NCERT Solutions for Class 12 Biology Chapter 12 Ecosystem

NCERT Solutions for Class 12 Biology Chapter 12 Ecosystem Download PDF

The NCERT Solutions PDF of the Ecosystem chapter can be downloaded from the link below. Students can access the Ecosystem Class 12 Questions and Answers PDF offline to do quick and effective revision. These solutions include energy flow diagrams, food chains, ecological pyramids, and biogeochemical cycles, making them ideal for board exams and NEET preparation.

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Also Read:

• NCERT Exemplar for Class 12 Biology Ecosystem

Class 12 Biology Chapter 12 Ecosystem NCERT Exercise Question Answer

The answers to all the questions given in the textbook are given below. Doing regular practice of the Class 12 Biology Chapter 12 Ecosystem question answer, prepared according to the NCERT guidelines, makes students learn how living and non-living things interact in an ecosystem.

Q1. Fill in the blanks.

(a) Plants are called as_________because they fix carbon dioxide.

Answer:

Plants are called autotrophs because they fix carbon dioxide.

Q1. Fill in the blanks.

(b) In an ecosystem dominated by trees, the pyramid (of numbers) is_________type.

Answer:

In an ecosystem dominated by trees, the pyramid (of numbers) is inverted.

Q1. Fill in the blanks.

(c) In aquatic ecosystems, the limiting factor for productivity is_________.

Answer:

In aquatic ecosystems, the limiting factor for productivity is light.

Q1. Fill in the blanks.

(d) Common detritivores in our ecosystem are_________.

Answer:

Common detritivores in our ecosystem are earthworms

Q1. Fill in the blanks.

(e) The major reservoir of carbon on Earth is_________.

Answer:

The major reservoir of carbon on Earth is the lithosphere (rocks as carbonates and fossil fuels).

Q2 . Which one of the following has the largest population in a food chain?

(a) Producers

(b) Primary consumers

(c) Secondary consumers

(d) Decomposers

Answer:

(a) Producers

Producers, such as plants and phytoplankton, form the base of a food chain and are the most abundant in number because they convert solar energy into chemical energy through photosynthesis, supporting all higher trophic levels. Decomposers are abundant in biomass but not in population size compared to producers.

Q3. The second trophic level in a lake is

(a) Phytoplankton

(b) Zooplankton

(c) Benthos

(d) Fishes

Answer:

(b) Zooplankton

In a lake, the first trophic level is formed by phytoplankton, while the second trophic level is formed by zooplankton.

Q4. Secondary producers are:

(a) Herbivores

(b) Producers

(c) Carnivores

(d) None of the above

Answer:

(d) None of the above

In a food chain, plants are the only producers; there are no other producers. Herbivores and carnivores are primary and secondary consumers, respectively.

Q5. What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?

(a) 100%

(b) 50 %

(c) 1-5%

(d) 2-10%

Answer:

(b) 50%

About 50% of total incident solar radiation is PAR (400–700 nm), and only 2–10% of this PAR is converted to chemical energy by plants.

Q6. Distinguish between

(a) Grazing food chain and detritus food chain

Answer:

Q6. Distinguish between

(b) Production and decomposition

Answer:

Q6. Distinguish between

(c) Upright and inverted pyramid

Answer:

Q6. Distinguish between

(d) Food chain and Food web

Answer:

Q6. Distinguish between.

(e) Litter and detritus

Answer:

Q6. Distinguish between.

(f) Primary and secondary productivity

Answer:

Q7. Describe the components of an ecosystem.

Answer:

An ecosystem refers to the functional unit of nature in which living organisms interact among themselves and also with their surrounding physical environment to perform nutrient cycling, energy flow, decomposition, and productivity. There are many types of ecosystems, such as pond ecosystems, forest ecosystems, etc.

Components of the ecosystem

The components of the ecosystem can be divided into abiotic components and biotic components

1. Abiotic components- These include the non-living components of nature, such as light, temperature, water, soil, air, inorganic nutrients, etc.

2. Biotic components- The biotic components of an ecosystem refer to the living organisms present in that ecosystem. The biotic components are divided into producers, consumers, and decomposers. Producers are plants, consumers include animals, which can be herbivores or carnivores, and decomposers include microorganisms like fungi and bacteria.

Q8. Define ecological pyramids and describe with examples, the pyramids of number and biomass.

Answer:

Ecological pyramid- The graphical representation of an ecological parameter, such as number, biomass, or energy, sequence-wise in various trophic levels of a food chain, in which producers are at the base, herbivores in the middle, and carnivores at the top level. Ecological pyramids can be upright, inverted, or spindle-shaped. The three common types of ecological pyramids include the pyramid of numbers, the pyramid of biomass, and the pyramid of energy.

1. Pyramids of numbers- It is the number of individuals per unit area at various trophic levels. It is generally upright; however, the pyramid of numbers in the case of a big tree is generally inverted because several insects that feed on the tree generally outnumber.

2. Pyramids of biomass- These represent the biomass in various trophic levels. A pyramid of biomass is upright except in an aquatic food chain. A pyramid of biomass in the sea is generally inverted because the biomass of fish is generally greater than that of phytoplankton.

3. Pyramids of energy- It is the graphic representation of the amount of energy trapped at different trophic levels per unit area. The pyramid of energy is always upright.

Q9. What is primary productivity? Give a brief description of factors that affect primary productivity.

Answer:

Primary productivity refers to the amount of organic matter or biomass produced by producers per unit area over some time. The primary productivity of an ecosystem depends upon several factors such as light, temperature, water, precipitation, availability of nutrients, etc.

Q10. Define decomposition and describe the processes and products of decomposition.

Answer:

Decomposition is the process of breaking down complex organic matter of detritus into inorganic substances such as carbon dioxide, water, and nutrients. Dead remains of plants and animals constitute detritus. The process of decomposition involves steps like fragmentation, leaching, catabolism, humification, and mineralization.

1. Fragmentation of Detritus- In this step, the detritus is broken down into small fragments by earthworms

2. Leaching- In leaching, the water-soluble nutrients seep down into the soil and become unavailable salts.

3. Catabolism- The small fragments are decomposed by decomposers like fungi and bacteria with the help of the action of enzymes.

4. Humification- In this step, humus is formed. Humus is a dark-coloured, amorphous solid substance that acts as a nutrient reserve.

5. Mineralisation- In this step, by the action of microbes, the inorganic nutrients are released from the humus.

Q11. Give an account of energy flow in an ecosystem

Answer:

Energy Flow in an Ecosystem:

All living organisms are dependent on their food producers, directly or indirectly. There is a unidirectional flow of energy from the sun to producers and then to consumers. Photosynthetically active radiation (PAR) is responsible for the synthesis of food by plants. Animals obtain their food from plants, so they are called consumers. The process of eating and being eaten is called a food chain, in which energy flows from producers to consumers. For example, in the Grazing food chain, the grass is eaten by goats, which are further eaten by man. Similarly, in the detritus food chain, the sequence begins with dead organic matter. It is made up of decomposers, which are heterotrophic organisms (fungi and bacteria). These are also known as saprotrophs. Decomposers secrete digestive enzymes that break down dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them. The natural interconnection of the food chain forms the food web. Thus, in an ecosystem, energy flow occurs through food chains and food webs.

NCERT Solutions for Class 12- Subject-wise

• NCERT Solutions for Class 12 Maths

• NCERT Solutions for Class 12 Chemistry

• NCERT Solutions for Class 12 Physics

How to Solve the Ecosystem Class 12 Question Answer?

To solve questions from the Ecosystem, follow these steps:

1. Start by knowing the living and non-living components of an ecosystem given in the NCERT.
2. Learn how energy is transferred from plants to animals. To gain clarity, students can take help from the Class 12 Biology Chapter 12 Ecosystem question answer.
3. Observe how organisms depend on each other and interact with one another.
4. Learn the fundamental nutrient cycles, such as carbon and nitrogen. All the cycles are well explained in the Class 12 Biology Ecosystem question answer.
5. Practice different questions given in the NCERT Solutions for Class 12 for better understanding.

NCERT Exemplar Class 12 Solutions

• NCERT Exemplar Class 12 Chemistry Solutions

• NCERT Exemplar Class 12 Mathematics Solutions

• NCERT Exemplar Class 12 Biology Solutions

• NCERT Exemplar Class 12 Physics Solutions

Main Topics of Class 12 Biology Chapter 12 Ecosystem

Ecosystems explain the structure and functioning of natural systems, highlighting how energy flows and nutrients cycle through different components. This chapter is important for NEET as it includes both conceptual and analytical questions from the NCERT books.

• Ecosystem: Structure and Function

• Components of an Ecosystem (Producers, Consumers, Decomposers)

• Productivity in Ecosystem (Gross Primary Productivity and Net Primary Productivity)

• Energy Flow in an Ecosystem

• Ecological Pyramids (Number, Biomass, Energy)

• Food Chains and Food Webs

• Decomposition and Nutrient Cycling

• Biogeochemical Cycles (Carbon, Nitrogen, Phosphorus cycle)

NCERT Class 12 Chapter 12 Ecosystem Important Questions

Given below are some of the important questions from this chapter, along with the answer. Students, by referring to this, understand how questions appeared in the exam. For more such questions, students can refer to the NCERT Solutions for Class 12 Biology Chapter 12 Ecosystem.

Q1 - A lake near a village suffered heavy mortality of fish within a few days.

Consider the following reasons for this:

I. Lots of urea and phosphate fertiliser were used in the crops in the vicinity.

Il. The area was sprayed with DDT by an aircraft.

III. The lake water turned green and stinky.

IV. Phytoplankton populations in the lake declined initially, thereby greatly reducing photosynthesis.

Which two of the above were the main causes of fish mortality in the lake?

Options:

1. ll and II

2. Ill and IV

3. I and III

4. I and lI

Answer: The correct answer is option (4).

Solution: A lake near a village suffered heavy mortality of fish within a few days because lots of urea and phosphate fertiliser were used in the crops in the vicinity, and the area was sprayed with DDT by an aircraft.

Inorganic phosphorus and nitrogen are responsible for the growth of algae. In polluted water, these increase, which causes algae to increase greatly at the surface of the water, forming a water bloom. Due to the death of these algae, their organic matter decomposes, which affects oxygen and aquatic animals.

Q2 - Edaphic factor refers to:

1. Water

2. Soil

3. Relative humidity

4. Altitude

Answer: The correct answer is option (2).

Solution: Edaphic factors refer to the soil-related components that influence the living organisms within an ecosystem. These factors include soil texture, pH, nutrient content, moisture, temperature, and the presence of microorganisms. Edaphic factors play a significant role in determining plant growth, species distribution, and overall ecosystem productivity. They interact with other environmental factors like climate and can be altered by human activities such as agriculture or urbanisation.

Q3 - The zone at the edge of a lake or ocean, which is alternatively exposed to air and immersed in water, is called:

1. Pelagic zone

2. Benthic zone

3. Lentic one

4. Littoral zone

Answer: The correct answer is option (4).

Solution: The littoral zone is the shallow region near the shore of a lake or ocean that is exposed to air during low tide and submerged during high tide. It supports a variety of aquatic plants and animals adapted to fluctuating conditions.

Q4 - During the process of ecological succession, the changes that take place in communities are:

1. Orderly and sequential

2. Random

3. Very quick

4. Not influenced by the physical environment.

Answer: The correct answer is option (1).

Solution: During ecological succession, communities undergo a series of stages, starting with pioneer species that modify the environment to make it more hospitable for other species. These changes include alterations in soil composition, nutrient availability, and habitat structures. As succession progresses, the community becomes more complex, with species diversity increasing until a stable climax community is formed, which is in equilibrium with the environment.

Q5 - The sequence of communities of primary succession in water is:

1. Phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses, and trees.

2. Phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses, and trees.

3. Free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses, and trees.

4. Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow, and trees.

Answer: The correct answer is option (4).

Solution: In primary succession in water (hydrosere succession), the process starts with phytoplankton and gradually progresses to rooted submerged plants, floating plants, reed swamp, sedges, meadow, and finally trees. This shows the transition from an aquatic to a terrestrial ecosystem.

Q6 – The reservoir for the gaseous type of bio-geochemical cycle exists in

1. stratosphere
2. atmosphere
3. ionosphere
4. lithosphere

Answer: The correct answer is option (2).

Solution: The gaseous form of the biogeochemical cycle has a reservoir in the atmosphere. In the gaseous cycles, including the nitrogen and carbon cycles, the atmosphere provides the primary storage for vital gases. This is important for nutrients to be easily transferred and interchanged between the atmosphere and the living organisms involved in processes such as photosynthesis and respiration. It is therefore vital that the atmosphere contains these gases, as it holds the ecological balance and allows life on Earth to thrive.

Q7 – An inverted pyramid of biomass can be found in which ecosystem?

1. Forest
2. Marine
3. Grassland
4. Tundra

Answer: The correct answer is option (2).

Solution: In marine ecosystems, the biomass pyramid is inverted because phytoplankton, though small, have a high turnover rate and are consumed quickly by larger organisms. Fish, which are much larger, accumulate more biomass despite consuming a lot of phytoplankton. As a result, the total biomass of fish is greater than that of the phytoplankton, creating an inverted pyramid.

Also, check the NCERT Books and the NCERT Syllabus here:

• NCERT Books Class 12 Biology

• NCERT Syllabus Class 12 Biology

• NCERT Books Class 12

• NCERT Syllabus Class 12

What Students Learn from Ecosystem NCERT Solutions?

Students explore how living organisms interact with their surroundings and how ecosystems maintain balance.

1. Learners understand the roles of biotic and abiotic components in sustaining ecosystems.

2. Students explore energy transfer through trophic levels, food chains, and ecological pyramids, which are discussed in the Ecosystem Class 12 question answer.

3. They get to know about the ecosystem services, such as processes of nutrient cycling, including the carbon and phosphorus cycles.

4. Students also learn ecological succession through the Class 12 Biology Ecosystem question answer.

Why Class 12 Biology Chapter 12 Ecosystem NCERT Solutions important?

The Ecosystem chapter explains how living organisms interact with each other and with the abiotic factors present around them. Given below are a few points mentioning the importance of the solutions to understand the ecosystem chapter.

• Class 12 Biology Chapter 12 Ecosystem NCERT Solutions explain the components of an ecosystem, which are the producers, consumers, and decomposers, along with examples.
• The solutions also include the explanation of energy flow, food chains, and food webs, with the help of well-labeled diagrams.
• The biogeochemical cycles, like the carbon and nitrogen cycles, are covered in the solutions using the flow charts.
• Students will also learn about the ecological succession, productivity, and ecosystem, which are frequently asked in the NEET exams.

What Extra Should Students Study Beyond the Class 12 Biology Chapter 12 Ecosystem NCERT for NEET?

Along with NCERT, students can refer to a few extra topics and resources to prepare better for NEET. A table is provided below for some of the extra concepts. Along with these topics, students can practice the diagrams and flow charts that are given in the NCERT Solutions for Class 12 Biology Chapter 12 Ecosystem.

NCERT Chapter-Wise Solutions for Class 12 Biology

The chapter-wise solutions for all chapters are given below. Students can use these solutions to understand the concepts easily, which allows them to perform well in exams.