CBSE Pathshala

Q  Name the cells having branches structure. Ans Nerve Cell. Q Why cells could not be observed before seventeenth century? Ans Cells could not be observed before seventeenth century because till that time microscope was not invented. Q Why plant cell have cell wall? Ans Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture, etc. They are exposed to these variations because they cannot move. That's why they have cell wall. Q Which organism has the smallest cell? Ans  Mycoplasmas, a bacteria has the smallest cell of the size of 0.1 micron i.e. ten thousandth part of a mill metre. ' Q  Which is the largest cell visible by unaided eye? Ans Ostrich egg has the largest visible cell by unaided eye. Q Name the four elements, which fonn major part of protoplasm. Ans These are carbon, hydrogen, oxygen and nitrogen. Q Give two examples of prokaryotes. Ans Bacteria and blue green algae. Q  Name the largest organ

1 The nearest star to the planet earth is: a) Venus b) Sun c) Moon d) Alpha 2  Orion is a name of a ____________________. a) star planet b) planet c) galaxy d) constellation 3  The largest planet of the solar system: a) Mars b) Sun c) Jupiter d) Saturn 4  A body revolving around another body is called as: a) Orion b) Stars c) Sun d) Satellite 5  Name the comet which appears after every 76 years: a) Hallet’s b) Meteor c) Halley’s d) Pole star 6  The first Indian satellite: a) Kalpana-1 b) Aryabhatta c) INSAT d) EDUSAT 7  Distances of stars are expressed in: a) km b) square meter c) light year d) meters 8  The star appears to be stationary from the Earth: a) Pole star b) Sirius c) Orion d) Ursa Major 9 The bright star like objects with a long tail app

 Q1. Define light year. Ans. Light year is the distance travelled by the light in one year. Q2. Name the star nearest to the earth after sun. Ans. Proxima centuari. Q3. Why do stars shine? Ans. Stars are giant ball of gases in space that shine through the darkness and are held together by the force of gravitation. These gasses are hydrogen and helium. Some of the hydrogen is converted into  helium. A star shines due to this reaction nit’s core releasing energy that radiates into the outer space. Q4. What are constellations? Ans. Group of stars that make an imaginary shape in the night sky is called constellations. There are 88 constellations known so far. Examples ursa major, Ursa Minor, Orion, Aries cancer, Cassiopeia, Gemini,  Leo. Q5. Write short note on pole star. Ans. Pole star rises in the east at night and sets in the west in the early morning. Pole star is situated above the axis of rotation of the earth, so it appears stationary from the earth. So it is u

Book resource: Science power Class 8 th Check point-01 [Formative Assessment]        1. Define Afforestation? Answer:  The practice of planting more and more trees is called Afforestation. 2. What is desertification? What causes desertification? Answer: The phenomenon of converting fertile land into desert is called desertification. Deforestation causes desertification. 3. What is the effect of deforestation on rainfall and climate? Answer:  Deforestation increases temperature and wind velocity that reduce rainfall. These changes led to climate change. Check point-02 [Formative Assessment]        1. What is wild life? Answer: Wild life is an area where organism lives in their natural habitat like dense forest, jungle and water bodies. 2. Give one difference between endangered and vulnerable ? Answer: Endangered are those animals that are not likely survive and will soon extinct where as Vulnerable are those animal which are likely to move in enda