Which of the following statements correctly describes how unicellular organisms obtain their food?
Show answer & explanation
Correct answer: B
Explanation
Correct Answer
Unicellular organisms like Amoeba use pseudopodia, while Paramecium uses cilia to direct food into a fixed spot
Explanation
Different unicellular (single-celled) organisms have evolved distinct and specialized mechanisms to capture and ingest their food since they lack complex digestive organs. An Amoeba takes in food using temporary, finger-like extensions of its cell surface called pseudopodia (false feet), which fuse over the food particle to form a food vacuole. On the other hand, Paramecium has a definite, fixed shape, and its food is taken in at a specific spot (the oral groove). Food is moved to this spot by the coordinated, rhythmic movement of thousands of tiny, hair-like structures called cilia that completely cover the cell surface.
Key Points
The process of engulfing solid food particles by forming pseudopodia around them is a type of holozoic nutrition known as phagocytosis (cell-eating).
Unlike Amoeba, which can capture food from any part of its shifting cell membrane, Paramecium relies on a fixed anatomical structure and a continuous sweeping motion of its cilia to ingest nutrients.
In both organisms, once the food enters the cell, it is enclosed within a food vacuole where complex substances are broken down into simpler ones by digestive enzymes inside the cell.
Additional Facts
Inside the food vacuole, the digested nutrients are absorbed directly into the cytoplasm by diffusion, and the remaining undigested material is moved to the surface of the cell and thrown out (egestion).
Other unicellular organisms, like Euglena, exhibit mixotrophic nutrition, meaning they can perform photosynthesis like plants in the presence of sunlight but act as heterotrophs (consuming external food) in the dark.
Single-celled fungi, such as yeast, obtain their nutrients differently by secreting digestive enzymes externally onto organic matter and absorbing the dissolved nutrients (saprophytic nutrition).
Important Questions
Question: What are the temporary finger-like projections used by an Amoeba to engulf food particles called?
Answer: Pseudopodia (or false feet).
Question: Which hair-like structures cover the body of a Paramecium and help sweep food particles into its specific ingestion site?
Answer: Cilia.