Grade 12 Zoology Note

Socially significant Human Diseases:

Any change from the normal stage that causes discomfort or disability or disturbs the health called a disease. All human disease can be classified into following ;

1.Congenital Disease: They are anatomical or physiological abnormalities present in the person from birth also called natural diseases. For example; sickle cell anaemia, diabetes mellitus, haemophilia , etc.

2.Acquired disease: These are acquired by the person at any time after birth. They are of two types namely; communicable and non- communicable.

Socially significant disease:

Drug abuse:

Drug  is chemical substance that alter the physiological state of a living organism. Drugs are widely use in medicine. The study of drug is called pharmacology.

Causes of drug addiction:

1. A person may experiment because he or her friend suggest it.

2.To satisfy own curiosity.

3.For the feeling of relaxation.

4.To escape from a difficult situation.

5.In search of a more satisfying life.

Types of drugs:

According to the mode of action the psychotropic drugs are classified into two types;

a.Narcotics drugs:

It leads temporary feeding of cell being, freedom from anxiety, produces normal sleep and relief from pain. The excess dose of these drugs lead rate of respiration reduces, reduces, reduces cardio vascular activities etc.

b. Stimulant or antidepressant drugs:

These drug Commonly called as mood elevating drugs. The right dose of intake may increase self confidence and mental alertness. The drug of these group can be called as Amphitamins. Such as tea, coffee.

Control measures of Drug addiction:

1.Treatment and hospitalization.


3.Psychological treatment

4.Imlemention of the strict rules and regulation.

5.Education and awareness program.


Alcoholism (Alcohol addiction)

Ethyl alcohol and alcohol is among the most commonly substances by human. Alcohol is manufactured by fermentation of sugar an organism like yeast.

Alcohol addiction: The prolonged use of alcohol may lead the dependence of the body on it is called alcohol addiction.

The reasons of alcohol addiction are ;

1.Feeling of independence.

2.Overcoming frustration, failures and disappointments.

3.Desire of Excitement and to do more work.

4.Relief from pain and  worries.

5.Curiosity and use of drink in social, cultural and religious function.

Effects of alcohol drinks:

1.Ill-effects alcoholic drinks on individual and health:

 Alcohol causes ill effects on various organs like on

a.Nervous system: Loss of will power, self control and judgment.

b.On stomach: Alcohol causes secretion of gastric juices which causes gastritis problem.

c.On liver: Liver changes alcohol in to highly toxic compound, which may the cause of death.

d.On heart: It increases the blood pressure and adversely affect on function of hearth.

e.On kidney: Alcohl interferes with the normal functioning of nephrons in kidney.

f.Alcohol lowers the blood sugar level.

g.On reproduction: In women, it particularly affects the ovulation and menstrual cycle.

2.Ill-effects of alcoholic drinks on family:

 Alcohol drinking has a socio-economic impact because excessive drinking or alcoholism affects the family, growth and development of children adversely.

3.Ill-effects of alcoholic drinks on community or society:

 Social crimes like corruption, rapes, accident, loss of social reputation and personality.

Symptoms of alcoholism:

1.Loss of will power, self-control, judgment and emotional control.

2.Visual problem like blurred vision , double vision and improper judgment of distances.

3.Leads to neuritis, amnesia, gastritis.

4.Increase the blood pressure and lower the sugar level.

5.In women it effect on menstrual cycle.

Control of alcoholism:

 1.Treatment and hospitalization.


3.Psychological treatment

4.Imlemention of the strict rules and regulation.

5.Education and awareness program.


The regular consumption of tobacco in form of either cigarette, or chewing causes dependency on tobacco is called smoking. In Nepal 55% of total population consumes tobacco. Among them 48% are below 15 years.

Tobacco contains highly poisonous alkaloid drug called nicotine. Its smoke contains approximately 400 different chemicals. Such as formaldehyde, polycyclic hydrocarbons like tar, carbon monoxide, etc.

Effect of Nicotine: 

1.Stimulate the conduction of nerve impulses.

2.Stimulate adrenal medulla to secrete adrenaline hormone.

3.Increase rate of heart beat and blood pressure.

4.Increase constriction of blood vessels.

Effect of smoking:

Following diseases are associated with smoking

1.Cancer:Cigarete smoke contains chemical substances called carcinogens, which causes cancer.

2.Bronchitis: When person smokes, a tiny particles in the smoke get stuck on the lining of the trachea and bronchial tubes.

3.Emphysema: The breakdown of alveoli wall  reduces alveolar surface of gaseous exchange. Eventually, lung tissues destroy so much and finally the patient dies.

4.Asthma: It is more serious diseases, the walls of bronchioles contract and the tubes become narrower. Breathing become diffucut.

5.Heart diseases: A chemical substance nicotine affects the heart, cause constriction of peripheral blood vessels and  increases heart beat.

Symptoms of smoking:

1.A nagging morning cough may be one of the sign of tobacco habit.

2.Shortness of breath, wheezing, etc.

3.Increases fatigue, decreases the smokers sense of smell and taste.

4.Dry mouth and lips and red eyes.


There are wide ranges of treatments like hypnotherapy, herbs, Acupuncture etc can help a smoker quit the habit.

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