CAPF AC 2021 Q24: Science & Technology – Biology
- (a) They require separate organ for food uptake.
- (b) Separate organ is not needed for respiration.
- (c) Waste of excretory material is produced by these organisms.
- (d) They remain in contact with external environment.
Answer: (a) They require separate organ for food uptake.
Explanation
Life processes in single-celled organisms
How to think: a single-celled organism is one cell only.
An organ is made of many cells and tissues.
So one cell cannot have a separate organ for anything.
| Life process | Single-celled organism (e.g. Amoeba) | Multicellular organism |
|---|---|---|
| Food uptake | Whole surface, by diffusion or food vacuoles | Special organs |
| Respiration | Gases diffuse through the surface | Lungs, gills |
| Excretion | Wastes diffuse out | Kidneys |
| Contact with surroundings | The entire surface touches the environment | Only some cells do |
Why organs are not needed: the whole surface of the cell is in contact with the environment.
Simple diffusion is enough.
Answer: (a) They require separate organ for food uptake.
Why each option is right or wrong
- (a) CORRECT. This statement is wrong: a single cell has no organs; food enters through its surface.
- (b) Incorrect. It is true that no separate organ is needed for respiration.
- (c) Incorrect. It is true that single-celled organisms produce wastes and remove them.
- (d) Incorrect. It is true that the cell stays in contact with the external environment.
Key point
In single-celled organisms the whole surface is in contact with the environment, so no special organs are needed for taking food, exchanging gases or removing wastes (NCERT, Life Processes).
Remember
One cell, no organs; diffusion does the work.
Common mistakes
- Missing the word not and marking a statement that is actually true.
- Thinking single-celled organisms do not produce any waste material.
- Calling a food vacuole or pseudopodia an organ; they are parts of one cell.
Exam tip
Educated guess: options (a) and (b) say opposite things about organs. One of them must be the wrong statement, and one cell cannot own an organ.
Sources
- NCERT Class X Science — Life Processes (what are life processes)
- NCERT Class IX Science — The Fundamental Unit of Life