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ScienceClass 9CBSE

If you live in a overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases (a) Cancer (b) AIDS (c) Air borne diseases Cholera

Soln: Answer is (c) Air borne diseases

ScienceClass 9CBSE

Which one of the following causes kala-azar? (a) Ascaris (b) Trypanosoma (c) Leishmania Bacteria

Soln: Answer is (c) Leishmania

ScienceClass 9CBSE

1. Making anti-viral drugs is more difficult than making anti-bacterial medicines because (a) viruses make use of host machinery (b) viruses are on the border line of living and non-living (c) viruses have very few biochemical mechanisms of their own viruses have a protein coat

Soln: Answer is (c) viruses have very few biochemical mechanisms of their own Explanation: Antibacterial drugs stop certain biochemical reaction in the bacteria that kills the bacteria. But in virus there are few biochemical processes which are difficulty to target hence making anti-viral drugs is difficult.

ScienceClass 9CBSE

AIDS cannot be transmitted by (a) sexual contact (b) hugs (c) breast feeding blood transfusion

Soln: Answer is(b) hugs Explanation; AIDS is transmitted by exchange of body fluids. When we hugs there cannot be exchange of any body fluids hence Aids cannot be transmitted by hugs.

ScienceClass 9CBSE

Which of the following can make you ill if you come in contact with an infected person? (a) High blood pressure (b) Genetic abnormalities (c) Sneezing (d) Blood cancer

Soln: Answer is (c) Sneezing Explanation: Sneezing is a symptom of common and other respiratory disease which are transmitted through inhaling of contaminated air. Other option provided in the question are not infectious disease hence they are not transmitted through human contact.

ScienceClass 9CBSE

Which one of the following has a long term effect on the health of an individual? (a) Common cold (b) Chicken pox (c) Chewing tobacco Stress

Soln: Answer is (c) Chewing tobacco Explanation: Common cold and chicken pox are acute disease which will not produce any long term effect. Stress can be managed and will not have long term effect. Chewing tobacco is dangerous as it produce a long term effect.

ScienceClass 9CBSE

Which one of the following diseases is caused by protozoans? (a) Malaria (b) Influenza (c) AIDS Cholera

Soln: Answer is (a) Malaria Explanation: Malaria is caused by protozoan Plasmodium vivax.

ScienceClass 9CBSE

Which one of the following disease is not caused by bacteria? (a) Typhoid (b) Anthrax (c) Tuberculosis Malaria

Soln: Answer is (d) Malaria Explanation: Malaria is cause by protozoans called Plasmodium vivax hence d) is the right answer

ScienceClass 9CBSE

Which one of the following disease is not transmitted by mosquito? (a) Brain fever (b) Malaria (c) Typhoid Dengue

Soln: Answer is (c) Typhoid Explanation: Typhoid is transmitted through food and water.

ScienceClass 9CBSE

Which one of the following is not a bacterial disease? (a) Cholera (b) Tuberculosis (c) Anthrax Influenza

Soln: Answer is (d) Influenza Explanation: Cholera is caused by Vibrio cholera bacterium Tuberculosis is caused by Mycobacterium tuberculosis bacteria Anthrax is caused by Bacillus anthracis bacteria. Influenza is caused by Influenza virus hence option d) is the right answer.

ScienceClass 9CBSE

Which one of the following is not a viral disease? (a) Dengue (b) AIDS (c) Typhoid Influenza

Answer is (c) Typhoid Explanation: Typhoid is caused by a bacterium called as Salmonella typhi

ScienceClass 9CBSE

Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?

Carbon-di-oxide is considered as a pollutant because it is a green-house gas which is responsible for the global warming. This results in change of earth’s climate. Along with that excess CO2 is harmful for the plants. Increased CO2 levels changes physiology, growth and chemistry of plants. High CO2 concentration also causes suffocation, hard breathing and choking issues.

ScienceClass 9CBSE

Explain the role of the Sun in the formation of soil.

Sunlight heats the rock in the afternoon which results in the expansion of rock. When it cools down in the night contraction takes place which is not at the rate of expansion. Because of this difference in the rate of expansion and contraction rock get cracked to form small rock particles.

ScienceClass 9CBSE

Justify “Dust is a pollutant” ?

Dust is a fine powder of tiny earth particles and waste matter. It is carried to the atmosphere by wind, dust causes allergy in humans and affects plant growth by blocking the stomata on the leaf surface. Dust also carries toxic substance from the environment to pollute the water bodies affecting the aquatic life.

ScienceClass 9CBSE

A motor car, with its glass totally closed, is parked directly under the sun. The inside temperature of the car rises very high. Explain why?

Infrared radiation emitted by the sun can pass the transparent glass and increases the temperature inside the car. These radiations have smaller wavelength than the radiations emitted by the car. For these waves transparent glass remain opaque further increasing the temperature.

ScienceClass 9CBSE

What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.

Causes of water pollution are given below Chemical Fertilizers and pesticides consists of poisonous chemical which reach the water body to turn water into toxic. Dumping of sewage directly into water bodies Release of industrial effluents into water Below are the steps we can take to reduce water pollution Stop connecting sewage lines directly to water Avoiding throwing garbage and other domestic waste into water Prevent dumping of toxic chemical into water Avoid washing of clothes near water

ScienceClass 9CBSE

Why are root nodules useful for the plants?

Root nodules are the home for nitrogen fixing bacteria called a Rhizobium. Rhizobium fixes atmospheric nitrogen thereby increasing soil fertility.

ScienceClass 9CBSE

Why step farming is common in hills?

In hills there are steep slopes which risk washout of topsoil by wind and rain. In order to conserve top soil step farming is done in hills.

ScienceClass 9CBSE

Fertile soil has lots of humus. Why?

Fertile soil has a number of microorganisms that decomposes dead and organic matter to convert to humus. Humus provides nutrients, absorb water and makes soil porous.

ScienceClass 9CBSE

Soil is formed by water.” If you agree to this statement then give reasons

Water causes soil formation by following steps. Water causes wear off of rock for a long period of Water makes rubbing between the rocks to smaller particles which are deposited as On freezing, water expands to cause breaks in the

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