The Endosymbiotic Theory

Background

Mitochondria and chloroplasts display numerous similarities with bacteria that led to the endosymbiont theory.

This theory states that an early ancestor of eukaryotic cells engulfed a prokaryotic cell. Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont (a cell living within another cell).

An evidence to support this theory is that the outer membranes of chloroplasts or mitochondria have structural and chemical similarities to the eukaryote cell membrane. The outer membranes would have been synthesised by the original ‘host’ cell and surround the ‘organelles’ when these ‘organelles’ were engulfed.

Derivation of double membrane of chloroplasts and mitochondria

Task

Your task is to find out more about The Endosymbiotic Theory by accessing the resources below:

A) The Endosymbiotic Theory: This website provides more information about the origins of eukaryotic cells and what the endosymbiotic theory is about

B) The Evolution of Organelles: This animation looks at the similarities between mitochondria, chloroplast and prokaryotes, and shows how the early eukaryotic cells may have come about with the proposed endosymbiotic theory.

Once you have gone through the resources in this page, click on Review (Assignment) found on the navigation sidebar to complete the tasks assigned to you.