Forests: Our Lifeline — Science STD 7 — Question

Wheat dough if left in the open, after a few days, starts to emit a foul smell and becomes unfit for use. Give reason.

What steps should be taken to avoid substance abuse?

What are secondary sexual characteristics? Provide examples in boys and girls.

Explain the relationship between sanitation and disease.

Sachin lives in a village, this village is surrounded by a forest. One day he noticed that in nearby pond sedimentation is increased so much that water has become muddy, streams are drying up. There is scarcity of fuel wood. He soon realised that he has to raise the issue of forest protection from cutting down trees, etc. Soon he gathered the nearby village people and made an organisation to take an initiative.
Now, answer the following questions
(i) What changes might have Sachin noticed in his area?
(ii) Give the probable reason for such changes mentioned above.

Draw and label a diagram showing the positions of the Sun, Earth, and Moon during a lunar eclipse.

A group of students noticed that a torch does not light up even though the batteries are new. They replaced the wire and it worked. What scientific approach did the students use to solve the problem? Explain the role of hypothesis and experiment in this scenario.

Give reasons why the diaphragm flattens, and the ribs are lifted when we breathe in.

Discuss vermi-processing toilets. Name the useful product obtained from such toilets.

Distinguish between a parasite and a saprotroph.