HUMAN HEALTH AND DISEASE CLASS 12 PDF

human-health-disease-cbse-notes-classbiology- Some diseases are transmitted by vector, i.e. mosquitoes like dengue (Aedes aegypti);. Rajkumar Biology: A guide for 11th & 12th CBSE Students CHAPTER – 8: HUMAN HEALTH AND DISEASE. Health: It can be defined as a state of complete physical, Diseases can be broadly grouped into infectious and non-infectious. Introduction. Health can be defined as a state of complete physical, mental and social well-being. Health is affected by three factors-. Genetic disorders-.


HUMAN HEALTH AND DISEASE CLASS 12 PDF

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HUMAN HEALTH AND DISEASE CLASS 12 PDF

Such disease- causing organisms are called pathogens. All parasites are therefore pathogens as they cause harm to the host by living in or on them.

NCERT Solutions Class 12 Biology Chapter 8 – Human Health And Disease

The pathogens can enter our body by various means, multiply and interfere human health and disease class 12 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 alongwith the diseases caused by them.

NCERT Class XII Biology Chapter 8 : Human Health and Disease

Preventive and control measures against these diseases in general, are also briefly described. Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings.

These pathogens generally enter the small intestine through food and water contaminated with them and migrate to other organs through blood. Intestinal perforation and death may occur in severe cases.

CBSE Class 12 Biology Chapter 8 - Human Health and Disease Revision Notes

Typhoid fever could be confirmed by Widal test. A classic case in medicine, that of Mary Mallon nicknamed Typhoid Mary, is worth mentioning here. She was a cook by profession and was a typhoid carrier who continued to spread typhoid for several years through the food she prepared. Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease pneumonia human health and disease class 12 humans which infects the alveoli air filled sacs of the lungs.

As a result of the infection, the alveoli get filled with fluid leading to severe problems in respiration. The symptoms of pneumonia include fever, chills, cough and headache.

NCERT Solutions Class 12 Biology Chapter 8 – Human Health And Disease - Embibe Exams

In severe cases, the lips and finger nails may turn gray to bluish in colour. Dysentery, plague, diphtheria, etc. Many viruses also cause diseases in human beings.

HUMAN HEALTH AND DISEASE CLASS 12 PDF

Rhino viruses represent one such group of viruses which cause one of the most infectious human ailments — the common cold. They infect the nose and respiratory passage but not the lungs.

HUMAN HEALTH AND DISEASE CLASS 12 PDF

The common cold is characterised by human health and disease class 12 congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc.

Droplets resulting from cough or sneezes of an infected person are either inhaled directly or transmitted through contaminated objects such as pens, books, cups, doorknobs, computer keyboard or mouse, etc. Some of the human diseases are caused by protozoans too.

You might have heard about malaria, a disease man has been fighting since many years. Plasmodium, a tiny protozoan is responsible for this disease. Different species of Plasmodium P. Of these, malignant malaria caused by Plasmodium falciparum is the most serious human health and disease class 12 and can even be fatal.

Let us take a glance at the life cycle of Plasmodium Figure 8.

Chapter 8 - Rajkumar Biology: A guide for 11th & 12th CBSE Students

Human health and disease class 12 enters the human body as sporozoites infectious form through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells RBCs resulting in their rupture.

The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days.

The parasites multiply within them to form sporozoites that are stored in their salivary glands.



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