CBSE Class 12 Biology Ecosystem Worksheet Set A

Read and download free pdf of CBSE Class 12 Biology Ecosystem Worksheet Set A. Students and teachers of Class 12 Biology can get free printable Worksheets for Class 12 Biology in PDF format prepared as per the latest syllabus and examination pattern in your schools. Standard 12 students should practice questions and answers given here for Biology in Grade 12 which will help them to improve your knowledge of all important chapters and its topics. Students should also download free pdf of Class 12 Biology Worksheets prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this academic year and solve important problems provided here with solutions on daily basis to get more score in school exams and tests

CBSE Class 12 Biology Ecosystem (1). CBSE issues sample papers every year for students for class 12 board exams. Students should solve the CBSE issued sample papers to understand the pattern of the question paper which will come in class 12 board exams this year. The sample papers have been provided with marking scheme. It’s always recommended to practice as many CBSE sample papers as possible before the board examinations. Sample papers should be always practiced in examination condition at home or school and the student should show the answers to teachers for checking or compare with the answers provided. Students can download the sample papers in pdf format free and score better marks in examinations. Refer to other links too for latest sample papers.

1 What does the base tier of the ecological pyramid represent?

2 In the North East region of India, during the process of jhum cultivation, forests are cleared by burning and left for regrowth after a year of cultivation. How would you explain the regrowth of forest in ecological term?

3 Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?

4 Why are oceans least productive?

5 Organisms at a higher trophic level have less energy available. Comment.

6 What are the shortcomings of ecological pyramids in the study of ecosystem?

7 How do you distinguish between humification and mineralisation?

8 List three parameters used for constructing ecological pyramids. Describe any one instance where the pyramid may look inverted.

9 Differentiate between a detritivore and a decomposer giving an example of each.

10 Construct an ideal pyramid of energy when 1,00,000 joules of sunlight is available. Label all its trophic levels.

11 Construct a pyramid of biomass starting with phytoplanktons. Label 3 trophic levels. Is the pyramid upright or inverted? Why?

12 Explain with the help of two examples how the pyramid of number and the pyramid of biomass can look inverted.

13 Justify the given statements:

a) Energy flow in an ecosystem is unidirectional

b) Secondary succession is faster than primary succession

14 What will happen to an ecosystem if:

a) All producers are removed

b) All organisms of herbivore level are eliminated

c) All top carnivore population is removed 


Important Questions for NCERT Class 12 Biology Ecosystem


Ques. Pyramid of numbers deals with number of
(a) species in an area
(b) individuals in a community
(c) individuals in a trophic level
(d) subspecies in a community. 

Answer: C


Ques. Pyramid of numbers in a pond ecosystem is
(a) irregular (b) inverted
(c) upright (d) spindle shaped.

Answer: C


Ques. Which of the following would appear as the pioneer organisms on bare rocks?
(a) Mosses (b) Green algae
(c) Lichens (d) Liverworts

Answer: C


Ques. During ecological succession
(a) the numbers and types of animals remain constant
(b) the changes lead to a community that is in near equilibrium with the environment and is called pioneer community
(c) the gradual and predictable change in species composition occurs in a given area
(d) the establishment of a new biotic community is very fast in its primary phase. 

Answer: C


Ques. Secondary succession takes place on/in
(a) newly created pond
(b) newly cooled lava
(c) bare rock
(d) degraded forest. 

Answer: D


Ques. The second stage of hydrosere is occupied by plants like
(a) Azolla (b) Typha
(c) Salix (d) Vallisneria.

Answer: D


Ques. Which one of the following statements is correct for secondary succession?
(a) It begins on a bare rock.
(b) It occurs on a deforested site.
(c) It follows primary succession.
(d) It is similar to primary succession except that it has a relatively fast pace. 

Answer: B


Ques. Both hydrarch and xerarch successions lead to
(a) medium water conditions
(b) xeric conditions
(c) highly dry conditions
(d) excessive wet conditions. 

Answer: A


Ques. The correct sequence of plants in a hydrosere is
(a) Volvox → Hydrilla → Pistia → Scirpus → Lantana → Oak
(b) Pistia → Volvox → Scirpus → Hydrilla → Oak → Lantana
(c) Oak → Lantana → Volvox → Hydrilla → Pistia → Scirpus
(d) Oak → Lantana → Scirpus → Pistia → Hydrilla → Volvox. 

Answer: A


Ques. An ecosystem which can be easily damaged but can recover after some time if damaging effect stops will be having
(a) low stability and high resilience
(b) high stability and low resilience
(c) low stability and low resilience
(d) high stability and high resilience. 

Answer: A


Ques. The primary succession refers to the development of communities on a
(a) forest clearing after devastating fire
(b) newly-exposed habitat with no record of earlier vegetation
(c) freshly cleared crop field
(d) pond, freshly filled with water after a dry phase. 

Answer: B


Ques. Natural reservoir of phosphorus is
(a) rock (b) fossils
(c) sea water (d) animal bones.

Answer: A


Ques. Which one of the following is not a gaseous biogeochemical cycle in ecosystem?
(a) Sulphur cycle (b) Phosphorus cycle
(c) Nitrogen cycle (d) Carbon cycle

Answer: B


Ques. About 70% of total global carbon is found in
(a) oceans (b) forests
(c) grasslands (d) agroecosystems.

Answer: A


Ques. Which of the following pairs is a sedimentary type of biogeochemical cycle?
(a) Phosphorus and nitrogen
(b) Phosphorus and sulphur
(c) Oxygen and nitrogen
(d) Phosphorus and carbon dioxide 

Answer: B


Ques. Match the following and select the correct option.
A. Earthworm (i) Pioneer species
B. Succession (ii) Detritivore
C. Ecosystem service (iii) Natality
D. Population growth (iv) Pollination
      A   B    C    D
(a) (i) (ii)  (iii) (iv)
(b) (iv) (i) (iii) (ii)
(c) (iii) (ii) (iv) (i)
(d) (ii) (i) (iv) (iii

Answer: D


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