A food stall owner was preparing dough for making bhaturas. He added a pinch of yeast and sugar to the dough and left it in a warm place. After few hours, the dough had risen. There was a sour smell too.
(a) Why did the dough rise?
(b) Why did the dough smell sour?
(c) Why was sugar added to the dough?
(d) What would have happened if the dough was kept in the refrigerator, soon after it was prepared?

5

(a)

Paheli participated in a 400 m race competition held at her school and won the race. When she came home she had mixed feelings of joy and pain as she had cramps in her leg muscles. After a massage, she was relieved of the pain. Answer the following questions related to the situation.
(a) What can be the possible reasons for the pain in her legs?
(b) Why did she fell comfortable after a massage?

5

(a)

It is not wise to sleep under a tree during night. Why?

5

(a)

(a) Respiratory process occurs in two phases, what are those two major steps of respiration? Describe each one.
(b) Define the term breathing rate.

5

(a)

List some animals around you. Now group them as follows:
(a) Animals that can breathe only through skin.
(b) The animal that can breathe through skin as well as through lungs.
(c) The animal that can breathe through lungs.
(d) Animals that can breathe through gills.
(e) Animals that can breathe through spiracle and tracheae?

5

(a)

A person put some warm water in an aquarium having fish during winter season. He thought that fish will be more comfortable in luke warm water than cold water. But he observed that fishes in the aquarium died. Why the fishes died in warm water?

5

(a)

Explain the respirating system in cockroach

5

(a)

Explain the respiration in plants

5

(a)

Write the differences between cellular respiration and breathing.

5

(a)

Distinguish between photosynthesis and respiration.

5

(a)