Question

Which of the following is a defining characteristic of living organisms?
A. Growth
B. Ability to make sound
C. Reproduction
D. Response to external stimuli

Answer 1

Hint: A defining characteristic is a property which is so distinctive that all the members of the certain groups should possess to determine their membership in that particular group.

Complete answer:
Growth is the defining characteristic of living organisms. But, sometimes in non-living organisms, the growth is seen by the accumulation of materials on the surface. Growth of crystal, sand dunes, mountains are some of the examples where we see external growth. So we can say that growth in living organisms is internal whereas growth in non-livings organisms is external as the material is accumulated on the surface. Hence, ‘option A’ is incorrect.
The ability to make sound is not found in lower animals and microorganisms. Some non-living objects such as motor, generator, car make sounds. That’s why making sound is not a defining characteristic of living organisms. Hence, ‘option B’ is incorrect.
All the living organisms have the capability to reproduce either by sexually or asexually. It is one of the most important processes by which a new organism is produced. Reproduction helps for the continuation of their species or else they could have become extinct. Non-living things don’t have these characteristics. But, there are some living organisms which can’t reproduce such as mule, liger, worker honey bee, etc. Infertile humans also lose the ability to reproduce. Hence, ‘option C’ is incorrect.
All living things respond to any change in the environments and that response is called a stimulus. Living organisms respond to light, sound, heat and chemical and mechanical contact. Thus it produces a response. Non-livings do not display this property.

Hence, the correct answer is option (D).

Note: Stimulus is a detectable change in the external or internal environment of an organism. This triggers sensory receptors which are sent to the central nervous system. The central nervous system decides how the body should respond. The response is called the effector.