31 December 2011

CBSE Class 8th Science Assignments

CLASS VIII LESSON-11(HUMAN EYE)

Q.1. Explain the structure of eye.
Q.2.How are we able to see in dim and bright light?
Q.3.What is the function of the ciliary muscles?
Q.4.What kind of image is formed by eye-lens?
Q.5.What are photo receptors?
Q.6.How we can see colours?
Q.7.What is persistence of vision?
Q.8.How does persistence of vision help to see the object as moving?
Q.9.How are we able to see a moving picture?
Q.10.Which principle is used in cinematography?
Q.11.What happens when an object is brought closer to the eye and why?
Q.12.What is the near point of the eye?
Q.13.What are the two defects of the eye?
Q.14.What are the different reasons for vision problems?
Q.15.Who developed Braille system?

LESSON ---- 15 ( REACHING THE AGE OF ADOLESCENCE )

Q.1.What initiates changes at puberty?
Q.2. Is there any role of hormones in completing life history of insects and frogs?
Q.3.What is the function of endocrine system?
Q.4.Name the major glands that make up the endocrine system.
Q.5. Write a short note on Adam’s apple.
Q.6. Name some vitamins and minerals needed by adolescents to build strong and healthy bones.
Q.7.Name the hormones released by the various glands in our body. Mention the function of each hormone.
Q.8.Write some habits that adolescents need to adopt to maintain personal hygiene.
Q.9.Discuss the consequences of taking drugs by the adolescents.
Q.10. Is mother responsible for determining the sex of a child? Give reasons for your answer.

Lesson 13 ( Synthetic Fibres and Plastics) 

Q1. Give some examples of Natural and Synthetic fibres.
Q2. What are monomers and polymers ?
Q3. What is polymerisation ?
Q4. What is Rayon ? Why is it not truly an artificial fibre ?
Q5.Give some features and uses of Terylene and acrylic fibres.
Q6. What are the advantages of synthetic fibres ?
Q7. Write some disadvantages of synthetic fibres.
Q8. What are plastics ? What are its different types ?
Q9. Differentiate between Thermoplastics and Thermosetting plastics.
Q10. What are the characteristics of synthetic plastics ?
Q11. Differentiate between biodegradable and non-biodegradable.
Q12. Give some measures to control the damage caused by plastic waste.
Q13. Name the first fully synthetic fibre. What are its different uses ?
Q14. Should the handle and bristles of a tooth brush be made of the same material ? Explain your answer.
Q15. Explain why the following materials are made of thermosetting plastics –
(i) Saucepan handles      (ii) Kitchenware

LESSON- 14 (REPRODUCTION IN ANIMALS )

Q.1. Define the following terms -- reproduction , hatching.
Q.2.Explain the process of budding in hydra and yeast.
Q.3. How does external fertilization take place in frogs?
Q.4. Explain the male reproductive system in humans.
Q.5.Draw the diagram of human sperm and explain its structure.
Q.6. Differentiate between asexual and sexual reproduction.
Q.7. Why does a child show some characteristics of the father and some of the mother?
Q.8. Explain the importance of reproduction in organisms.
Q.9. Differentiate between oviparous and viviparous animals.
Q.10.Why do fish and frogs lay eggs in hundreds whereas a hen lays only one egg at a time?

CHAPTER – 9(CROP PRODUCTION AND ITS MANAGEMENT) 

Q1 What is crop production?
Q2 Define agriculture and agricultural practices.
Q3 What are rabi crops?
Q4 Write agricultural practices required for growing crops.
Q5 What is soil made up of ?
Q6 Write short note on ”SOWING”and “SEED DRILL”.
Q7 What is manuring? Why is it important?
Q8 How do farmers prepare manure?
Q9 What are the advantages of manure?
Q10 Why is overuse of fertilizer harmful?
Q11 How do leguminous plants help in increasing the nitrogen content of the soil?
Q12 Define irrigation. How is it done ?
Q13 Why is the minimum use of pesticides advised?
Q14 What is harvesting? What are its different methods?
Q15 What is winnowing? How is it done?
Q16 Why do we sundried the grains before storing?
Q17 What is green revolution?
Q18 Why were Mexican wheat introduced in India?
Q19 Define – Hybridization , Emasculation .
Q20 Why is cross breeding done?
Q21 Where is hybridization done?
Q22 How can we provide food to a large number of people in our country?
Q23 Why can paddy not be grown in the winter season?
Q24 Why do some plants grow better than others?
Q25 Explain how fertilizers and manures are different from each other.
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