Class 12 · Organisms and Populations

Verhulst-Pearl Logistic Growth — Sigmoid Curve and Carrying Capacity

✅ Asked in NEET 2026
✅ NEET 2026 PYQ · Asked 4 times

Which equation depicts Verhulst-Pearl logistic population growth?

Q1 of 4NEET 2026 (cancelled)

Which equation depicts Verhulst-Pearl logistic population growth?

Q2 of 4NEET 2024

The population growing in a habitat with limited resources will show: A. Lag phase, followed by phases of acceleration and deceleration and finally an asymptote. B. The ability to realise its innate potential to grow in number and reach enormous densities in a short time. C. Exponential growth D. Logistic growth Choose the correct answer from the options given below:

Q3 of 4NEET 2023

Match List-I with List-II: (NEET 2023) List-I (Population Term) A. Logistic growth B. Exponential growth C. Expanding age pyramid D. Stable age pyramid List-II I. Unlimited resource availability condition II. Limited resource availability condition III. % individuals: Pre > Reproductive > Post IV. % individuals: Pre ≈ Reproductive

Q4 of 4NEET 2017

Asymptote in a logistic growth curve is obtained when: (NEET 2017)

Answer & NCERT explanation

Correct answer: B dN/dt = rN(K-N)/K

The Verhulst-Pearl logistic growth equation is dN/dt = rN(K-N)/K, where K is the carrying capacity, r is intrinsic rate of natural increase, and N is population density.

Read more NCERT concept on the PYQ

📖 NCERT Source

A population growing in a habitat with limited resources show initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth and is described by the following equation:

NCERT Biology · Class 12 · Chapter 11 · Paragraph 32
🎨 Visual Reference
Verhulst-Pearl Logistic Growth — Sigmoid Curve and Carrying Capacity — diagram
How NTA Uses This Concept

When resources are limited, populations cannot grow exponentially indefinitely. Verhulst and Pearl described logistic growth with the equation dN/dt = rN(K-N)/K, where N = population size, r = intrinsic growth rate, K = carrying capacity. This produces a characteristic S-shaped (sigmoid) curve with four phases: (1) lag phase — slow start as population is small, (2) acceleration — rapid growth as N is still much smaller than K, (3) deceleration — growth slows as resources diminish, and (4) asymptote — when N equals K, dN/dt = 0 and growth stops. The sigmoid curve is the defining feature of logistic growth and contrasts with the J-shaped curve of exponential growth.

🔬 Deeper than NCERT

NCERT gives the equation but NTA tests your ability to identify it from wrong alternatives. The critical term is (K-N)/K — this is the fraction of carrying capacity still available. When N approaches K, this term approaches zero, slowing growth to a halt. The wrong options in NEET use (K+N)/K or (K-N)/N — memorise that the denominator must be K (not N), and the numerator must be (K-N) not (K+N). The asymptote at K=N is where dN/dt = 0, which is the mathematical definition of the asymptote condition.

⚠️ The NTA Trap
✗ Common wrong answer

dN/dt = rN(K+N)/K — students confuse the + and - sign, or place N in the denominator instead of K.

✓ The correct framing

dN/dt = rN(K-N)/K — always (K-N) in numerator and K in denominator. When N=K, growth = 0.

💡 Memory hook

K-N over K: as N fills K, the fraction SHRINKS to zero — growth stops at K=N (asymptote)

📌 Key Facts
  • When N = K (population equals carrying capacity): dN/dt = 0 — this is the mathematical asymptote condition.
  • Logistic growth produces S-shaped (sigmoid) curve; exponential growth produces J-shaped curve.
  • K = carrying capacity = maximum population the environment can sustainably support.
  • Expanding age pyramid: pre-reproductive > reproductive > post-reproductive (% individuals). Stable pyramid: pre-reproductive ≈ reproductive.
🎯 Bonus Practice from MedicNEET
QuestionMedicNEET Practice

Match List-I (Population Growth Term) with List-II (Correct Description): List-I A. Logistic growth asymptote B. r-value approaches zero C. dN/dt = rN D. (K-N)/K approaches zero List-II I. Exponential growth equation II. Occurs when N = K III. Population growth slowing but not zero IV. Population is near carrying capacity

View bonus solution & explanation

Correct answer: A A-II, B-III, C-I, D-IV

A-II: Asymptote occurs when N=K (dN/dt=0). B-III: When r approaches zero, growth slows but doesn't necessarily equal K=N (distinguishes from asymptote). C-I: dN/dt = rN is the exponential growth equation (no K term). D-IV: (K-N)/K approaches zero when N approaches K — meaning population is near carrying capacity. This tests precise understanding of all logistic growth terms.

❓ Frequently Asked Questions
What is Verhulst-Pearl Logistic Growth?
When resources are limited, populations cannot grow exponentially indefinitely. Verhulst and Pearl described logistic growth with the equation dN/dt = rN(K-N)/K, where N = population size, r = intrinsic growth rate, K = carrying capacity.
What did NEET 2026 ask on Verhulst-Pearl Logistic Growth?
In NEET 2026, the question was: "Match List-I (Population Growth Term) with List-II (Correct Description):" The correct answer is A — A-II, B-III, C-I, D-IV.
What is the most common NEET trap on Verhulst-Pearl Logistic Growth?
Common wrong answer: dN/dt = rN(K+N)/K — students confuse the + and - sign, or place N in the denominator instead of K. Correct: dN/dt = rN(K-N)/K — always (K-N) in numerator and K in denominator. When N=K, growth = 0.
How do you remember Verhulst-Pearl Logistic Growth for NEET?
K-N over K: as N fills K, the fraction SHRINKS to zero — growth stops at K=N (asymptote) Key fact: When N = K (population equals carrying capacity): dN/dt = 0 — this is the mathematical asymptote condition.
What are the key components of Verhulst-Pearl Logistic Growth?
(1) When N = K (population equals carrying capacity): dN/dt = 0 — this is the mathematical asymptote condition. (2) Logistic growth produces S-shaped (sigmoid) curve; exponential growth produces J-shaped curve. (3) K = carrying capacity = maximum population the environment can sustainably support.

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