Exploring Logistic Growth Limits

00:00 12 marks

  • Exam Style - Paper 3
  • HL
  • Tier 3
  • Exponential equations
  • Mathematical Modeling
  • Limits
  • Logistic growth

Consider the logistic function \(P(t) = \frac{L}{1+e^{-k(t-t_0)}}\), where \(L\) is the carrying capacity, \(k\) is the growth rate, and \(t_0\) is the inflection point.

(a) Derive the limit of \(P(t)\) as \(t \to \infty\) and explain its significance.

(b) Given that \(L=1000\), \(k=0.5\), and assuming \(t_0=0\), determine the value of \(t\) when \(P(t)=900\).

(c) Discuss how the limit from part (a) and the threshold solution from part (b) can be applied in real-world ecological models.

Part a

4 minutes 4 marks

Question

Derive the limit of the logistic function \(P(t) = \frac{L}{1+e^{-k(t-t_0)}}\) as \(t \to \infty\) and explain its significance.



Hint Hint

Hint

Consider the behavior of \(e^{-k(t-t_0)}\) as \(t\) increases indefinitely.

  • Answer Answer

Complete Answer

The limit is \(L\), which represents the carrying capacity of the system.

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Part b

4 minutes 4 marks

Question

Given \(L=1000\), \(k=0.5\), and \(t_0=0\), determine the value of \(t\) when \(P(t)=900\).



Hint Hint

Hint

Set \(\frac{1000}{1+e^{-0.5t}}=900\) and solve for \(t\) by isolating the exponential term.

  • Answer Answer

Complete Answer

Approximately \(t \approx 4.39\)

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Part c

4 minutes 4 marks

Question

Discuss how the limit from part (a) and the threshold solution from part (b) can be applied in real-world ecological models.



Hint Hint

Hint

Think about how the carrying capacity and the time to approach a threshold can impact resource and population management in ecology.

  • Answer Answer

Complete Answer

The limit \(L\) represents the carrying capacity, indicating the maximum population size an ecosystem can sustainably support. The time \(t\) calculated in part (b) shows how quickly a population approaches a significant threshold (90% of \(L\) in this case). In ecological models, these parameters are crucial for understanding population dynamics, managing resources, predicting stabilization periods, and assessing the impact of environmental changes or interventions on population growth.

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