Environmental Science PYQ May 2025 69/MAY/4

NIOS Environmental Science Question Paper April 2025

CORE MODULE

OBJECTIVE QUESTIONS TYPE–I

1. Primitive humans used fire to

I. cook food

II. scare away animals

III. make ornaments

IV. make tools

Select the most appropriate option. 1

(A) I and II

(B) I and III

(D) III and IV

Ans: (B) I and III

2. Azolla is a/an

(A) water fern in which blue-green algae grow

(B) symbiotic bacteria found in root nodules of legume plants

(D) fungus that grows on roots of forest trees 1

Ans: (A) water fern in which blue-green algae grow

3. BEE stands for

(A) Bureau of Energy Efficiency

(B) Branch of Energy Efficiency

(D) Basis of Energy Efficiency 1

Ans: (A) Bureau of Energy Efficiency

4. Homo erectus used tools made up of

(A) bones

(B) pebbles

(D) wood 1

Ans: (C) stones

5. Slums are

(A) clusters of huts in parts of cities

(B) clusters of huts in parts of villages

(D) clusters of huts on the banks of a river 1

Ans: (A) clusters of huts in parts of cities

6. The consequence of deforestation is

(A) soil erosion

(B) land subsidence

(D) ozone layer depletion 1

Ans: (A) soil erosion

7. The scientific study of the relationship of living organisms with each other and with their environment is known as

(A) biology

(B) zoology

(D) physiology 1

Ans: (C) ecology

8. Immigration of rural folks towards cities is due to

(A) good chances of employment

(B) wish for simple living

(D) joint family system 1

Ans: (A) good chances of employment

9. Interaction between two populations in an ecosystem in which both species are harmed to some extent is called

(A) amensalism

(B) predation

(D) commensalism 1

Ans: (C) competition

10. Grasslands found in South America are called

(A) Prairies

(B) Savanna

(D) Steppes 1

Ans: (C) Pampas

11. Absorption, storage and release of gases is one of the

(A) regulative functions of forests

(B) productive functions of forests

(D) chemical functions of forests 1

Ans: (A) regulative functions of forests

12. Blue-baby disease is caused due to

(A) increased levels of nitrate in groundwater

(B) exposure to increased amount of DDT

(D) exposure to tobacco smoke 1

Ans: (A) increased levels of nitrate in groundwater

13. Hazardous waste will not exhibit

(A) toxicity

(B) reactivity

(D) productivity 1

Ans: (D) productivity

OPTIONAL MODULE—8A (Water Resource Management )

14. The fraction of total water available on Earth as freshwater is about

(A) 97·3%

(B) 2·14%

(D) 0·5% 1

Ans: (C) 2·7%

15. Pits, aquifers, and trenches are structures used for

(A) distribution of groundwater

(B) storage of rainwater

(D) recharge of groundwater 1

Ans: (D) recharge of groundwater

16. Artificial recharge of groundwater in urban areas can be done by

(A) reduction in open soil surface area

(B) rooftop collection of rainwater

(D) more dependence on groundwater use 1

Ans: (B) rooftop collection of rainwater

OPTIONAL MODULE—8B ( Energy and Environment )

14. Wind turbine transforms wind energy into

(A) electrical energy

(B) hydropower energy

(D) potential energy 1

Ans: (A) electrical energy

15. Methanogenesis is a/an

(A) microbial process

(B) heating process

(D) evaporation process 1

Ans: (A) microbial process

16. Energy intensity is an indicator to show how

(A) Fast energy is used in the economy

(B) Slow energy is used in the economy

(D) Inefficiently energy is used in the economy 1

Ans: (C) Efficiently energy is used in the economy

CORE MODULE

OBJECTIVE QUESTIONS TYPE–II

17. (a) How does biodiversity represent a potential source of wealth?

(b) Mention any two causes of biodiversity loss. 1+1=2

Ans:

a) Biodiversity represents a potential source of wealth in the form of (a) new crops; (b) medicinal plants; (c) petroleum substitutes; (d) biocides and other products.

b) There are several causes for biodiversity loss:-

Hunting, poaching and commercial exploitation.
Elimination and disturbance of wildlife habitats.

18. Answer the following questions in one or two sentences (15–20 words): 1×6=6

(a) Name any two important aspects of Environmental Impact Assessment.

Ans: The important aspects of EIA are:

risk assessment,
environmental management and
post product monitoring.

(b) What is a village forest?

Ans: Reserved forests assigned to a village community are called village forests.

(c) How does crop rotation practice improve soil quality?

Ans: Crop rotation practice increases soil fertility by growing legumes as a rotational crop, decreases soil erosion, and controls pests and diseases.

(d) What is GAP? When was its first phase completed?

Ans: Ganga Action Plan (GAP) is an ambitious and first-of-its-kind river cleaning project. The first phase of the project was completed in 1993.

(e) How do CFCs damage ozone layer?

Ans: Chlorine contained in the CFCs, on reaching the ozone (O₃) layer, splits the ozone molecules to form oxygen (O₂). This creates an ozone hole.

(f) Which species of wildlife are found in the Kaziranga Sanctuary and Gir Forest in India?

Ans: Kaziranga – One-horned rhinoceros, Gir Forest- Lion

19. Answer the following questions in one word only: 1×6=6

(a) Which tool helps to evaluate environmental impact of proposed developmental projects?

(b) Which convention provides framework for international cooperation for conservation of wetland habitats?

(c) Which is the most dangerous outcome of population explosion?

(d) What is the genetic relationships between different groups of species known as?

(e) Name the trees that shed leaves in autumn and grow new foliage in spring.

(f) Which metal does battery scrap leave in the environment?

Ans:

a) Environmental Impact Assessment
b) Wetland Convention (Ramsar Convention)
c) Poverty
d) Taxonomic or phylogenetic diversity
e) Deciduous trees
f) Lead

20. Fill in the blanks with the words given below: 1×4=4

(pathogen, terrestrial, developer, energy)

(a) The three EIA participants are government, _____ and public.

(b) The capacity to do work is called _____.

(c) Tundra is an example of _____ ecosystem.

(d) Vector is carrier of _____.

Ans:

a) developer
b) energy
c) terrestrial
d) pathogen

21. Write the following statements as True or False: 1×3=3

(a) Land is one of the environmental components of EIA.

(b) It is sensible to irrigate plants and lawns in the afternoon.

(c) Mangroves are littoral forest ecosystems and are examples of ecotone.

Ans: a) True, b) False, c) True.

OPTIONAL MODULE—8A ( Water Resource Management )

22. What harm does arsenic cause if consumed with water contaminated with it? 1

Ans: Arsenic may cause several skin disorders or even cancer.

23. How can rainwater harvesting be effectively used for water conservation? 1

Ans: Rainwater harvesting, simply put, is putting water back into soil where it is stored in underground rivers and reservoirs so that it can be drawn when needed.

24. Mention two benefits of reuse of water. 1

Ans: Reuse of treated wastewater has the following benefits:

Make up for the shortage of water supply (reduces demand for good quality water)
Reduces the wastewater discharge, thus reducing water pollution.
Results in cost reduction.

OPTIONAL MODULE—8B ( Energy and Environment )

22. What is tidal energy? What is the main criterion for a tidal power generation site? 1

Ans: Tidal energy is derived from waves and tidal waves of oceans and seas. The main criteria for a tidal power generation site are that the mean tidal range must be greater than 5 metres.

23. Give two examples of liquid biofuels. 1

Ans: Ethanol and Methanol.

24. Give two ways by which energy can be conserved while cooking. 1

Ans:

Using a solar box cooker for cooking of food.
We should use “lids-on” cooking to prevent temperature overheating.
Begin cooking on the highest heat until the liquid begins to boil. Then lower the settings and allow the food to simmer until fully cooked.

CORE MODULE

SUBJECTIVE PART

25. Match the items in Column I with the options of Column II: 2

Column—I	Column—II
(a) The Air Act	(i) 1977
(b) The Environment Act	(ii) 1974
(c) The Water Act	(iii) 1981
(d) The Water Cess Act	(iv) 1986

Ans:

Column—I	Column—II
(a) The Air Act	(iii) 1981
(b) The Environment Act	(iv) 1986
(c) The Water Act	(ii) 1974
(d) The Water Cess Act	(i) 1977

26. What is IPM? What is its aim? 2

Ans: IPM stands for Integrated Pest Management. The aim of IPM is not to eradicate the pest population but to keep the crop damage to an economically tolerable level.

Write one benefit and one controversy on use of GM products.

Ans:

Benefit: Enhanced taste and quality.
Controversy: Potential human health impact: allergens, transfer of antibiotic resistance markers, and unknown effects.

27. Why is solar energy (power) promotion good for India? Which agencies encourage us to use solar energy system? 2

Ans: India is both densely populated and has high solar insolation, providing an ideal combination

for using solar power in India. Agencies that encourage us to use solar energy systems are the Ministry of New and Renewable Energy (MNRE) and the Indian Renewable Energy Development Agency (IREDA).

28. What are hotspots? What is the criterion for determining a hotspot? 2

Ans: Hotspots are regions that show the highest biodiversity, species richness, and endemic forms. Hot spots are the richest and most threatened reservoirs of plant and animal life on Earth. The criteria for determining a hot spot are:

i) The area should support >1500 endemic species,
ii) It must have lost over 70 % of its original habitat

29. List two factors that lead to rise in population in the world. 2

Ans: Any two

Improved agricultural practices have helped increase food production, making food more available.
Progress in medicine prevented deaths due to injury and epidemic diseases.
The average longevity of humans has increased since heart, lung and kidney disorders, as well as other diseases, can now be diagnosed and treated through modern medical technology.

30. How a habitat can be designed for cows? 2

Ans: A habitat for cows must have ample space, shelter from rain and sun, must be clean and hygienic, must have a proper waste management system, and accessibility to water and fodder.

31. Differentiate between rural and urban settlements on the basis of their

(a) occupation;

(b) social interactions. 2

Ans:

	Rural	Urban
Occupation	Agriculture- cultivators and their families are in the majority. Few in non-agricultural pursuits.	Mostly industrial workers, traders, professionals, and those working in offices. Mostly engaged administration. All non-agricultural occupations.
Social interactions	More durable and sincererelationships due to simplicity.	Numerous contacts and wide interactions. Casual, short-lived relations, formal and mostly superficial.

State two major problems emerging from use of modern technology in farming.

Ans:

Runoff from crop fields carries soil and chemicals, including pesticides and fertilizers, into water sources. This causes eutrophication and algal blooms. Eutrophication kills aquatic life, including fish, which are an important source of food for villages.
Excessive irrigation leads to waterlogging and salinization of the soil (excessive accumulation of salt in the soil, which in turn adversely affects fertility).

32. Define deforestation and write its two consequences. 2

Ans: Cutting of trees in forests is called deforestation. Consequences of deforestation are,

Soil erosion: Plants’ roots hold the soil in place. With loss of protective cover of plants, the topsoil, which is rich in organic matter, is washed away, and the soil loses its fertility..
Landslides: Removal of trees from forests leads to soil erosion. Ultimately cause landslides in hilly areas. This is because the roots of trees hold the soil in position.
Silting: The loss of trees from forests also causes silting of rivers and lakes as loose soil gets washed with rainwater and reaches water bodies.
Loss of wild habitat: Wild animals live in forests. Cutting forests means loss of their habitat, which in turn renders them endangered or even extinct.

Define desertification and mention two human activities that accelerate desertification.

Ans: Desertification can be defined as ‘the diminution or destruction of the biological potential of the land which can ultimately lead to desert-like conditions’.

Most of the deserts of recent origin have resulted from one or more of the following human activities.

(i) Uncontrolled and overexploitation of grazing land, indiscriminate cutting of trees and forest resources leading to drought, soil erosion, and deterioration of soil fertility, which results in stunted plant growth.
(ii) Excessive mining in arid and semi-arid regions for the extraction of minerals, coal or limestone, resulting in loss of trees and green cover, and leading to destruction of conditions conducive to vegetation growing.
(iii) Uneconomic land use for agriculture by cultivation on marginal lands affecting adjacent fertile lands and causing soil erosion.
(iv) Intensive and uneconomic exploitation of water resources leading to a fall in the water table, seepage and problems of excessive salinization of soil.

33. What is a biosphere reserve? What are its various zones? Explain diagrammatically. 4

Ans: Biosphere Reserves are representative parts of natural and cultural landscapes extending over large areas

areas of terrestrial or coastal/marine ecosystems which are internationally recognized within UNESCO’s Man and the Biosphere Programme.

A Biosphere Reserve consists of core, buffer and transition zones.

(a) The core zone is fully protected and a natural area of the Biosphere Reserve, least disturbed by human activities. It is a legally protected ecosystem in which entry is not allowed except with permission for some special purpose. Destructive sampling for scientific investigations is prohibited.
(b) The buffer zone surrounds the core zone and is managed to accommodate a greater variety of resource use strategies and research and educational activities.
(c) The transition zone, the outermost part of the Biosphere Reserve, is an area of active cooperation between the reserve management and the local people, wherein activities like settlements, cropping, forestry, recreation and other economic activities are in harmony with the conservation goals.

Explain any two techniques of ex-situ conservation of plant species of biodiversity.

Ans:

Gene Banks: Ex-situ collection and preservation of genetic resources is done through gene banks and seed banks. The National Bureau of Plant Genetic Resources (NBPGR), New Delhi, preserves seeds of wild relatives of crop plants as well as cultivated varieties; the National Bureau of Animal Genetic Resources at Karnal, Haryana, maintains the genetic material for domesticated animals, and the National Bureau of Fish Genetic Resources, Lucknow, for fish.
Cryopreservation (“freeze preservation”) is particularly useful for conserving vegetatively propagated crops. Cryopreservation is the storage of material at ultra-low temperature of liquid nitrogen (-1960C) and essentially involves suspension of all metabolic processes and activities. Cryopreservation has been successfully applied to meristems, zygotic and somatic embryos, pollen, protoplast cells and suspension cultures of several plant species.

34. What is meant by demography? If N is the total number of individuals in the population, then define birthrate, death rate, and growth rate of the population. Also, give expressions for each one of them for their determination. 4

Ans: The study of various aspects of a population is called demography.

Birth rate: The Rate at which births occur in a population

If B = number of births per unit time in the total population N

Birth rate b = B/N

Death rate: The Rate at which deaths occur in the population

N = Total number of individuals in the population

D = Total number of deaths per unit time in the population ‘N.’

Death rate d = D/N

Growth rate: The growth rate (g) is the result of the number of births minus the number of deaths per unit time divided by the total number of individuals in the population.

B = total number of births per unit time.

D = total number of deaths per unit time

G = the difference between the total births and the deaths of the individuals

per unit time.

N = The total number of individuals in the population.

g = growth rate for that per unit time

g = (B-D)/N

g = G/N

35. Define an ecosystem. Taking example of a pond as an ecosystem, explain its various components. 5

Ans: An ecosystem is a functional unit of nature encompassing complex interactions between its biotic (living) and abiotic (non-living) components. For example, a pond is a good example of an ecosystem.

(a) Abiotic components

(i) Light: Based on the extent of penetration of light, a pond can be divided into euphotic (eu=true,photic=light), mesophotic and aphotic zones. Plenty of light is available to plants and animals in the euphotic zone. No light is available in the aphotic zone.
(ii) Inorganic substances: These are water, carbon, nitrogen, phosphorus, calcium and a few other elements like sulphur, depending on the location of the pond. The inorganic substances like O₂and CO₂ are in a dissolved state in water. Other inorganic salts are held in reserve in the bottom sediment and inside the living organisms. A very small fraction may be in the dissolved state.
(iii) Organic compounds: The commonly found organic matter in the pond is amino acids and humic acids, and the breakdown products of dead animals and plants. They are partly dissolved in water and partly suspended in water.

(b) Biotic components

(i) Producers or autotrophs: synthesize food for all the heterotrophs of the pond. They can be categorized into two groups:-
- (a) Floating microorganisms (green) and plants are called phytoplankton (“phyto”- plants, “plankton” –floating). They are microscopic organisms. Sometimes they are so abundant in the pond that they make it look green in colour, e.g. Spirogyra, Ulothrix, Cladophora, Diatoms, and Volvox.
- (b) Rooted plants: These are arranged in concentric zones from the periphery to the deeper layers. Three distinct zones of aquatic plants can be seen with increasing depth of water in the following order:
  - i) Zone of emergent vegetation: . eg, Typha, Bulrushes and Sagittaria
  - ii) Zone of rooted vegetation with floating leaves. eg. Nymphaea
  - iii) Zone of submergent vegetation: e.g., all pond weeds like Hydrilla, Rupia, musk grass, etc.
(ii) Consumers/Heterotrophs are animals which feed directly or indirectly on autotrophs eg. Tadpole, snails, sunfish, bass, etc. Pond animals can be classified into the following groups
- (a) Zooplanktons are floating animals. Cyclops, Cypris
- (b) Nektons are the animals that can swim and navigate at will. Eg. fishes
- (c) Benthic animals are the bottom dwellers: beetles, mites, mollusks and some crustaceans.
(iii) Decomposers: They are distributed throughout the entire pond, but in the sediment most abundant. There are bacteria and fungi. (Rhizopus, Penicillium, Curvularia, Cladosporium) are found at the bottom of the pond.

36. What is meant by air pollution? Name various particulates and gaseous air pollutants, their sources and harmful effects. How can air pollution be prevented and controlled? Give four measures. 5

Ans: Air pollution may be defined as the presence of any solid, liquid or gaseous substance, including noise and radiation, in the atmosphere in such concentration that may be directly and indirectly injurious to humans or other living organisms, plants, property or interferes with the normal environmental processes.

Air pollutants are of two types

(1) suspended particulate matter such as fly ash from smoke released from chimneys, suspended particulate in the smoke from domestic, industrial and vehicular soot
(2) gaseous pollutants like carbon dioxide CO₂ from automobile exhaust, nitrogen oxides (NO_x) from automobile exhaust, and atmospheric reactions.

Air Pollution Prevention

Use of wood and dung cakes should be replaced by cleaner fuels such as biogas, kerosene or electricity.
Kerosene is also limited.
Improved stoves for looking like smokeless chullahs have high thermal efficiency and reduced emission of pollutants, including smoke.
Use of cleaner fuels such as liquefied natural gas (LNG) in power plants, fertilizer plants, etc., which is cheaper in addition to being environmentally friendly.
Employing environmentally friendly industrial processes so that the emission of pollutants and hazardous waste is minimized.
Closing industries which pollute the environment.
Development and maintenance of a green belt of adequate width.

Explain the following terms: 1×5=5

(a) Ozone hole

(b) Greenhouse effect

(c) Radiation

(d) Thermal pollution

(e) Soil pollution

Ans:

(a) Ozone hole: Chlorine contained in the CFCs, on reaching the ozone (O3) layer, splits the ozone molecules to form oxygen (O2). This creates an ozone hole.
(b) Greenhouse effect: Atmospheric gases like carbon dioxide, methane, nitrous oxide, water vapour, and chlorofluorocarbons are capable of trapping the outgoing infrared radiation from the earth. Infra-red radiations trapped by the Earth’s surface cannot pass through these gases and increase thermal energy or heat in the atmosphere. Thus, the temperature of the global atmosphere has increased. As this phenomenon of increase in temperature is observed in greenhouses, in the botanical gardens, these gases are known as greenhouse gases, and the heating effect is known as green house effect.
(c) Radiation: Radiation is a form of energy travelling through space.
(d) Thermal pollution: Discharge of hot water from power and nuclear plants increases the temperature of the water in the rivers and oceans by 10 to 15 °C above the ambient water temperature, which is called thermal pollution.
(e) Soil pollution: Addition of substances which adversely affect the quality of soil or its fertility is known as soil pollution.

OPTIONAL MODULE—8A ( Water Resource Management )

37. Explain the following terms: 1×2=2

(a) Pathogenic pollution

(b) Eutrophication

Ans:

a) A major portion of the wastewater generated from human settlements is not properly transported and treated before discharging into natural waters. This results in contamination of both surface and ground waters, leading to the spread of pathogens. This is called pathogenic pollution.
b) The discharge of domestic wastewater, agricultural return water or run-off water and many industrial effluents contribute nutrients like phosphates and nitrates. These nutrients promote excess growth of algae in water bodies (algal blooms). This is called eutrophication.

38. How will you perform the water audit of your home? 2

Ans: Water audit at home involves checking for

Leaks and drips.
Toilets and urinals that do not have a water-saving device installed.
Garden hoses that are left on during the day.
Taps that are left on while teeth are brushed or dishes, etc., are washed.

List any four reasons for the growing water shortage throughout the world.

Ans: Throughout the world, the shortage of water is growing due to increasing:

Droughts,
Irrigation demand,
Industrial demand,
Pollution, reducing the usability of water resources, and
Wastage and irresponsible attitude towards water.

39. Give an example of a community-level effort to overcome water scarcity. 2

Ans: A noteworthy example of students’ participation in such an endeavour took place in 1955-98 at Bhavnagar University under the guidance of the then Vice Chancellor of the university, Prof. Vidyut Joshi. The coastal city of Bhavnagar was facing a severe drinking water shortage. Prof. Joshi initiated the digging of a percolation tank in the university premises. About 650 students, 245 teachers and other employees of the university worked as voluntary labour. During the following monsoon, all the bore wells in the university as well as those in the adjoining areas, were recharged.

What can an individual do to conserve water? Mention any four ways.

Ans: We can follow some of the simple things listed below for water conservation:

Use only the amount you actually need.
Do not leave the tap running while you are brushing your teeth or soaping you is your face.
Avoid flushing the toilet unnecessarily.
Put a brick or any other device that occupies space to cut down on the amount of water needed for each flush.
When washing the car, use water from a bucket and not a hosepipe.

OPTIONAL MODULE—8B ( Energy and Environment )

37. Differentiate between renewable and non-renewable energy sources along with examples. 2

Ans:

Renewable energy is the term used to describe energy that comes from sources whose supplies are regenerative and virtually inexhaustible. Renewable energy sources can be replenished in a short period of time. Some of the important renewable sources of energy are solar energy, wind energy, hydropower, etc.
Non-renewable energy resources have a limited amount of stock available. The regeneration rate of non-renewable energy resources is negligible when compared with the rate of consumption. That is, non-renewable energy that we are using up cannot be recreated in a short period of time or at least, in our lifetime. Fossil fuels (coal, lignite, peat) are found under the ground and below the sea floor (petroleum, etc.) in liquid and gaseous form.

38. Mention any two environmental impacts of geothermal energy. 2

Ans: Geothermal energy can pose several environmental problems, including on-site noise,

emissions of gas and disturbance at drilling sites, disposal sites, roads and pipelines, and power plants during its development.

Diagrammatically explain the working of hydrogen fuel cell.

Ans:

39. Mention any two ways for energy conservation at community level for housing complexes. 2

Ans:

All unnecessary lights should be turned off, especially when conference rooms, etc., are not in use.
Energy use should be minimized during peak demand hours.
Set computers, monitors, photocopiers and other business equipment to their energy-saving mode. Turn them off during long idle hours, such as lunch breaks.
Skylights should be used for warehouses.
Ensure that offices with air conditioning have proper windows and all doors are closed when the air conditioner is in use.

Mention four technologies or equipment that were used during construction of Auroville Visitors Centre in Pondicherry that led it to win Hassan Fathy International Award in 1992.

Ans: The following technologies and equipment were used during its construction.