Class 12 Biology Chapter 14 Ecosystem

Class 12 Biology Chapter 14 Ecosystem The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 14 Ecosystem Question Answer.

Class 12 Biology Chapter 14 Ecosystem

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 14 Ecosystem Solutions for All Subjects, You can practice these here.


Chapter – 14


Very Short Answer Type Questions

Q.1. Many individuals of a species living together in a defined area form ___

Ans : Population. 

Q.2. Net primary productivity (NPP) ___ Respiration. 

Ans : Gross primary productivity (GPP). 

Q.3. Process of breakdown of detritus into smaller particles is called _____

Ans : Fragmentation. 

Q.4. _____ is the process by which bacterial and fungal enzymes degrade detritus into simple inorganic substances. 

Ans : Catabolism.

Q.5. The mass of living material at a particular time in a trophic level is called _____ 

Ans : Standing crop. 

Q.6. Pyramid of biomass in sea is generally _____

Ans : Inverted. 

Q.7. Out of the total cost of various ecosystem services, the soil formation accounts for about_____ per cent. 

Ans : 50. 

Q.8. Vertical distribution of different species occupying different levels is called _____

Ans : Strata.

Q.9. Of the incident solar radiation (on earth) less than 50% of it is ____

Ans : Utilised (absorbed). 

(B). True Or False (1 mark each) : 

Q.1. Horizontal distribution of different species’ occupying in different spatial position is called stratification. 

Ans : False.

Q.2. Marginal plants are autotrophic components of a pond ecosystem.  

Ans : True. 

Q.3. Fragmentation, leaching and catabolism during decomposition operate sequentially one after another. 

Ans : True. 

Q.4. Flow of energy in ecosystem is unidirectional. 

Ans : True. 

Q.5. Photosynthetic activation radiation constitutes less than 50% of the incident solar radiation. 

Ans : True.

Q.6. Grasses, are usually pioneer species in’ primary succession on rocks. 

Ans : False.

Q.7. Detritus food chain begins with dead organic matter. 

Ans : True. 

(C). Very Short Answer Questions: (1 Mark Each) 

Q.1. What is ecosystem? 

Ans : Ecosystem can be defined as the functional unit of nature where living organisms interact among themselves and also with the surrounding physical environment. 

Q.2. What are the two basic categories of ecosystem? 

Ans : The two basic categories of ecosystem are Terrestrial and Aquatic. 

Q.3. What are the autotrophic components of pond ecosystem? 

Ans : The autotrophic components of pond ecosystem are algae including all the green plants. 

Q.4. At which part of a pond ecosystem decomposers are abundant? 

Ans : Decomposers are abundant in the bottom of the pond.

Q.5. Define gross primary productivity. 

Ans : Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. 

Q.6. What is net primary productivity? 

Ans : The available biomass for the consumption to heterotrophs is known as net primary productivity. 

Q.7. Explain the process of leaching during decomposition. 

Ans : The process by which water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts is known as leaching.

Q.8. Define mineralization during decomposition. 

Ans : The human produced during decomposition is further degraded by some microbes and release of organic nutrients by a process known as mineralization. 

Q.9. Which type of food chain is dominant in sea? 

Ans : In sea the food chain starts from phytoplanktons to big fishes. So grazing type of food chain is dominant here. Here the pyramid is inverted. Phytoplankton – insects – small fishes – big fishes. 

Q.10. How much photosynthetically active radiation (in percentage) is captured by plants? 

Ans : 2-10 percent. 

Q.11. Except deep sea what is the only energy source for all ecosystems?  

Ans : Solar energy.

Q.12. Why measurement of biomass in terms of dry weight is more accurate? 

Ans : The biomass when measured in fresh condition it is not accurate because there may contain water and other liquid. substances which can evaporate. So, when the dry weight is taken it is more accurate because there is no chance of evaporation of water. 

Q.13. What are green plants known as? 

Ans : Green plants are known as producer. 

Q.14. What is the role of fungi in an ecosystem? 

Ans : Fungi acts as decomposer in an ecosystem. 

Q.15. What is trophic level? 

Ans : Based on the source of nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level. 

Q.16. What is ecological succession? 

Ans : The gradual and fairly predictable changes in the species composition of a given area is called ecological succession. It is of two types – Hydrarch and Xerarch. 

Q.17. What are the different types of succession? 

Ans : There are two main types of succession – Hydarch and Xerarch. 

Q.18. What is climax community? 

Ans : The climax community is a natural stable community unit which the process of succession goes on. On reaching climax community no further succession occurs in that area until they are destroyed. 

Q.19. Why rate of succession is much faster in secondary succession? 

Ans : Because, they have more nutrition, and climatic factors. 

(D). Short Answer Questions (2 Marks Each) : 

Q.1. Define vertical stratification with example. 

Ans : Vertical distribution of different species occupying different levels is called vertical stratification. For example – trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layers. 

Q.2. State the functional components of ecosystem. 

Ans : The functional component of an ecosystem can be divided into two types : 

(i) Biotic. And 

(ii) Abiotic. 

(i) Biotic component : includes air, water, soil.

(ii) Abiotic component : includes producer, consumer and decomposer. 

Q.3. What are the different types of primary productivity? State the relation between them. 

Ans : There are mainly two types of primary productivity- 

(i) Gross primary productivity. and 

(ii) Net primary productivity. 

Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. 

Net primary productivity is the available biomass for the consumption of heterotrophs. 

The relation between them is : GPP – R= NPP 

Q.4. Why earthworm is called as “Farmer’s Friend”? 

Ans : Earthworm is called formers friend because they help in the breakdown of complex organic matter as well as in loosening of the soil. 

Q.5. What is the raw material for decomposition called? What are its components? 

Ans : The raw material for decomposition is called detritus which constitute dead plant, animal remains such as leaves, bark, flowers and faecal matters etc. 

The components of detritus are lignin, chitin, nitrogen, sugars and many water soluble substances etc. 

Q.6. What is humus? State its importance. 

Ans : Humus is a dark coloured amorphous substance produced as a result of humification during decomposition in the soil and is colloidal in nature. 

Humus is very important because it is highly resistant to microbial action and undergoes decomposition at a very slow rate. Due to colloidal in nature it serves as the reservoir of nutrients.

Q.7. State the difference between grazing food chain and detritus food chain. 

Ans :       

Grazing food chainDetritus food chain
(i) It starts from the producers.(i) It starts from the dead organic matter.
(ii) These contain both auto- trophs and heterotrophs. Eg. Grass-Deer-Lion(ii) These contain only heterotroph Eg. Plant lent-Earthworm- Microbes.

Q.8. Why energy is less at secondary consumer level than the producer? 

Ans : The producers accumulate only 10 percent of total energy they receive from sun. In the next level the consumers of the first order utilize this c 8. but they can store only 10 percent of it. So the process continues energy and the energy gets depleted at every level. Hence, it can be said that energy is less at consumer level than the producers. 

Q.9. What is food web? How it differs from food chain?

Ans : The natural interconnection of food chains form a food web.  

Q.10. What is Standing crop? How it is measured? 

Ans : Each trophic level has a certain mass of living material at particular time called as the standing crop. It is measured as the number in a unit.

Q.11. Define 10% law of energy flow. Why the number of levels in a grazing food chain is restricted? 

Ans : When we study the trophic levels it is seen that in each higher levels the number of animals or its biomass decreases. It is because the transfer of energy follows 10 percent law that is only 10 percent of the energy is transferred to each trophic level from its lower trophic level. Each trophic level acquires energy from its lower trophic level and 90 percent of that energy it utilized by them and the rest is utilised in respiration. So only 10 percent of the energy remains of the next trophic level and like this in every level 90 percent of the total energy is utilised and 10 percent goes to the higher levels. This is known as 10 percent law of energy flow. For example- the number of trophic levels in the grazing food chain is restricted as the transfer of energy follow 10 percent law. 

Q.12. Which type of pyramid is always upright and why? 

Ans : In most ecosystems, all the pyramids, of number, of biomass are upright. Here the energy and biomass is more in number at lower trophic levels than the higher. 

Q.13. Distinguish between primary and secondary succession.

Ans :    

Primary SuccessionSecondary Succession
(i) In primary succession, starts in a bare area like bare rocks or in areas that somehow lost all the living organisms that existed there.(i) In secondary succession, it begins in areas where natural biotic communities have been destroyed such as abandoned form lands, burned of cut for- ests, land that have been flooded.
(ii) No living organisms were found found in these areas before the starting of this type of succession.(ii) Living organisms were  in these areas before the starting of these type of community.

Q.14. Distinguish between hydrarch succession and xerarch succession. 

Ans :       

Hydrarch SuccessionXerarch Succession
(i) Hydrarch succession takes place in wetter areas.(i) Xerarch succession takes place in wetter areas.
(ii) The successional series pro- gress from hydric to mesopic conditions.(ii) The series progress from xeric to mesopic conditions.

Q.15. In a nutshell how can you define Ecosystem services? 

Ans : The products of ecosystem processes are named as ecosystem services like healthy forest ecosystems purify air and water, mitigate droughts and floods, cycle nutrients, generate fertile soils, provide wildlife habitat, maintain biodiversity, pollinate crops, provide storage site for carbon and also provide aesthetic, cultural and spiritual values etc. 

Q.16. What is a sedimentary cycle? 

Ans : Sedimentary cycle is a part of nutrient cycle which include sulphur and phosphorus cycle. Here the reservoir is located in earths crust. Environmental factors soil, moisture, pH, temperature etc. regulate the rate of release of nutrients into the atmosphere. 

Q.17. What are different levels of consumers? In grazing food chain what is the position of a goat? 

Ans : The different levels of consumers all aA 

(a) Primary consumer (herbivorous) 

(b) Secondary consumer (Carnivorous) 

(c) Tertiary consumer (Top carnivorous) 

In grazing food chain the position of goat’s primary consumer a herbivorus. 

Q.18. State the factors for invasion of species in secondary succession. 

Ans : Invasion involves successful establishment of a species in a bare area it is volves the three steps- 

(a) Migration : It involves reaching of seed, spices etc. in a bare atul area through the agencies like air, water etc. 

(b) Ecesis : It involves the successful adjustment of a species with h the prevailing conditions of that area. 

(c) Aggregation : It involves the increase in member of organisms Innov through the process of reproduction.

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