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NCERT Class 12 Biology Textbook Chapter 8 With Answer PDF Free Download
Chapter 8: Human Health and Disease
Health, for a long time, was considered as a state of body and mind where there was a balance of certain ‘humor’.
This is what early Greeks like Hippocrates as well as the Indian Ayurveda system of medicine asserted. It was thought that persons with ‘black bile’ belonged to hot personalities and would have fevers.
This idea was arrived at by pure reflective thought. The discovery of blood circulation by William Harvey using the experimental method and the demonstration of normal body temperature in persons with black bile using a thermometer disproved the ‘good humor’ hypothesis of health.
In later years, biology stated that the mind influences, through the neural system and endocrine system, our immune system and that our immune system maintains our health.
Hence, the mind and mental state can affect our health. Of course, health is affected by –
(i) genetic disorders – deficiencies with which a child is born and deficiencies/defects which the child inherits from parents from birth;
(ii) infections and
(iii) lifestyle including food and water we take, rest and the exercise we give to our bodies, habits that we have or lack, etc
The term health is very frequently used by everybody. How do we define it? Health does not simply mean ‘absence of disease’ or ‘physical fitness. It could be defined as a state of complete physical, mental and social well-being.
When people are healthy, they are more efficient at work. This increases productivity and brings economic prosperity.
Health also increases the longevity of people and reduces infant and maternal mortality.
A balanced diet, personal hygiene, and regular exercise are very important to maintain good health. Yoga has been practiced since time immemorial to achieve physical and mental health.
Awareness about diseases and their effect on different bodily functions, vaccination (immunization) against infectious diseases, proper disposal of wastes, control of vectors, and maintenance of hygienic food and water resources are necessary for achieving good health.
When the functioning of one or more organs or systems of the body is adversely affected, characterized by various signs and symptoms, we say that we are not healthy, i.e., we have a disease. Diseases can be broadly grouped into infectious and non-infectious.
Diseases that are easily transmitted from one person to another, are called infectious diseases.
Infectious diseases are very common and every one of us suffers from these at some time or other.
Some infectious diseases like AIDS are fatal. Among non-infectious diseases, cancer is the major cause of death. Drug and alcohol abuse also affect our health adversely.
8.1 Common Diseases In Humans
A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man.
Such disease-causing organisms are called pathogens. Most parasites are therefore pathogens as they cause harm to the host by living in (or on) them.
The pathogens can enter our body by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage.
Pathogens have to adapt to life within the environment of the host.
For example, the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes.
A few representative members from different groups of pathogenic organisms are discussed here along with the diseases caused by them.
Preventive and control measures against these diseases, in general, are also briefly described.
| Author | NCERT |
| Language | English |
| No. of Pages | 22 |
| PDF Size | 2.9 MB |
| Category | Biology |
| Source/Credits | ncert.nic.in |
NCERT Solutions Class 12 Biology Chapter 8 Human Health and Disease
1. What are the various public health measures, which you would suggest as a safeguard against infectious diseases?
Solution:
Public health measures are the measures taken to prevent and check the spread of different infectious diseases. It is taken to lessen contact with infectious agents.
Some of these preventive measures are as follows:
- Isolation – it prevents the spreading of air-borne diseases (chickenpox, pneumonia, tuberculosis, etc) which is required to isolate an infected person to reduce the chances of diseases spreading
- Vaccination – is the protection of the body from diseases that can be communicated which is done by administering some agents which impersonate the microbe in the body. This helps in rendering passive immunization to the body. Vaccines are available for some the diseases such as mumps, polio, measles, etc
- Vector eradication – diseases such as dengue, malaria, etc that spread through vectors can be prevented by ensuring a clean environment and checking the breeding of mosquitoes which is facilitated by regulating water, and looking for it to not stagnate in residential areas. Some other measures are periodic cleaning of coolers, and the use of mosquito nets and insecticides. It can also be controlled by introducing Laxvivorous fish such as Gambusia in ponds, as they control mosquito larvae breeding in stagnant water
- Maintaining public and personal hygiene is one of the most important practices to prevent the spread of infectious diseases as it includes maintaining a clean body, consuming healthy and nutritious food, clean water, etc. Proper disposal of wastes, excreta, and disinfection of water reservoirs is some of the measures that can be adopted as part of public hygiene.
2. In which way has the study of biology helped us to control infectious diseases?
Solution:
Biology is a vast field of Science dealing with life forms and their processes. It has helped in controlling infectious diseases in the following ways:
- Complete eradication of fatal diseases such as smallpox was possible with the use of immunization schemes and vaccines
- Other infectious diseases such as Diptheria, polio, pneumonia, etc have been successfully controlled with the use of vaccines
- Treatment of several infectious diseases has successfully been carried out with the use of antibiotics and other drugs
4. What measure would you take to prevent water-borne diseases?
Solution:
Measures taken to prevent water-borne diseases are as follows:
- Provision of clean water for drinking
- Industries should be prohibited from discharging wastes into water bodies
- Frequent cleaning and disinfecting of water tanks and reservoirs
5. Discuss with your teacher what ‘a suitable gene’ means, in the context of DNA vaccines.
Solution:
The term ‘suitable gene’ is used to refer to a particular section of DNA that can be altered in the host in order to synthesize a particular protein that attacks and kills a specific disease-causing entity.
6. Name the primary and secondary lymphoid organs.
Solution:
Primary lymphoid organs are – Thymus and bone marrow
Secondary lymphoid organs are – Mucosal-associated lymphoid tissues (MALT), Lymph nodes, spleen, Peyer’s patches (small intestine)
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