Biology Evolution PMC 2020
PMDC Verified Question 43 of 47
This theory says that mitochondria and chloroplasts are in fact ancient bacteria which now live inside the larger cells.
A
Darwin's theory of evolution
B
Neo Darwinism
C
Endosymbiont theory
D
Lamarckism
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Endosymbiont theory
Concept:

The origin of eukaryotic organelles is a key evolutionary concept explaining how complex cells developed from simpler prokaryotic ancestors.

Solution:

  • The Endosymbiotic theory (or endosymbiont hypothesis) states that mitochondria and chloroplasts were once free-living ancient bacteria (prokaryotes).
  • They were engulfed by an ancestral eukaryotic cell and established a mutually beneficial (symbiotic) relationship.
  • Mitochondria are thought to derive from aerobic eubacteria, while chloroplasts derive from photosynthetic bacteria (cyanobacteria).


Why other options are incorrect:

  • Darwin's theory / Neo-Darwinism: Focus on natural selection and genetic variation on a macroscopic or population scale, not the specific intracellular origin of organelles.
  • Lamarckism: Focuses on the inheritance of acquired traits based on use and disuse, which is historically inaccurate.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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