Which theory for the evolution of mitochondria in eukaryotic cells is depicted in the image below?

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BlackTom AI · Accepted Answer

To determine which theory is depicted, begin by listing the options and what each theory generally proposes.
Option 1: Endosymbiotic theory. This theory posits that mitochondria originated as free-living prokaryotes that were engulfed by a host cell and eventually became organelles. The image shows a prokaryotic cell being incorporated into a larger cell, followed by the development of membranes and an internal organization that resembles mitochondria, which aligns with endosymbiotic reasoning.
Option 2: Pro-eukaryotic theory. This would suggest that eukaryotic features arose within a single lineage without a symbiotic merger of distinct cells. The depicted stepwise engulfment of a prokaryote into a host cell does not support a purely progressive, non-symbiotic origin, making this option inconsistent with the endosymbiotic narrative.
Option 3: Chemiosmotic theory. This theory explains how ATP is produced via proton gradients across membranes and is more about the mechanism of ATP synthesis rather than the evolutionary origin of mitochondria. The image emphasizes the origin story (engulfment and membrane formation) rather than the biochemical process of ATP generation itself, so this does not match the depicted evolution scenario.
Option 4: Endomembrane theory. This alternative focuses on the development of internal membrane systems within a single cell, such as the endomembrane system, rather than suggesting mitochondria originated from an engulfed organism. The steps shown in the illustration highlight a host cell acquiring another cell, not just internal membrane elaboration, making this option unlikely to match the image.
Option 5: Phagocytotic theory. While phagocytosis is involved in the engulfing process, this label alone is less precise as a standalone theory for mitochondrial origin. The classic endosymbiotic explanation specifically describes an engulfed prokaryote becoming a symbiont, rather than a general phagocytosis mechanism, so this option is incomplete compared to the endosymbiotic framework.
In summary, the visual sequence—an engulfing event, formation of a vesicle, and the emergence of a double-membrane-bound organelle with inner structure—best corresponds to the endosymbiotic scenario in which mitochondria originated from free-living prokaryotes that became integrated into a host cell.

2025 T3 DP DPST1051 BLSC1342 Molecules, Cells and Genes

Which theory for the evolution of mitochondria in eukaryotic cells is depicted in the image below?

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