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Class 12th Biology 2013 Set3 Delhi Board Paper Solution

Question 16

A student on a school picnic to a park on a windy day started sneezing and having difficulty in breathing on reaching the park. The teacher enquired whether the student was allergic to something.
(a) What is an allergy?
(b) Write the two unique characteristics of the system involved in the response observed in the student.

(a) The exaggerated response of the immune system to certain antigens present in the environment is called allergy.
(b) The system involved is immune system. It unique characteristics are:
(i) It recognizes foreign antigens & responds to them.
(ii) It has memory so it remembers antigens