Vardaan Learning Institute

Topic: Our Environment

Class: 10 (Science) Type: Bonus Practice Paper Max. Marks: 50
Name:
Date:
SECTION A: OBJECTIVE TYPE QUESTIONS (1 Mark Each)
1. Which of the following is an abiotic component of an ecosystem?
  1. Bacteria
  2. Plants
  3. Temperature
  4. Fungi
2. In a food chain, the third trophic level is always occupied by:
  1. Carnivores
  2. Herbivores
  3. Decomposers
  4. Producers
3. The main cause of depletion of ozone layer is:
  1. Carbon dioxide
  2. Chlorofluorocarbons (CFCs)
  3. Methane
  4. Nitrogen dioxide
4. Which of the following limits the number of trophic levels in a food chain?
  1. Decrease in energy at higher trophic levels
  2. Deficient food supply
  3. Polluted air
  4. Water
5. Which of the following groups contain only biodegradable items?
  1. Grass, flowers and leather
  2. Grass, wood and plastic
  3. Fruit-peels, cake and lime-juice
  4. Cake, wood and grass
6. The decomposers in an ecosystem:
  1. Convert inorganic material to simpler forms
  2. Convert organic material to inorganic forms
  3. Convert inorganic material into organic compounds
  4. Do strictly none of these
7. In an ecosystem, the 10% law of energy transfer was proposed by:
  1. Mendel
  2. Lindeman
  3. Darwin
  4. Lamarck
8. Which of the following is an artificial ecosystem?
  1. Pond
  2. Crop field
  3. Lake
  4. Forest
9. Organisms which synthesise particular carbohydrates from inorganic compounds using radiant energy are called:
  1. Decomposers
  2. Producers
  3. Herbivores
  4. Carnivores
10. Excessive exposure to ultraviolet radiation causes:
  1. Meningitis
  2. Skin cancer
  3. Lung cancer
  4. Liver cirrhosis
Directions (Q11-Q14): In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
11. Assertion (A): Energy flow in a food chain is unidirectional.
Reason (R): Energy captured by autotrophs does not revert back to the solar input.
12. Assertion (A): Ozone protects the earth from harmful UV radiations.
Reason (R): Ozone is formed by the action of UV rays on oxygen.
13. Assertion (A): Biological magnification is the process of accumulation of toxic chemicals at higher trophic levels.
Reason (R): Humans occupy the top level in any food chain, so maximum concentration of chemicals is found in human bodies.
14. Assertion (A): Biodegradable substances result in the formation of manure.
Reason (R): They are broken down by microorganisms into simpler substances.
SECTION B: SHORT ANSWER QUESTIONS (3 Marks Each)
15. What is Biological Magnification? Will the levels of this magnification be different at different levels of the ecosystem?
16. What is Ozone? How is it formed in the upper atmosphere?
17. What are decomposers? What will be the consequence of their absence in an ecosystem?
18. Construct a food chain with four trophic levels. Why are food chains generally consisting of only 3 or 4 steps?
19. Differentiate between biodegradable and non-biodegradable substances with examples.
20. "The flow of energy in an ecosystem is unidirectional." Justify this statement.
SECTION C: LONG ANSWER QUESTIONS (5 Marks Each)
21. (i) What are the problems caused by the non-biodegradable wastes that we generate?
(ii) Suggest any three methods of disposal of waste.
22. (i) Diagrammatically represent the transfer of energy in a food chain.
(ii) In the following food chain, if 10,000 J of energy is available to the plants, how much energy will be available to the hawks?
Plants $\rightarrow$ Grasshopper $\rightarrow$ Frog $\rightarrow$ Snake $\rightarrow$ Hawk.
SECTION D: CASE STUDY (4 Marks)
23. Read the following text and answer the questions:
Our environment is changing due to human activities. Ozone layer depletion and waste disposal are major concerns. The ozone layer shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.

(i) Write the chemical formula of Ozone. (1 Mark)
(ii) Name the synthetic chemicals responsibly for ozone depletion. (1 Mark)
(iii) Suggest any two ways to reduce the problem of waste disposal. (2 Marks)
24. Read the following text and answer the questions:
Pesticides and chemicals are used to protect crops from diseases and pests. These chemicals are either washed down into the soil or into water bodies. From soil, they are absorbed by plants and from water bodies, by aquatic plants and animals. They enter the food chain and getting accumulated progressively at each trophic level. This phenomenon is known as biological magnification.

(i) Why do pesticides accumulate in the food chain? (1 Mark)
(ii) Which group of organisms will have the maximum concentration of pesticides? (1 Mark)
(iii) Why is biological magnification a concern for humans? (2 Marks)
"All the best!"