Class-8 General Science Notes (By Gaba Books)- Unit-6 -The living environment - SLO-Based Short and Brief Questions and Answers

Class-8 General Science Notes (By Gaba Books)
Unit-6 -The living environment
SLO-Based Short and Brief Questions and Answers

Q1. What is an environment?

Ans.

The interaction between living organisms and their surroundings (both living and non-living things) is called environment.

Q2. What is a biosphere?

Ans.

The part of the earth where living things exist is called the biosphere.

Q3. What is a habitat?

Ans.

The environment of a living organism in which it lives is called its habitat.

Q4. What is a population?

Ans.

The total number of living organisms of the same kind, living together at a place or habitat is called a population.

Q5. What is a community?

Ans.

Different populations or species living together and interacting with one another form a community.

Q6. What is a member of a species called? give examples.

Ans.

The living organisms that have maximum common features and can breed with each other to produce fertile offspring are called members of a species. For example cats, pigeons, rose plants etc, are different species.

Q7. Write the factors that increase or decrease the population of an area.

Ans.

The major factors that increase or decrease the population of an area are listed as follows:

a. Migration from villages to cities

If people from outside come to settle in an area, the population increases in that area, and this is called migration. While, if some individuals move out of an area results in a decrease in the population of that area and this is called exodus.

For example, due to greater job opportunities and better education and health facilities, many people from villages migrate to cities. Because of this practice, the population of cities increases, and population of villages decreases.

b. Difference between birth rate and death rate

If the death rate is lower than the birth rate, the population shows an increase, but if the death rate is higher than the birth rate, the population decreases. The growth rate tells us how fast a population is increasing.

c. Climatic conditions

Climatic conditions also play an important role in changing population balance. Natural climates like annually cold or hot weather, drought, excessive rains, floods, and earthquakes have adverse effects on populations of an environment.

d. Diseases, famine and wars

Outbreaks of epidemics such as plague, typhoid, cholera, malaria, and smallpox have had disastrous effects on the human population. For example, the spread of bubonic plague in the middle of the 14th century killed about 25% of the population in Central Europe and Asia. Due to this disease, the population of England was reduced to half between 1379 and 1384.

Contrary to this situation, if better health, hygiene, and sanitation facilities are available, the death rate (especially in children) sharply declines and there is an increase in population.

Famines and wars can also claim many lives in a short time period.

Q8. What is the growth rate?

Ans.

The difference between birth rate (number of births per thousand population) and death rate (number of deaths per thousand) is called the growth rate.

Q9. In Pakistan during 1998, the birth rate was 35 per thousand and the death rate was 9 per thousand. Calculate the growth rate in Pakistan in 1998.

Ans.

As we know that

Q10. Why the determination of the growth rate for a place is important?

Ans.

Determination of the population growth rate is helpful to scientists, town planner and the people who plan for the future needs of the population.

Q11. What is overpopulation?

Ans.

The condition in which the population exceeds the limit, and the resources become insufficient, causes upset in the balance between population and resources, such a condition is called overpopulation.

Q12. What is the current population of the world? What predictions has made about world population increase in the future by the United Nations Department of Economic and Social Affairs?

Ans.

The current population of the world is 7.3 billion.

United Nations Department of Economic and Social Affairs expected to reach world population 8.7 billion by 2030, 9.7 billion in 2050 and 11.2 billion in 2100.

Q13. What will be the effects of over-population on the environment?

Ans.

More space is needed to accommodate large numbers of people.
As land is cleared for housing and agriculture and is taken up by humans, there is less land available for other organisms.
Population growth places a greater demand on resources such as minerals, fuels, and food.
Over-population causes destruction of habitats and loss of biodiversity.
Pollution and human health problems are directly related to overpopulation.

Q14. Write some names of the human activities that are disturbing the environment.

Ans.

The imbalance in nature is mainly caused by human activities. These include:

Excessive use of energy resources,
Over-exploitation of resources (Resource depletion)
Industrialization
Urbanization
Mechanized farming,
Deforestation
Depletion of the ozone layer

Q15. Briefly describe the role of humans in disturbing the environment.

Ans.

The actions of human beings that are responsible for disturbing the environment are:

(i) Excessive use of energy resources:

A lot of energy that could do useful work is wasted by man which is called misuse of energy and resources. For instance, instead of using public transport, personal motorcycles and cars are used which consume a lot of fuel. Similarly, household appliances like irons, fans, bulbs, tube lights, air conditioners etc. are left running even when no one is using them.

(ii) Resource depletion

Our Industrial society is highly dependent on the use of non- renewable natural resources like oil, coal, minerals, trees and animals are natural resources. So, these resources may get depleted soon.

(iii) Industrialization

In industries, energy is obtained from fossil fuels to run machines in the factories. In addition to fossil fuels, many chemicals are also used. Smoke, polluted water, wastes, and other effluents from factories are major sources of environmental degradation.

(iv) Urbanization.

Enlarging city population is the root cause of many environmental problems. Some of them are given below:

The increasing number of vehicles on roads pollutes the atmosphere with dust and the smoke emitted by them.
Many people are forced to live in slums and this situation is causing many social problems.
Useful agricultural land is used for residential purposes.
Domestic and Industrial wastes cause pollution of air, water bodies, and land.
Outbreak of epidemics and diseases is more likely in congested and over-crowd localities with poor civic and hygiene facilities.

(v) Mechanized farming:

Mechanized farming makes use of machines, for example, tractors, harvesters, and tube wells. Fertilizers and pesticides increase the production of crops and food but at the same time, they cause environmental problems for example land pollution.

(vi) Deforestation,

Deforestation has many adverse effects on the environment. Some important effects are given below:

As a result of deforestation, habitats of wildlife and plants are destroyed. Therefore, wildlife extinction risk is increased.

Deforestation is one of the causes of changes in weather and climate.

Fertile soil is lost through soil erosion.

(vii) Greenhouse effect and global warming

Due to industrialization, the proportion of some gases in air, such as carbon dioxide. chlorofluorocarbons (CFCs) and methane (CHA) has increased. Presence of these gases in air in higher proportion has produced the green house effect. Due to the green house effect, temperature of the earth is rising. This is called global warming.

(viii) Depletion of ozone layer,

Certain chemical substances, called chlorofluorocarbons, are released from refrigerators, air conditioners, and cans of spray. These chemicals react with ozone and cause thinning and destruction of the ozone layer. Consequently, ultraviolet rays can reach the earth. These rays may cause skin cancer, eye disease, etc. in human beings. These rays are also harmful to animals and plants.

Q16. Describe briefly the importance of a forest.

Ans.

Forests are playing a very important role in our daily life. They are our great wealth. Forests are important to us in many ways. Some of them are given below:

Forests bring healthy changes in the climate of an area. They stop storms and bring rains. Rain is necessary for us because it refills water reservoirs.
Forests are the source of many useful materials such as timber, firewood, resins, gums and herbal products for medicines.
They prevent soil erosion.
They provide habitat to a wide variety of wildlife.

Q17. What is greenhouse and greenhouse effect?

Ans.

The greenhouse is a room made of glass or nylon nets. These houses are used to grow plants in them. They trap the sun's beams and prevent their heat waves from going out. This results in an increase in the temperature of the greenhouse. This phenomenon is called the greenhouse effect.

Q18. How the Ozone layer is important to us?

Ans.

Ozone is a gas which is present in the form of an envelope around the earth in the upper atmosphere. This layer prevents ultra-violet radiations from the sun from reaching the earth. These rays may cause skin cancer, eye disease, etc. in human beings. These rays are also harmful to animals and plants.

Q19. What are the causes of environmental degradation?

Ans.

The unsustainable use of natural resources such as air, water and soil is environmental degradation which can lead to the destruction of the ecosystem and natural habitat, and extinction of species and pollution.

The basic cause of environmental degradation is humans and their activities. To get better facilities for life, humans make excessive and unnecessary use of natural resources. We are polluting our atmosphere

with smoke and poisonous gases (oxides of sulphur, carbon and nitrogen) emitted by vehicles.

Domestic wastes and industrial effluents are thrown into streams, rivers, and other water bodies without being treated. This renders water of these water bodies unfit for human use. The life of aquatic animals and plants is also threatened. Fertilizers and agricultural chemicals are washed away into the water bodies. Forests are being cleared for obtaining timber, firewood, and space. Thus, unwise and excessive utilization of resources is the major cause of environmental degradation.

Q20. What steps should we take to prevent environmental degradation?

Ans.

There are some important suggestions for the conservation of our environment and resources which are given below:

Do not throw used and waste materials here and there. Dispose them off properly.
Do not throw industrial and domestic refuse into the air, land, and water without treatment. This may be done voluntarily by people and organizations. The government must also make laws and enforce them effectively.
Use green or pollutant-free fuels in transport.
Minimize resource utilization. Improved technologies can reduce resource use and, thus, pollution.
Conserve resources. Switch off lights, fans, and air conditioners when no one is using them. Close water taps when not needed.
Recycle plastic, glass, paper articles, etc.
Prefer public transport over personal vehicles.
Prevent the practice of cutting trees and plan to plant maximum trees whenever it possible.

Exercise Q/A.

A. Answer these questions:

1. What do you understand by population and community?

Ans.

Population:

The total number of living organisms of the same kind, living together at a place or habitat is called a population.

Community:

Different populations or species living together and interacting with one another form a community.

2. How increase in population lead to environmental problems?

Ans.

Population growth, especially exponential population growth can lead to environmental problems:

More space will be needed to accommodate increased numbers of people.
Land will be cleared for housing and agriculture and is taken up by humans, there is less land available for other organisms.
Population growth places a greater demand on resources such as minerals, fuels, and food. So, depletion of resources may occur.
Over-population may cause destruction of habitats and loss of biodiversity.
Pollution and human health problems are directly related to the increase in population.
Domestic and Industrial wastes cause pollution of air, water bodies, and land.
Outbreak of epidemics and diseases is more likely in congested and over-crowd localities with poor civic and hygiene facilities.

3. What type of environmental problems arise from urbanization?

Ans.

Enlarging city population is the root cause of many environmental problems. Some of them are given below:

The increasing number of vehicles on roads pollutes the atmosphere with dust and the smoke emitted by them.
Many people are forced to live in slums and this situation is causing many social problems.
Useful agricultural land is used for residential purposes.
Domestic and Industrial wastes cause pollution of air, water bodies, and land.
Outbreak of epidemics and diseases is more likely in congested and over-crowd localities with poor civic and hygiene facilities.

3. Describe benefits of forests and harmful effects of deforestation.

Ans.

Forests are playing a very important role in our daily life. They are our great wealth. Forests are important to us in many ways. Some of them are given below:

Forests bring healthy changes in the climate of an area. They stop storms and bring rains. Rain is necessary for us because it refills water reservoirs.
Forests are the source of many useful materials such as timber, firewood, resins, gums, and herbal products for medicines.
They prevent soil erosion.
They provide habitat to a wide variety of wildlife.

Harmful effects of deforestation:

Deforestation has many adverse effects on the environment. Some important effects are given below:

As a result of deforestation, habitats of wildlife and plants are destroyed. Therefore, wildlife extinction risk is increased.
Deforestation is one of the causes of changes in weather and climate.
Fertile soil is lost through soil erosion.

Q. Write a short note on the following topics.

Greenhouse effect
Global warming
Ozone depletion

Ans.

Greenhouse effect

Global warming

The proportion of greenhouse gases in air, such as carbon dioxide. chlorofluorocarbons (CFCs) and methane (CHA) have increased because of rapid growth in industrialization. The presence of these gases in the air in higher proportion has produced the greenhouse effect. Due to the greenhouse effect, the temperature of the earth is rising. This is called global warming.

Ozone depletion

Because of industrialization, the proportion of some gases in air, such as carbon dioxide. chlorofluorocarbons (CFCs) and methane (CHA) has increased. Presence of these gases in air in higher proportion has produced the green house effect. Due to the green hous effect, temperature of the earth is rising. This is called global warming. And sizes

Ozone is a gas which is present in the form of an envelope around the earth in the upper atmosphere. Certain chemical substances, called chlorofluorocarbons, are released from refrigerators, air conditioners, and cans of spray. These chemicals react with ozone and cause thinning and destruction of the ozone layer is called Ozone depletion. Consequently, ultraviolet rays can reach the earth. These rays may cause skin cancer, eye disease, etc. in human beings. These rays are also harmful to animals and plants.