Absolute vs Relative Growth Rate — NEET Biology
📚 Practice ConceptQuantitative comparisons between the growth of living system can also be made in two ways: (i) measurement and the comparison of total growth per unit time is called the absolute growth rate. (ii) The growth of the given system per unit time expressed on a common basis, e.g., per unit initial parameter is called the relative growth rate. In two leaves, A and B, are drawn that are of different sizes but shows absolute increase in area in the given time to give leaves, A¹ and B¹. However, one of them shows much higher relative growth rate. Which one and why?
Which of the following statements regarding the comparison of growth rates are NOT correct? S1: If leaf X has an initial area of 10 cm² and increases to 20 cm², its absolute growth rate is 10 cm² per unit time. S2: For leaf X (initial area 10 cm²), its relative growth rate after increasing to 20 cm² is 100%. S3: If leaf Y has an initial area of 100 cm² and increases to 110 cm², its absolute growth rate is higher than leaf X. S4: Comparing leaf X and leaf Y, leaf Y would exhibit a higher relative growth rate due to its larger initial size. S5: Relative growth rate is calculated by expressing the growth of a system per unit time on a common basis, typically per unit initial parameter.
View solution & NCERT explanation
Correct answer: B — S3 and S4
This question requires an understanding of absolute and relative growth rates and their application in comparing growth scenarios. S1: Correct. Absolute growth is the total increase in size. For leaf X, the increase is 20 cm² - 10 cm² = 10 cm². (NCERT Page 171, Para 1, Line 3-4) S2: Correct. Relative growth rate = (Absolute growth / Initial size) * 100. For leaf X, (10 cm² / 10 cm²) * 100 = 100%. (NCERT Page 171, Para 1, Line 5-6) S3: Incorrect. For leaf Y, the absolute growth is 110 cm² - 100 cm² = 10 cm². This is the same absolute growth as leaf X (10 cm²), not higher. (NCERT Page 171, Para 1, Line 3-4) S4: Incorrect. For leaf Y, the relative growth rate is (10 cm² / 100 cm²) * 100 = 10%. Leaf X has a relative growth rate of 100%, which is much higher than leaf Y. A larger initial size with the same absolute growth typically results in a *lower* relative growth rate. (NCERT Page 171, Figure 13.7 and its explanation) S5: Correct. This is the definition of relative growth rate. (NCERT Page 171, Para 1, Line 5-6) Therefore, statements S3 and S4 are NOT correct. The tested concept is the application and interpretation of absolute and relative growth rates.
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