Intrinsic Rate of Natural Increase (r) — Norway Rat, Flour Beetle, Human
📚 Practice ConceptTo give you some idea about the magnitude of r values, for the Norway rat the r is 0.015, and for the flour beetle it is 0.12. In 1981, the r value for human population in India was 0.0205. Find out what the current r value is. For calculating it, you need to know the birth rates and death rates.
Norway rat has the highest intrinsic rate of natural increase (r = 0.015) among NCERT examples.
FLOUR BEETLE has the highest r at 0.12 — much higher than Norway rat (0.015) and human (0.0205 in India, 1981).
Order: Flour beetle 0.12 > Human 0.0205 > Norway rat 0.015. Smaller + shorter generation = higher r.
- Norway rat: r = 0.015 (NCERT exact).
- Flour beetle: r = 0.12 (highest of the three NCERT examples).
- Human population in India (1981): r = 0.0205.
- Higher r generally correlates with smaller body size and shorter generation time.
Consider the following statements about the intrinsic rate of natural increase (r): S1: The r value for Norway rat is 0.015 according to NCERT. S2: The r value for flour beetle is 0.12, the highest among the NCERT-cited examples. S3: The r value for the human population in India in 1981 was 0.0205. S4: Norway rat has the highest r among Norway rat, flour beetle and human. S5: Calculation of r requires knowledge of birth rates and death rates.
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Correct answer: A — S1, S2, S3 and S5
S1 CORRECT: Norway rat r = 0.015 (NCERT). S2 CORRECT: Flour beetle r = 0.12 — highest of the three. S3 CORRECT: Human (India 1981) r = 0.0205. S4 WRONG: FLOUR BEETLE (0.12) has the highest r, NOT Norway rat (0.015). This is the classic ordering trap. S5 CORRECT: NCERT explicitly says you need birth rates and death rates to calculate r (r = b − d in the simplest expression).
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