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Assertion . Senescence is the time when ...

Assertion . Senescence is the time when age associated defects are manifested
Reason . Certain genes may be undergoing sequential switching on and off during one's life

A

If both A and R are true and R is the correct explanation of A

B

If both A and R are true but R is not the correct explanation of A

C

If A is true and R is false

D

If both A and R are false

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The correct Answer is:
A
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In the atmosphere, carbon dioxide is found in two forms, i.e., ^12CO_2 and ^14CO_2 . Plants absord CO_2 during photosynthesis in presence of chlorophyll, plants synthesise glucose 6CO_2 +6 H_2O rarr C_6H_12O_6 + 6O_2uarr Half life of ^14CO_2 is 5760 years. The analysis of wooden artifacts for ^14C and ^12C gives useful information for determination of its age. All living organisms, because of their constant exchange of Carbon dioxide with the surroundings have the same ratio of C-14 to C-12, i.e. 1.3xx10^-12 . When an organism dies, the C-14 in it keeps on decaying as follows: 6^14Crarr7^14N+(-1)^0e +Energy Thus, the ratio of C-14 and C-12 decreases with the passage of time. We can measure the proportion of C-14 in the remains of dead organism and determine how long ago it died. The method of carbon dating can be used to date anything made or organic matter, e.g., bone, skeleton, wood, etc. Using carbon dating, materials have been dated to about 50,000 years with accuracy. C-14 exists in atmosphere due to:

In the atmosphere, carbon dioxide is found in two forms, i.e., ^12CO_2 and ^14CO_2 . Plants absord CO_2 during photosynthesis in presence of chlorophyll, plants systhesise glucose 6CO_2 +6 H_2O rarr C_6H_12O_6 + 6O_2uarr Half life of ^14CO_2 is 5760 years. The analysis of wooden artifacts for ^14C and ^12C gives useful information for determination of its age. All living organisms, because of their constant exchange of Carbon dioxide with the surroundings have the same ratio of C-14 to C-12, i.e. 1.3xx10^-12 . When an organism dies, the C-14 in it keeps on decaying as follows: 6^14Crarr7^14N+(-1)^0e +Energy Thus, the ratio of C-14 and C-12 decreases with the passage of time. We can measure the proportion of C-14 in the remains of dead organism and determine how long ago it died. The method of carbon dating can be used to date anything made or organic matter, e.g., bone, skeleton, wood, etc. Using carbon dating, materials have been dated to about 50,000 years with accuracy. A piece of wood from an archeological source shows a C-14 activity which is 60% of the activity found in fresh wood today. The age of archeological sample will be:

TRUEMAN BIOLOGY-Plant Physiology -ASSERTION AND REASON
  1. Assertion: Sigmoid growth curve consists of four parts. Reason : La...

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  2. [A] : 2,4-D is a herbicide [R] : It is not used during sowing of cro...

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  3. [A] : Nastic movements occur in the directions of stimuls [R] : "Tou...

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  4. [A] : Germinating seeds which store fats as reserve food material are ...

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  5. [A] : Gibberellic acid , when added to isolated aleurone , induce amyl...

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  6. [A] : When apical bud is removed, the next axial bud begins to grow ou...

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  7. [A]: Xanthium will not flower if the long dark period is interrupted b...

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  8. [A]: Senescence is induced by the applica- tion of cytokinin in plants...

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  9. Assertion : A correct concentration of auxin and cytokinin is required...

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  10. [A]: The endogenous level of plant hormones is measured by Bioassay te...

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  11. [A] : Bolting of rosette plants is caused by Gibberellins. [R]: Gibb...

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  12. (A]: Cytokinins help in retention of cholorophyll and delayed senescen...

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  13. [A]: Plants hormones are called phytohor- mones [R]: They increase ...

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  14. [A] : Senescence occurs in all non meristematic cells. [R]: Meristem...

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  15. Assertion . Senescence is the time when age associated defects are man...

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  16. Assertion: Photosynthetically C(4) plants are less efficient than C(3)...

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  17. Assertion. The atmospheric concentration of CO(2) at which photosynthe...

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  18. Assertion: C(4) photosynthetic pathway is more efficient than the C(3)...

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  19. Assertion : Photomorphogenetic responses are controlled by the pigment...

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  20. [A] : Some plants flower only in summers & some only in winters. [R]...

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