Biology · The Living World · NEET
No. Reproduction is a characteristic of life, but it is NOT a defining property. NCERT is very clear on this. A defining property must be true for EVERY living thing. But some living organisms cannot reproduce — for example a mule (born from a horse and a donkey), sterile worker bees and worker ants, and human couples who are infertile. These are all fully alive but cannot reproduce. So reproduction fails the test of being a defining property. Only metabolism is the true defining property that no living thing can do without.
A characteristic is a feature that many living things show, but not all. A defining property is a feature that ALL living things must have, with no exception. Reproduction, growth, and consciousness are characteristics — they can be absent in some living organisms (a mule does not reproduce, a fully grown adult tree grows very little). Metabolism is the only DEFINING property, because there is no living thing that does not carry out metabolism. For NEET, remember: exceptions exist for reproduction and growth, but there is NO exception for metabolism.
In unicellular organisms, such as bacteria and Amoeba. In these organisms, growth means an increase in the number of cells by cell division. But cell division is also how they reproduce and make more individuals. So in unicellular organisms, growth and reproduction are the SAME process — they are synonymous. This exact point was asked in NEET 2016. In multicellular organisms, growth (increase in body size) and reproduction (making new individuals) are two different processes.
Because being alive does not depend on reproduction. A mule shows metabolism (all the chemical reactions inside its body), it responds to its environment, it has cellular organisation, and its cells self-replicate. All these prove it is living. Reproduction is only one feature that MAY be present. Since the mule shows every defining property except reproduction, it is 100% living. This is exactly why NCERT says reproduction cannot be a defining property of life.
Yes, NCERT does say living organisms reproduce to form offspring (progeny) similar to themselves. This describes what reproduction IS. But NCERT immediately adds the important twist: there are MANY organisms that do not reproduce (mules, sterile workers, infertile couples). Because these organisms are still living, reproduction cannot be used as the single rule to define life. So reproduction is described as a property but then ruled out as a DEFINING property. Read both lines together — that is the common trap.
Study the four statements (A–D) given below and select the two correct ones out of them: A. Definition of biological species was given by Ernst Mayr. B. Photoperiod does not affect reproduction in plants. C. Binomial nomenclature system was given by R.H. Whittaker. D. In unicellular organisms, reproduction is synonymous with growth. The two correct statements are:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is a characteristic of life, but NOT a defining property. All living things do not reproduce (for example mules and sterile bees), so it cannot define life. Only metabolism is the defining property.
Mules (horse + donkey hybrid), sterile worker bees and worker ants, and infertile human couples. They are fully alive but cannot produce offspring.
With growth. In organisms like bacteria and Amoeba, an increase in cell number by cell division is both growth and reproduction, so the two mean the same thing.
Metabolism — the sum of all chemical reactions in the body. No living thing can exist without metabolism, so it is the only defining property, unlike reproduction and growth which have exceptions.
Because it is a classic trap. NCERT first says organisms reproduce, then says many living organisms do not reproduce. Students who read only one line pick the wrong answer, so NTA loves testing this exception.
