Explain endosymbiosis theory (Or \"How cells got mitochondria and chloroplasts\") Solution Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other it\'s called endosymbiosis. Endosymbiosis occurred as: a) The primitive eukaryotic cell was also eventually able to eat prokaryotes, a marked improvement to absorbing small molecules from its environment; b) The process of endosymbiosis commenced when the eukaryote engulphed but did not digest a autotrophic bacterium. Evidence suggests this engulfed bacterium was an alphaproteobacteria, an autotroph that uses photosynthesis to acquire energy. c) The eukaryote then began a mutually beneficial (symbiotic) relationship with it whereby the eukaryote provided protection and nutrients to the prokaryote, and in return, the prokaryotic endosymbiont provided additional energy to its eukaryotic host through its respiratory cellular machinary. d) The relationship became permanent over time completing primary endosymbiosis as the endosymbiont lost some genes it used for independent life and transferred others to the eukaryote\'s nucleus. The symbiont thus became dependent on the host cell for organic molecules and inorganic compounds. The genes of the repiratory machinary became a mitochondrion. Endosymbiotic theory hypothesizes the origin of chloroplasts similarly, where chloroplasts a eukaryote with mitochondria engulfs a photosynthetic cyanobacteruim in a symbiotic relationship ending in the chloroplast organelle. Endosymbiosis has gained ever more acceptance in the last half century, especially with the relatively recent advent of sequencing technologies. There are many variants to the theory, regarding what organism(s) engulfed what other organism(s), as well as how many times and when it occurred across geological time..

1. Explain endosymbiosis theory (Or "How cells got mitochondria and chloroplasts")
Solution
Symbiosis occurs when two different species benefit from living and working together. When
one organism actually lives inside the other it's called endosymbiosis.
Endosymbiosis occurred as:
a) The primitive eukaryotic cell was also eventually able to eat prokaryotes, a marked
improvement to absorbing small molecules from its environment;
b) The process of endosymbiosis commenced when the eukaryote engulphed but did not digest a
autotrophic bacterium. Evidence suggests this engulfed bacterium was an alphaproteobacteria, an
autotroph that uses photosynthesis to acquire energy.
c) The eukaryote then began a mutually beneficial (symbiotic) relationship with it whereby the
eukaryote provided protection and nutrients to the prokaryote, and in return, the prokaryotic
endosymbiont provided additional energy to its eukaryotic host through its respiratory cellular
machinary.
d) The relationship became permanent over time completing primary endosymbiosis as the
endosymbiont lost some genes it used for independent life and transferred others to the
eukaryote's nucleus. The symbiont thus became dependent on the host cell for organic
molecules and inorganic compounds. The genes of the repiratory machinary became a
mitochondrion. Endosymbiotic theory hypothesizes the origin of chloroplasts similarly, where
chloroplasts a eukaryote with mitochondria engulfs a photosynthetic cyanobacteruim in a
symbiotic relationship ending in the chloroplast organelle.
Endosymbiosis has gained ever more acceptance in the last half century, especially with the
relatively recent advent of sequencing technologies. There are many variants to the theory,
regarding what organism(s) engulfed what other organism(s), as well as how many times and
when it occurred across geological time.