2nd Year NotesBiology class 12th

2nd Year Biology Chapter 27 Man & His Environment

2nd Year Biology Chapter 27 Man & His Environment Question And Answer

Short And Simple Question And Answer

Q 1. What is Ozone layer?

Ans. The Ozone layer is a region in the Earth’s atmosphere, extending from 10-50 km above the Earth, which filters out ultraviolet rays from the sun.

Q 2. What do you mean by non-renewable resources?

Ans. Non-renewable resources are finite and cannot be replaced once consumed.

Q 3. What is the difference between deforestation and afforestation?

Ans. Deforestation involves the destruction of trees, leaving soil barren, often for town planning, cultivation, or timber, and it can lead to desertification. Afforestation is the creation of new forests in previously treeless areas, benefiting the environment and preventing desertification.

Q 4. What do you know about biodiversity?

Ans. Biodiversity refers to the number and variety of organisms in a particular area.

Q 5. What is water pollution?

Ans. Water pollution refers to the presence of harmful substances in water that can be detrimental to living organisms.

Q 6. Define the greenhouse effect?

Ans. The greenhouse effect is the rise in the Earth’s temperature due to the retention of heat rays.

Q 7. What is acid rain?

Ans. Acid rain is a process where acidic substances fall to the Earth, either dissolved in rain or as microscopic dry particles.

Q 8. What is algal bloom?

Ans. Algal bloom is a natural process where water becomes excessively enriched with nutrients, leading to the growth of a large amount of organic material.

Q 9. Differentiate between renewable and non-renewable sources?

Ans. Renewable Sources are those that are naturally recycled and never depleted (e.g., air, water, wildlife, land). Non-Renewable Resources are finite and cannot be replaced once consumed (e.g., metals, non-metals, fossil fuels).

Q 10. Why are trees called environmental buffers?

Ans. Trees are environmental buffers because they:

  • Slow down heavy rainfall, releasing water gradually into the soil.
  • Prevent soil erosion by anchoring soil particles with their roots.
  • Absorb CO2 and release oxygen, contributing to a healthier atmosphere.
  • Help maintain stable climatic conditions.

Q 11. What are the advantages and disadvantages of fossil fuels?

Ans. Advantages:

  • Fossil fuels fulfill approximately 95% of our energy needs.
  • They are widely usable, including for domestic purposes.


  • Fossil fuels are finite and will eventually deplete.
  • Burning fossil fuels can lead to pollution, releasing harmful gases like CO2, CO, SO2, etc.

Q 12. Why is wildlife sometimes considered non-renewable?

Ans. Wildlife is technically renewable, but factors like over-hunting, over-grazing, and deforestation can lead to the extinction of species, making them functionally non-renewable.

Q 13. How does a tidal barrage generate electricity?

Ans. A tidal power station includes a tidal barrage, which harnesses the difference in water height between high and low tides. This flow of water turns turbines connected to generators, producing electricity.

Q 14. What is stone cancer, and what causes it?

Ans. Stone cancer is the corrosive effect of sulfuric acid in acid rain on building stone, damaging it over time.

Q 15. How can the nutrient cycle balance be upset?

Ans. The nutrient cycle balance can be disrupted when there is not enough food produced, too much food is consumed, or decayed nutrients are not returned to the ground.

Q 16. What is the nutrient cycle?

Ans. The nutrient cycle is a natural process in which dead materials decay and become food for other living organisms, maintaining a continuous cycle of nutrients.

Q 17. What is the environment?

Ans. The environment comprises all types of resources essential for sustaining life on Earth.

Q 18. What is the composition of air?

Ans. Air primarily consists of nitrogen (79%), oxygen (20%), carbon dioxide (0.03%), and traces of inert noble gases.

Q 19. In which sources are energy classified?

Ans. Energy sources are classified as either inexhaustible (e.g., solar energy, hydro-power) or exhaustible (e.g., fossil fuels like coal, oil, and natural gas).

Q 20. Why are fossil fuels called so?

Ans. Fossil fuels are named as such because they are derived from the remains of ancient plants and animals that were buried and fossilized in the Earth’s deeper layers.

Q 21. What is hydroelectric power?

Ans. Hydroelectric power is generated by harnessing the kinetic energy of falling water, which turns turbines to produce electricity.

Q 22. Where are geothermal power plants found?

Ans. Geothermal power plants are found in locations like New Zealand and Iceland.

Q 23. What is geothermal energy?

Ans. Geothermal energy is the natural heat energy trapped underground, released through volcanoes, hot springs, and geysers.

Q 24. What is the use of solid wastes?

Ans. Solid wastes, such as trash, paper, organic matter, and plastics, can be converted into oil and gas through processes like hydrogenation, pyrolysis, or bio-conversion.

Q 25. What is the disadvantage of nuclear energy?

Ans. Nuclear power stations have a limited lifespan (about 30 years), produce nuclear waste and radiation, and require strict safety measures to prevent radiation pollution.

Q 26. Define demography?

Ans. Demography is the study of human populations and factors that affect them.

Q 27. What are the consequences of population increase?

Ans. Population increase can lead to over-crowding, starvation, depletion of food supply, and environmental destruction.

Q 28. What is environmental pollution?

Ans. Environmental pollution refers to the contamination of the environment by substances produced by humans that can harm human life and other living organisms.

Q 29. What are pollutants?

Ans. Pollutants are harmful substances in the environment that cause pollution, such as oxides of nitrogen, CFCs, SO2, and lead.

Q 30. What are the features of ozone in pure form?

Ans. In pure form, ozone is a bluish, explosive, and highly poisonous gas composed of O3 molecules, made up of three oxygen atoms bound together.

Q 31. What are the effects of ozone layer depletion on Earth’s life?

Ans. Ozone layer depletion results in increased ultraviolet rays reaching the Earth, which can lead to temperature rise, skin cancers, cataracts, and harm to crops, plants, trees, marine plankton, and weather patterns.

Q 32. Define air pollution?

Ans. Air pollution is the contamination of air by substances harmful to living organisms.

Q 33. What is ozone depletion, and what causes it?

Ans. Ozone depletion is the thinning of the ozone layer caused by the increasing levels of chlorofluorocarbons (CFCs), releasing chlorine that destroys ozone molecules.

Q 34. What are the causes of the greenhouse effect?

Ans. Urbanization, deforestation, and industrialization contribute to the greenhouse effect, leading to a gradual increase in Earth’s temperature, known as “Global Warming.”

Q 35. What are greenhouse gases?

Ans. Greenhouse gases are substances that trap heat and prevent it from escaping, including CO2, H2O vapors, and nitrogen oxides.

Q 36. What is ocean thermal gradient, and why is it important?

Ans. Ocean thermal gradient is the temperature difference between surface and deep ocean water. It’s important because this gradient can be harnessed to generate electricity using turbines.

Q 37. What are the sources of air pollution?

Ans. Sources of air pollution include CFCs from aerosol spray foams, sulfur dioxide from power stations and fossil fuels, lead compounds from leaded petrol, oxides of nitrogen from burning fossil fuels, and carbon monoxide from incomplete combustion.

Q 38. What are the major sources of CO, and what are its health effects?

Ans. Carbon monoxide (CO) is produced from incomplete burning of carbonate and carbon compounds, as well as from cigarette smoke. It combines irreversibly with hemoglobin (Hb), blocking its ability to carry oxygen and can lead to death.

Q 39. What is the leading cause of deforestation?

Ans. Rapid increases in population growth and the growing need for food and shelter are the leading causes of deforestation. Trees are cut to make way for agriculture and to provide wood for housing.

Q 40. What are the main causes of water pollution?

Ans. The main sources of water pollution include sewage with incomplete treatment, which contains harmful bacteria and chemicals, and the pollution of water bodies by oil and detergents.

Q 41. Why is there a need for the protection and conservation of the environment?

Ans. There is a need to protect and conserve the environment due to the limited nature of Earth’s energy resources. Balanced and planned use of these resources is essential for the survival of life on Earth.

Q 42. What is eutrophication?

Ans. Eutrophication is the natural process of excessive nutrient enrichment of water, leading to the rapid growth of organic matter in the water.

Q 43. What is wildlife?

Ans. Wildlife encompasses all non-cultivated plants and non-domesticated animals.

Q 44. What are fertilizers?

Ans. Fertilizers are chemical substances used to add additional nutrients to the soil, thereby increasing its fertility.

Q 45. What is a pesticide?

Ans. A pesticide is a chemical that is used to destroy agricultural pests or competitors. Different types include insecticides (for killing insects), fungicides (for parasitic fungi), and herbicides (for weed plants).

Q 46. What are pathogenic diseases?

Ans. Pathogenic diseases are diseases caused by organisms that can be transmitted to others. Examples include diphtheria, malaria, smallpox, tuberculosis, cholera, gonorrhea, and AIDS.

Q 47. Give at least two ways to conserve energy?

Ans. Ways to conserve energy include developing and using energy-efficient machines, engines, and manufacturing processes, as well as reducing wastage through recycling.

Q 48. What is erosion?

Ans. Erosion is the process of the topsoil being washed away, carrying essential nutrients, due to the flow of water.

Q 49. Define soil?

Ans. Soil can be defined as “the upper layer of Earth’s crust,” essential for plant growth and agriculture.

Q 50. What do you mean by effluents?

Ans. Effluents refer to the chemical waste produced by industries, including toxic chemicals and harmful liquids.

Q 51. Write the reasons for the world population explosion?

Ans. The reasons for the world population explosion include advances in disease prevention medicine, improvements in nutrition through efficient agriculture, better housing and living standards, and enhanced child care, maternity, parent craft, and welfare services.

Q 52. Write the effect of bacteria in eutrophic lakes?

Ans. Bacteria in eutrophic lakes deplete the water’s oxygen content, leading to the suffocation of aquatic animals due to an oxygen deficiency.

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