Exploring Forces — Science STD 8 — Question

Describe the ‘in vitro fertilization’ technique of reproduction in humans.

How do viruses differ from other micro-organisms such as bacteria?

What are migratory birds? Name one migratory bird which comes to warmer regions of India every year.

Explain the function of mitochondria in a cell.

What is meant by ‘cloning’? State whether gametes are involved in cloning or not. Name two animals which have been produced by cloning.

Answer in brief. What are the causes and consequences of deforestation?

Activity: To make an electric pen.
Materials required: Potassium iodide salt, water, metal sheet, starch solution, paper napkin, copper wire, battery.
Procedure
1. Take potassium iodide salt solution in a beaker, battery and a metal sheet.
2. Connect the metal sheet to the negative terminal of the battery.
3. Add a few drops of starch solution to it
4. Soak a paper napkin in the potassium iodide solution and place it on the metal sheet.
5. Connect another wire to the positive terminal of the battery. Write with the positive terminal on the paper napkin.
Answers the following questions.
(i) Are you able to write?
(ii) Why is it possible?

Look at this food chain:
Grass → Grasshopper → Frog → Snake
If frogs disappear from this ecosystem, what will happen to the population of grasshoppers and snakes? Why?

Paddy is a major cereal crop in our country.
(i) In which season is paddy cultivated ?
(ii) Discuss the method of sowing
(iii) What measures must be taken to prevent spollage and insect attack of harvested grains ?