Biology Evolution NUMS 2023
PMDC Verified Question 26 of 47
This theory states that 'mitochondria and chloroplasts are, in effect, ancient bacteria which now live inside the larger cells':
A
Darwin's theory of evolution
B
Endosymbiont hypothesis
C
Neo-Darwinism
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 B: Endosymbiont hypothesis
Concept:

The origin of complex eukaryotic cells is explained by the assimilation of simpler prokaryotic cells.

Solution:

  • The Endosymbiont hypothesis (formulated robustly by Lynn Margulis) proposes that crucial eukaryotic organelles (mitochondria and chloroplasts) originated as free-living ancient bacteria.
  • These bacteria were engulfed by a primitive host cell, forming a mutually beneficial (symbiotic) relationship.
  • Evidence includes the fact that mitochondria and chloroplasts have their own circular DNA, ribosomes, and reproduce via binary fission, exactly like modern bacteria.


Why other options are incorrect:

  • Darwinism, Neo-Darwinism, and Lamarckism describe macro/micro-evolutionary mechanisms at the population and organismal level, not the specific cellular origins of organelles.

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.

Previous Question All Evolution MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App