Subject

Biology

Class

ICSE Class 12

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51.

Explain:

(i) Exponential population growth

(ii) Environmental Resistance

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52. Explain the origin of Bread Wheat.

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53. How does palaeontological evidence support the theory of organic evolution ? Explain with an example.

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54. What complications will arise if the blood of an Rh +ve person is transferred to a Rh -ve person and vice versa ?

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55.

What is feedback control ? Illustrate feedback mechanism of homeostasis by an example of hormones.

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56.

Explain the following :

(i) Tidal volume
(ii) Portal vein
(iii) Ultrafiltration

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57.

Give an account of the cohesion and transpiration pull theory of ascent of sap.

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C₃ Plants	C₄ Plants
CO₂ acceptor is RuBP (Ribulose bisphosphate).	CO₂ acceptor is PEP (Phosphoenol pyruvate).
Only one type of chloroplasts occur in the cells. Grana present in chloroplasts.	Two types of chloroplasts, bundle sheath chloroplasts possess C₃ cycle and do not have grana; mesophyll chloroplasts possess C₄ cycle and have grana.
Plant photosynthesize well if CO₂ concentration is high.	Plants synthesize well even if CO₂concentration is low.
They possess photorespiration that results in low overall efficiency in synthesis of carbohydrates.	They lack photorespiration and conserve more organic food and thus an overall higher photosynthetic efficiency.
Excess of atmospheric oxygen inhibits photosynthetic activity.	Excess of atmospheric oxygen has no effect on photosynthesis.