Very Short Questions: Our Environment

Q1: Give an example each of natural and an artificial ecosystem.
Ans:

• Natural ecosystem: Forest or pond. A forest or a pond includes many plants, animals and microorganisms interacting with non-living factors (soil, water, air) and functions largely without human help.
• Artificial ecosystem: Crop field or aquarium. These are created and maintained by humans and need regular care, such as watering, feeding or cleaning.

Q2: What is the full form of CFCs and UNEP?
Ans:

• CFC = Chlorofluorocarbons. These are synthetic chemicals formerly used in refrigerants, aerosol propellants and foam-making agents.
• UNEP = United Nations Environment Programme. It is the global organisation that coordinates environmental activities and helps countries in formulating environmental policies.

Q3: Define ecosystem and name its components.
Ans: An ecosystem is a functional unit where living organisms interact with one another and with their non-living environment.
Components of an ecosystem are: Biotic (living) and abiotic (non-living). Biotic components include producers (plants), consumers (animals) and decomposers (microorganisms). Abiotic components include sunlight, air, water, soil and minerals.

Q4: What is the role of ozone? Why is it being depleted?
Ans: Ozone in the upper atmosphere absorbs harmful ultraviolet (UV) radiation from the Sun, protecting organisms on Earth from skin damage and other harmful effects. It is being depleted because chemicals such as chlorofluorocarbons (CFCs) release chlorine atoms in the stratosphere, and these chlorine atoms break down ozone molecules.

Q5: What is ten per cent law?
Ans: Ten per cent law states that, on average, only about 10% of the energy available at one trophic level is transferred to the next trophic level. Most energy is lost as heat and used in organisms' life processes, so only a small fraction becomes available as biomass for the next level.

Q6: List two advantage of decomposers to the environment.  [CBSE 2008]
Ans: Advantage of decomposers:

• They replenish the soil nutrients by breaking down dead plants and animals into simpler inorganic substances that plants can absorb.
• They help to clean the environment by decomposing dead remains and organic waste, preventing the buildup of litter and reducing the spread of disease.

Q7: What is the ultimate source of energy in an ecosystem? Which process helps to trap this energy in producers?
Ans: The Sun is the ultimate source of energy in an ecosystem. Photosynthesis is the process by which producers (green plants and algae) trap sunlight and convert it into chemical energy stored as food.

Q8: What is the major cause of ozone depletion? Where are these substances used?  [CBSE 2012]
Ans: Chlorofluorocarbons (CFCs) are a major cause of ozone depletion. They have been used in refrigerators and air conditioners as refrigerants, in aerosol sprays as propellants, and in the manufacture of foam products.

Q9: Why should biodegradable and non-biodegradable wastes to be discarded in two separate dustbins?  [CBSE 2015]
Ans: Biodegradable and non-biodegradable wastes should be discarded separately because separation makes recycling and composting easier. It prevents recyclable materials from being contaminated, saves time and energy in waste processing, reduces the amount sent to landfills and helps convert organic waste into useful compost.

Q10: What will happen if we kill all the organisms in one trophic level?  [CBSE 2011]
Ans: Killing all organisms in one trophic level will disrupt the food chain. The trophic level above will face a shortage of food and may decline in number, while the level below may increase due to reduced predation or grazing. This imbalance can lead to collapse of parts of the food web and loss of ecosystem stability.