NCERT Class 10 Science Chapter 13 Our Environment
MCQs
- Which of the following is a biotic component of an ecosystem?
(A) Air
(B) Soil
(C) Plants
(D) Water
Answer: (C) Plants - What is the primary source of energy for life on Earth?
(A) Wind
(B) Sun
(C) Water
(D) Soil
Answer: (B) Sun - Which of these organisms are decomposers?
(A) Fungi and bacteria
(B) Herbivores
(C) Carnivores
(D) Autotrophs
Answer: (A) Fungi and bacteria - What is the average energy transfer efficiency at each trophic level?
(A) 1%
(B) 10%
(C) 50%
(D) 90%
Answer: (B) 10% - Which phenomenon causes harmful chemicals to accumulate in the food chain?
(A) Energy flow
(B) Biological magnification
(C) Decomposition
(D) Photosynthesis
Answer: (B) Biological magnification - What is the main function of decomposers in an ecosystem?
(A) Produce energy
(B) Consume plants
(C) Break down dead organisms
(D) Provide shelter
Answer: (C) Break down dead organisms - Which gas is responsible for the depletion of the ozone layer?
(A) Carbon dioxide
(B) Methane
(C) Chlorofluorocarbons
(D) Nitrogen oxide
Answer: (C) Chlorofluorocarbons - Which trophic level has the greatest number of organisms?
(A) Primary consumers
(B) Secondary consumers
(C) Producers
(D) Tertiary consumers
Answer: (C) Producers - Non-biodegradable materials are primarily harmful because they:
(A) Decompose quickly
(B) Persist in the environment for a long time
(C) Provide nutrients to the soil
(D) Generate energy
Answer: (B) Persist in the environment for a long time - What percentage of sunlight is captured by green plants?
(A) 1%
(B) 10%
(C) 50%
(D) 90%
Answer: (A) 1%
Fill in the Blanks
- The __________ captures sunlight and converts it into chemical energy.
Answer: producers - The flow of energy in an ecosystem is __________.
Answer: unidirectional - Ozone in the upper atmosphere protects us from __________ radiation.
Answer: ultraviolet - __________ substances can be broken down by biological processes.
Answer: Biodegradable - The loss of energy at each trophic level limits the number of __________ in a food chain.
Answer: trophic levels - The main cause of ozone layer depletion is the use of __________.
Answer: chlorofluorocarbons (CFCs) - The phenomenon of __________ explains the accumulation of harmful chemicals at higher trophic levels.
Answer: biological magnification - Substances like __________ persist in the environment for a long time because they are non-biodegradable.
Answer: plastics - A __________ is a series of organisms taking part at various biotic levels.
Answer: food chain - The energy transfer between trophic levels is approximately __________ percent.
Answer: 10
Essay Type Questions
- Explain the components of an ecosystem with suitable examples.
Answer: An ecosystem consists of biotic components such as plants, animals, and microorganisms, and abiotic components such as air, water, soil, and sunlight. For example, a pond ecosystem includes algae (producers), fish (consumers), and decomposers like bacteria. - Describe the process of energy flow in an ecosystem and its significance.
Answer: Energy flows in an ecosystem through the food chain, starting from producers that convert solar energy into chemical energy. This energy is transferred to primary consumers, secondary consumers, and decomposers, with a loss of energy at each trophic level. - Discuss the phenomenon of biological magnification and its impact on the environment.
Answer: Biological magnification is the progressive accumulation of harmful chemicals like pesticides in organisms at higher trophic levels. It can lead to toxic effects, such as diseases in humans and reduced reproductive rates in wildlife. - How does the depletion of the ozone layer affect living organisms, and what steps can be taken to prevent it?
Answer: Ozone layer depletion increases UV radiation, causing skin cancer and other health issues. Steps to prevent this include banning CFCs, using eco-friendly products, and international agreements like the Montreal Protocol. - Explain the difference between biodegradable and non-biodegradable substances with examples.
Answer: Biodegradable substances like vegetable peels decompose naturally, while non-biodegradable substances like plastic persist in the environment, causing pollution. Proper waste management is essential to address this issue.