Worksheet Solutions: Our Environment - 2

Q1: Multiple Choice Questions.

(i) Which of the following is a natural greenhouse gas?
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Hydrogen
Ans: (b)
Explanation: Carbon dioxide is a naturally occurring gas in the atmosphere that traps some of the Sun's heat, helping to keep Earth warm enough for life. When its concentration increases due to human activities, it strengthens this warming effect and can raise global temperatures.

(ii) What is the primary source of energy for the water cycle?
(a) Wind
(b) Sun
(c) Earth's core
(d) Moon
Ans: (b)
Explanation: The Sun supplies the heat energy needed for evaporation, which turns water from oceans, rivers and soil into vapour. This movement of water through evaporation, condensation and precipitation is what drives the water cycle.

(iii) Which activity contributes to air pollution?
(a) Planting trees
(b) Using public transportation
(c) Burning fossil fuels
(d) Recycling paper
Ans: (c)
Explanation: Burning fossil fuels such as coal, oil and petrol produces pollutants like carbon dioxide, sulphur dioxide and nitrogen oxides. These gases and particles contaminate the air, harm health and contribute to problems such as smog and acid rain.

(iv) What is the main purpose of the ozone layer in the atmosphere?
(a) To produce oxygen for breathing
(b) To prevent the greenhouse effect
(c) To absorb harmful UV rays
(d) To regulate the Earth's rotation
Ans: (c)
Explanation: The ozone layer, found high in the atmosphere, absorbs most of the Sun's harmful ultraviolet (UV) radiation. This protection reduces the risk of skin damage, eye problems and harm to plants and animals.

(v) Which environmental problem is caused by the excessive use of synthetic fertilizers and pesticides?
(a) Global warming
(b) Soil erosion
(c) Acid rain
(d) Deforestation
Ans: (c)
Explanation: Chemicals from synthetic fertilisers and some pesticides can be converted in the air into acidic compounds. These fall with rain as acid rain, which damages plants, soil and buildings and harms aquatic life.

Q2: Fill in the Blanks.

(i) The process by which green plants make their food is called __________.
Ans: Photosynthesis
Photosynthesis is the process by which green plants use sunlight, carbon dioxide and water to make glucose (their food) and give out oxygen. 

(ii) __________ is the thin layer of gases that surround the Earth.
Ans: Atmosphere
The atmosphere is the layer of gases around Earth that we breathe. It also protects us by reducing harmful radiation and helps keep the planet at a comfortable temperature.

(iii) The process of water turning into vapor is called __________.
Ans: Evaporation
Evaporation happens when heat from the Sun makes water change from a liquid into water vapour. This vapour rises into the air and is the first step of the water cycle.

(iv) The three main types of pollution are air pollution, water pollution, and __________.
Ans: Soil pollution
Soil pollution means the soil becomes dirty or harmful because of chemicals, waste or other substances. It can stop plants from growing well and can harm animals and people who use the land.

(v) __________ is the excessive cutting down of trees.
Ans: Deforestation
Deforestation is when large areas of forest are cut down. This removes homes for wildlife, reduces air purification by trees and can change rainfall and soil conditions.

Q3: Match the Column.

Match the items in Column A with their corresponding descriptions in Column B.

Ans:

Q4: True or False.

(i) The ozone layer helps in protecting the Earth from harmful ultraviolet (UV) rays of the sun.
(ii) Overpopulation has no impact on the environment.
(iii) All types of plastic are biodegradable.
(iv) Recycling helps reduce the amount of waste in landfills.
(v) Cutting down trees has no effect on the water cycle.
Ans: 
(i) True: The ozone layer absorbs most harmful UV radiation from the Sun, protecting living things from its damaging effects.
(ii) False: Overpopulation increases demand for land, water and resources, leading to habitat loss, pollution and greater waste, which harm the environment.
(iii) False: Most plastics are not biodegradable and can take many years to break down, causing long-term pollution if not managed properly.
(iv) True: Recycling turns used materials into new products, so less waste goes to landfills and fewer raw materials are needed.
(v) False: Trees help regulate the water cycle by absorbing water from the soil and releasing it into the air through transpiration; removing trees disrupts this process and can affect rainfall.

Q5: Short Answer Questions.

(i) What is biodiversity, and why is it important for the environment?
Ans: Biodiversity is the variety of living things-plants, animals and microorganisms- in a place. It is important because:

• It keeps ecosystems balanced and healthy.
• It provides useful things for people, such as food, medicine and materials.
• Different species help each other-for example, pollinators help plants produce fruits and seeds.

(ii) Describe the greenhouse effect and its impact on global temperatures.
Ans: The greenhouse effect is a natural process where certain gases in the atmosphere, like carbon dioxide and water vapour, trap some of the Sun's heat and keep Earth warm enough for life. When people burn fossil fuels and cut down forests, extra greenhouse gases are released, which trap more heat and make the planet warmer. This rise in temperature is called global warming and can change weather patterns, melt ice and affect plants and animals.

(iii) What are the three Rs in waste management, and how do they help reduce environmental impact?
Ans: The three Rs are Reduce, Reuse and Recycle. They help in these ways:

• Reduce: Buying and using less lowers the amount of waste produced.
• Reuse: Using items again saves resources and reduces the need to make new things.
• Recycle: Turning waste into new products cuts down on raw material use and saves energy.

(iv) Explain the concept of the food chain with an example.
Ans: A food chain shows how energy moves from one living thing to another. For example: Grass (producer) → Grasshopper (primary consumer) → Frog (secondary consumer) → Snake (tertiary consumer). Each arrow shows which organism eats which, and energy passes along the chain.

(v) How can individuals contribute to conserving the environment in their daily lives?
Ans: Individuals can help by:

• Saving water and electricity at home.
• Using public transport, cycling or carpooling instead of using private vehicles.
• Recycling paper, plastic and glass and avoiding single-use plastics.
• Planting trees and taking part in local clean-ups.
• Choosing eco-friendly products and repairing items instead of throwing them away.