Holozoic nutrition in protozoa — which statement correctly defines this feeding mode?
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APhagocytosis of solid nutrients followed by formation of phagocytic (food) vacuoles
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BPinocytosis of solid nutrients with phagocytic vacuole formation
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CPhagocytosis of soluble nutrients with phagocytic vacuole formation
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DPhotosynthesis of organic matter from light and CO2
Answer
Correct Answer: Phagocytosis of solid nutrients followed by formation of phagocytic (food) vacuoles
Explanation
Introduction:Holozoic nutrition describes animal-like feeding. Protozoa with this habit ingest particulate food and digest it intracellularly, analogous to macrophage phagocytosis.
Given Data / Assumptions:
- We must focus on solid vs soluble food and the uptake mechanism.
- Food vacuole formation is central to intracellular digestion.
Concept / Approach:Holozoic = ingestion of solid particles. Pinocytosis takes up fluids/solutes; photosynthesis is autotrophic, not holozoic. Therefore the accurate description centers on phagocytosis of solids and food vacuole formation.
Step-by-Step Solution:
Identify holozoic hallmark: phagocytosis of solid prey ✔Confirm subsequent digestion occurs in food vacuoles ✔Exclude pinocytosis (fluids) ✘Exclude photosynthesis (autotrophy) ✘Verification / Alternative check:Classic amoebae feed by engulfing bacteria/algae fragments and digesting them in vacuoles; microscopy confirms stepwise phagosome to phagolysosome maturation.
Why Other Options Are Wrong:
- Pinocytosis of solids: solids are not pinocytosed; pinocytosis targets fluids.
- Phagocytosis of soluble nutrients: “soluble” contradicts phagocytosis.
- Photosynthesis: not a feeding mode of holozoic protozoa.
Common Pitfalls:Confusing pinocytosis with phagocytosis; assuming any vacuole equals food vacuole.
Final Answer:Phagocytosis of solid nutrients followed by formation of phagocytic (food) vacuoles