2. Endosymbiotic theory
This theory was first proposed by Russian botanist Konstantin Mereschkowski in
He was propose Symbiogenesis or Endosymbiotic theory .
This theory states that “ Some eukaryotic cell orgenelles , such as mitochondria
and plastids , which are evolved from free living prokaryotes “ .
3. Define Symbiogenesis ?
It is the leading evolutionary theory of the origin of eukaryotic cells
from prokaryotic organisms .
What is endosymbiosis ?
It is a symbiosis ,in which one symbiont dwells with in the body of the
other is called endosymbiosis .
5. Types of endosymbiosis
1.The process in which a eukaryotic cell engulfs
another living prokaryote.
2.Thought to have occurred first.
3.Either cell does not depend on each other.
4. Results in the formation of the first
membrane , which belongs to the smaller
1.The process in which a eukaryotic cell
engulfs another eukaryotic cell that has already
undergone primary endosymbiosis .
2.They are occurred later.
3.The smaller cell depends on the larger cell.
4.Results in the formation of three plasma
membranes , like the first membrane which is
originating from cyanobacteria , second
membrane is the eukaryote that engulfed the
cyanobacteria ,and third membrane from the
eukaryote which is engulfed the primary
6. What are endosymbionts ?
Endosymbionts are organisms that from a symbiotic relationships
with another cell or organisms is called endosymbionts .
Some endosymbionts can be found either inside cell is called Intracellular.
Some are attach to the surface of the cell is called Extracellular .
Example :- In the corals, the host animal is a cnidarin and the endosymbiont is a
unicellular alga called dinoflagellate .The host serves as a protected environment
providing the alga with a constant supply of nutrients in the form of nitrogen
,phosphorus and sulfur .
Beneficial relationship between both host and endosymbiont .
Endosymbiotic bacteria in plants
Symbiosis between Rhizobium bacteria and legumes plants which
leads to formation of the root nodule .The endosymbiotic bacteria in
polyploid host cells as membrane which is surrounded by vesicle , where
they reduce atmospheric nitrogen to support plant growth by supplying
ammonia in exchange for carbon sources and energy .
9. Why Rhizobium is play role as endosymbiotic
bacteria in plants ?
• Rhizobium can not prepare its own food ,it establishes it self in the
roots of the plants and provides nutrients for plants . In turn
plants provide the bacteria with food and shelter.
11. Endosymbiotic bacteria in insects
Endosymbionts are vertically transmitted from mother to offspring
and they provide hosts with specific nutritional compounds that
are important for their survival and development .
Wolbachia is a maternally transmitted bacterium that lives inside
arthropod cells. Parasite that manipulates host reproduction but
more recently ,it discovered that Wolbachia can also protect
Drosophila species against infection by RNA virus .
It is also present in insects ,butter flies ,bees .
Wolbachia infection turns unfertilized eggs into diploid , which
those are hatch into females .This means that infected females
produce daughters from both fertilization and parthenogenesis .
12. WhyWolbachia is play roles as endosymbiotic
bacteria in insects ?
• In arthropods Wolbachia producers reproductive manipulations
such as male killing , fertilization , parthenogenesis , and
cytoplasmic incompatibility for its propagation and provides an
additional fitness benefit for the host to protect against