Gujarat Board GSEB Solutions Class 8 Social Science Chapter 7 Environmental Changes Textbook Exercise Important Questions and Answers, Notes Pdf.

Gujarat Board Textbook Solutions Class 8 Social Science Chapter 7 Environmental Changes

GSEB Class 8 Social Science Environmental Changes Textbook Questions and Answers

Answer the following questions:

Question 1.
What is climate ?
Answer:
The average condition of rain, temperature, and moisture for over 35 years in a region is called ‘Climate’.

Question 2.
What do you mean by ‘Greenhouse Effect’ ?
Answer:
Countries with cold climate receive less heat from the sun. This hampers growth of plants and vegetables. Thus, arrangements are made to conserve heat by having a roof of glass or cloth to allow sunrays to reach inside and sustain heat which is created due to production of carbon dioxide and water vapour. This is known as ‘Greenhouse Effect’ and this type of farming is called ‘Greenhouse Farming’.

Question 3.
What is global warming ?
Answer:
Global warming means unequal and continual rise in average temperature in Earth’s climate due to greenhouse effect. Certain gases trap infrared rays (UV radiation) so that the temperature of earth increases. The planet becomes warmer. This effect is known as ‘Global Warming’.

Question 4.
List down the possible adverse effects of global warming.
OR
Write a short note on: Discuss the adverse effects of climate change.
Answer:
Adverse effects of global warming / climate changes are :

• Changes in growth and development of vegetation.
• Some birds like sparrows and vultures are disappearing from Earth.
• Nearly 2000 glaciers of Himalayas have receded / melted.
• Frequency of natural calamities like drought, excessive rainfall and cyclones has increased since last 10 years.
• Places of heavy rainfall receive less rains anqfc those of scanty rainfall receive heavy rains.
• Production of pulses has decreased and so has ground water level.
• Melting of glaciers has increased ocean water level causing extensive erosion along the coastline. Also areas near the coast of Maldives, Bangladesh, Australia, etc. have been submerged.
• Dehydration and malnutrition occurs in humans due to increase in temperature.
• The season cycle is changing.
• Salinity of soil in Gujarat is increasing.
• Agriculture produce has declined sharply.
• Frequency of diseases like cholera, dengue, malaria, swine flu, etc. has increased.
• Flowers are losing their fragrance and beehives are fast disappearing.
• The ‘Greenpeace’ institution predicts that about 55 lakh people living in Gujarat will have to migrate in 2100 C.E.

Question 5.
List down the home appliances of daily use that add to global warming.
Answer:
Home appliances of daily use that add to global “warming are televisions, air conditioners, tubelights, bulbs, computers, laptops, refrigerators, geysers, heaters, all types of vehicles like cars, buses, scooters, etc., all kinds of phones, electric motors, pumps, etc.

Question 6.
Which country hosted the last world convention to protect the environment?
Answer:
The country that hosted the last world convention to protect the environment was held at Copenhagen, Denmark, in December, 2009.

Fill in the blanks with proper words or numbers:

1. Increase in the proportion of the ……………….. gas has led to an increase in the global temperature.
Answer:
carbon dioxide

2. CFC gas is released in maximum due to the use of ………………. appliances.
Answer:
electronic

3. There has been an increase of ……………….. °C in the temperature of the Earth in the last 100 years.
Answer:
0.6

4. It is necessary to make ……………….. use of resources to check the increase in global temperature.
Answer:
judicious

Write Short note on

Question 1.
What steps should be taken to prevent global warming ?
OR
Write a short note on: Necessary steps to prevent global warming
Answer:
Steps to be taken to prevent global warming:

1. Reduce the use of sources which release CO₂.
2. Afforestation and conservation of forests.
3. Growing plants and trees around your house to reduce carbon dioxide.
4. Avoid using plastic.
5. Optimum and judicious use of manure, pesticides, household appliances, natural resources, petroleum products, electricity, means of transport and water.
6. Control population.
7. Add biotics in food for animals.
8. Adopt organic farming by using green or cattle manure.
9. Increase the use of eco-friendly paper, CNG and non-conventional sources of energy.
10. Practice rainwater harvesting.

Question 2.
Discuss the adverse effects of climate change.
Answer:
Adverse effects of global warming / climate changes are :

• Changes in growth and development of vegetation.
• Some birds like sparrows and vultures are disappearing from Earth.
• Nearly 2000 glaciers of Himalayas have receded / melted.
• Frequency of natural calamities like drought, excessive rainfall and cyclones has increased since last 10 years.
• Places of heavy rainfall receive less rains anqfc those of scanty rainfall receive heavy rains.
• Production of pulses has decreased and so has ground water level.
• Melting of glaciers has increased ocean water level causing extensive erosion along the coastline. Also areas near the coast of Maldives, Bangladesh, Australia, etc. have been submerged.
• Dehydration and malnutrition occurs in humans due to increase in temperature.
• The season cycle is changing.
• Salinity of soil in Gujarat is increasing. .
• Agriculture produce has declined sharply.
• Frequency of diseases like cholera, dengue, malaria, swine flu, etc. has increased.
• Flowers are losing their fragrance and beehives are fast disappearing.
• The ‘Greenpeace’ institution predicts that about 55 lakh people living in Gujarat will have to migrate in 2100 C.E.

Activities
(1) Organise a ‘Tree Plantation Programme’ in your school premises as a part of the celebration of ‘WORLD OZONE DAY’ (16th September).
(2) Visit the ‘Gir Foundation’ Institute, an environment- oriented institute at Gandhinagar and gather some information about it.
(3) Arrange a group discussion or elocution competition or an essay competition or a debate on ‘Remedies to Reduce Environmental Pollution’.

GSEB Class 8 Social Science Environmental Changes Intext Questions and Answers

Question 1.
Why are the doors and windows made of glass – in countries that have cold climate?
Answer:
Due to glass windows, solar heat which enters the house is retained inside the house. The house gets natural light during the day. Thus windows and doors of houses in cold regions are made of glass.

Question 2.
We know that a definite quantity of sugar or salt has to be added in tea or vegetables. What would happen if we add more sugar or salt? In the same way, there is a balance of proportion of gases in the atmosphere. Imagine what would happen to this balance if the proportion of carbon dioxide increases in the atmosphere?
Answer:
If the proportion of carbon dioxide increases in the atmosphere, the average temperature of the earth will rise. Carbon dioxide enhances the greenhouse effects. If that increases, climatic changes will become more acute.

Question 3.
What kind of residence should we have to protect ourselves from the effect of increase in temperature ?
Answer:
To protect ourselves from the effect of increase in temperature :

• The doors, windows and roof of our house should be constructed in such a way that they will allow enough sunlight and air into the house.
• The roof should have a slope and the roof tiles should be so arranged that the roof does not get heated.
• A chimney should be installed in the kitchen so that the smoke arising from cooking goes directly out of the house.

GSEB Class 8 Social Science Environmental Changes Additional Important Questions and Answers

Choose the correct alternative from those given below each question:
1.
Question 1.
Which of the following countries experiences maximum temperature ?
A. Iran
B. Brazil
C. Philippines
D. Saudi Arabia
Answer:
D. Saudi Arabia

Question 2.
Which of the following countries experiences maximum cold ?
A. Norway
B. Russia
C. Iran
D. Brazil
Answer:
A. Norway

Question 3.
Which of the following countries gets maximum rainfall ?
A. Russia
B. Brazil
C. Philippines
D. Iran
Answer:
C. Philippines

Question 4.
Which gas is most effective as a greenhouse gas ?
A. Hydrogen
B. Oxygen
C. Nitrogen
D. Carbon dioxide
Answer:
D. Carbon dioxide

Question 5.
Which of the following gases is known as a green house gas ?
A. Oxygen
B. Hydrogen
C. Methane
D. Nitrogen
Answer:
C. Methane

Question 6.
How many tonnes of methane is produced by paddy cultivation ?
A. 15 crore
B. 12 crore
C. 7 crore
D. 21 crore
Answer:
A. 15 crore

Question 7.
How many tonnes of methane gas is produced by decomposition of bio-degradable waste ?
A. 7 crore
B. 2 crore
C. 9 crore
D. 11 crore
Answer:
A. 7 crore

Question 8.
How many tonnes of methane is produced due to exhaling and metabolism of animals ?
A. 15 crore
B. 7 crore
C. 18 crore
D. 14 crore
Answer:
D. 14 crore

Question 9.
When is ‘Ozone Day’ celebrated in the world ?
A. 28th October
B. 16th September
C. 1st January
D. 5th June
Answer:
B. 16th September

Question 10.
In which city was the global meet to save environment held in 1972?
A. At Rio de Janeiro in Brazil
B. In Stockholm, the capital of Sweden
C. In Copenhagen, the capital of Denmark
D. In Delhi, the capital of India
Answer:
B. In Stockholm, the capital of Sweden

2.
Question 11.
In which city was the conference to save the environment held after 1972 ?
A. At New York in USA
B. At London in England
C. At Kolkata in India
D. At Rio de Janeiro in Brazil
Answer:
D. At Rio de Janeiro in Brazil

Question 12.
In which city was the global meet to protect environment held in December, 2009 ?
A. At Tokyo in Japan
B. At Sydney in Australia
C. In Copenhagen, the capital of Denmark
D. In Rome, the capital of Italy
Answer:
C. In Copenhagen, the capital of Denmark

Question 13.
How many metric tonnes of carbon dioxide does an average person in the world produce ?
A. 4.5
B. 20.6
C. 1.2
D. 8.5
Answer:
A. 4.5

Question 14.
How many metric tonnes of carbon dioxide does an average Indian citizen produce ?
A. 20.6
B. 4.5
C. 3.8
D. 1.2
Answer:
D. 1.2

Question 15.
How many metric tonnes of carbon dioxide does an average citizen of USA produce ?
A. 4.5
B. 20.6
C. 1.2
D. 10.6
Answer:
B. 20.6

Fill in the blanks with proper words or numbers:

1. The sphere which envelops the world from all sides is known as …………….. .
Answer:
atmosphere

2. In countries that have cold climates walls and windows are made of ……………… .
Answer:
glass

3. Proportion of nitrous oxide has increased from 270 PPM to ……………. PPM.
Answer:
319

4. According to the U.N. Resolution, 16th September – is celebrated as ……………… day.
Answer:
ozone

State whether the following statements are true or false:

1. Our environment is polluted due to smoke from industries, factories, power stations and auto vehicles.
Answer:
True

2. The average condition of temperature, moisture and rain for a period of over 35 years is called ‘weather’.
Answer:
False

3. Problem of climate change has emerged due to reduction in greenhouse gases.
Answer:
False

4. The proportion of CO₂ which was 275 PPM 100 years ago has increased to 350 PPM at present.Answer:
True

5. The proportion of nitrous oxide which was 270 PPM before, is now 470 PPM.
Answer:
False

6. Beehives are disappearing fast due to global warming.
Answer:
True

Answer the following questions in one or two sentences:

Question 1.
What is atmosphere ? OR What is meant by atmosphere ?
Answer:
The air that envelops Earth from all sides is called ‘atmosphere’.

Question 2.
How is atmosphere polluted ?
Answer:
Atmosphere is polluted by smoke from industries, factories, power stations, vehicles, domestic fuel, etc.

Question 3.
What is environmental change ?
Answer:
Changes occuring in temperature, wind direction, rainfall, etc. due to global warming are known as ‘Environmental Changes’.

Question 4.
What is weather ?
Answer:
The condition of temperature, humidity and rainfall in a region at a particular point of time is called ‘Weather’.

Question 5.
How did the problem of climatic change emerge ?
Answer:
Carbon dioxide, methane, nitrous oxide, chlorofluorocarbon (CFC), halo carbon, etc. are known as greenhouse gases. These gases retain heat. Increase in their proportion leads to problems of global warming and climatic changes.

Question 6.
What is the proportion of nitrous oxide in the atmosphere ?
Answer:
The proportion of nitrous oxide in the atmosphere is 319 PPM (parts per million).

Question 7.
What increases the proportion of chlorofluoro¬carbon (CFC) in the atmosphere?
Answer:
Due to increased use of foam, plastic, fridge, A.C. circuit, aerosol spray, etc. the level of chlorofluorocarbon (CFC) has increased in the atmosphere.

Question 8.
Which are non-conventional sources of energy?
Answer:
Solar energy, wind energy, tidal energy, geothermal energy, biogas, etc. are non-conventional sources of energy.

Question 9.
When and where was the first global convention to think of ways to protect environment held?
Answer:
Conferences were held first at Stockholm, the capital of Sweden in 1972, and then at Rio de Janeiro of Brazil to think of ways to protect environment.

Question 10.
What was decided at the world meeting at Copenhagen in December, 2009 ?
Answer:
In a meeting held at Copenhagen, the capital of Denmark, in 2009 it was observed that developed nations had not accepted ‘carbon cut’ (technique to reduce emission of greenhouse gases). It was decided in this conference that the developed countries like USA should adopt the ‘Carbon Cut’ policy seriously as every US citizen produces 20.6 metric tonnes of greenhouse gases, and the developing countries like India should be given permission to release more carbon for their progress as every Indian releases 1.2 metric tonnes of greenhouse gases. Developing countries should be given an aid to the tune of about 100 billion dollars.

Box Questions and Answers
Find out the places that experience extreme rain, heat, cold and extreme climatic conditions with the help of the given table. Also find out the reasons for the same:

Answer:
Reasons for the climatic conditions of each country are as follows :
(1) Russia: Russia lies in northern temperate and frigid zones. So the average maximum temperature remains around 15 °C and the minimum temperature is around – 20 °C. In Steppes and in interior regions, there is scanty rainfall. During winter, most of the country experiences snowfall.

(2) Iran : Iran is located to the north of Tropic of Cancer and in the western part of Asia. Most of the country is a desert, so the climate is continental. Average maximum temperature is about 30 °C and the average minimum temperature is about 10 °C. Due to insufficient humidity, Iran gets about 50 cm of rainfall.

(3) Brazil: It lies between the Equator and the Tropic of Cancer. So the average maximum temperature is – 38 °C and the minimum is 25 °C. Permanent winds blow over this region. There are forests and so the country gets about 250 cm of rainfall.

(4) Norway: It lies between the northern temperate zone and the frigid zone. Average maximum temperature here is 10 °C and the minimum is -40°C. The region gets about 50 cm of rainfall mainly due to the warm current of North Atlantic ocean. Snowfall occurs during winter.

(5) Philippines : There are many islands in this country, and it is located between 10° to 20° latitudes north of equator. Due to marine climate, the temperature remains around 30 °C to 35 °C. Humid trade winds blow from the sea over this region, so the region gets about 300 cm of rainfall.

(6) Saudi Arabia: The country is located between 15° north to 30° north latitudes. The Tropic of Cancer passes through the centre of this country. Most of the country is a desert. So the average maximum temperature is around 45 °C and the minimum is about 29 °C. By the time they reach here, the moisture bearing winds become almost dry, hence the region gets hardly 10 cm of rainfall.

Answer the following questions:
Question 1.
State the reasons for increase in the amount of methane gas (CH₄) in the atmosphere. How much methane is added due to each reason?
Answer:
Major reasons for increase in the amount of methane (CH₄) are :

Question 2.
See the map of India given on page no. 37 of the textbook. Think and write about the weather at different places in India.

Answer:
It can be seen from the map that winter season prevails over India. It is very cold in North India, while eastern and western India have mild cold and south India experiences the least cold. Maximum temperature of 39 °C is recorded at Hyderabad and minimum temperature of 17°C is recorded at Dibrugarh. Overall the sky is clear except in some parts of northern mountainous regions and West Bengal and Odisha where the sky is totally covered by clouds. Rain is likely to occur in these regions, while there may be rain or snow in the Himalayan region.