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Assignment for Class 12 Biology Chapter 12 Ecosystem
Class 12 Biology students should refer to the following printable assignment in Pdf for Chapter 12 Ecosystem in Class 12. This test paper with questions and answers for Class 12 Biology will be very useful for exams and help you to score good marks
Chapter 12 Ecosystem Class 12 Biology Assignment
Question. Some amount Carbon dioxide that is removed from carbon circulation is stored in
(a) Organic material in living organism
(b) Plants
(c) Microbes
(d) Sediments
Answer: D
Question. Rocks contain phosphorus in the form of
(a) Phosphite
(b) Phosphoric acid
(c) Phosphates
(d) None of the options
Answer: C
Question. What percentage of global carbon is found dissolved in oceans
(a) 49%
(b) 85%
(c) 25%
(d) 71%
Answer: D
Question. According to estimate what quantity of carbon dioxide is fixed in biosphere by photosynthesis
(a) 4*1013kg
(b) 4*1016kg
(c) 4*1016kg
(d) 4*1016tonnes
Answer: A
Question. Product of ecosystem processes are known are
(a) Ecosystem results
(b) Ecosystem services
(c) Ecosystem effect
(d) None of the options
Answer: B
Question. Researchers have put an average price tag of_____ nature’s life supporting services
(a) USD 33×103 billion
(b) USD 33 billion
(c) USD 33×103 million
(d) none of the options
Answer: A
Very Short Answer Type Questions
Question. Why green plants are not found beyond a certain depth in the ocean?
Answer: Beyond a certain depth in the ocean, sunlight is not able to penetrate. Due to which green plants cannot photosynthesise and thus, do not survive.
Question. What is detritus?
Answer: Dead organic matter or remains of plant such as leaves, bark, flower and dead remain of animals, including faecal matter constitute detritus.
Question. “Man can be a primary as well as a secondary consumer.” Justify this statement.
Answer: Man has a varied diet. When on vegetarian diet, they are primary consumers and when on nonvegetarian diet, they are secondary consumers.
Question. Define mineralisation.
Answer: It is the process in which the humus is degraded by certain microbes and thus inorganic nutrients are released in the soil.
Question. Mention the role of pioneer species in primary succession on rocks.
Answer: The pioneer species invade a bare area and pave way for other species.
Question. Name the pioneer species:
(i) on a bare rock
(ii) in a water body
Answer: (i) Lichens
(ii) Phytoplanktons
Question. Why is an earthworm called a detritivore?
Answer: This is because earthworm breaks down detritus into smaller particles.
Question. Under what conditions would a particular stage in the process of succession revert back to an earlier stage?
Answer: Natural or human induced disturbances like fire, deforestation, etc.
Short Answer Type Questions
Question. What would happen to the successive trophic levels in the pyramid of energy, if the rate of reproduction of phytoplanktons was slowed down? Suggest two factors which could cause such a reduction in phytoplankton reproduction.
Answer: If the rate of reproduction of phytoplanktons slows down then the net primary productivity decrease. As a result, flow of energy will also decrease in the successive trophic level.
The following two factors cause reduction in phytoplankton reproduction:
(i) Less water availability
(ii) Less nutrient availability.
Question. What could be the reason for the faster rate of decomposition in the tropics?
Answer: The rate of decomposition is regulated by climatic factors like temperature and soil moisture as they have an effect on the activities of soil microbes. The tropics with its hot and humid climatic condition provides an environment which is ideal for the microbes to speed up the process of decomposition.
Question. Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity of the successive seral communities developing in the water body.
Answer: Pioneer species — Phytoplanktons
Climax species — Forest or trees
Biomass will be gradually increased and phytoplanktons are replaced by free-floating angiosperms then by rooted hydrophytes followed by different seral communities thus, biodiversity also increases.
Question. (a) Describe primary succession that occurs on bare rock.
(b) Differentiate between xerarch and hydrarch successions.
Answer: (a) Refer to Basic Concepts Poiiin). 14
(b) (i) Hydrarch succession: The plant succession which takes place in wet area or water, leading to successional series, progress from hydric to the mesic conditions.
(ii) Xerarch succession: The plant succession which takes place in a dry area, leading to successional series from xeric to mesic conditions.
Question. Explain the function of ‘reservoir’ in a nutrient cycle. List the two types of nutrient cycles in nature.
Answer: The function of the reservoir is to meet the deficit of nutrients which occurs due to imbalance in the rate of influx and efflux.
The two types of nutrient cycles are:
(i) Gaseous, and (ii) Sedimentary
Question. Define decomposition and describe the process and products of decomposition.
Answer: Steps in Decomposition
(i) Fragmentation: The process of breaking down of detritus into smaller particles is called fragmentation, e.g., as done by earthworm (= farmer’s friend).
(ii) Leaching: The process by which water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts is called leaching.
(iii) Catabolism: The enzymatic process by which bacterial and fungal enzymes degrade detritus to simpler inorganic substances is called catabolism.
Decomposition produces a dark coloured nutrient rich substance called humus which on degradation releases CO2, water and other nutrients in the soil.
Question. (a) Name the type of detritus that decomposes faster. List any two factors that enhance the rate of decomposition.
(b) Write the different steps taken in humification and mineralisation during the process of decomposition.
Answer: (a) O Detritus rich in nitrogen decomposes faster. These are water-soluble substances like sugar.
O Factors enhancing rate of decomposition: Warm temperature, moist environment, availability of oxygen.
(b) Humification: Accumulation of dark coloured amorphous substance called humus which is resistant to micorbial action and undergoes decomposition at a very slow rate.
Mineralisation: Humus is further degraded by microbes releasing inorganic nutrients.
Question. What are the shortcomings of ecological pyramids in the study of ecosystem?
Answer: The ecological pyramid assumes a simple food chain and does not accommodate food webs.
Thereby, it does not take into account the fact that species may belong to two or more trophic levels at a time. Also saprophytes despite their vital role in ecosystem are given no place in the ecological pyramids.
Question. How does primary succession start in water and lead to the climax community? Explain.
Answer: Primary succession in water
• The pioneer species are phytoplanktons.
• The phytoplanktons are replaced by free-floating angiosperms.
Question. (a) Colonisation of a rocky terrain is a natural process. Mention the group of organisms which invade this area first. Give an example.
(b) Over the years, it has been observed that some of the lakes are disappearing due to urbanisation. In absence of human interference, depict by making a flow chart, how do the successional series progress from hydric to mesic condition.
(c) Identify the climax community of hydrarch and xerarch succession.
Answer: (a) Pioneer species invade the area first. For example, lichen
(b) Phytoplankton – (hydr→ic) Submerged plant stage → Submerged free floating plant stage → Reed swamp stage → Marsh – meadow stage → Scrub stage → Forest stage (Mesic condition)
(c) Forest is the climax community for both successions.
Question. What are the limitations of ecological pyramids?
Answer: Limitations of ecological pyramids:
(i) It never takes into account the same species belonging to
(ii) It assumes a simple food chain, which never exists in nature. It does not accommodate a food web.
(iii) In spite of the vital role played by saprophytes/decomposers, they are not given any position in ecological pyramids.
Long Answer Type Questions
Question. Describe the components of an ecosystem.
Answer: An ecosystem consists of two types of components, i.e., biotic or living and abiotic or non-living.
There are three main types of biotic components on the basis of mode of obtaining their food—producers, consumers and decomposers.
(i) Producers (autotrophs): They are photosynthetic or autotrophic plants that synthesise their own organic food from inorganic raw materials with the help of solar radiations. Common producers are algae, plants and photosynthetic bacteria. Phytoplanktons are the producers of aquatic ecosystems.
(ii) Consumers (heterotrophs): They are animals which feed on other organisms or producers for obtaining their nourishment. Common consumers are deer, goat, etc.
(iii) Decomposers: They are saprotrophs which obtain nourishment from organic remains. They release digestive enzymes to digest the organic matter. Common decomposers are detritivores, e.g., earthworm. Abiotic component of ecosystem consists of non-living substances and factors which are as follows:
(a) Temperature (b) Light
(c) Wind (d) Humidity
(e) Precipitation (f) Water, etc.
Question. Define ecological succession. Give three differences between seral stages and climax community during succession.
Answer: The sequential, gradual and predictable changes in the species composition in an area are called succession or ecological succession.
Table 14.13: Differences between seral stages and climax community
Question. (a) With suitable examples, explain the energy flow through different trophic levels. What does each bar in this pyramid represent?
(b) Write any two limitations of ecological pyramids.
Answer: (a) In an ideal energy pyramid, the primary producers use only 1% of the energy in the sunlight available to them. The subsequent trophic levels pass on 10% of the energy received from previous trophic level to the next trophic level.
Each bar or level in the pyramid represents the amount of energy transferred to the next trophic level.
(b) (i) It does not take into account the same species belonging to two trophic levels.
(ii) It assumes simple food chain and not food web.
(iii) Saprophytes are not considered. (Any two)
Question. (a) Draw a simplified model of phosphorus cycling in a terrestrial ecosystem.
(b) Write the importance of such cycles in ecosystems.
Answer: (a)
(b) Such cycles recycle nutrients again and again and maintain the balance in ecosystem.
Question. Describe the process of decomposition of detritus under the following heads: Fragmentation; leaching; catabolism; humification and mineralisation.
Answer: The process of breaking down complex organic matter into inorganic substances like—, water
and nutrients is called decomposition. The raw material for decomposition is called detritus.
They are dead remains of plants and animals.
Steps in decomposition:
(a) Fragmentation: The process of breaking down of detritus into smaller particles is called fragmentation, e.g., as done by earthworm.
(b) Leaching: The process by which water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
(c) Catabolism: The enzymatic process by which degraded detritus is converted into simple inorganic substances is called catabolism.
(d) Humification: The process of accumulation of a dark coloured amorphous substance called humus, that is, highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
(e) Mineralisation: The process by which humus is further degraded by some microbes and release inorganic nutrients is called mineralisation.
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CBSE Class 12 Biology Ecosystem Assignment Set B |
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CBSE Class 12 Biology Chapter 12 Ecosystem Assignment
We hope you liked the above assignment for Chapter 12 Ecosystem which has been designed as per the latest syllabus for Class 12 Biology released by CBSE. Students of Class 12 should download and practice the above Assignments for Class 12 Biology regularly. We have provided all types of questions like MCQs, short answer questions, objective questions and long answer questions in the Class 12 Biology practice sheet in Pdf. All questions have been designed for Biology by looking into the pattern of problems asked in previous year examinations. You can download all Revision notes for Class 12 Biology also absolutely free of cost. Lot of MCQ questions for Class 12 Biology have also been given in the worksheets and assignments for regular use. All study material for Class 12 Biology students have been given on studiestoday. We have also provided lot of Worksheets for Class 12 Biology which you can use to further make your self stronger in Biology.
What are benefits of doing Assignment for CBSE Class 12 Biology Chapter 12 Ecosystem?
a. Score higher marks: Regular practice of Biology Class 12 Assignments for chapter Chapter 12 Ecosystem will help to improve understanding and help in solving exam questions correctly.
b. As per CBSE pattern: All questions given above follow the latest Class 12 Biology Sample Papers so that students can prepare as per latest exam pattern.
c. Understand different question types: These assignments include MCQ Questions for Class 12 Biology with answers relating to Chapter 12 Ecosystem, short answers, long answers, and also case studies.
d. Improve time management: Daily solving questions from Chapter 12 Ecosystem within a set time will improve your speed and accuracy.
e. Boost confidence: Practicing multiple assignments and Class 12 Biology mock tests for Chapter 12 Ecosystem reduces exam stress.
How to Solve CBSE Class 12 Biology Chapter 12 Ecosystem Assignment effectively?
a. Start with Class 12 NCERT and syllabus topics: Always read the chapter carefully before attempting Assignment questions for Class 12 Biology Chapter 12 Ecosystem.
b. Solve without checking answers: You should first attempt the assignment questions on Chapter 12 Ecosystem yourself and then compare with provided solutions.
c. Use Class 12 worksheets and revision notes: Refer to NCERT Class 12 Biology worksheets, sample papers, and mock tests for extra practice.
d. Revise tricky topics: Focus on difficult concepts by solving Class 12 Biology MCQ Test.
e. Maintain notebook: Note down mistakes in Chapter 12 Ecosystem assignment and read them in Revision notes for Class 12 Biology
How to practice CBSE Class 12 Biology Chapter 12 Ecosystem Assignment for best results?
a. Solve assignments daily: Regular practice of Chapter 12 Ecosystem questions will strengthen problem solving skills.
b.Use Class 12 study materials: Combine NCERT book for Class 12 Biology, mock tests, sample papers, and worksheets to get a complete preparation experience.
c. Set a timer: Practicing Class 12 Biology Chapter 12 Ecosystem assignment under timed conditions improves speed and accuracy.
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All topics given in Chapter 12 Ecosystem Biology Class 12 Book for the current academic year have been covered in the given assignment
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Latest syllabus issued for current academic year by CBSE has been used to design assignments for Chapter 12 Ecosystem Class 12
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