500 Selected Problems in Science

NCERT Class 8 Science Solutions

IMPORTANT QUESTIONS

1. Collect data on the number of children in your class who exercise regularly and who do not exercise regularly. Did you notice any difference in their fitness and health? Prepare a report on the benefits of regular exercise.

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2. Collect information from magazines or from doctors and prepare a note on the importance of consuming iodised salt. You can also look for this information on the internet.

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3. Use the data given in Activity 10.1 to draw a graph. Take age on the X-axis and per cent growth in height on the Y-axis. Highlight the point representing your age on the graph. Find out the percentage of height you have already reached. Calculate the height you might eventually reach. Tally your graph with the one given here (Fig. 10.2).

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4. The following chart gives the average rate of growth in height of boys and girls with age. The figures in columns 2 and 3, give the percentage of the height a person has reached at the age given in column 1. For example, by the age 11, a boy has reached 81 % of this probable full height, while a girl has reached 88% of her full height. These figures are only representative and there may be individual variations. Use the Table for your friends and work out how tall they are likely to be. Find out who is likely to be the tallest and who might be the shortest in your class.

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5. The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

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6. Word game: Use the clues to work out the words. Across: 3. Protruding voice box in boys 4. Glands without ducts 7. Endocrine gland attached to brain 8. Secretion of endocrine glands 9. Pancreatic hormone 10. Female hormone Down: 1. Male hormone 2. Secretes thyroxine 3. Another term for teenage 5. Hormone reaches here through blood stream 6. Voice box 7. Term for changes at adolescence

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7. Write notes on: (a) Adam’s apple (b) Secondary sexual characters. (c) Sex determination in the unborn baby.

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8. Choose the correct option. (a) Adolescents should be careful about what they eat, because:

   • (i) proper diet develops their brains.
   • (ii) proper diet is needed for the rapid growth taking place in their body.
   • (iii) adolescents feel hungry all the time
   • (iv) taste buds are well developed in teenagers.

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9. What are sex hormones? Why are they named so? State their function

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10. Prepare a table having two columns depicting names of endocrine glands and hormones secreted by them.

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