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NCERT Exemplar Solutions Class 12 Biology Chapter 14, Ecosystem: Ecosystem introduces the basic concept that all living things have interactions with their environment, creating a dynamic system of biotic and abiotic elements. The chapter first discusses the ecosystem, describing its structure, function, and energy transfer. It presents various types of ecosystems, such as terrestrial and aquatic, noting their specific features and importance. This NCERT Exemplar Solutions chapter categorizes ecosystems according to components and structure, describing how energy is transferred through food chains and food webs. It also highlights ecological pyramids, depicting the trophic levels and the distribution of energy among producers, consumers, and decomposers. The chapter describes nutrient cycles, such as the carbon cycle and the nitrogen cycle, and their roles in ecological balance.
The chapter also discusses ecosystem productivity, decomposition, energy flow models, and ecological succession, which explains the manner in which ecosystems evolve. The effects of human activities on ecosystems, including deforestation and pollution, are also covered. The chapter is vital in understanding ecological relationships, environmental sustainability, and life interlinkages on Earth. Also, visit NCERT Solutions for Class 12 Science for other chapters.
Question:1
Decomposers like fungi and bacteria are:
i. autotrophs
ii. heterotrophs
iii. saprotrophs
iv. chemo-autotrophs.
Choose the correct answer:
(a) i and iii, (b) i and iv (c) ii and iii, (d) i and ii
Answer:
The answer is the option (c) (ii) and (iii)Question:2
The process of mineralization by microorganisms helps in the release of:
a. inorganic nutrients from humus
b. both organic and inorganic nutrients from detritus
c. organic nutrients from humus
d. inorganic nutrients from detritus and formation of humus.
Answer:
The answer is the option (a) inorganic nutrients from humusQuestion:
Productivity is the rate of production of biomass expressed in terms of:
i. (kcal m–3) yr–1
ii. g–2 yr–1
iii. g–1 yr–1
iv. (kcal m–2) yr–1
(a) ii, (b) iii, (c) ii and iv, (d) i and iii
Answer:
The answer is the option (c) (ii) and (iv)Question:4
An inverted pyramid of biomass can be found in which the ecosystem?
a. Forest
b. Marine
c. Grassland
d. Tundra
Answer:
The answer is the option (b) MarineQuestion:5
Which of the following is not a producer?
a. Spirogyra
b. Agaricus
c. Volvox
d. Nostoc
Answer:
The answer is the option (b) AgaricusQuestion:6
Which of the following ecosystems is most productive in terms of net primary production?
a. Deserts
b. Tropical rain forests
c. Oceans
d. Estuaries
Answer:
The answer is the option (b) Tropical rainforestsQuestion:7
Pyramid of numbers is:
a. Always upright
b. Always inverted
c. Ether upright or inverted
d. Neither upright nor inverted.
Answer:
The answer is the option (c) Ether upright or invertedQuestion:8
Approximately how much of the solar energy that falls on the leaves of a plant is converted to chemical energy by photosynthesis?
a. Less than 1%
b. 2-10%
c. 30%
d. 50%
Answer:
The answer is the option (b) 2-10%Question:9
Among the following, where do you think the process of decomposition would be the fastest?
a. Tropical rain forest
b. Antarctic
c. Dry arid region
d. Alpine region
Answer:
The answer is the option (a) Tropical rain forestQuestion:10
How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?
a. 1%
b. 10%
c. 40%
d. 90%
Answer:
The answer is the option (b) 10%Question:1
Name an organism found as a secondary carnivore in an aquatic ecosystem.
Answer:
SharkQuestion:3
Answer:
Under natural or human-induced disturbances, a particular stage in the process of succession would revert to an earlier stage.Question:4
Answer:
Teak → Amaranths → Shrubby plants →GrassQuestion:6
Justify the pitcher plant as a producer.
Answer:
Pitcher plant contains chlorophyll and carries out photosynthesis. It feeds on insects only to obtain nitrogen from them. Hence, a pitcher plant is a producer.Question:7
Name any two organisms which can occupy more than one trophic level in an ecosystem.
Answer:
Sparrow: It is a primary consumer when it feeds on grains but becomes a secondary consumer when it feeds on worms and insects.Question:8
Answer:
In this case, regrowth of forests is an example of ecological succession. After clearing of forests, the conditions become xerarch which proceeds to mesarch condition after the growth of forests.Question:9
Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?
Answer:
Soil becomes available after primary succession. It provides an ideal condition for the growth of bigger plants. Secondary succession can be obtained quickly as compared to primaryQuestion:10
Among bryophytes, lichens and fern which one is a pioneer species in a xeric succession?
Answer:
Lichens are considered as a pioneer species in a xeric succession.Question:11
What is the ultimate source of energy for the ecosystems?
Answer:
The sun is the ultimate source of energy for the ecosystems.Question:12
Is the common edible mushroom an autotroph or a heterotroph?
Answer:
The common edible mushroom is a Heterotroph.Question:13
Why are oceans least productive?
Answer:
Availability of solar radiation is least in oceans, especially in deep oceans. Due to this, oceans are the least productive.Question:14
Why is the rate of assimilation of energy at the herbivore level called secondary productivity?
Answer:
Secondary productivity is the rate of formation of new organic matter by consumers. The consumers get raw materials for this purpose from producers, which is made possible through assimilation. Due to this, the rate of assimilation of energy at the herbivore level is called secondary productivity.Question:15
Why are nutrient cycles in nature called biogeochemical cycles?
Answer:
Nutrients are cycled through biotic components as well as through abiotic components. The term 'bio' shows biotic components, while 'geo' shows abiotic components. Hence, the nutrient cycles in nature are called biogeochemical cycles.Question:16
Give any two examples of xerarch succession.
Answer:
Lichen → Bryophytes → Pteridophytes → Gymnosperms and AngiospermsQuestion:17
Answer:
A sustainable system without relying on any external input is called a self-sustainable system. This ability of the system is referred to as self-sustainability. Natural ecosystems are self-sustainable.Question:18
Given below is a figure of an ecosystem. Answer the following questions.
i. What type of ecosystem is shown in the figure?
ii. Name any plant that is characteristic of such an ecosystem.
Answer:
(a) Desert ecosystemQuestion:19
What is common to the earthworm, mushroom, soil mites and dung beetle in an ecosystem?
Answer:
All of them are part of the detritus food chain.Question:1
Organisms at a higher trophic level have less energy available. Comment.
Answer:
As per the law of 10%, just 10% of the total energy consumed by an organism at a particular trophic level is available for the organism at next trophic level. Therefore, a producer converts whatever energy into biomass; just 10% of it is available for the primary consumer. Similarly, just 10% of the energy consumed by the primary consumer is available for the secondary consumer. Due to this, organisms at a higher trophic level have less energy available.Question:2
The number of trophic levels in an ecosystem is limited Comment
Answer:
In any ecosystem, the number of trophic levels can go up to a maximum of five, and in that case, the food chain will look like the following:Question:3
Is an aquarium a complete ecosystem?
Answer:
The aquarium is a man-made ecosystem, and it has its own limitations. The confined space of an aquarium cannot have an endless supply of inorganic materials for producers. For supporting even a small number of consumers, there is a need for a large number of producers, which is not possible in a small space provided in an aquarium.Question:4
What could be the reason for the faster rate of decomposition in the tropics?
Answer:
Decomposition is largely an oxygen-requiring process. Moreover, ambient temperature and moisture are also required for this. If detritus is rich in nitrogen and water-soluble substances, then decomposition is faster. All these conditions are available in the tropical climate. Hence, there is a faster rate of decomposition in the tropics.Question:5
Human activities interfere with the carbon cycle. List any two such activities.
Answer:
Following are the two activities, which interfere with the carbon cycle:Question:6
Answer:
About 90% of the energy consumed by an organism at a particular trophic level is dissipated in the form of heat energy. This leaves just 10% for the organism at the next trophic level. By the time, it reaches the topmost trophic level; the available energy is an extremely small portion of the energy, which was originally converted by the producer. Due to this, energy flow is unidirectional through various trophic levels and is non-cyclic.Question:7
Answer:
Productivity, decomposition, energy flow and nutrient cycling are integral features of any ecosystem. Plants and animals play important roles in productivity. Some microbes play a role in productivity as some of the microbes are autotrophs, e.g. some algae and some chemosynthetic bacteria. Most of the microbes are heterotrophs. Parasitic microbes get nutrition from the host on which they depend. Many microbes are saprotrophs. They get nutrition from detritus, i.e. they are an important part of the detritus food chain.Question:8
Answer:
Tigers are at the top of the food pyramid in the forest ecosystem and are tertiary consumers. A tertiary consumer helps in checking the uncontrolled population growth of secondary and primary consumers. If all tigers are killed, then no animal will be left to control the population of herbivores. This will result in quick exhaustion of producers. Finally, in the absence of producers, the herbivores will die because of starvation. This will destroy the whole ecosystem.Question:9
Answer:
We know that just 10% of the energy consumed at a trophic level is available for the next trophic level. Here 10 kg of deer's meat means 10kg of biomass at the level of primary consumer. Out of this, the deer for its own needs utilizes 90%. Rest 10%, i.e. just 1 kg, is available for the lion. Hence, it is correct to say that 10 kg of deer's meat is equivalent to 1 kg of lion's flesh.Question:10
Primary productivity varies from ecosystem to ecosystem. Explain?
Answer:
Primary productivity is the biomass produced per unit area over some time by photosynthesis. In simple terms, we can say that it is the amount of biomass produced by green plants in a particular ecosystem. Plant population varies from one ecosystem to another. The number of plants is higher in tropical rainforests compared to deserts. Therefore, primary productivity would be much higher in tropical rainforests than in deserts. This shows that primary productivity varies from one ecosystem to another ecosystem.Question:11
Answer:
This entire sequence of communities that successively change in a given area is called sere (s). All the biotic and abiotic factors play a crucial role in this transition process and thus enable a community to reach the climax. If biotic and abiotic factors are not supportive enough for the climax, then the community may remain in a particular seral stage without reaching the climax. The presence of sparse vegetation at Tabletop Mountain can be one example of a community in the seral stage. The community at the tabletop mountain may be in a stage in which only ferns and mosses may be present. In due course of time, it would pave the way for higher plants.Question:12
What is an incomplete ecosystem? Explain with the help of a suitable example.
Answer:
An ecosystem, which is devoid of certain biotic or abiotic factors, is called an incomplete ecosystem. An incomplete ecosystem cannot be a self-sustaining ecosystem. The aquarium is a good example of an incomplete ecosystem. The aquarium may be having producers and consumers, but it does not have decomposers. Lack of decomposers necessitates frequent cleaning of the aquarium.Question:13
What are the shortcomings of ecological pyramids in the study of the ecosystem?
Answer:
The following are the shortcomings of ecological pyramids:Question:14
How do you distinguish between humification and mineralization?
Answer:
Both humification and mineralization are important aspects of the detritus food chain. Humification leads to the formation of a dark-coloured amorphous substance called humus, while decomposition leads to the formation of inorganic compounds from organic matter.Question:15
Fill in the trophic levels (1, 2, 3 and 4) in the boxes provided in the figure.
Answer:
1: Producer, 2: Primary Consumer, 3: Secondary Consumer, 4: Tertiary Consumer.Question:1
A farmer harvests his crop and expresses his harvest in three different ways.
a. I have harvested 10 quintals of wheat.
b. I have harvested 10 quintals of wheat today in one acre of land.
c. I have harvested 10 quintals of wheat in one acre of land, 6 months after sowing.
Do the above statements mean the same thing? If your answer is yes, give reasons. And if your answer is no, explain the meaning of each expression.
Answer:
No, they do not mean the same thing.As per latest 2024 syllabus. Maths formulas, equations, & theorems of class 11 & 12th chapters
Question:2
Answer:
Gross Primary Productivity (GPP) is the rate of production of organic matter in an ecosystem. We get Net Primary Productivity (NPP) on removing respiratory losses (R) from GPP. Nature contributes various factors (biotic and abiotic) to improve the GPP. In other terms, nature tends to increase GPP.Question:3
Answer:
A young forest will have a lower tree density and thus, lower primary productivity. Shallow polluted lake may also have a lower density of flora due to toxicity from pollution. An Alpine meadow is full of grass and thus, a lower tree density.Question:4
Answer:
Following are the three types of ecological pyramids: -Question:5
Write a short note on the pyramid of numbers and a pyramid of biomass.
Answer:
Pyramid of Numbers: It is arranged from the lower trophic levels at the bottom to higher trophic levels above and shows the number of individuals at each level. Mostly, these pyramids have a wider base (higher producer population)Question:6
Given below is a list of autotrophs and heterotrophs. With your knowledge about the food chain, establish various linkages between the organisms on the principle of 'eating and being eaten'. What is this inter-linkage established known as?
Algae, hydrilla, grasshopper, rat, squirrel, crow, maize plant, deer, rabbit, lizard, wolf, snake, peacock, phytoplankton, crustaceans, whale, tiger, lion, sparrow, duck, crane, cockroach, spider, toad, fish, leopard, elephant, goat, Nymphaea, Spirogyra
Answer:
This linkage that has been established herewith is known as a food web. It pertains to the interlocking between two or more types of the food chain at several tropic levels.Question:7
"The energy flow in the ecosystem follows the second law of thermodynamics." Explain.
Answer:
The entropy of an isolated system never decreases, and such a system will proceed towards thermodynamic equilibrium. A system in thermodynamic equilibrium will have maximum entropy. An ecosystem requires a constant supply of energy for the synthesis of molecules. Energy always flows unidirectionally in an ecosystem. This is because a reverse flow of energy will make the system unstable (non-equilibrium state). Producers get energy from the sun and become the supplier of energy to the higher trophic levels. Energy always flows from a lower trophic level to a higher one.Question:8
What will happen to an ecosystem if:
a. All producers are removed.
b. All organisms of herbivore level are eliminated; and
c. All top carnivore population is removed
Answer:
(a) If all producers are removed from the ecosystem, primary consumers will die due to lack of food. In turn, the secondary and tertiary consumers will also become extinct as they will also lose their source of nutrients. Essentially, the ecosystem will end.Question:9
Answer:
Natural EcosystemQuestion:10
Answer:
A rich diversity of flora which can support a larger and diverse consumer set will lead to greater biodiversity of a community.Question:11
Answer:
P/R ratio of a community is the ratio of gross production and community respiration. This can be one, less than one or more than one.NCERT Exemplar Class 12 Solutions Subject Wise:
Chapter 14 of Biology deals with the functional unit of nature, called the ecosystem where different organisms interact with the outside environment as well as among themselves. Ecosystems can vary from a small pond to a whole forest. There are several different ecosystems existing at a time but they are all connected and linked to one another through direct or indirect relations. The NCERT exemplar Class 12 Biology chapter 14 solutions cover all the important methods, structures and functions happening around us in ecosystems that are linked to one another.
The ecosystem, its input, transfer of energy and output in brief to different terms and concepts introduced in this chapter. The chapter also focuses much on different relationships, cycles, and webs of energy flow existent in the ecosystem simultaneously, and how they all help each other directly or indirectly.
Also, Check NCERT Books and NCERT Syllabus here
Also, Read NCERT Solution subject-wise
Class 12 Biology NCERT exemplar solutions chapter 14 will help students to learn about different methods and processes happening around them in the ecosystem and how are all these connected and linked to one another. The chapter also teaches how the biotic and abiotic components of ecosystem regulate and balance the ecological process through maintenance of nutrient cycle and energy flow among different components of nature.
The explanations are very accurate and are created under expert guidance and review that will help you to prepare for your exams perfectly. They have been thoroughly checked and reviewed by professionals in biology over the years providing a simplified approach to different concepts for better understanding and learning.
NCERT Exemplar Class 12 Biology Chapter Wise Links
Below are the NCERT Exemplar Class 12 Biology:
All of the important topics of Chapter 14, ecosystem have been thoroughly explained and elaborated for simplified learning. Some of the important topics to learn from NCERT exemplar Class 12 Biology solutions are ecosystem, their structure, their functions, and cycles and terms of productivity, decomposition, energy flow, and nutrient cycling. NCERT Exemplar Class 12 Biology solutions chapter 14 also covers the concept of ecological succession that occurs among different communities of ecosystems and how such succession helps or affects different cycles of ecosystems.
The chapter also covers diagrammatic representation of different concepts happening around in the ecosystem and working of cycles, and webs in the ecosystem that will give students an upper hand at scoring and presentation in exams.
Must Read NCERT Notes subject-wise
Ecosystem gives a deep insight into the ecosystems and their operation. It brings out the complex interactions of biotic and abiotic elements, the exchange of energy, and the process of nutrient cycling that support life on our planet. The chapter also stresses maintaining ecological balance and the effects of human actions on the environment. Through the study of ecosystems, students learn about the intricate nature of nature, which is essential for encouraging environmental conservation and sustainability.
Some of the most basic and important topics to study from chapter 14, ecosystem are structures and function of ecosystem, the concept of productivity, decomposition, energy flow, relationship between different organisms at varied tropical levels of the food chain, system of ecological succession and different services provided by the ecosystem.
Yes, the chapter is important from the view of Board exams and helps students to learn better with the help of proper guidance and solutions provided.
The ecosystem has been defined as the functional unit of nature that is an organization of biotic and abiotic components interacting with one another.
Yes, the solutions have been prepared by experts of biology in simple language to aid students, and are accessible offline in the form of pdf download through NCERT exemplar Class 12 Biology solutions chapter 14 pdf download.
The 10% law of energy transfer in an ecosystem explains that only roughly 10% of the energy at one trophic level is transferred to the next, and the rest of the 90% is lost as heat, utilized in metabolic processes, or not consumed. This indicates that energy is reduced at each subsequent trophic level. Consequently, fewer organisms are able to be sustained at higher trophic levels. The law exemplifies the inefficiency in energy transfer via food chains.
According to the NCERT Exemplar, decomposers are responsible for recycling nutrients in an ecosystem. Decomposers decompose dead and decaying organic matter, including plant and animal tissues, into simpler compounds like nitrogen and carbon. This process makes necessary nutrients available for producers by returning them to the soil. Decomposers ensure ecosystem balance through continuous energy and nutrient flow.
Human activities affect ecosystems by deforestation, pollution, climate change, and habitat destruction. Deforestation diminishes biodiversity and interferes with carbon cycling, while pollution contaminates the environment by polluting air, water, and land. Climate change, caused by human emissions, changes temperature and weather, influencing species distribution. These activities upset the equilibrium of ecosystems and compromise their sustainability.
In Chapter 14, three types of ecological pyramids are explained:
Pyramid of Numbers – Represents the number of organisms at each trophic level, showing the population size.
Pyramid of Biomass – Illustrates the total biomass (organic matter) present at each trophic level.
Pyramid of Energy – Depicts the flow of energy through each trophic level, always showing a decrease in energy as it moves upward.
Biotic factors, such as plants, animals, and microorganisms, interact with abiotic factors like sunlight, temperature, water, and soil to form a functional ecosystem. For example, plants rely on sunlight and water for growth, while animals depend on plants for food. In turn, the presence of organisms can influence abiotic factors, such as nutrient levels in the soil. This continuous interaction maintains ecological balance and supports life processes.
Primary productivity is the rate of conversion of solar energy to chemical energy by producers (such as plants and algae) using photosynthesis. Secondary productivity is the rate of conversion of chemical energy contained in food to new biomass by consumers (herbivores and carnivores). Primary productivity is the basis for an energy flow in an ecosystem, whereas secondary productivity relies on the presence of primary producers.
Trophic levels are the position of organisms in a food chain according to their feeding relationships. The producers (plants) form the first trophic level and convert solar energy into chemical energy. Primary consumers (herbivores) form the second level, then secondary consumers (carnivores) at the third level, and so on. Each level is dependent on the lower level for energy, and energy is lost as it proceeds up the food chain.
Natural ecosystems are self-sustaining, while artificial ecosystems often require human intervention for maintenance. Natural ecosystems have a balanced flow of energy and nutrients, while artificial ecosystems may need external inputs like fertilizers or artificial light.
Natural Ecosystems – These occur naturally without human intervention, such as forests, lakes, and deserts, where species interact naturally within their environment.
Artificial Ecosystems – These are man-made, created for specific purposes, like crop fields, aquariums, and gardens, where human management influences the ecosystem's structure and function.
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