Introduction
The question “What is living?” is the starting point of Class 11 Biology, Unit-1: Diversity in Living World. According to NCERT, living organisms show certain basic characteristics which distinguish them from non-living things. This topic is conceptual and frequently tested in NEET. In this post, you will study the NCERT definition of living, important characteristics, and exam-oriented points.
🎥 Students who prefer video explanation can watch the lecture first. NCERT-based notes are given below.
What is Living? (NCERT Concept)
Living organisms are those which show growth, reproduction, metabolism, cellular organization, and response to stimuli. However, no single characteristic alone can define living organisms.
📌 NCERT Key Line:
“No single property can define living organisms.”
Characteristics of Living Organisms
1️⃣ Growth
Increase in mass or number of cells is called growth
Living organisms grow from inside
Growth in plants is indefinite
Non-living objects may increase in size by external addition, which is not true growth
📌 NEET Point: Growth alone cannot define life (e.g., crystals grow but are non-living).
2️⃣ Reproduction
Ability to produce offspring
Modes:
Asexual reproduction (bacteria, fungi)
Sexual reproduction (plants, animals)
❗ Important NCERT Exception:
Some living organisms do not reproduce:
Mules
Sterile worker bees
Infertile humans
📌 Conclusion: Reproduction is not an absolute defining property of life.
3️⃣ Metabolism (Most Important) ⭐
All chemical reactions occurring inside the body are called metabolism
Includes:
Anabolism (building reactions)
Catabolism (breaking reactions)
📌 NCERT Golden Line (Very Important for NEET):
“Metabolism is a defining feature of all living organisms.”
❗ Metabolic reactions never occur in non-living objects.
4️⃣ Cellular Organisation
All living organisms are made up of cells
Cells are the basic structural and functional units of life
Non-living objects do not show cellular organisation
📌 NEET Focus: Cellular organisation is a universal property of life.
5️⃣ Consciousness (Response to Stimuli) ⭐
Ability to respond to environmental stimuli like:
Light
Temperature
Chemicals
Touch
📌 Examples:
Plants bend towards light
Humans respond to heat or pain
📌 NCERT Point:
Consciousness is the most obvious and technically complicated feature of life.
Can Viruses Be Considered Living? (Conceptual Question)
Viruses are living only inside host cells
Outside the host, they behave as non-living particles
📌 NEET Tip:
Viruses are placed at the borderline of living and non-living.
Important NCERT Points for NEET
No single characteristic defines life
Metabolism is the defining property of living organisms
Reproduction is not essential for defining life
Consciousness is a unique property of living beings
All living organisms show cellular organisation
Quick Revision Box (Exam Ready)
Growth → internal in living beings
Reproduction → not universal
Metabolism → defining feature ⭐
Cells → basic unit of life
Consciousness → response to stimuli
Common NEET Traps (Be Careful ⚠️)
❌ Growth = life (Wrong)
❌ Reproduction = life (Wrong)
✅ Metabolism = life (Correct)
Conclusion
The concept of “What is Living?” forms the foundation of Biology. For NEET, understanding NCERT statements and exceptions is more important than memorising definitions. Focus especially on metabolism and consciousness, as these are high-yield areas for examination.
