Q.Growth is one of the characteristic of all living organisms. Do unicellular organisms also grow? If so, what are the parameters?

Yes, unicellular organisms also grow, even though they consist of just one cell. Since growth is fundamentally an increase in the amount of protoplasm, a single cell can show this increase directly, and it would be measured using the same kinds of parameters used for any growing cell — increase in cell size (volume), increase in fresh or dry weight, and, once the cell eventually divides, an increase in cell numb …

Growth is defined as an irreversible, permanent increase in the size of an organ, its parts, or even of an individual cell, and at the cellular level this increase is essentially a consequence of increasing protoplasm. Nothing in this definition requires the organism to be multicellular — a single cell is fully capable of showing a genuine, irreversible increase in its own material.

For a unicellular organism, then, growth is measured using the same general kinds of parameters applied to any growing cell:

• an increase in the cell's fresh weight or dry weight,
• an increase in its length, area or volume, and …

Method: Applying the General Growth Definition to a New Case

Use this method whenever asked whether a given organism/organ/cell "grows," and what parameters would measure it.

Steps

Step 1: Start from the definition, not the example

Growth is defined as an irreversible, permanent increase in mass (protoplasm) and/or size — not tied to any particular body plan. Nothing in this definition requires multiple cells, so the test for "does X grow?" is simply: does X show this kind of irreversible increase?

Step 2: Check the case against the definition

Apply the definition to the specific case in the question. If the entity in question can increase its own protoplasm/size irreversibly, the definition is satisfied — the answer is yes, regardless of how small or simple the organism is.

Step 3: Choose parameters appropriate to what can actually be measured …