xeric to mesic conditions. 

  • The species that attack an uncovered area are called pioneer species. In essential succession on rocks lichens are pioneer species that emit acids to break up the stone for enduring to frame soil.
  • In essential succession in water, the pioneer species are the little phytoplanktons that are supplanted by free gliding angiosperms.
  • Primary succession is the moderate procedure as the soil isn’t accessible for pioneer species however auxiliary succession is relatively quicker because of the accessibility of soil or different nutrients. A peak network arrives at a lot quicker if there should arise an occurrence of optional succession.

primary and secondary succession

Supplement Cycling 

The development of nutrients components through the different parts of a biological system is called supplement cycling. It is additionally called as biogeochemical cycles. There are two kinds of supplement cycles-

  • Gaseous – exist in climate.
  • Sedimentary-exists in the earth outside.

Natural elements like soil, dampness, pH, temperature manage the pace of arrival of nutrients into the climate. The capacity of the repository is to meet with the shortage which happens because of lopsidedness in the rate fo deluge and efflux.

Carbon Cycle

Carbon burning happens through environment, sea and through the living and dead creatures. A large portion of the carbon is fixed by plants during the procedure of photosynthesis and comes back to the environment in the type of CO2 during the breath. Consuming of wood, timberland fire and ignition of natural issue, petroleum product, and volcanic action are different wellsprings of delivering CO2 in the climate.

Carbon cycle in environment

Phosphorus Cycle

The common supply of phosphorus is a rock which contains phosphorus as phosphates. On enduring, a minute measure of phosphates break down in soil arrangement and consumed by the underlying foundations of the plants. The waste results of dead life forms are decayed by microscopic organisms to deliver phosphorus. Vaporous trade among creature and condition is unimportant when contrasted with carbon. 

phosphorous cycle

Biological system Services

The results of biological system forms are called environment administrations. It incorporates

  • The solid woods biological system sanitize air and water
  • Mitigates floods and dry seasons
  • Cycle nutrients
  • Generate fruitful soil
  • Provide untamed life living space
  • Maintain biodiversity and so forth.

Specialists have put a normal sticker price of US $33 trillion per year on these essential biological systems administrations which are taken allowed on the grounds that they are free in spite of the fact that its worth is double the all-out worldwide gross national item (GNP).


  1. Which of the accompanying life forms eat natural issue and return the nutrients to the dirt?
  2. Maker
  3. Decomposer
  4. Scanvenger
  5. Nothing unless there are other options

Sol: b. Decomposer

A few creatures eat dead creatures. They are called scroungers. They help separate or decrease natural material into little pieces. Decomposers at that point eat these little pieces. Decomposers eat dead materials and separate them into concoction parts. Creatures and plants, at that point, use nitrogen, carbon and different nutrients. Decomposers help the world in tidying up the dead plants and creatures.

REEII ©  All rights reserved.