Ques. 1NEET 2016 (Phase 1)
When does the growth rate of a population following the logistic model equal zero? The logistic model is given as dN/dt = rN(1-N/K)
- When death rate is greater than birth rate.
- When N/K equals zero.
- When N/K is exactly one.
- When N nears the carrying capacity of the habitat.
Answer
(3) When N/K is exactly one.
Solution
As per NCERT, logistic growth: dNdt = rN ( K-NK )
⇒ dNdt = 0 when 1 - NK = 0
∴ NK = 1, i.e. N = K exactly (population at carrying capacity).
∵ When N only nears K, growth rate is small but not zero; when N/K = 0, there is no population at all.
Answer: (3)