Important Questions Class 12 Biology Chapter 14

Important Questions Class 12 Biology Chapter 14

Important Questions for CBSE Class 12 Biology Chapter 14 – Ecosystem

Class 12 Biology Chapter 14 Important Questions show that an ecosystem is a working unit of nature, where living things constantly interact with one another and with their surrounding physical environment.

With these Class 12 Biology Chapter 14 Important Questions, students will come to know that an ecosystem can range widely in size from a small lake to a big forest or an ocean, among other characteristics. It is readily separated into two main categories, such as aquatic (pond, lakes, sea, and ocean), and terrestrial, due to its enormous variety, complexity, and size (grassland, forest, desert). Some ecosystems are artificial ecosystems because they were created by humans.

Moreover, with these Class 12 Biology Chapter 14 Important Questions, Extramarks will provide students with detailed and authentic solutions to important questions according to CBSE past years’ question papers so that students can prepare for their examination according to the CBSE syllabus. The engaging format of important questions in Class 12 Biology Chapter 14 will make it easier for students to understand and retain the concepts.

CBSE Class 12 Biology Chapter 14 Important Questions

Study Important Questions for Class 12 Biology Chapter 14 – Ecosystem

1.What is the difference between Hydrarch and Xerarch Succession? 


Hydrarch Succession Xerarch Succession 
In moist environments, this succession takes place. In arid environments, this succession takes place.
From hydric (aquatic) to mesic (neither dry nor wet) environments, this sequence occurs. From xeric (bare rocks) to mesic (neither dry nor wet) conditions, there is a succession in this environment.
The stage of phytoplankton is the first in this sequence. In the beginning, there are only bare rocks.

2. What are some of the limitations of ecological pyramids? 

Ans. The following are some of the limitations of ecological pyramids:

    • They do not take into consideration species that are comparable across two or more trophic levels.
    • It assumes a straightforward food chain and ignores a food web.
    • Ecological pyramids have been designed to not include saprophytes.

3. State why secondary succession is faster than primary succession.

Ans. The formation of a community in a location that was previously inhabited by highly developed communities in which the environment is both organic and inorganic is known as secondary succession. Considering that these barren areas contain sufficient soil for healthy development, secondary succession occurs more quickly than primary succession.

4. What is the difference between upright and inverted pyramids?


Upright pyramid  Inverted pyramids
With each trophic level in a food chain, the quantity and biomass of species in an ecosystem decline from their highest point at the producer level. When compared to other trophic levels in a food chain, the producer level has the lowest quantity and biomass of species in an ecosystem.
Greater energy is found in the lower trophic level than in the higher trophic level. Less energy is present in the lower trophic level than in the higher trophic level.

5. Why is the scale of the food chain in an ecosystem typically restricted to three to four trophic levels? Give an example.

Ans. Because the energy transferred for the first three to four trophic levels is enough to conduct labour, and only 10% of that energy is passed to the next level, the length of a food chain in an ecosystem is often restricted to trophic levels. This is due to the 10% law of energy transfer, which states that in a food chain, 10% of energy is passed to the next trophic level and 90% of energy is converted to heat at each trophic level.

6. What does ecological succession mean? How would you describe the various stages of succession?

Ans. Ecological succession is a phenomenon that is regulated by the community and involves a systematic and orderly change in the community’s structure and composition that finally results in the emergence of a climax community.


  • Invasion: An invasion is the appearance of propagating organs on a bare area of primary or secondary succession, such as seeds, spores, bulbils, etc. When conditions are favourable, those seeds germinate in a new location, and some of them mature into plants. Pioneers are these recent outside immigrants.
  • Establishment is the process by which immigrants settle into new environments after moving there. Germination, growth, and reproduction are the three key processes that make it up.
  • Aggregation is the term for the gathering of individuals from different species in one location.
  • Competition: Species with similar nutritional needs are referred to as competing species, whilst those with distinct needs are complementary species.
  • Reaction: It is the modifications made to the habitat by colonisers. Until a permanent community emerges there, the influence of vegetation on the site is referred to as a response.

7. “Energy flow is always unidirectional in an ecosystem”. Justify this assertion. 

Ans. An ecosystem’s energy flow is always unidirectional, which means it never reverses and is always transported from one trophic level to the next. As an illustration, consider how the energy of the sun is captured by producers, used by the primary consumer, and then transported to the next trophic level.

8. Higher trophic level creatures have a lower energy availability. Why?

Ans. In the ecosystem, the 10% energy flow law proposed by Lidman is applied. According to this law, only 10% of the available energy at each trophic level gets transferred to the subsequent trophic level. Heat is lost as a result of the remaining (during respiration). The energy that is available to entities keeps dwindling as we get closer to the upper levels. As a result, the top carnivore in a food chain obtains the least quantity of calories.

9. Why are the trophic levels in the ecosystem limited? 

Ans. There are only about 4-5 levels since only 10% of energy is transferred from one advancing trophic level to the next, and this decreases as we reach higher levels. Respiration and other vital processes for the maintenance of life consume the leftover energy. If there are more levels, the available energy will be depleted to the point that it cannot support any trophic level through energy flow. Levels are thus restricted.

10. How can the problem of “tiger poaching” impact the ecosystem’s ability to function?

Ans. Tigers play a significant role in the food web and assist in preserving ecological balance. In order to symbolise the health of the forest, it controls the widespread growth of herbivores and aids in removing ill and elderly animals from the group. Since tigers cannot exist where they hunt (herbivores or trees), protecting tigers also means saving forests, and ensuring that everyone has access to food and water.

11. Why do abiotic elements like temperature, oxygen availability, and soil pH affect the rate of decomposition?

Ans. The structure of basophilic and acidophilic bacteria is influenced by the pH of the soil. Anaerobic processes take place in the absence of oxygen and only partially degrade a substance, whereas aerobic processes take place in the presence of oxygen and completely degrade a substance. At greater temperatures, microorganisms are unable to develop to their full potential; nevertheless, at low or high temperatures, stress-tolerant microbes thrive.

12. Describe the importance of the ecosystem.

Ecosystems keep the environment in balance. It gives us access to clean air to breathe while also storing carbon to control the climate. In order to provide us with access to clean drinking water without the use of expensive procedures, it cycles the nutrients via numerous biogeochemical cycles. Many living things can find food and refuge in it. Additionally, it offers raw materials for various home and commercial uses.

13. When compared to how man tends to increase net primary productivity, how does nature favour increasing gross primary productivity?

Ans. An ecosystem’s energy moves unidirectionally from one trophic level to the next. Nature works in a way that is advantageous to entities engaged in a certain activity. Photosynthesis is carried out by plants. It is both the plant’s main endeavour and it is the main source of gross primary productivity. This plant activity is reliant on the inputs and increases in inputs cause it to produce at its highest level. Humans, on the other side, rely on vegetation. They don’t care whether a particular plant has a high or poor gross primary productivity because it is a component of their net primary productivity.

14. Describe how the law of thermodynamics is supported by energy flows in an ecosystem.

Ans. According to the second rule of thermodynamics, all transformation-related activities, with the exception of deep hydrothermal ecosystems, resulting in energy loss in the form of heat and an increase in disorder. Only 2-10% of the total PAR (Photosynthetically Active Radiation) is absorbed by organisms engaged in photosynthesis, which results in the production of organic matter. Additionally, the energy is used for metabolic processes, food production, and biomass storage (very less). According to Lindeman’s law, biomass or the trapped energy is transferred to the following trophic level. 10% of the energy reserves are transferred from one trophic level to the next.

15. What do you mean by an ecosystem’s productivity? What forms of productivity also discuss the variables that affect an ecosystem’s production? 

Ans. The rate at which solar radiation energy is fixed by an ecosystem’s vegetation per unit area and per unit time is known as the ecosystem’s productivity. Typically, it is stated as a unit of energy (cal) produced in a unit area (m) per unit of time (year).

There are two forms of productivity:

  • Primary productivity is the quantity of biomass or organic matter created by plants during photosynthesis over a specific time period per unit area. The two categories of primary productivity are as follows:

Gross primary productivity (GPP) is a term used to explain how much food is produced overall by producers during photosynthesis.

Net primary productivity (NPP) is the difference between respiration loss (R) and gross primary productivity.


  • Secondary productivity: The rate of storage at the consumer level is known as secondary productivity. It is described as the pace at which consumers synthesise organic materials over a specific time frame.

Indicators of primary productivity includes:

  1. A variety of environmental conditions
  2. Nutritional availability
  3. Plants’ ability to photosynthesize

16. Define decomposition. Describe the many steps involved in decomposition.

Ans. Decomposing organisms (bacteria, fungus) aids in the conversion of complicated organic matter into straightforward inorganic elements like CO2, H O2, and minerals. Decomposition is the term for this action. Detritus is made of the remains of dead plants, such as leaves, bark, and flowers, as well as the remains of dead animals and faeces. The following are crucial breakdown processes.

  • Fragmentation: Organisms called detritivores fragment debris into smaller pieces.
  • Leaching: Water-soluble inorganic nutrients enter the soil horizon through leaching and then precipitate as salts that are inaccessible to plants.
  • Catabolism: Enzymes from bacteria and fungi break down waste into basic inorganic compounds.
  • Humification is the process by which humus, an amorphous substance with a dark colour, accumulates. This decomposes at an incredibly slow rate and is very resistant to microbial action.
  • Mineralization: Some microorganisms further decompose the humus, which causes the mineralization process to release inorganic nutrients.

17. Explain the biogeochemical cycle. What role does the reservoir play in this cycle? Give an illustration of a sedimentary cycle using a reservoir found in the earth’s crust.

Ans. A biogeochemical cycle is the flow of nutrient molecules via various ecosystem components. Sedimentary and gaseous nutrient cycles are the two different types. The reservoir for the gaseous type of cycle is the atmosphere (nitrogen cycle), while for the sedimentary cycle, the reservoir is the earth’s crust (phosphorus cycle). The reservoir’s purpose is to be able to make up for any deficit caused by an imbalance in the flow of outflow and influx. The rate at which nutrients are released into the atmosphere is governed by a number of environmental parameters, including temperature, soil moisture content, pH, and others.

The phosphorus cycle, whose natural reservoir is the earth’s crust, is an example of a sedimentary cycle since it originates on land, travels to the ocean below, and then returns to the land. Phosphates, which are phosphates, are found in rocks. They get into water bodies due to weathering and soil erosion. Phosphates are exposed on the land surfaces as a result of seafloor uplift caused by movements of the crustal plates. Phosphates are released through weathering over time, and they become softer in the soil, where they are then absorbed by plant roots. Producing organisms supply this element to herbivores and other creatures. Phosphorus is released during the decomposition of dead creatures and trash by phosphate-solubilizing bacteria.

FAQs (Frequently Asked Questions)

1. Explain the biotic components and abiotic components of an ecosystem with examples.

In an ecosystem, the biotic and abiotic components are interconnected.

  • In an ecosystem, biotic components comprise various life forms. Biological elements can be divided into autotrophs, heterotrophs, and saprotrophs according to their nutritional requirements (or decomposers).
  • The nonliving part of an ecosystem is included in the category of abiotic components. Abiotic components include things like air, water, soil, minerals, sunlight, temperature, nutrients, wind, height, and turbidity.

2. What is the pyramid of biomass?

The ecological pyramid comes in three varieties. The relationship between an energy community’s biomass and trophic level at a certain period is described by the pyramid of biomass.

3. What exactly are the terrestrial ecology and the aquatic environment? Give instances.

Aquatic ecosystem: An aquatic ecosystem is an ecosystem that exists in or around a body of water. Two different kinds of aquatic ecosystems exist.

  • Aquatic ecosystem
  • Ecosystem of freshwater

Terrestrial ecosystems: The term “terrestrial ecosystems” refers to ecosystems that are only found on land. Terrestrial ecosystems come in four main varieties and are found throughout diverse geological zones.

  • Ecosystems in deserts
  • Ecosystems in forests
  • Ecosystems of the tundra
  • Ecosystems of grasslands

4. What is an incomplete ecosystem? Describe with an example.

An ecosystem is lacking if its biotic and abiotic components are scarce or unavailable. An aquatic ecosystem’s benthic zone serves as an example.