NCERT Solutions for Class 12 Biology Chapter 8

NCERT Solutions for Class 12 Biology Chapter 8 Human Health and Diseases to Study Online without downloading or download in PDF form. NCERT Books based on latest Curriculum is also available to download.

NCERT Solutions for class 12 Biology Chapter 8

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Solutions for 12 Biology Chapter 8

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NCERT Solutions for Class 12 Biology Chapter 8 Human Health and Diseases
NCERT Solutions for Class 12 Biology Chapter 8

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12 Biology chapter 8 answers

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Points to Remember
  • Addiction: A psychological attachment to effects like euphoria and temporary well-being associated with drugs and alcohol.
  • Interferon: The glycoproteins produced by our body cells in response to a viral infection.
  • Incubation Period: The time period between infection and tire appearance of symptoms.
  • Metastasis: The property in which the cancer cells spread to different sites through blood and develop secondary tumours.
  • Oncogenes: Viral genome which causes cancer/Cancer causing genes.
  • Retrovirus: A virus having RNA as genetic material and forms DNA by reverse transcription and then replicate e.g., Human Immunodeficiency Virus (HIV).
  • Withdrawal Syndrome: If a drug dependent person stop taking drugs then his body stop functioning normally and he feels severe physical and psychological disturbance called withdrawal syndrome.
  • Contact Inhibition: It is a property of normal cells in which the cells stop dividing when comes in contact with its surrounding cells.

Infectious Diseases
  1. Viral Diseases e.g., polio, common cold, measles, rabies
  2. Bacterial diseases e.g., Typhoid, Pneumonia, Diptheria, Tetanus.
  3. Fungal diseases e.g., Ring worm & Scabies
  4. Helminthic diseases e.g. Ascariasis, Filariasis, Taeniasis
  5. Protozoan diseases e.g. Malaria, Amoebiasis.

Prevention of Dengue and Chikungunya: Protection against mosquitoes by wearing long sleeves and full pants. Window and doors should have wire gauze screens, use mosquito repellents and there should be no stagnant water nearby.

Two types of Immunities.
  1. Innate immunity: inherited by the organism from the parents and present at the time of birth.
  2. Acquired Immunity: Acquired by a person after birth by vaccination or contacting the disease.


A preparation of weakened or attenuated pathogen is introduced in the human body. Antibodies are formed against the pathogen. B and T memory cells are generated that recognises the pathogen quickly on subsequent exposure a kills it with quick and massive production of antibodies.


Substances to which immune system shows exaggerated response. e.g. mites in dust, pollens, animal dander, perfume, wool, nail polish and drugs.
Lymphoid Organs: Organs where lymphocytes are formed proliferate and mature are called lymphoid organs.
Bone Marrow: It is a primary lymphoid organs. Lymphocytes maturing here are called B-lymphocytes.
Thymus: Lymphocyte which mature in thymus are called T-lymphocyte.