Suggest some preventive measures for the diseases of poultry birds.

Weeds affect the crop plants by:

Sahil's grandfather had a prostate problem. The doctor advised him to go in for an ultrasound. Sahil accompanied his grandfather to a diagnostic centre. His grandfather went through the process and was given a photograph.
$(a)$ What is the principle of ultrasound? What waves are used for this purpose?
$(b)$ Name four other areas in which the ultrasound is used as a diagnostic tool.
$(c)$ What value did Sahil imbibe about ultrasound?

Ram's teacher was showing the structure of a cell under a compound microscope,highlighting different parts like the cell wall,cell membrane,and nucleus. The teacher explained the difference between plant and animal cells,noting that the cell wall is found only in plant cells. Everyone observed the structure carefully and understood its structural importance.
$(a)$ What kind of qualities are shown by Ram?
$(b)$ Why is the cell called the structural and functional unit of life?

Differentiate between inland fisheries and marine fisheries.

How is a fumigant different from a pesticide? Name one natural substance which can be used in place of a fumigant.