Chloroplast Cell Organelle: A Symbiotic Cyanobacteria

 An archaic ancestor 
(a prokaryotic Cyanobean symbiont) 

resides in our cell, 

a case of organisms within organisms,  

providing mutual benefit, 

the recipe for long-term evolutionary success.

Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis and other chemical reactions. Chloroplasts capture the sun's light energy, store it in the energy storage molecules ATP and NADPH and use it in the process called photosynthesis to make organic molecules from carbon dioxide and free oxygen from water.

All chloroplasts contain the green pigment chlorophyll a, but not all chloroplasts are green because accessory pigments may be present that can change or override the green colour. The word chloroplast (χλωροπλάστης) is derived from the Greek words chloros (χλωρός), which means green, and plastis (πλάστης), which means "the one who forms". Chloroplasts are members of a class of organelles known as plastids.

Origin:They are considered to have originated from cyanobacteria through endosymbiosis. This was first suggested by Mereschkowsky in 1905 after an observation by Schimper in 1883 that chloroplasts closely resemble cyanobacteria. All chloroplasts are thought to derive directly or indirectly from a single endosymbiotic event (in the Archaeplastida), except for Paulinella chromatophora, which has recently acquired a photosynthetic cyanobacterial endosymbiont which is not closely related to chloroplasts of other eukaryotes. In that they derive from an endosymbiotic event, chloroplasts are similar to mitochondria, but chloroplasts are found only in plants and protista. The chloroplast is surrounded by a double-layered composite membrane with an intermembrane space; further, it has reticulations, or many infoldings, filling the inner spaces. The chloroplast has its own DNA , which codes for redox proteins involved in electron transport in photosynthesis; this is termed the plastome.

Humans must think like a Chloroplast: Parasites that do not debilitate their host can get along indefinitely.  But the relationship that works the best is that of symbiont.  Bacteria have been at it for literally billions of years.  At some point prokaryotic cells found a comfortable shelter inside larger cells, and lent their particular expertise to their host’s success.  The chloroplasts within the cells of leaves have their own distinct DNA.  They do the photosynthesizing to provide the abundant supply of energy that the plants enjoy.  Within animal cells, mitochondria do something similar, in that they are small powerhouses providing benefit to the cell.  They, too, show evidence of their colonial past in their distinct DNA.Organisms within organisms, providing mutual benefit, the recipe for long-term evolutionary success. 

If we are wise, we will mimic this strategy.  We will seek ways to become a contributor to the overall health of the greater organism.  Chloroplasts and mitochondria didn’t plan out their success; it wasn’t intelligently designed.  Countless millions of other viruses and bacteria were mutating, evolving, swapping genetic code .......and this worked.  It was perpetuated.

*Note: all pictures thankfully shared from various sources.