(A) (a) Analyse the given situations and interpret the possible reason for each:

(i) Iodine deficiency in diet increases the possibility of a disease of swollen neck in a person.

(ii) Some people in population may have very short heights (dwarfs).

(iii) Thick facial hairs develop in boys at the age of 10-12 years.

(b) Explain two reasons which necessitate the need of chemical communication in multicellular organisms.

OR

(B) (a) Differentiate between voluntary and involuntary action.

(b) Define reflex action. With the help of a flow diagram, show the correct sequence of path of Nerve impulse from place of its origin.

(A) (a) (i) Iodine deficiency in diet increases the possibility of a disease of swollen neck in a person because iodine is necessary for the production of thyroid hormones, which regulate growth and development.

(ii) Some people in population may have very short heights (dwarfs) due to the deficiency of growth hormone.

(iii) Thick facial hairs develop in boys at the age of 10-12 years due to the increased production of androgens.

(b) Two reasons which necessitate the need of chemical communication in multicellular organisms are:

(i) Electrical impulses have limitations, such as they can only reach cells connected by nervous tissue and cells take time to reset their mechanisms before generating and transmitting a new impulse.

(ii) Chemical communication allows for the transmission of information to all cells in the body, not just those connected by nervous tissue.

OR

(B) (a) Voluntary action is a conscious movement that is under the control of an individual, while involuntary action is an unconscious movement that is not under the control of an individual.

(b) Reflex action is a sudden, automatic response to a stimulus that does not involve any thinking or consciousness.