Biology:2004:CBSE:[ Delhi ]:Set-II
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Q1
Define vernalisation. Marks:1View AnswerAnswer:
Vernalization – This is the chilling treatment of the plant responsible for an early flowering in them.
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Q2
Many villagers near industrial area suffer from "blue baby syndrome". How is this problem caused? Marks:1View AnswerAnswer:
The disease can be caused by in-take of water and vegetables high in nitrate, exposure to chemicals containing nitrate, or it can even be hereditary. -
Q3
A cardiologist observed an elevated St segment in the ECG of a patient. What is it indicative of? Marks:1View AnswerAnswer:
Elevation of ST region in an ECG signifies abnormal Ventricular contraction due to myocardial infarction.
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Q4
Why is quarantine a must before introduction of a plant species from a different country?
Marks:1View AnswerAnswer:
It is essential to protect managed crops and natural flora from harmful pests and diseases.
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Q5
How does saliva act in body defence? Marks:1View AnswerAnswer:
Saliva contains an enzyme lysozyme which dissolves the bacterial walls entering our body through mouth. -
Q6
Where is pneumotoxic centre located in humans? What is its significance in breathing? Marks:2View AnswerAnswer:
Pneumatic centre is a group of neurons present in the Pons region of the brain. It can moderate the respiratory rhythm by sending a neural signal to reduce the duration of inspiration and finally the respiratory rate.
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Q7
How is a disease-resistant plant selected for successful breeding? Marks:2View AnswerAnswer:
In the selection of disease-resistant plants for successful breeding : - First of all, the plants are exposed to the disease causal organisms. - After that, those plants will be selected which do not show any symptoms of the disease. - These will be self pollinated for 2-3 generations and after confirmation, if these plants are not showing any symptoms in these generations, these will be used for breeding experiments. -
Q8
How is opening and closing of stomata controlled? Explain. Marks:2View AnswerAnswer:
Out of syllabus
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Q9
Why is the length of a food chain in an ecosystem generally limited to 3 - 4 trophic levels? Explain with an example. Marks:2View AnswerAnswer:
Food chain’s length of natural communities usually range from 3-4 and rarely exceed five because according to 10% law of flow of energy, only 10% of the total energy is available to the next trophic level. The larger the food chain, the lesser is the energy available to the final trophic level of the food chain. Hence, the food chains usually have 3-4 trophic levels.
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Q10
What is hydroponics? Give one application of this technique. Marks:2View AnswerAnswer:
Hydroponics is the cultivation of plants in water not in soil.Nutrients are dissolved in water.
This technique is used to grow plants in a controlled medium.
