The wild ancestor of bread wheat i.e., Triticum boeoticum (2n = 14) which grew as early as 10,000-15,000 B.C. The cultivated diploid species was T. monococcum (2n = 14) T. monococcum was naturally fertilized by will goat grass, T. speltoides having 2n = 14. The diploid hybrid of these species was sterile, which became fertile and allotetraploid (4n = 28),now known as T. turgidum. A natural mutant of T. turgidum is represented by tetraploid T. durum (4n = 28) which crossed with diploid grass, Aegilops squarrosa (2n = 14) under natural conditions. The resultant triploid hybrid was sterile which on doubling of chromosomes produced the hexaploid bread wheat, T. aestivum (6n = 42).
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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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58.Write the differences between C3 and C4 cycles.
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59.Explain the development of the different types of endosperms in angiosperms.
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60.How does the human body protect itself from infection ?
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