Science:2010:CBSE:[All India]:Set-III
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Q1
Give one reason why multicellular organisms require special organs for exchange of gases between their body and their environment.
Marks:1View AnswerAnswer:
In multicellular organisms, all the cells are not in direct contact with the external environment; therefore, direct exchange of gases cannot take place. Hence, they require special organs for exchange of gases.
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Q2
Mention one example of chemotropism.
Marks:1View AnswerAnswer:
The growth of pollen tube towards the ovule is an example of chemotropism.
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Q3
State any one difference between autotrophic and heterotrophic modes of nutrition.
Marks:1View AnswerAnswer:
Organisms which adopt autotrophic mode of nutrition depend upon inorganic raw materials like CO2, H2O and sunlight for their nutritional requirement.
Organisms which adopt heterotrophic nutrition depend upon autotrophs for their nutritional requirements. -
Q4
Name the component of white light that deviates the least and the component that deviates the most while passing through a glass prism.
Marks:1View AnswerAnswer:
The least deviated component of white light is red and the most deviated component of white light is violet.
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Q5
Which bases are called alkalis? Give an example of alkalis.
Marks:1View AnswerAnswer:
The bases which are soluble in water are called alkalis. For example: NaOH, KOH.
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Q6
Write the names and chemical formulae of the products formed by the action of chlorine on slaked lime.
Marks:1View AnswerAnswer:
Chlorine acts on slaked lime and the products formed are bleaching powder and water.
Ca(OH)2 + Cl2 ® CaOCl2 + H2O
Slaked lime Bleaching powder
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Q7
A person is advised to wear spectacles with concave lenses. What type of defect of vision is he suffering from?
Marks:1View AnswerAnswer:
He is advised to use concave lens as he cannot see the distant objects clearly, so he is suffering from myopia.
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Q8
What will be the observed colour of the sky on a planet where there is no atmosphere? Why?
Marks:1View AnswerAnswer:
The sky would appear to be dark because no light would be scattered to the observer’s eye.
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Q9
What change in colour is observed when white silver chloride is left exposed to sunlight? State the type of chemical reaction in this change.
Marks:1View AnswerAnswer:
White silver chloride when exposed to sunlight changes to grey coloured metallic silver.
This is a type of photo-decomposition reaction.
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Q10
Construct an aquatic food chain showing four trophic levels.
Marks:2View AnswerAnswer:
Algae
Krill Smelt(Fish)Herring
Trophic levels 1 2 3 4
