Ch 10Human Health and Diseases — Class 12 Biology, concept-first.

Health is far more than simply the 'absence of disease' or physical fitness — the World Health Organization defines it as a state of complete physical, mental and social well-being, not merely the abs…

Immunity (literally 'freedom' or 'exemption') is the traditional term for the host's resistance to injury caused by pathogens and their products — though immune responses are actually much broader, re…

i. Innate immunity or Inborn immunity : Innate immunity (also called inborn immunity) is the resistance to infection an individual is simply born with, by virtue of their genetic make-up.

ii. Acquired immunity : Acquired immunity (also called adaptive or specific immunity) is the resistance an individual builds up over the course of their life, through the formation of antibodies that…

B. Cells of Immune System : Two main categories of cell carry out the work of the acquired immune system: lymphocytes and antigen-presenting cells.

C. Vaccination : Vaccination is the administration of a vaccine — an inactivated pathogen or an antigenic portion of it — to protect against that particular pathogen.

Antibodies, also called immunoglobulins (Igs), are highly specific glycoproteins produced by plasma cells (themselves derived from activated B-lymphocytes) in response to antigenic stimulation — matur…

Antigen on Blood Cells : The surface of human red blood cells (RBCs) carries a number of genetically determined antigens, which give rise to several distinct blood-group systems — ABO, Rh, Duffy, Kidd…

Disease is defined as a condition of disturbed or deranged functioning of one or more organs or organ systems, caused by infection, a defective diet, or heredity.

A. Malaria : Malaria is a vector-borne infectious disease caused by the protist genus Plasmodium. Four species infect humans — P. vivax, P. ovale, P. malariae and P.

B. Amoebiasis : Amoebiasis, also known as amoebic dysentery, is caused by the protist parasite Entamoeba histolytica.

C. Ascariasis : Ascariasis is an infectious disease of the human intestinal tract caused by the endoparasitic roundworm (nematode) Ascaris lumbricoides.

D. Filariasis / Elephantiasis : Filariasis, also called elephantiasis in its classic form, is caused by thread-like nematode worms transmitted from person to person by mosquito bite.

E. Typhoid : Typhoid is an acute infection of the intestine caused by the Gram-negative bacterium Salmonella typhi, found in the intestinal lumen of infected people.

F. Pneumonia : Pneumonia is an inflammatory condition of the lungs or their alveoli. It can be caused by a variety of pathogens — viruses such as influenza virus, adenovirus, parainfluenza virus and R…

G. Common Cold : Common cold is a viral infectious disease of the upper respiratory tract, also known as nasopharyngitis, acute viral rhinopharyngitis, or acute coryza.

H. Ring Worm (Dermatophytosis) : Ringworm, medically called dermatophytosis, is a fungal infection of the skin caused by several species of fungi belonging to the genera Trichophyton and Microsporum,…

I. Dengue : Dengue fever is a painful, debilitating vector-borne disease caused by any one of four closely related dengue viruses.

J. Cancer : Cancer results from abnormal, uncontrolled and purposeless division of cells, forming a mass of undifferentiated cells called a tumor (or neoplasm, except in leukaemia, where no solid mass…

K. AIDS : AIDS (Acquired Immuno Deficiency Syndrome) is a usually fatal illness caused by a retrovirus (a single-stranded RNA virus) called the Human Immunodeficiency Virus (HIV), which weakens the bo…

Adolescence is the transitional stage of physical and mental development that begins with the appearance of secondary sexual characters and ends with the cessation of somatic (body) growth — broadly,…

Addiction is a complex condition marked by the compulsive use of a substance despite its harmful consequences; it can involve substances such as alcohol, opioids, cocaine and nicotine, or behaviours s…

Surveys consistently show rising drug and alcohol use, especially among youth — a real cause for concern given the harm it can cause.

Q.1 of the textbook exercise (p244): eleven multiple-choice questions.

Q.2 of the textbook exercise (p244): twelve very-short-answer questions.

Q.3 of the textbook exercise (pp244-245): eight short-answer questions.

Q.4 of the textbook exercise (p245): the second set of ten short-answer questions.

Q.5 of the textbook exercise (p245): one matching question.

Q.6 of the textbook exercise (p245): seven long-answer questions.

The textbook's end-of-chapter Project (p245): two information-collection tasks. A guided approach is given for each.

Sample papers and previous-year board questions for this subject.