Class 11 · Plant Growth and Development

Sigmoid Growth Curve in Living Organisms — NEET Biology

✅ Asked in NEET 2015
✅ NEET 2015 PYQ

Typical growth curve in plants is: (AIPMT 2015 Cancelled Paper)

QuestionNEET 2015

Typical growth curve in plants is: (AIPMT 2015 Cancelled Paper)

Answer & NCERT explanation

Correct answer: D Sigmoid

Typical plant growth curve is SIGMOID (S-shaped). According to NCERT, it has three phases: slow initial lag phase, rapid exponential phase, and stationary phase where growth rate decreases. This creates an S-shaped curve. Linear growth would be constant rate, stair-steps and parabolic don't represent typical plant growth patterns accurately.

Read more NCERT concept on the PYQ

📖 NCERT Source

Let us now see what happens in geometrical growth. In most systems, the initial growth is slow (lag phase), and it increases rapidly thereafter – at an exponential rate (log or exponential phase). Here, both the progeny cells following mitotic cell division retain the ability to divide and continue to do so. However, with limited nutrient supply, the growth slows down leading to a stationary phase. If we plot the parameter of growth against time, we get a typical sigmoid or S-curve. A sigmoid curve is a characteristic of living organism growing in a natural environment. It is typical for all cells, tissues and organs of a plant. Can you think of more similar examples? What kind of a curve can you expect in a tree showing seasonal activities?

📐See NCERT Figure 13.6 for the diagram.
NCERT Biology · Class 11 · Chapter 13 · Paragraph 14
How NTA Uses This Concept

NTA tests the sigmoid (S-shaped) curve as the characteristic growth pattern of living organisms in natural environments. This curve has three distinct phases: lag phase (slow initial growth), log/exponential phase (rapid growth), and stationary phase (growth slows due to limited nutrients). Students often confuse sigmoid curves with J-shaped (exponential) curves, forgetting that resources are always limited in real environments, preventing indefinite exponential growth. Remember: sigmoid curves are typical for ALL cells, tissues, organs, and organisms—this is the key distinguishing feature NTA wants you to know for any organism growth question.

❓ Frequently Asked Questions
What does NCERT say about Let us now see?
Let us now see what happens in geometrical growth. In most systems, the initial growth is slow (lag phase), and it increases rapidly thereafter – at an exponential rate (log or exponential phase).
Has this concept appeared in NEET?
Yes — appeared in NEET 2015. Sigmoid curve characteristic of living organisms explicitly mentioned
Which chapter is this from?
Plant Growth and Development, Class 11 NCERT Biology.

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