Your younger brother observes some mosquitoes sucking juices of cut fruit pieces,though it is common knowledge that mosquitoes suck blood of humans. How will you explain this behaviour to him?

Fill in the blanks:
$(a)$ . . . . . . disease continues for many days and causes . . . . . . on the body.
$(b)$ . . . . . . disease continues for a few days and causes no long-term effect on the body.
$(c)$ . . . . . . is defined as physical,mental,and social well-being and comfort.
$(d)$ Common cold is a/an . . . . . . disease.
$(e)$ Many skin diseases are caused by . . . . . . .

Priya's mother uses iodised salt at home. One day while cooking,Priya asked her mother about iodised salt. She said people who do not use iodised salt suffer from deficiency of iodine which leads to goitre and hypothyroidism.
$(a)$ What are the physical symptoms of goitre and hypothyroidism?
$(b)$ How will you inform others about the importance of iodised salt?
$(c)$ Is iodine a metal or a non-metal?
$(d)$ What are the physical properties of iodine?
$(e)$ What is the difference between iodised salt and normal salt?

Explain giving reasons:
$(a)$ Balanced diet is necessary for maintaining a healthy body.
$(b)$ The health of an organism depends upon the surrounding environmental conditions.
$(c)$ Our surrounding area should be free of stagnant water.
$(d)$ Social harmony and good economic conditions are necessary for good health.

$(a)$ State the principle of immunisation. Name two diseases for which vaccines are available.
$(b)$ Mention two basic principles of prevention of infectious diseases.

Microbes are classified as: