Endosymbiotic Theory Summary

Endosymbiotic Theory Overview

• Explains evolution of eukaryotic cells from prokaryotic ancestors.

• Occurred around 2 billion years ago.

Key Processes

• Larger prokaryotes engulf smaller bacteria through endocytosis.

• Instead of being digested, bacteria survive inside larger cells.

• This establishes a symbiotic relationship:

  • Smaller bacteria provide energy/food.

  • Larger cells provide protection/resources.

Evolution of Organelles

• Oxygen-using bacteria evolved into mitochondria (powerhouse of eukaryotic cells).

• Photosynthetic bacteria evolved into chloroplasts (in plant cells).

Supporting Evidence

• Mitochondria and chloroplasts have:

  • Their own DNA.

  • Double membranes, similar to bacteria.

  • Ability to reproduce independently within cells.

Modern Implications

• Animal cells typically contain mitochondria.

• Plant cells contain both mitochondria and chloroplasts.