Why do single-celled organisms do not need specific organs for taking in food, exchanging gases, or removing wastes?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2: Their entire surface is in contact with the environment.
Explanation:
The entire body of unicellular organisms (such as Amoeba and Paramecium) consists of just a single cell.
Since their bodies are extremely minute, their entire outer surface (the cell membrane) remains in direct contact with the surrounding environment.
Due to this direct contact with the environment, they do not require any specialized organs for ingesting food, taking in oxygen, releasing carbon dioxide, or expelling waste products. All these functions are carried out directly through the cell surface via a simple process known as 'Diffusion'.
Key Points:
Diffusion: This is the process by which particles move from a region of higher concentration to a region of lower concentration. Unicellular organisms rely primarily on this process for their daily metabolic activities.
Difference from Multicellular Organisms: In large and complex organisms like humans, not all body cells are in direct contact with the external environment; therefore, we require specialized organs such as lungs, a digestive system, or an excretory system.
Nutrition in Amoeba: Amoeba captures its food with the help of its 'pseudopodia' (false feet).
Questions for Upcoming Examinations:
Question: By which physical process does the exchange of gases occur in unicellular organisms?
Answer: Diffusion.
Question: Which temporary structure assists Amoeba in locomotion and in capturing food?
Answer: Pseudopodia.
Question: Which structure regulates the movement of substances into and out of the cell?
Answer: Plasma membrane (Cell membrane).