NCERT Solutions Class 12 Biology Chapter 14

NCERT Solutions for Class 12 Biology Chapter 14

Biology is a vast science that studies life in various sizes, from single molecules to complexed species to the entire ecosystems. Biologists can work in all these domains of study and applied sectors such as health and medicine, environmental protection, education, and various other fields. Furthermore,  Ecology is the study of how organisms interact with their surroundings..

The Chapter 14 of Class 12 is ‘’Biology is Ecosystem’’. Ecosystem Structure and Function, Productivity, Decomposition, Energy Flow, Ecological Pyramids, Ecological Succession, Nutrient Cycling, and Ecosystem Services are all discussed in this chapter. 

Some students find Biology to be a complex and lengthy subject. A topic such as an Ecosystem can be  a bit vast. For this reason, Extramarks has come up with Class 12 Biology Chapter 14 NCERT Solutions; these solutions comprehensively include  precise & important information of the chapter . After significant research, the subject matter experts of Extramarks have prepared  Chapter 14 Biology Class 12 NCERT Solutions. 

Apart from this , Extramarks is a powerhouse of quality study material. Material such as NCERT books, CBSE revision notes, CBSE sample papers, CBSE previous year question papers, and more can be easily found on the Extramarks’ website for all classes.

Key Topics Covered in NCERT  Solutions for  Class 12  Biology Chapter 14

Mentioning below all the key topics that are covered in NCERT Solutions for Class 12 Biology Chapter 14- Ecosystem: 

Ecosystem- Structure and Function
Energy Flow
Ecological Pyramids
Ecological Succession
Nutrient Cycling
Ecosystem Services

These topics help students comprehend the different shades and complexity of the Earth’s current Ecosystems. Also, this is one of the most critical and high-scoring topics in the Class 12 Biology syllabus. Let us look at Extramarks in-depth information on each subtopic in NCERT Solutions for Class 12 Biology Chapter 14- Ecosystem.

Ecosystem- Structure and Function

NCERT Solutions for Class 12 Biology Chapter 14 explain Ecosystem and biosphere concepts.

The Ecosystem is a natural functional unit in which living species interact with one another and their physical surroundings.

The interaction of biotic and abiotic components will result in a physical structure that is characteristic of each type of ecosystem. Identification and enumeration of different plant and animal species of an ecosystem give its species composition. The vertical distribution of different species occupying different levels is called stratification. For example, trees occupy the top vertical strata or top layer of a forest, shrubs are the second layer and herbs, grasses, etc., occupy the bottom layers. 

The different components of the ecosystem are seen to function as a unit when we consider the below aspects:

  1. Productivity; 2. Decomposition; 3. Energy flow; and 4. Nutrient cycling.

To better understand the ethos of an aquatic ecosystem, let us take a small pond as an example. This is fairly a self-sustainable unit and a rather simple example that explains even the complex ecosystem interactions that exist in an aquatic environment. A pond is a shallow water body in which all the above-mentioned four basic components of an ecosystem are well exhibited. The water with all the inorganic and organic substances and the rich soil deposit at the bottom form the abiotic component. The solar rays, the cycle of temperature, day and night length, and other climatic conditions will regulate the rate of function for the pond ecosystem. The autotrophic components consist of the phytoplankton, algae, and marginal plants found at the edges of the pond. Zooplankton, the free-swimming and bottom-dwelling forms, can be considered as the consumers. Bacteria, fungi and flagellates, which are abundant in the bottom of the pond, will be the decomposers.

This pond ecosystem performs all the functions of any ecosystem and of the biosphere as a whole.


A steady supply of solar energy is a necessity for any ecosystem.

Plants create biomass per unit area in each period during photosynthesis, which is referred to as primary production. It is measured in grammes (gm-2) or calories per metre squared (kcal m-2).

Productivity: The rate at which the biomass is produced is defined as Productivity. It is written as gm-2 yr-1 or (kcal m-2) yr-1.

Gross Primary Productivity (GPP): GPP (gross primary Productivity) is the rate at which organic matter is produced during photosynthesis in an ecosystem.

Net Primary Productivity: The net primary productivity (NPP) is defined as gross direct output fewer respiration losses (R) (NPP). 

The net primary productivity is the amount of biomass available for heterotrophs, herbivores, and decomposers to consume.

Secondary Productivity refers to the rate at which consumers create new organic matter.

Plant species and numerous environmental conditions determine the primary Productivity of an ecosystem and hence vary by location.

The yearly net primary production of the biosphere is around 170 billion tonnes (dry weight) of organic matter. Despite covering approximately 70% of the planet’s surface, the production by sea is just about 55 billion tonnes.

In the above section, NCERT Solutions for Class 12 Biology Chapter 14 discusses different topics under Productivity, such as primary Productivity, secondary Productivity and more. Refer to Extramarks to know more about these.


NCERT Solutions for Class 12 Biology Chapter 14 defines Decomposition as the activity of decomposers on complex organic matter to break it down into simpler inorganic components like carbon dioxide, water, and nutrients.

Steps in Decomposition:

Dead plant remains such as leaves, bark, flowers and dead remains of animals, including faecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation

  • Fragmentation: Detritivores break down the trash into smaller particles, known as fragmentation.
  • Leaching: Water-soluble nutrients sink to the soil horizon and precipitate as salts that aren’t accessible, known as leaching.
  • Catabolism: Catabolism is the degradation of detritus by bacterial and fungal enzymes into simpler inorganic nutrients.
  • Humification: Humification is the process of forming and depositing a dark-coloured organic amorphous material known as humus. Humus is extremely resistant to microbial activity and decomposes at a glacial pace. In addition, it works as a nutrition reservoir because of its colloidal nature.
  • Mineralisation: Mineralisation is when some bacteria break down humus further to produce simple inorganic nutrients.

Energy Flow

NCERT Solutions for Class 12 Biology Chapter 14 explains that for all ecosystems on Earth, the Sun is the ultimate source of energy (except for the deep-sea hydrothermal Ecosystem).

PAR (Photosynthetically Active Radiation): Solar radiation plants may be used for photosynthesis. Only half of all incidents of solar energy are PAR. Plants can only catch 2-10 per cent of the PAR, yet this energy keeps entire life on Earth alive.

The energy from the Sun goes unidirectionally from the Sun to the producers and then to the consumers. As a result, all species rely on the Sun directly or indirectly. Therefore, the First and Second Laws of Thermodynamics apply to all ecosystems.

  • The first law of Thermodynamics: States that energy may be changed from one form to another in the presence of work, heat, and internal energy but that it cannot be generated or destroyed under any conditions.
  • The second law of Thermodynamics: The Second Law of Thermodynamics says that the entropy of the entire universe, seen as an isolated system, will constantly rise with time. The second law states that changes in the entropy of the cosmos can never be negative.

Ecosystems require a steady energy source to create the chemicals they need to combat the general trend toward greater disorderliness.

The food chain serves as a conduit for energy transfer in the environment.

All green plants in the environment use solar energy for photosynthesis. Therefore, they are usually obligate autotrophs.

Producers: All green plants which synthesise their own food through photosynthesis using  solar energy are called producers . They are autotrophs.

Consumers: All heterotrophs that rely on plants for nutrition, whether directly or indirectly, are referred to as consumers. Organisms are classified as primary, secondary, tertiary, or quaternary based on their position in the food chain.

The Grazing Food Chain (GFC) is the primary energy channel in an aquatic environment. However, a substantially more significant portion of energy passes through the detritus food chain (DFC) in a terrestrial environment than the GFC. Students can visit Extramarks website or app to get detailed information on DFC and other components.

Ecological Pyramids

NCERT Solutions for Class 12 Biology  Chapter 14 states that a graphical depiction of the interaction between different creatures in an environment is an ecological pyramid.

Each trophic level, as well as its order, is represented by a bar on the pyramid. The sequence is determined by who is being eaten. This is a representation of energy flow.

The producers or first trophic level are represented at the base of each pyramid, while the tertiary or top-level consumers are shown at the apex of the pyramid. .

The following are the three most widely researched ecological pyramids:

  • Pyramid of energy
  • Pyramid of number
  • Pyramid of biomass

NCERT Solutions for Class 12 Biology Chapter 14 discuss that a single creature can be a component of many food chains and hence, belongs to multiple trophic levels. In most ecosystems, the biomass, energy, and number of pyramids are upright. The producers outnumber the herbivores, the herbivores outnumber the carnivores, and so on.

The number and biomass pyramids can be inverted in rare circumstances, but the energy pyramid is always upright. This is because some energy is wasted as heat when it moves from one level to another.

Ecological Succession

NCERT Solutions for Class 12 Biology Chapter 14 explains Ecological succession as the gradual change in the composition of an ecological community’s species through time. For example, after a significant extinction, the period might be decades or perhaps millions of years. This transformation happens logically and systematically, in tandem with changes in the physical world.

  • Pioneer Species: Pioneer species are species that conquer a barren region.
  • Pioneer Community: A pioneer community can infiltrate a barren area.
  • Climax Community: The climax community is a community that is almost in balance with its surroundings.
  • Sere: From the original pioneer community to the last climax community, a series of ecological communities emerge in a given region.

NCERT Solutions for Class 12 Biology Chapter 14 explains namely two types of Successions:

  • Primary succession: The biological and ecological succession of plant life is primary succession. It happens in a situation when a new substrate is being deposited. There are no plants or other creatures on this new substrate. It is also frequently devoid of soil and organic materials. It can be found on land following a lava flow or in the region left behind by a receded glacier where no organisms ever exited, like a bare rock
  • Secondary succession: Secondary succession is a natural and ecological plant succession that occurs in a previously occupied ecosystem that has been disrupted or degraded. Regions where vegetation has been eradicated, for example (due to tree-felling in a woodland or destructive events such as fires).

Nutrient Cycling

NCERT Solutions for Class 12 Biology Chapter 14 says that Nutrient cycling is the flow of nutrients through the many components that make up an ecosystem. It’s also called biogeochemical cycles (bio: living organism, geo: rocks, air, and water).

Types of the nutrient cycle:

  • Gaseous
  • Sedimentary

The reservoir for gaseous nutrient cycles  (carbon and nitrogen), lies in the atmosphere  Whereas for  the sedimentary nutrient cycle (sulphur, phosphorus, etc.) the reservoir is in  the Earth’s crust. Environmental variables control the rate at which nutrients are released into the atmosphere. The reservoir works to compensate for the shortfall caused by an imbalance in input and outflow.

Ecosystem Services

Ecological services are the effects or outcomes of ecosystem activities.

NCERT Solutions for Class 12 Biology Chapter 14 explains that the Healthy Forests Ecosystems provide the following services:

  • Air and water purification
  • Drought and flood mitigation.
  • Nutrient cycling is essential.
  • Fertile soils are created.
  • Providing wildlife with habitat.
  • Biodiversity preservation
  • Crop pollination is the process of transferring pollen from one plant to another.
  • To provide a carbon storage facility.
  • Aesthetic, cultural, and spiritual qualities are provided.
  • The cost of these ecosystem services is estimated to be US $ 33 trillion per year on average. This is about twice the size of the world’s gross domestic product (US$ 18 trillion).

NCERT Solutions for Class 12 Biology Chapter 14 Exercise and Solutions

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Students may access NCERT Solutions for Class 12 Biology Chapter 14 and other chapters by clicking here. In addition, students can also explore NCERT Solutions for other classes below.

Students can easily understand all the Ecosystem concepts by getting access to NCERT Solutions for Class 12 Biology Chapter 14.

Key Features of NCERT Solutions for Class 12 Biology Chapter 14

As discussed above, Extramarks is a one-stop solution for students of all classes. There are various platforms in the market, but Extramarks manages to stand out because of its high-quality educational content. Here are  some more reasons for choosing Extramarks:

  • Extramarks NCERT Solutions are exclusively and authentically produced for students by subject specialists.
  • These solutions have been prepared to keep in mind all the guidelines laid by CBSE .
  • These  solutions help students in revising their concepts through detailed answers of the chapter end questions. By this, they also get a fair idea of how to attempt questions in exams and how to manage time efficiently. .

Q.1 Fill in the blanks:
(a) Plants are called as because they fix carbon dioxide.
(b) In an ecosystem dominated by trees, the pyramid (of numbers) is type.
(c) In aquatic ecosystems, the limiting factor for the productivity is .
(d) Common detritivores in our ecosystem are .
(e) The major reservoir of carbon on earth is .


(a) producers

(b) upright

(c) light

(d) earthworm, bacteria and fungi

(e) oceans

Q.2 Which one of the following has the largest population in a food chain?
(a) Producers
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers


(d) Decomposers

Decomposers are heterotrophic organisms, which meet their energy and nutrient requirements by degrading dead organic matter. Thus, they can act on any level of the food chain.

Q.3 The second trophic level in a lake is
(a) Phytoplankton
(b) Zooplankton
(c) Benthos
(d) Fishes


(b) Zooplankton

The first level is always plants, as they are the producers.

Q.4 Secondary producers are
(a) Herbivores
(b) Producers
(c) Carnivores
(d) None of the above


(d) None of the above

There is no secondary producer. Plants are the only producers. They are autotrophs and synthesize food in the presence of sunlight by performing photosynthesis.

Q.5 What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?
(a) 100%
(b) 50%
(c) 1-5%
(d) 2-10%


(b) 50%

Sun is the main source of energy for all ecosystems on Earth. Plants along with photosynthetic and chemosynthetic bacteria (also called autotrophs) capture 2-10% of this photosynthetically active radiation and make food from simple inorganic material.

Q.6 Distinguish between
(a) Grazing food chain and detritus food chain
(b) Production and decomposition
(c) Upright and inverted pyramid
(d) Food chain and Food web
(e) Litter and detritus
(f) Primary and secondary productivity


(a) Grazing food chain and detritus food chain

Grazing food chain Detritus food chain
1. The grazing food chain begins with a plant (autotroph). The first trophic level of the chain is occupied by an autotroph such as a plant. All other animals (heterotrophs) depend on plants for their food needs. 1. Detritus food chain begins with a decomposer or detritivores e.g earthworms, bacteria and fungi.
2. In a simple grazing food chain, the producer is eaten up by primary consumer which in turn is consumed by the secondary consumer. Energy flow occurs at each level. 2. Decomposers secrete digestive enzymes that breakdown dead and waste material into simple, inorganic material which is finally absorbed by them.
3. Sun is the source of energy. 3. Decomposers derive energy from dead, decaying organic matter.
4. Grazing food chain forms the major energy flow channels on the land systems. 4. Detritus food chain forms the major energy flow channels in the aquatic systems.

(b) Production and decomposition

Production Decomposition
1. The process of preparing organic food by the producers of the ecosystem using the energy from the sun is called production. 1. The process of breaking down of complex organic biomass of dead plants and animals into simpler inorganic form is called decomposition.
2. Producers are responsible for production. 2. Decomposers are responsible for decomposition.
3. Sunlight is a must for production. 3. Sunlight is not necessary for decomposition.
4. Energy from the atmosphere is trapped in the living system during the process of production. 4. Energy from the living system is released back into the atmosphere during the process of decomposition.

(c) The upright and inverted pyramid

Upright pyramid Inverted pyramid
1. The food chain where the number or the biomass of the producers is more as compared to consumers of successively higher levels results in an upright pyramid. 1. The food chain where the number or the biomass of the producers is less as compared to consumers of successively higher levels results in an inverted pyramid.
2. Pyramid of energy is always upright pyramid. 2. Pyramid of biomass can be either upright or inverted.

(d) Food chain and Food web

Food Chain Food Web
1. A food chain is a linear sequence of species starting from a producer to consumer to decomposer depicting the nature of the dependence of each of these on the previous level. 1. Food web is an interlinked sequence of many separate food chains which are dependent on each other.
2. Food chains are straight and linear. 2. Food web is a complex network and is never linear.
3. Consumers in the food chain depend upon a single species for their food. 3. Consumers are dependent upon many species for their food.

(e) Litter and detritus

Litter Detritus
1. Litter is all kind of waste that is generated above the ground and has been disposed of inappropriately in a location without consent. 1. Detritus is remains of the dead plant such as leaves, bark, flowers and dead animals, including faecal material.
2. It is the result of human action and can be biodegradable or non-biodegradable. 3. It is the raw material for decomposition and is biodegradable.

(f) Primary and secondary productivity

Primary productivity Secondary productivity
1. Primary productivity is the rate at which solar energy is captured by producers for the synthesis of organic matter per unit area over a period of time. It is expressed in terms of (kcal m-2) yr-1 1. Secondary productivity is defined as the rate of formation of new organic matter by consumers over a period of time.
2. It results from the conversion of organic matter from inorganic matter during this process. 2. It results from the conversion of organic matter of one level into an organic matter of the next level of the food chain.


Q.7 Describe the components of an ecosystem.


An ecosystem consists of all the living populations in a given area, along with the physical environment. Thus, an ecosystem consists of both biotic or living and abiotic or nonliving components. There is a continuous interaction that happens between the two components of the ecosystem resulting in a physical structure that is unique for each type of ecosystem. The biotic and the abiotic components function as a unit with respect to the productivity, decomposition, energy flow and nutrient cycle. Let us describe the two components of the ecosystem little in detail:

  1. Biotic component: The living components of the ecosystem can be categorized as either producers or consumers. Producers are autotrophic organisms with the capability of carrying on photosynthesis and making food for themselves. They indirectly make food for other populations. In terrestrial ecosystems, the producers are mainly green plants, while in an aquatic ecosystem, the varied algal species are the major producers. Consumers are heterotrophic organisms that use preformed food. There are 4 types of consumers depending upon the kind of food they consume. Herbivores feed directly on green plants and thus are termed primary consumers e.g. caterpillar feeds on leaves. Carnivores feed only on other animals and thus are secondary consumers e.g. lion feeds on other animals. Omnivores feed on both plants and animals e.g. a human being. The fourth consumers are decomposers, which feed on the remains of plants and animals following their death (detritus) e.g bacteria, fungi, earthworms and convert them into simple inorganic matter. Decomposers form the largest group of the biotic component of the ecosystem.
  2. Abiotic component: The non-living parts of the ecosystem form the abiotic components. The non-living components include soil, water, light, inorganic nutrients, and weather variables. They play a major role in deciding the structure and function of the entire ecosystem.

Q.8 Define ecological pyramids and describe with examples, pyramids of number and biomass.


Ecological pyramids are graphical representation or summarization of the trophic structure of an ecosystem. The base of the pyramid depicts the producer trophic level and is usually broad. The apex, which narrows down, is the tertiary or some higher-level consumer and the other consumer levels are depicted in between these two.

Ecological Pyramid

Q.9 What is primary productivity? Give brief description of factors that affect primary productivity.


Primary productivity is defined as the rate at which biomass or organic matter is produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (g-2 yr-1) or energy (kcal m-2) yr-1. Thus, primary productivity is the rate at which solar energy is stored in organic matter. This primary productivity can be divided into gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A good amount of GPP is used by plants by themselves during the process of respiration. Net primary productivity is GPP minus respiration losses.

Factors affecting primary productivity:

  1. Plant species inhabiting the area in question.
  2. Environmental factors like light, temperature, soil, water, precipitation, etc.
  3. Availability of nutrients and photosynthetic capacity of the plants.

Q.10 Different ecological parameters like number of organisms at each trophic level (pyramid of number), the biomass of living material (pyramid of biomass) or availability of energy (pyramid of energy) at each trophic level can be depicted by different kinds of ecological pyramids. Let us discuss pyramids of number and pyramids of biomass in detail.

Pyramid of number:

Pyramid of the number represents the number of organisms at each trophic level in a food chain. In most ecosystems, the pyramid of number is upright which means that the members at the successively higher levels are smaller in number with some exceptions where the pyramid of number is inverted. This means that producers are more in number than herbivores and herbivores are more in number than carnivores. A very simple example of a pyramid of number is a representation of the relationship between green grass/herbs/shrubs (producer) with deer (herbivore) and lion (carnivore) in a grassland ecosystem. Another example is of a pond where the lowest trophic level is represented by algae and diatoms, which are the largest in number. The second trophic level is represented by herbivorous zooplanktons which are less abundant in number. While the third and fourth trophic levels are occupied by smaller and larger fish, respectively. There is a considerable reduction in the number of individuals from the base to the top of the pyramid. Thus, as we go up the food chain, the number of organisms at each trophic level decreases in most of the ecosystem resulting in an upright pyramid of the number, if represented graphically. However, in a marine ecosystem, the number of fishes is much more than phytoplankton. Thus it is inverted. The same holds true for the parasitic food chain.

Pyramid of Biomass:

Biomass is the weight of living material at some particular time. To calculate biomass for each trophic level, first an average weight for the organisms at each level is determined, and then the number of organisms at each level is estimated. The average weight is then multiplied with the estimated number which gives the approximate biomass for each trophic level. This kind of pyramid is usually upright in most of the studied ecosystems. The pyramid of biomass in the sea is usually inverted because the biomass of fishes far exceeds that of phytoplankton.


Q.10 Define decomposition and describe the processes and products of decomposition.

Decomposition is defined as the process by which decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients. The raw material for decomposition is detritus which is nothing but the dead plant remains such as leaves, bark, flowers, dead remains of animals, faecal material, etc. This process requires oxygen and factors that affect the decomposition process are the chemical nature of detritus and climatic factors. Decomposition forms a very important step in the functioning of an ecosystem.

The various processes and products of decomposition are mentioned below:

  1. Fragmentation: The process by which detritus is broken down into smaller particles by the action of detritivores (e.g. earthworm) is called fragmentation. This makes the decomposition process easier and quicker.
  2. Leaching: The process by which water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts is called leaching.
  3. Catabolism: The process by which bacterial and fungal enzymes degrade detritus into simpler inorganic substances is called catabolism.
  4. Humification: The process by which dark coloured amorphous substance (humus) accumulates in the soil as a result of decomposition is called humification. This humus is highly resistant to the action of microbes and undergoes further decomposition at a very slow rate.
  5. Mineralisation: The slow process by which humus is further degraded by microbes releasing inorganic nutrients into the soil is called mineralisation.

Q.11 Give an account of energy flow in an ecosystem.

The flow of energy in an ecosystem follows the two laws of thermodynamics. The first law says that energy cannot be created or destroyed and the second law says that when energy is transformed from one form to another, there is always some loss of energy as heat. Ecosystems need a constant input of energy from an external source. Sun is the ultimate source of energy for our planet.

Energy Flow:

Energy flows through an ecosystem from producers to consumers constituting a food chain. Producers or autotrophs capture solar energy. Of the incident solar radiations, about 50% of them are photosynthetically active radiation (PAR). Out of this, only about 2-10% of PAR is captured by photosynthetic plants and microorganisms to produce food from simple inorganic material by the process of photosynthesis. They are called producers. These producers are consumed by consumers (animals that are dependent on others for energy source) thus, passing the captured energy to the next level. The consumers that feed on the herbivores or producers are called primary consumers. Those animals that depend on the primary consumers for food are called secondary consumers and so on. This constitutes the food chain with various trophic levels which clearly indicates who eats whom in the ecosystem and how energy flows. There are various food chains in the ecosystem and each of them do not work in isolation, but are interlinked, making a food web. This unidirectional flow of energy from the sun to producers and then to consumers is what makes the ecosystem function continuously. Energy trapped into an organism does not remain in it forever. It is continuously passed to the next level of the food chain.

The energy does not remain trapped in these levels alone. Once producers and consumers die, they are acted upon by the process of decomposition by decomposers like fungi and bacteria. They break down the complex organic matter of these organisms into the simple inorganic matter and release the trapped energy in the atmosphere.

Based on the feeding relationship with other organisms and the source of nutrition, each organism occupies a particular place in the community or food chain. This place in the food chain is known as a trophic level. Producers belong to the first trophic level, herbivores (primary consumers) to the second and carnivores (secondary consumers) to the third. The amount of energy decreases as one goes up these trophic levels in the food chain.

Q.12 Write important features of a sedimentary cycle in an ecosystem.

The sedimentary cycle is the cycling of nutrients, whose reservoir is located in Earth’s crust, through various components of an ecosystem. Sulphur and phosphorus cycles are examples of sedimentary cycles. They are found in the earth crust and their release in the ecosystem is a very slow process. It is when the rocks weather, minute amounts of these minerals are dissolved in soil solutions and are absorbed by the roots of plants. Herbivores and other consumers obtain these from plants and during the process of decomposition, they are released back in the soil. Some important features of such sedimentary cycles are as follows:

  • The slow movement of nutrients across various levels of the food chain.
  • Involvement of very minute amounts of nutrients.
  • No gaseous phase is involved in the sedimentary cycle.
  • The atmospheric contribution is minimal.

Q.13 Outline salient features of carbon cycling in an ecosystem.

Carbon Cycle

The reservoir of Carbon: 71% of the total quantity of global carbon is dissolved in oceans and it is this oceanic reservoir of carbon that controls the amount of carbon dioxide in the atmosphere. At any given time, the atmosphere contains only 1% of the total global carbon. Other reservoirs of carbon are fossil fuels.

Recycling: Carbon cycling occurs through atmosphere, ocean and through the living and dead organisms. According to an estimate, 4 X 103 kgs of carbon is fixed in the biosphere through photosynthesis annually. Carbon constitutes 49% dry weight of organisms. A good amount of carbon returns to the atmosphere as CO2 through respiratory activities of the producers and consumers of the ecosystem. Decomposers also play an important role in the recycling of carbon through the process of decomposition. Some amount of carbon is lost to sediments and removed from circulation. Burning of wood, forest fire and combustion of organic matter, fossil fuel, volcanic activity are some more ways by which CO2 is released in the atmosphere.

To put it more precisely, carbon recycles in the ecosystem in the following ways:

  1. Carbon moves from the atmosphere to plants by the process of photosynthesis.
  2. Carbon moves from plants to animals through the food chain.
  3. Carbon moves from plants and animals to the ground through the process of decomposition.
  4. Carbon moves back to the atmosphere from plant and animals by the process of respiration.
  5. Carbon moves from fossil fuels to the atmosphere each time these fuels are burnt.
  6. Carbon moves to and from water bodies.

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FAQs (Frequently Asked Questions)

1. For board examinations, how crucial is Chapter 14 of Class 12 Biology?

The Ecosystem is an essential topic that has an immense  weightage in board exams. Though the chapter is simple to comprehend, students may find the NCERT questions difficult to answer. To make this process smooth, students can  refer to Extramarks NCERT Solutions for Class 12 Biology Chapter 14 to get detailed answers  of the chapter.

2. What is the focus of Class 12 Biology Chapter 14?

Chapter 12 of Biology  Class 12 is about the structure and functions of an ecosystem. This chapter takes students on a journey across terrestrial and marine environments. Energy Flow, Ecosystems, and the Ecological Pyramid will also be covered. Ecological Successions, the Nitrogen Cycle, and the Phosphorus Cycle are examples of environmental cycles. Students should use NCERT Solutions to gain in-depth information. Refer to Extramarks’ website for further details.