General Science
7th Class
Chapter 3
Immunity and Diseases
Questions
3.1 Encircle the correct option.
1. A pigment in the skin that protects harmful effects of sunlight:
a. melanin b. haemoglobin c. lymphocyte d. lysozyme
2. Hydrochloric acid is found in:
a. saliva b. gastric juice c. bile d. pancreatic juice
3. ________ is the inflammation of liver.
a. tuberculosis b. typhoid c. COVID-19 d. hepatitis
4. Billions of new blood cells are produced daily in:
a. heart b. lever c. spleen d. bone-marrow
5. Nuclear membrane is not found in:
a. plant cell b. animal cell c. bacterial cell d. fungal cell
3.2 Give short answers.
i. Define the following:
(a) Pathogen
(b) Antigen
(c) Infection
(d) Phagocytosis
Ans.
(a) Pathogen
Microorganisms that cause diseases in human body are called pathogen.
(b) Antigen
An antigen is a toxin or other foreign substances which induces an immune response in the body, the production of antibodies.
(c) Infection
Entry and growth of microorganisms into our body called infection.
(d) Phagocytosis
Phagocytosis is a cellular process of ingesting and eliminating foreign substances and microorganisms.
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