Class 9 Science Chapter 14 – Natural Resources

 

Class 9 Science Chapter 14 – Natural Resources

We know that everything that surrounds us is called the environment. It acts as a life-supporting unit. It provides us everything- food, water, air, etc. that is important to us for our survival. Let us study about it and its components. 

Biosphere and its components

Do you know that what is the region of the earth’s crust where life exists called? It is Biosphere. Let us study about it.
It is the unit that comprises of the earth’s crust and the atmosphere in which we live. It can be basically divided into three layers:

• Atmosphere
• Hydrosphere
• Lithosphere

Lithosphere is the outer solid crust of earth called as land, hydrosphere is the water component of earth and Atmosphere is the protective blanket that surrounds us.

The two components of the Biosphere are:

• Biotic component
• Abiotic component

Abiotic component- That is all non living factors that surround us which includes climatic factors, topographic factors, water bodies, etc.
Biotic factors- It includes all living forms.
Please note: Both abiotic and biotic factors interact to meet the basic needs of life forms

Types of natural resources

Natural resources are actually living and non living components of nature which are used by us to fulfill our needs. They are also called as earth resources as they are found on the earth. Let us study about their different types.

• Exhaustible
• In-exhaustible

In Exhaustible resources
The resources that occur in such abundance that they are not likely to get exhausted despite continuous use. Like Sun, water, air, etc.

Exhaustible resources
The resources that are available in limited quantity and get depleted if wise use is not done. Example: fossil fuels, etc.

 

Air and Air pollution

We know, if we look at the Sun, we have many layers of gaseous envelopes between us. These gaseous envelopes allow the light to reach us, affect climate and contain many essential elements.

The gaseous envelope that surrounds us is called atmosphere.

Atmosphere is divided into five layers:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

Troposphere
It is the lowest region of the atmosphere which contains air. It extends from 8 to 20km. Mostly all climatic events like thunder, storm, etc. occur in this region only.

Air: It is a mixture of gases such as:

• Nitrogen 78%.
• Oxygen 21%.
• Carbon dioxide 0.03%.
• Water vapour.
• Suspended dust particles.
• Gases like methane, etc. in traces.

 

Importance of atmosphere

• It helps in climatic control.
• Atmosphere helps in keeping the temperature steady during the night and day.
• It causes wind to blow that is land breeze and sea breeze.
• It causes rain.

Land breeze
During the day time land gets heated faster than water. The air closer to the land gets heated and rises up.

 

 

This creates a low pressure in the area. But in the case of sea, it doesn’t get heated up so readily. Due to this, the pressure in that region increases and it starts moving towards land to fill the space. This is called Land breeze.

Sea Breeze
During the night, water loses heat much faster than land. Therefore, the air above the sea gets heated and rises up, creating low pressure.

 

 

To fill that space, the air from land moves towards sea due to increased pressure.

Air pollution

 

 

 

The contamination of air with unwanted and undesirable substances is called air pollution.

Causes

• Natural causes like forest fires, dust storms, etc.
• Man made causes like :
• Burning of fossil fuels.
• Gaseous emission from industries, vehicles, etc.
• Particulate pollutants like SPM ( is smoke, soot, etc.).
• Fly ash and dust.
• Gases like sulphur dioxide and nitrogen dioxide, Carbon monoxides.

Effects of air pollution

 

 

• SPM causes asthma, bronchitis, allergic cold.
• Pollutant gases cause irritation in eyes, throat and lungs. They injure lungs, kidneys, spleen, cause heart related diseases, etc.
• Hydrocarbon vapours causes cancer.
• It affects plants also like falling of leaves, reduced growth, degeneration of chlorophyll, etc.
• It leads to acid rain.
• It causes global warming.
• It causes depletion of the ozone layer.

 

Ozone and ozone depletion

 

Ozone is a molecule of three oxygen atoms i.e. O₃. This is present in the stratosphere that is a layer of the atmosphere. Ozone Is formed when u-v rays in upper atmosphere split oxygen atoms and then the oxygen atom combines with oxygen molecule to form ozone.
Ozone protects us from ultraviolet radiations as it doesn’t allow them to enter the earth’s atmosphere. If they enter the earth’s atmosphere, they may harm us in many ways such as:

• They may raise the temperature of the earth.
• It can cause global warming.
• It may cause skin disorders.
• It can cause eye disorders and many more.

Ozone depletion

There are certain harmful substances that affect the ozone. Mostly, the vapours of these substances move to the upper atmosphere, react with ozone causing its dissociation. When dissociated, the ozone molecule breaks into oxygen atoms and oxygen molecules. This leads to its depletion.
The thinning of the ozone layer by air pollutants is called ozone depletion. For this, some synthetic chemicals are responsible like Chloro Fluoro Carbons that are used in refrigerators, air conditioners, etc.
There are certain measures that are taken to protect this layer like emphasizing the use of alternatives of these substances and freezing the use of harmful substances that cause thinning.

 

Water

We know that the hydrosphere layer consists of water component which is an inexhaustible resource. Water usually exists as a liquid above zero degree Celsius and below 100 degree Celsius. There are different types of water available like surface water, runoff water, ground water, etc. But out of all, only capillary water is available to plants. Let us study about it.
All water bodies like oceans, rivers, lakes, etc. constitute the hydrosphere. Hydrosphere comprises of water that is an inexhaustible resource.

 

Water harvesting

 

It is capturing, collection and storage of rainwater and surface run off for filling either small bodies or recharging ground water.

 

Benefits

• It ensures water availability.

2.     It reduces the chances of flooding during the rainy season.

3.     The groundwater is regularly recharged.

Khadian system

It is a traditional rainwater harvesting for agriculture practised in Rajasthan. It consists of very long earthen embankment down the slope of catchment areas which helps in retaining run off water.

 

 

A shallow well is often dug behind the embankment to store extra overflow water. The stored water slowly percolates down into the ground. The area is then used for growing crops and for vegetation .

Advantage of watershed management

(a)Growing more trees in watershed areas increases the retention of more rain water and protection of soil from erosion.
(b)It enhances the productivity and increases the income of watershed community.
(c) it reduces draughts and floods.
(d)It increases the life of downstream dams and reservoirs because of less silting.

 

Water pollution 

 

The contamination of water bodies with harmful and undesirable substances is called water pollution.

Water pollutants

• Physical water pollutants : like heat and oil spills.
• Chemical pollutants like detergents, fertilizers, pesticides, etc.
• Biological pollutants like viruses, bacteria, etc.

Sources of water pollution

• Sewage.
• Industrial waste.
• Soaps, detergents .
• Petroleum oil, etc.

Harmful effects of water pollution

• It causes human diseases like typhoid, cholera, Jaundice, etc.
• It leads to ecological imbalance.
• It causes water bloom leading to eutrophication.
• It causes a change in temperature.
• It leads to biological magnification.
• It causes decomposition of organic matter.
•  

Eutrophication

 

The excess disposal of chemicals in water bodies leads to excess growth of algae in water bodies that take up the dissolved oxygen of water due to which aquatic life starts disappearing. This is called eutrophication.

Biological magnification

 

 

It is defined as an increase in the concentration of some harmful substances at trophic levels. Sometimes some harmful chemicals may enter into the food chain. It is surprising to note that at each step, the concentration does not decrease like energy, rather it keeps on increasing at each level and the maximum sufferer is the last organism. Like in the given figure, the maximum sufferer is the lion.

 

Soil

It is the part of earth that consists of degraded rock and decaying organic matter.

Formation of soil
We have seen soil many times. But do you know what exactly it is and how it is formed. It is actually a portion of earth’s surface consisting of disintegrated rocks and organic matter. Plants grow in soil and their growth is affected by the fertility of soil. Also, the soil acts as a home for various organisms. Let us study more about it and its formation.

Soil is formed by the process of weathering of rocks.

 

 

In this process, the bigger rocks break up into smaller rocks and finally, into such smaller parts that it forms soil. The factors that are responsible for weathering are: Physical factors like temperature, wind, rain, water, etc. The water seeps inside the rocks and that causes cracks in rocks. Biological factors like lichens, etc. grown on rocks, secrete certain acids that degrade by penetrating into rocks through their roots. These cracks cause weathering of rocks.

Soil profile
If we take the soil in our hands and observe the substances and particles present in it, we can clearly make out that it consists of different sized particles. Let us see the types.

Soil profile: It is the different types of layers that make soil.

The soil is divided into different layers:

By looking at the figure we can see the difference in the composition,Size and type of particles in soil . That is the reason it is divided into different regions.

• A horizon: it is the top soil that is rich in humus. The roots of plants are embedded in this layer.
• B-horizon : this layer is composed of minerals.
• C-horizon : this layer consist of unconsolidated parent material.
• D- horizon: it consist of rocks.

Composition of soil
The soil consists of four types of rock particles which differ in size, looks and texture. It consists of gravel, sand particles, silt particles and clay particles.

 

 

• Gravel: these are larger particles which can be picked up by hand. Particle size of gravel is greater than 2mm in diameter.
• Sand particles: they are coarse to touch and have a particle size ranging from 0.05mm to 2,00mm. They can be seen with naked eyes.
• Silt particles : These soil particles have particle size between 0.005 to 0.05mm.
• Clay particles: These are the smallest soil particles with size less than 0.005mm.

 

 

Types of soil

 

Sandy soil
This soil contains a large amount of sand particles and a small amount of silt and clay. It cannot hold much water.

Clayey soil

The soil contains clay particles and a small quantity of humus and silt. It can hold water but cannot trap air.

Loamy soil
It contains silt, sand and humus. It has good water holding capacity and also allows aeration of roots.

 

Soil erosion

It is the removal of the top layer of soil by wind, water, etc.

Causes of soil erosion

• Winds
• Heavy rains
• Improper farming
• Human actions like expansion of urban sector, etc.
• Dust storms
• Frequent floods

Effects of soil erosion

• Loss of fertile soil
• Landslides
• Floods
• Silting of water reservoirs

Prevention of soil erosion

• Terrace farming
• Wind breaks
• Proper drainage canals around fields
• Making strong embankments along river banks

 

Biogeochemical cycles

We have already discussed that the biotic and abiotic components interact with each other and as a result they form a stable system. Their interactions result in the transfer of energy and matter between different components of the biosphere. As a result, the nutrients are added to the soil when the organisms die and then, through the same cycle, these nutrients are picked up by different organisms through different modes and then again added to the soil. So, in that way, the composition of the nutrient pool is maintained.
It is the recycling of nutrients (from nutrient pool) through living and non living components of the biosphere.
Let us study different nutrient biogeochemical cycles :

 

Water cycle

When the Sun rays falls on the earth, the water from water bodies gets evaporated. The vapours formed, rise up in the atmosphere,where they condense to form clouds. When the cloud becomes big enough, then precipitation occurs and water moves back to earth in the form of rain. So, we can say that water vapour mainly consists of the processes of evaporation, condensation and precipitation.

 

Oxygen cycle

 

The plants carry out photosynthesis in the presence of sunlight and release oxygen as bi- product. This oxygen is taken up by animals for breathing and they release carbon dioxide. Again this carbon dioxide is picked by plants and the cycle repeats.

 

Nitrogen cycle

 

The atmospheric nitrogen is fixed by nitrogen fixing bacteria like rhizobium which is present in the root nodules of leguminous plants (nitrogen fixation).
This nitrogen is first converted into ammonia by bacteria (ammonification) and then to nitrites and nitrates by bacteria nitrosomonas and nitrobacter (nitrification). Then these nitrates are further converted into free atmospheric nitrogen by bacteria like pseudomonas (de-nitrification).
Further, the other source is that this nitrogen, through soil is taken by plants, which are further eaten by animals. The animals’ excretory product is urine that has ammonia which again can be changed to nitrites, nitrates and back to atmospheric nitrogen.

Carbon cycle

 

 

The carbon in the atmosphere exists as carbon dioxide. This gas is taken by plants for photosynthesis. The plants are eaten up by animals. The animals respire and they release carbon dioxide. Also, the factory emissions and vehicle exhausts consist of carbon dioxide which is further released in air and hence, its value is maintained.

 

Natural Resources Class 9 Question Answers

Q1. How is our atmosphere different from atmosphere on Venus and Mars?

Ans. Differences between atmosphere over earth and atmosphere over Venus and Mars

 

Atmosphere over earth	Atmosphere over Venus and Mars
1. It contains nitrogen and oxygen. 2. CO2 content is low (0.03%). 3. Water vapours present. 4. Living beings maintain composition of atmosphere.	1. Both are absent. 2. CO2 is major component 95-75%. 3. Water vapours absent. 4. Living beings are absent and play no role.

 

Q2.How does atmosphere act as a blanket?

Ans. Atmosphere acts as a blanket because of following reasons:
1. Air is a bad conductor of heat.
2. The atmosphere keeps the average temperature of earth fairly steady during the day and even during the course of the whole year.
3. The atmosphere prevents the sudden increase or decrease in temperature.

 

Q3. What causes winds?

Ans: All movements of air are caused by the uneven heating of the atmosphere in different regions of earth. Air above the land gets heated faster and being light, starts rising. As the air rises, a region of low pressure is created. Due to this, the air over the sea moves into this area of pressure.

Factors which control movement of wind
1. The rotation of earth and presence of mountain ranges are order factors which cause winds.
2. Uneven heating of land in different parts of earth.
3. Differences in heating and cooling of land and water.

 

Q4. How are clouds formed?

Ans. Clouds are formed by the condensation of water droplets in the air. It occurs as large amount of water evaporates and goes into the air. Air rises up, it expands and cools. The cooling causes the water vapour in the air to condense in the form of tiny droplets. These water droplets get bigger and form clouds.

 

Q5. List any three human activities that you think should lead to air pollution.

Ans. 1. Combustion of fossil fuels.
2. Industrial pollutants.
3. Release of radioactive substances by nuclear explosions.

 

Q6. Why do organisms need water?

Ans: Organisms need water for the following reasons-

• All cellular processes take place in water medium.
• Water is the universal solvent. All reactions that take place within our body and within the cells occur between substances that are dissolved in water.
• Substances are also transported from one part of the body to the other in a dissolved form.
• The availability of water is the major resource which determines the diversity of life on land.
• Water is required by organisms for many activities such as agriculture.

Thus, water is essential for maintenance and very existence of life.

 

Q7. What is the major source of freshwater in the city/town/village where you live?

Ans. The sources of freshwater are as follows-

• Fresh water is found in ice-caps and on snow covered mountains.
• The underground water and the water in rivers, lakes and ponds is also fresh.
• This water is available for human use. Underground water in rivers, tanks and ponds are available for human use.

Q8. Do you know any activity which may be polluting the water sources?

Ans. Activities which pollute water sources are as follows-

• Sewage from towns and cities and waste from factories released into water bodies.
• Discharging hot water from cooling towers into water bodies affect living organisms.

 

Q9. How is soil formed?

Ans: The breaking up of rocks at or near the surface of the earth over long periods of time result in soil formation. They are broken down by various physical, chemical and biological processes. The end products of this breaking down are the fine particles of soil. There are many other factors which play a vital role in the formation of soil. These factors are :
(1) The Sun – It causes heating of rocks which causes cracking and ultimately breaking up into smaller pieces.
(2) Water – It breaks rocks both by freezing and fast flow.
(3) Wind – It causes erosion of rocks.
(4) Living organisms – Lichens and mosses growing on rock surface form cracks in them and result in their breakdown.

 

Q10. What is soil erosion?

Ans. Soil erosion – Removal of useful components from the soil which affects the fertility of soil is called soil erosion.

 

Q11. What are the methods of preventing or reducing soil erosion?

Ans. Prevention of Soil erosion
1. It can be prevented by intensive cropping.
2. It can be prevented by providing proper drainage canals around the fields.
3. Soil erosion in hilly areas can be prevented by practicing terrace farming.
4. It can be prevented by planting trees and sowing grasses.
5. It can be prevented by constructing strong embankments along the river banks.

 

Q12. What are the different states in which water is found during water cycle?

Ans. Water is found in gaseous state, liquid state and solid state during water cycle. Ground water, surface water, water vapours, water droplets, clouds.

 

Q13. Name two biologically important compounds that contain both oxygen and nitrogen.

Ans. Proteins and nucleic acids (DNA and RNA)

 

Q14. List any three human activities which would lead to an increase in CO2 of air.

Ans: Three human activities which would lead to an increase in CO2 of air are as follows-

• Industries due to burning of fuel and combustion of fossil fuels to provide energy for various needs like heating, cooking, transportation, etc.
• Respiration.
• Deforestation.

 

Q15. What is greenhouse effect?

Ans. Greenhouse Effect – The increase in global temperature due to rise in CO2 is called the Greenhouse effect. It causes global warming.

 

Q16. What are two forms of oxygen found in the atmosphere?

Ans.1. Oxygen is about 21% in the air.
2. In the upper region such as stratosphere oxygen is found in the form of ozone.

 

Q17. Why is atmosphere essential for life?

Ans: Atmosphere is essential for life because of the following reasons-

• It acts as a protective blanket.
• It causes winds.
• Rain and rainfall patterns are decided by winds.
• Air provide us oxygen to breathe.
• Atmosphere absorbs ultraviolet rays that protects living organisms.

 

Q18 Why is water essential for us?

Ans:

• Water makes 60-70% of our body weight.
• All the reactions take place in our body and within the cells occur between substances that are dissolved in water.
• It is required for the transport of materials.
• It is a universal solvent.

 

Q19. How are living organisms dependent on soil?

Ans: Living organisms are dependent on soil due to the following reasons-

• It plays an important role in plant growth by providing nutrients, water, etc.
• It supports the growth of crops, forests and grasslands.
• Soil is an important resource and decides the diversity of life in an area.

 

Q20. Write the role how forests influence the quality of air, soil and water resources?

Ans:

• They have moderate effects on climate.
• They prevent floods.
• They release oxygen in the atmosphere during photosynthesis.
• The forests help in increasing the amount and periodicity of rainfall.
• It plays an important role in preventing pollution.

 

Chapter 13 – Why Do We Fall ill

 

Chapter 13 – Why Do We Fall ill

We all do a lot of activities like exercises,eating meals, fruits, etc. in order to achieve good health. But do we know exactly what is good health? Are we actually healthy? Let us learn about the meaning of being healthy and unhealthy. We know that our body is formed of many organs and also, there are so many systems operating in the body. If one organ stops working, then other functions are also affected. This leads to uneasiness.

 

Health

It is a state of physical, mental and social well being. For being healthy, one needs to eat a balanced diet, take rest, take proper sleep, live in a hygienic place, etc . But sometimes, certain signs appear in a person that cause uneasiness. This uneasiness is called disease.

 

Disease

It is a state when the body is not functioning properly due to one or more reasons. We do not actually feel comfortable in carrying out routine tasks like there can be pain in the body or body part or we may suffer from certain problems in breathing or it can be any other uneasiness. This all comes under diseases.

Health is influenced by many factors like community and personal hygiene. As we know, we live in societies, our social environment also plays a key role like-

1.     We should keep our houses clean.

2.     Proper sewage disposal system should be maintained.

3.     No stagnant water should be there.

4.     No open drains, etc. should be there.

Similarly, personal hygiene is important like –

1.     One should take bath regularly.

2.     One should wear clean clothes.

3.     Drink clean water.

4.     Eat adequate nutritious food.

5.     One should maintain social harmony and equality.

 

Sources of diseases

We have seen that there are many factors that can cause infection or spread disease. There can be different factors responsible for uneasiness. Let us check them out .

There are different sources of diseases, out of which the main factors are as follows-

1.     Intrinsic factors

2.     Extrinsic factors

Intrinsic factors

These are those factors that are within the human body. These diseases are caused by internal factors, therefore, they are also called organic diseases.

The internal factors can be as follows-

1.     Malfunctioning of any body part

2.     Genetic disorder

3.     Hormonal imbalance

4.     Malfunctioning of immune system

Diseases can also be caused by improper secretion of hormones like Goiter, Diabetes, Cretinism, Addison’s disease, etc.

Extrinsic factors

The diseases that are caused by factors that are not present within the body.

The extrinsic factors can be the following-

1.     pathogens.

2.     Unbalanced diet.

3.     Environmental pollution.

4.     Narcotic drugs, etc.

 

Types of diseases

(a)Diseases caused by pathogens

 

 

(b)Diseases caused by inadequate diet

 

 

(c) Diseases caused by environmental pollution

 

  

Classification of diseases

(a) Depending upon the harm it can cause to the body, the diseases fall in different categories as given below-

1.     Physical diseases that affect organs

For example: bone fracture, leprosy, etc.

2.     Infectious diseases that are spread by pathogens.

For example: typhoid, AIDS, malaria, etc.

3.     Deficiency diseases that occur due to nutrient deficiency.

For example: scurvy, Marasmus, Kwashiorkor, etc.

4.     Inherited diseases that occur due to default genetic makeup.

For example: sickle cell anemia, etc.

5.     Degenerative disease that is caused due to a gradual increase in age.

For example: poor sight, poor hearing, etc.

6.     Mental disorders that occur due to certain tensions.

For example: depression, etc.

7.     Social disorder that is due to certain bad habits.

For example: drug addiction, etc.
(b) Depending upon whether the disease can spread from a sick person to a healthy person or not.

1.     Communicable diseases

2.     Non communicable diseases

Communicable diseases: Those diseases that can spread from a sick person to a healthy person by contact are called communicable diseases. They are mostly caused by external factors. They are transmitted through direct contact or through air, water, vector, etc. They are also called infectious diseases.

 

 

For example: Common cold, Cholera Tuberculosis, Pneumonia, Malaria, etc. These diseases are mainly spread through pathogens and the mode of transmission is either air, water, vector or sexual contact. As you must have seen that sometimes, if our friend is suffering from cold and we sit close to him or use his handkerchief, we also fall sick. The reason behind this is that the virus passes to us as well and we suffer from the infection. Let us see how these factors help in the transmission of diseases.

 

Mode of transmission of diseases

a) Air borne infections

The diseases that are passed by air are called air borne infections. They are transferred by droplet infection.

 

For example, if any person having cold sneezes, then he releases the droplets in air. The same air is inhaled by an infected person which passes the disease causing agents to a healthy person. For example : common cold, cough, etc.

 

b) Water borne infections

If the infected agent is spread by dirty water, then the infection is called water borne infection.

 

 

For example: if the stool of any sick person passes into a water body and that water is not purified and by any chance it mixes with drinking water. This water, when taken, causes infections. For example: cholera.

 

c) Sexually transmitted diseases

They are caused due to Sexual contact with a sick person, use of same syringes, etc. For example: Syphilis and AIDS, etc.

 

 

d) Vector borne infections

Vectors are those carriers that do not directly affect us but they transfer the disease causing agent to us.

 

 

For example: Female anopheles mosquito carry malaria pathogen plasmodium in its saliva. When this mosquito comes in contact, it mixes its saliva containing pathogens with our blood. Due to which the pathogen is transferred to us. So, in the case of malaria, vector is female mosquito and pathogen is plasmodium.

Non communicable diseases

The diseases that are not transferred from sick person to a healthy person. For example: arthritis, kidney failure, etc.

 

 

For example: if a person is suffering from kidney failure or pancreas infection and you sit close to him then the disease will not be transferred to you.

(c) Depending upon the duration for which the disease lasts in us, we have different types of diseases as given

1.     Acute disease

2.     Chronic disease

Acute diseases

They are the diseases that last only for a short span. They do not cause such long term bad effects. For example : cold, Cough, Typhoid, etc.

Chronic diseases

They are those diseases that last for a long time. They cause long term bad effects. For example: elephantiasis, diabetes, etc.

(d) Depending upon the time at which the disease is present in the body.

1.     Congenital diseases

2.     Acquired diseases

 

 

Congenital diseases

These are those diseases that are present since birth. These are caused due to a genetic defect or malfunctioning of body parts or metabolic disorder etc .They are permanent. They may pass to children. For example: sickle cell anemia, etc.

Acquired diseases

They are not present from childhood or we can say that they are acquired during lifespan. They can be communicable or noncommunicable. For example: Arthritis.

 

Symptoms and signs

 

Whenever there is occurrence of some disease- short term or long term, there are always certain signs of uneasiness that are felt or seen by us. Like, if somebody is infected by malarial parasite, then before the disease can be diagnosed, certain signs are seen like one feels excessively cold, high fever, loss of appetite, weakness, etc. These all signs appear during the incubation period when the infection is just spreading. They indicate the presence of disease.

The symptoms of each disease are particular. We often confuse symptoms with signs. So, let us see that what is the sign of a disease.

Signs

They actually are the symptoms that are not general or are particular for a particular disease. For example: in below given picture we can see that it can be headache, eye pain, rashes, nausea, etc.

  

Prevention of diseases : vaccination and immunization

 

If there can be diseases, obviously, we have treatments to prevent or cure them. There are very few diseases that do not have a cure. Let us see how we can prevent or cure them.

We can remove the disease by following either of two steps:

1.     Reduce the effects of disease

That is – we can take proper medication to destroy the infection causing agent in our body.

 

2. Remove the causes of microorganisms

That is- we can take certain measures in order to prevent the spread of microorganisms.

 

Prevention of diseases

1. General ways of prevention

For air borne infections

1.     Keep the house ventilated.

2.     Do not be in overcrowded places.

3.     Live in a clean environment ,maintain personal and community hygiene .

 

For water borne infections

Drink clean and pure water

For vector borne disorder

1.     Do not chase street dogs.

2.     Do not let water to stand near your houses.

3.     Keep food items covered.

 

2.Specific ways of prevention

If we have strong immune system, then the infecting agent or its toxin can’t affect us.

 

Immunity

Suppose if you and your one or more friends are sitting close to an infected person. After a while, you feel uneasy but your friend doesn’t. This can happen as there may be a chance that your body does not possess the power to fight infections but your friend’s body may have the power to resist or fight infections. Here comes the factor of immunity. Let us learn about it.

Immunity: It is the resistance against diseases. To raise our immunity level, vaccination is done.

Vaccination

You must have seen that when a child is born, the doctor injects him with a few medicines. This is done in order to enhance the immunity of the newly born child. As we know, the newly born child is going to encounter a new environment, so he may take time to adapt himself. Therefore, injections provide artificial immunity to him so that he can resist himself from infections.

Vaccination: It is the process of injecting either killed or weakened microorganisms in a person’s body so as to raise his immunity level.

It functions in the following manner- when vaccine is given, that is killed or weakened microorganism is injected, the body fails to recognize it and in response, secretes certain antibodies that try or kill the infection causing foreign agent. These antibodies, once made, remain in the body and protect us throughout our life from the particular antigen.

The first vaccine was prepared by Edward Jenner in 1796 against smallpox. Now- a- days, many vaccines are given to a newborn child in order to raise its immunity.

 

Why do we fall ill Class 9 Question Answers

 

1.State any two conditions essential for good health?

Ans : Balanced diet, community and personal hygiene are the two conditions essential for good health.

 

2. What are the various means by which infections are spread?

Ans : Infections are spread by air, Water, Vector and Sexual contact.

 

3. What is immunization?

Ans : Immunization is the process of making people immune to a disease by artificial methods.

 

4. What precautions will you take at school to reduce the incidence of infectious diseases?

Ans :The precautions to be taken at school to reduce the incidence of infectious diseases are – drinking clean water, availability of proper food, proper ventilation and to stay away from an infected person.

 

5. What are antibiotics?

Ans :Antibiotics are the medicines that are advised by doctor in case of microbial infections.

 

6.Why are we advised to take balanced diet when we are sick?

Ans : Nourishing food is good for health and simple food and is easy to digest. It helps in strengthening the body and increases our immunity.

 

7.In which case would the long term effects on your health be most unpleasant?

1.     If you get jaundice

2.     If you get acne

3.     If you get lice

Ans : Jaundice will be chronic as it has long term harmful effects. It can also be fatal.

 

8.Under which condition you are most likely to fall sick :

1.     When you are giving exams

2.     When you are travelling in bus or train for two days

3.     When your friend is suffering from measles.

why?

Ans : In case my friend is suffering from measles, I will be most likely to fall sick because it is an infectious and contagious disease.

 

9.Under what condition person is most likely to fall sick?

1.     When she is recovering from Malaria.

2.     When she has recovered from malaria and is taken care of someone who is suffering from chicken pox.

3.     When she is on four day fast after recovering from malaria and is taking care of a person suffering from chicken pox.

why?

Ans : When a person is on a four day fast after recovering from malaria and is sitting with a person suffering from chicken pox, he is likely to fall sick soon because of less food in the body. Organs such as liver do not recover so soon. A person will get infected with chickenpox as his immunity is not too strong.

 

10.A baby is not able to tell his caretakers that he is sick. What would help us to find out :

1.     That the baby is sick?

2.     What is the sickness?

Ans : Signs of diseases like :Baby is cranky, restlessness is seen, baby feels hot, eyes start watering, cough, loose motions, vomiting indicate that the baby is sick.

But Sickness can be known by consulting a doctor.

 

11. Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by localites to prevent diseases.

Ans : The common diseases are: loose motions, cough and cold and malarial fever.
Prevention:

1.     Reduce the effect of infectious diseases.

2.     Public cleanliness needed.

3.     Immunisation.

4.     Use of clean drinking water.

 

12.A doctor is exposed to many sick persons than others in a community. Find out how he avoids getting sick?

Ans : To reduce the incidence of infections, the following can be done:

1.     Immunisation

2.     Wear gloves and masks

3.     Take prophylactic medicines

4.     Wearing coat

5.     Washing hands with soap after examining.

 

13. What changes can we make in our habits to prevent diseases?

Ans : The following changes can be made in our habits to prevent diseases-

1.     Avoid contact with infected person

2.     Drinking clean water

3.     Consume balanced diet

4.     Community and personal cleanliness

5.     Proper disposal of waste