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Discussion 4 – Endosymbiosis 40 48
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Directions: The mitochondria and chloroplast are thought to have once
been free-living prokaryotes that were engulfed by an early eukaryote and
incorporated into the functioning of that cell. For this discussion, describe
the theory of endosymbiosis in your own words and discuss some of the
evidence for this theory. You can use your textbook as a reference and
research this theory online as well. For full credit, I will be looking for unique
thoughts (compared to other classmate submissions) on the evidence for
the theory of endosymbiosis and your interaction with classmates.
Submission: After you have posted your initial post, read and respond to
two or more of your classmates’ posts. Be sure to make substantive and
constructive comments (just posting “nice post” doesn’t count). For
example, add something from your own experience, something you’ve read
or seen. If the situation calls for it, feel free to state an opinion, but be sure
to state any points with which you agree and/or those with which you
disagree, as well as your reasons for agreeing or disagreeing.
Grading: This discussion is worth 30 points and will be graded using
the Discussion Rubric. Pease use it as a guide toward successful completion
of this assignment.
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Harun Vatres (https://canvas.fscj.edu/courses/71848/users/106498)
Jun 4, 2023
The theory of endosymbiosis suggests that mitochondria and
chloroplasts, two important organelles found in eukaryotic cells, were
once independent prokaryotic organisms that became incorporated into
the functioning of a host cell through a process of engulfment. According
to this theory, an ancestral eukaryotic cell engulfed a free-living
prokaryote, forming a symbiotic relationship where both the host cell and
the engulfed prokaryote benefited.
There are several lines of evidence supporting the theory of
endosymbiosis:
1. Structural Similarities: Mitochondria and chloroplasts have their own
distinct structures resembling those of free-living prokaryotes.
2. DNA Evidence: The DNA of mitochondria and chloroplasts is similar to
that of prokaryotes rather than the nuclear DNA of eukaryotic cells.
3. Replication: Mitochondria and chloroplasts replicate independently
within the eukaryotic cell, similar to the way prokaryotes replicate. They
have their own machinery for DNA replication, transcription, and
translation, which is distinct from the host cell’s machinery.
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Jomer Ibarreta
(https://canvas.fscj.edu/courses/71848/users/26650)
Jun 12, 2023
Great information Harun! Mitochondria and chloroplasts are about
the same size as free-living bacteria, and they both divide in two to
make more of themselves, just like bacterial cells do. The cell splits
into two equal parts during this process of binary fission.
Mitochondria and chloroplasts are important parts of living things.
Without them, there would be no life as we know it. “The
Endosymbiotic Theory” says that these organelles are thought to have
come from free-living bacteria that were eaten by bigger cells billions
of years ago. This idea explains how mitochondria and chloroplasts
work inside cells and how they are similar to free-living bacteria.
Reference:
“The Endosymbiotic Theory.” Encyclopædia Britannica, Encyclopædia
Britannica, Inc., 11 June 2019,
www.britannica.com/science/endosymbiotic-theory
(http://www.britannica.com/science/endosymbiotic-theory)
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Beyonce Miranda-Gomez (She/Her)
(https://canvas.fscj.edu/courses/71848/users/129249)
Jun 15, 2023
Hello Harun! I appreciate the information given in your post. I also
wrote about the contribution replication does to this theory. I learned
that the mitochondria replicates in a “pinch.” Basically, it pinches
apart and forms two. It was quite fascinating to learn!
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Eliana Curry (https://canvas.fscj.edu/courses/71848/users/148561)
Jun 19, 2023
Great information Harun!
Also, a cool fact about the theory of endosymbiosis is that it explains
how eukaryotic cells obtained the ability to perform aerobic
respiration, which is the process by which cells convert glucose into
energy using oxygen. This allowed eukaryotes to become much more
metabolically efficient than prokaryotes, and paved the way for the
evolution of complex multicellular organisms.
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Onix Crespo (https://canvas.fscj.edu/courses/71848/users/122748)
Jun 20, 2023
Reply
Short and precise explication with in depth and irrefutable evidence.
Found it interesting that the engulfed prokaryotes also enjoy benefits
from this symbiosis, beforehand I only saw it as a “parasitic” type of
relationship between the phagosome and the phagocyte.
(https://canvas.fscj.edu/courses/71848/users/137133)
Claudia Huerta (https://canvas.fscj.edu/courses/71848/users/137133)
Jun 5, 2023
The theory of endosymbiosis suggests that eukaryotic cells evolved from
the merging of two or more free-living prokaryotic cells. Specifically, it
proposes that mitochondria and chloroplasts found in eukaryotic cells
were once free-living bacteria that were engulfed by a larger host cell,
forming a mutually beneficial relationship.
There is compelling evidence in support of this theory. One of the most
convincing pieces of evidence is the fact that mitochondria and
chloroplasts have their own circular DNA, which is similar to that of
prokaryotic cells, rather than linear like that of eukaryotic cells.
Additionally, the DNA sequences of mitochondria and chloroplasts are
more similar to those of free-living bacteria than to the nuclear DNA of
eukaryotic cells.
Another piece of evidence is the fact that the membranes of mitochondria
and chloroplasts are similar in structure and composition to the
membranes of prokaryotic cells. Specifically, they contain lipids that are
not found in the membranes of eukaryotic cells, and they have their own
unique set of membrane proteins.
Furthermore, the size of mitochondria and chloroplasts is similar to that
of free-living bacteria, and they both reproduce by binary fission, just like
prokaryotic cells do.
Taken together, these lines of evidence strongly suggest that the
mitochondria and chloroplasts found in eukaryotic cells today were once
free-living bacteria that were incorporated into the functioning of the host
cell through endosymbiosis.
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Tiara Taylor (https://canvas.fscj.edu/courses/71848/users/13719)
Jun 8, 2023
Hi Claudia,
I enjoyed reading your post. I like how you broke it down when you
stated that mitochondria and chloroplasts have their own circular
DNA, which is similar to that of prokaryotic cells, rather than linear
like that of eukaryotic cells. It’s interesting to learn all of this
material. Especially for me seeing how I never knew about a lot of
these different cells and how they play off of one another. I never
knew about lipids. I never knew that mitochondria and chloroplasts
are found in eukaryotic cells. It’s quite fascinating to learn about all
of these cells and how they benefit so many different things in us,
animals and plants.
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Corbin Miller (https://canvas.fscj.edu/courses/71848/users/54253)
Jun 8, 2023
Hello Claudia,
You did a good job of clarifying the definition of endosymbiosis. I
also agree that one of the biggest pieces of evidence proving this
theory is the similar style DNA that is found in both the organelles
and prokaryotic cells. I did not know that they also split in a similar
way to the prokaryotic cells.
Great discussion!
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Bonni Haber (She/Her)
(https://canvas.fscj.edu/courses/71848/users/107427)
Jun 11, 2023
Claudia, this was by far the best explanation I’ve read thus far.
Sometimes I have a harder time following explanations of things like
this and your post helped me more than about ten different websites!
Great post.
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Jomer Ibarreta
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Jun 12, 2023
Reply
Wonderful post, Claudia! Both mitochondria and chloroplasts are very
small, about the same size as bacteria that live on their own. This is
because they both divide in two, the same way that bacterial cells do.
Binary fission is a type of asexual reproduction that happens when a
single cell splits into two cells that are exactly the same. Because of
this, mitochondria and chloroplasts stay about the same size because
they can’t get bigger before splitting. This is also why they are both
about the same size as germs that live on their own. So, mitochondria
and chloroplasts are about the same size as free-living bacteria, and
they both divide into two parts to make more of themselves, just like
bacterial cells do.
“Binary Fission.” Khan Academy, Khan Academy, 22 Oct. 2020,
https://www.khanacademy.org/science/biology/cellular-respirationand-fermentation/cellular-respiration-in-depth/a/binary-fission
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Onix Crespo (https://canvas.fscj.edu/courses/71848/users/122748)
Jun 20, 2023
Hello Claudia, found it very interesting and thought stimulating that
you brought up the unique set of membrane proteins that differ on
both organisms.
(https://canvas.fscj.edu/courses/71848/users/13719) Tiara Taylor (https://canvas.fscj.edu/courses/71848/users/13719)
Jun 6, 2023
The theory of endosymbiosis is one of the most important theories in cell
biology. It helps us to understand how eukaryotic cells evolved and how
they function. Thus, allowing us to be able to continue learning.
The theory of endosymbiosis states that some of the organelles in
eukaryotic cells were once free-living prokaryotic cells. Over time, these
prokaryotic cells were engulfed by other prokaryotic cells and evolved to
live in a symbiotic relationship. The engulfed cell provided the host cell
with new capabilities, like the ability to produce energy or to perform
photosynthesis. The host cell provided the engulfed cell with a safe
environment and a source of nutrients.
One piece of evidence is the fact that mitochondria and chloroplasts, two
of the most important organelles in eukaryotic cells, have their own DNA.
This DNA is different from the DNA of the nucleus, which is the control
center of the cell. Meaning that mitochondria and chloroplasts were once
free-living cells.
Another piece of evidence for endosymbiosis is that mitochondria and
chloroplasts have their own ribosomes (ribosomes are the structures that
make proteins). The ribosomes in mitochondria and chloroplasts are
different from the ribosomes in the cytoplasm of the cell. The
mitochondria and chloroplasts were once free-living cells that had their
own protein-making machinery.
(https://www.albert.io/blog/endosymbiosis-ap-biology-crash-course/)
https://www.biologyonline.com/dictionary/endosymbiotic-theory
https://www.biologyonline.com/dictionary/endosymbiotic-theory
(https://www.biologyonline.com/dictionary/endosymbiotic-theory)
https://www.khanacademy.org/science/ap-biology/cell-structureand-function/cell-compartmentalization-and-itsorigins/a/chloroplasts-and-mitochondria
(https://www.khanacademy.org/science/ap-biology/cell-structure-andfunction/cell-compartmentalization-and-its-origins/a/chloroplasts-andmitochondria)
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Corbin Miller (https://canvas.fscj.edu/courses/71848/users/54253)
Jun 8, 2023
Hello Tiara,
I agree with you that this is one of the most important theories as
this is where the life of the eukaryotic cell is formed. With out it there
would be no human life. Also your evidence of ribosomes, I did not
know that, is also convincing towards this theory.
Great discussion!
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Cori Perry (https://canvas.fscj.edu/courses/71848/users/113155)
Jun 12, 2023
Reply
Tiara,
This theory is so important, I concur with what Corbin said, without it
there would be no life. Thank you for your post, it was a great read.
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Corbin Miller (https://canvas.fscj.edu/courses/71848/users/54253)
Jun 8, 2023
The endosymbiotic theory shows that the ancestorial history of the
eukaryotic cell was derived through one larger prokaryotic cell absorbing
other prokaryotic cells (early mitochondria and chloroplast which would
be aerobic bacteria at the time). The cell than would then divide into
more. This would help explain the presence of mitochondria and
chloroplast in the eukaryotic cells versus not in the prokaryotic cells.
Breaking the word endosymbiosis down it translates to one organism
that is living “within” another with organism. There is multiple pieces of
evidence that proves this theory. One big piece of evidence to this theory
is the evidence of circular DNA inside of mitochondria and chloroplast
just like how prokaryotic cells have circular DNA. This alone is a big clue
to the origin of the existence of these organelles in eukaryotic cells.
These organelles also have double membranes which is evidence of
being engulfed by other prokaryotic cells.
Fowler, S., Roush, R., & Wise, J. (2017). Chapter 3.3 & Chapter 13.2. In
Concepts of Biology. essay, OpenStax.
THE ORIGIN OF MITOCHONDRIA. The brain from top to bottom. (n.d.).
https://thebrain.mcgill.ca/flash/a/a_05/a_05_cl/a_05_cl_her/a_05_cl
_her.html#:~:text=The%20double%20membrane%20found%20in,fr
om%20the%20host%20cell%20itself
(https://thebrain.mcgill.ca/flash/a/a_05/a_05_cl/a_05_cl_her/a_05_cl_her.ht
ml#:~:text=The%20double%20membrane%20found%20in,from%20the%20
host%20cell%20itself) .
Understand endosymbiotic theory – AP biology. Private Tutoring. (n.d.).
https://www.varsitytutors.com/ap_biology-help/understandendosymbiotictheory#:~:text=a%20single%20membrane-,Explanation%3A,the%2
0origin%20of%20eukaryotic%20cells
(https://www.varsitytutors.com/ap_biology-help/understand-endosymbiotictheory#:~:text=a%20single%20membrane-,Explanation%3A,the%20origin
%20of%20eukaryotic%20cells) .
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Tiara Taylor (https://canvas.fscj.edu/courses/71848/users/13719)
Jun 10, 2023
Hi Corbin,
I like how you broke down endosymbios. It’s crazy to me to be
learning all of these new things and how they all function with one
another. This is something that I did not learn in school and really
wish I did. Like how did so many cells come bout, as well as how they
know to mix with other cells in order to function the way that they do.
Or what would happen if they were to ever stop functioning altogether
or with certain ones. Does this cause like a domino effect for the
worse or will this cause something new to be discovered and learned
about. Nice post.
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Bonni Haber (She/Her)
(https://canvas.fscj.edu/courses/71848/users/107427)
Jun 11, 2023
Corbin, great detail in you post and so easy to follow! “This alone is a
big clue to the origin of the existence of these organelles in
eukaryotic cells. These organelles also have double membranes
which is evidence of being engulfed by other prokaryotic cells.” was a
great way to sum up that information and make it clear and precise.
Great discussion!
Reply
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Cori Perry (https://canvas.fscj.edu/courses/71848/users/113155)
Jun 12, 2023
Corbin,
Great way to break it down and make it easier to understand!
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Bonni Haber (She/Her)
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Jun 11, 2023
Reply
The Endosymbiotic Theory states that the mitochondria and chloroplast
in eukaryotic cells were once aerobic bacteria (prokaryote) that were
ingested by a large anaerobic bacteria (prokaryote). This theory explains
the origin of eukaryotic cells. Endosymbiosis can best be described as
one organism living completely inside another. The evidence backing this
theory comes from a few different views, some of them are
that Mitochondria (and chloroplasts) aren’t free-living bacteria anymore.
The first eukaryotic cell evolved more than a billion years ago. Since
then, these organelles have become completely dependent on their host
cells. For example, many of the key proteins needed by the
mitochondrion are imported from the rest of the cell. Sometime during
their long-standing relationship, the genes that code for these proteins
were transferred from the mitochondrion to its host’s genome. Scientists
consider this mixing of genomes to be the irreversible step at which the
two independent organisms become a single individual.
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Brooklyn Rossi (https://canvas.fscj.edu/courses/71848/users/24335)
Jun 16, 2023
It is interesting that the proteins transferred from one to the other.
An interesting question that would like to look at further is what
would have happened had this not occurred so long ago. It is
possible the cell structure we see today would be very different. That
being said, it seems unavoidable when one is engulfed in the other
for as long as it was.
(https://canvas.fscj.edu/courses/71848/users/113155) Cori Perry (https://canvas.fscj.edu/courses/71848/users/113155)
Jun 12, 2023
The theory of endosymbiosis is the theory of how organelles like
mitochondria and chloroplasts arose in eukaryotic cells from symbiotic
relationships between ancestral prokaryotic cells. According to this
theory, a larger cell engulfed a smaller cell by endocytosis or
phagocytosis and did not digest it, but rather kept it in its cytoplasm. The
smaller cell then survived and provided benefits to the host cell, such as
energy or photosynthesis. The smaller cell also replicated in sync with the
host cell, so that the offspring of the host cell inherited the symbiotic
cell. This theory is widely accepted and explains the origin of different
organelles in eukaryotes.
Some of the evidence that proves this theory:
1.) The presence of DNA – Mitochondria and Chloroplast DNA exists in
closed circular form as it does in a prokaryotic cell. This DNA of the
chloroplast is very similar to photosynthetic blue-green bacteria, while
the mitochondrion DNA is very similar to the aerobic bacteria. Both
organelles lack histones and introns like bacteria.
2.) Inhibition by antibiotics – Several antibiotics kill or inhibit bacteria
by disrupting their 70s ribosomal function. The same antibiotics also
inhibit ribosomal function in mitochondria and chloroplast. Like bacteria,
mitochondria and chloroplast are sensitive to chloramphenicol,
streptomycin, etc.
3.) Same Size – Mitochondria and chloroplast are the same in size as
bacteria. The size of bacteria is commonly 0.1-10 micrometers, while the
size of mitochondria and chloroplast is 0.5-10 micrometers and 1- 10
micrometers respectively.
These are just a few of the ways to prove the theory of endosymbiosis.
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Beyonce Miranda-Gomez (She/Her)
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Jun 15, 2023
Hello Corey!
I appreciate the format of your response and how it was generally
written. It makes it easier to understand the similarities between the
chloroplast and mitochondria and prokaryotes. One similarity that I
did not mention was the presence of DNA, I was actually surprised by
the contribution of DNA. Thanks for your response!
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Eliana Curry (https://canvas.fscj.edu/courses/71848/users/148561)
Jun 19, 2023
Hello Cori! I love that you added the different types of evidence that
proves the theory of endosymbiosisz!
Some evidence that supports the theory of endosymbiosis includes
the fact that mitochondria and chloroplasts have their own DNA (which
you mentioned) , which is circular like that of prokaryotes, and that
they replicate through binary fission, like prokaryotes. Additionally,
both organelles have a double membrane, which is consistent with the
idea that they were engulfed by a host cell.
Reply
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Jomer Ibarreta (https://canvas.fscj.edu/courses/71848/users/26650)
Jun 12, 2023
DNA data shows that the DNA of mitochondria and chloroplasts is more
like the DNA of prokaryotes than the nuclear DNA of eukaryotic cells.
This shows that mitochondria and chloroplasts were once free-living
prokaryotes that were eaten by the ancestor of eukaryotic cells in a
process called endosymbiosis. This endosymbiosis theory explains why
the DNA of mitochondria and chloroplasts is more like the DNA of
prokaryotes than the nuclear DNA of eukaryotes. This idea has been
accepted as a way to explain how eukaryotic cells came to be because
DNA evidence backs it up.
The idea that coral and dinoflagellates live together is an interesting one.
It says that these two organisms have a symbiotic connection in which
the coral gives the dinoflagellates food and shelter, and the
dinoflagellates give the coral energy through photosynthesis. This link is
important for coral reefs to stay healthy and helps them do well in their
environments. We know a lot about coral reefs and how they interact with
their environment because of the idea of endosymbiosis between coral
and dinoflagellates.
References:
“Endosymbiosis.” Encyclopædia Britannica, Encyclopædia Britannica,
Inc., 2 May 2020, www.britannica.com/science/endosymbiosis
(http://www.britannica.com/science/endosymbiosis)
Glynn, Peter W. “The Symbiotic Relationship between Corals and
Dinoflagellates.” The Smithsonian Institution, The Smithsonian
Institution, 11 Apr. 2019, www.si.edu/spotlight/coral-reefs/symbiosis
(http://www.si.edu/spotlight/coral-reefs/symbiosis)
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Brooklyn Rossi (https://canvas.fscj.edu/courses/71848/users/24335)
Jun 16, 2023
I believe that the proof that we see the same thing occur in nature
like the coral you mentioned is a great argument for the theory of
endosymbiosis. We have examples of this occurring in ecosystems,
communities, populations, and organisms. It is good reasoning to
believe it caries down even to the cells.
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Brianna Neeley
(https://canvas.fscj.edu/courses/71848/users/139670)
Jun 17, 2023
Awesome post, Your Coral analogy is a great example of how this
theory of an exchange of energy can take place in many sectors of
life.
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Beyonce Miranda-Gomez (She/Her)
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Jun 15, 2023
I would describe the theory of endosymbiosis as the idea that the
mitochondria and chloroplast were once able to survive with no oxygen.
Also, the theory states that they were able to be ingested by larger cells,
like plant or animals cells, which helped the functioning of the cell.
According to an article titled, “Understanding Evolution,” there is a lot of
evidence backing up this idea and theory. The evidence is mainly
focused on the mitochondria. First, the topic of membrane. The
mitochondria has it’s own cell membranes, which is similar to prokaryote
cells. Next, reproduction, Mitochondria pinches apart in replication, this
is how the mitochondria reproduces. Similarly, bacteria also reproduces.
Other evidence leads towards the chloroplast. The main claim is that
chloroplasts are very similar to the mitochondria. Hence, chloroplasts are
similar to mitochondria, mitochondria’s are similar to prokaryotes, which
means it comes full circle, Chloroplasts are also similar to Prokaryote.
https://evolution.berkeley.edu/it-takes-teamwork-howendosymbiosis-changed-life-on-earth/evidence-for-endosymbiosis/
(https://evolution.berkeley.edu/it-takes-teamwork-how-endosymbiosischanged-life-on-earth/evidence-for-endosymbiosis/)
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Robin Patterson
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Jun 18, 2023
Hi Beyonce,
The explanation that chloroplasts are very similar to the
mitochondria, chloroplasts are similar to mitochondria, mitochondria
are similar to prokaryotes, really brings all of the together. The
relationship for these organelles is beneficial and the use of the
diagram was a nice touch.
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Ashley Burris (https://canvas.fscj.edu/courses/71848/users/142506)
Jun 19, 2023
Hi Beyonce!
Thanks for adding the visual, I am a visual learner and love to review
diagrams! I am learning that mitochondria are a very complex cell, I
wrote about how it has its own DNA, and you have included here that
it has its own membrane. Fun fact about mitochondria, it produces
90% of the energy in our bodies! My mitochondria must be running
low today… mom joke!
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Heidi Street (She/Her)
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Jun 19, 2023
Beyonce,
Awesome visual! I think the evidence strongly supports
Endosymbiosis and evolution. Additionally, mitochondria contains a
double membrane, similar to prokaryotic cells. So cool!
Best wishes, Brooke
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Alexis Clements
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Jun 19, 2023
Reply
Hello Beyonce,
Thank you for your response to this discussion board. I first want to
thank you for adding a visual for those of us who are visual learners. I
did my own research on the topic and still learned from your
response. I also appreciated you giving supporting evidence outside
of DNA evidence. Great response to the discussion board and very
detailed.
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Claudia Pena (https://canvas.fscj.edu/courses/71848/users/70051)
Sunday
Hello Beyonce,
I loved you use a picture to your post, this caught my attention, and
your explanation help me to understand better this topic. It is very
creative you state the mitochondria pinches apart in replication
because for me it is a creative way to explain binary fission process.
Thank you for sharing. Great job!
Claudia.
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Brooklyn Rossi (https://canvas.fscj.edu/courses/71848/users/24335)
Jun 16, 2023
The theory of Endosymbiosis is that mitochondria and chloroplast started
as a possible bacteria that got into a another prokaryote. After the
mitochondria/chloroplast entered the prokaryote, they benefited each
other and continued to regenerate together. Eventually they became
completely reliant on each other. The primary evidence for this is that
mitochondria/chloroplast contain DNA, their membranes, and their
reproduction. Mitochondria/chloroplast both contain DNA which makes
them unique as they are not the nucleus of the cell. They both have their
own membranes within the cell membrane. Cells are incapable of
building their own mitochondria/chloroplast on their own. They have to
replicate by splitting. This is the same way the prokaryotes replicate. This
theory makes sense in ways. If you look at nature, we as living things
often could function in many different situation, but once we become
reliant on it after a while. There are many examples of ecosystems where
a new organism is introduced and it becomes a symbiotic relationship. It
would be a stretch to believe that this didn’t occur in the very cells that
build us.
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Brooklyn Rossi (https://canvas.fscj.edu/courses/71848/users/24335)
Jun 16, 2023
My apologies here is my citation
(2021). Retrieved from https://evolution.berkeley.edu/it-takesteamwork-how-endosymbiosis-changed-life-on-earth/evidence-forendosymbiosis/
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Brianna Neeley
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Jun 17, 2023
Good job Brooklyn! This is a beautiful way to describe The
Endosymbiotic Theory. I agree that it is true that this kind of
relationship can reflect to other situations here on earth where
different substances choose to conjoin due to good chemistry.
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Heidi Street (She/Her)
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Jun 19, 2023
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Hi Brooklyn,
I agree that is is hard to deny the theory as a fact with the amount of
supporting evidence. We see similar instances in nature often when
new organisms are created. I believe the evidence not only supports
the theory of endosymbiosis but it supports evolution as well.
Best wishes,
Brooke
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Brianna Neeley (https://canvas.fscj.edu/courses/71848/users/139670)
Jun 17, 2023
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The Endosymbiotic theory states that some of the organelles in
eukaryotic cells were once prokaryotic microbes.
Evidence: Mitochondria and Chloroplasts have circular single stranded
DNA. This is found exclusively in Prokaryotes. This supports the theory of
endosymbiosis because these characteristics suggest that mitochondria
and chloroplast’s can survive on their own. They are also the same size
and can divide by binary fission.
Endosymbiotic theory – Definition and Examples – Biology Online
Dictionary (https://www.biologyonline.com/dictionary/endosymbiotictheory)
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Robin Patterson (https://canvas.fscj.edu/courses/71848/users/148704)
Jun 18, 2023
The theory of endosymbiosis is the theory that eukaryotic cells may have
evolved when multiple cells joined together. This is a mutually beneficial
relationship in which one organism lives within another. Some organelles
in today’s eukaryotic cells were previously prokaryotic microbes. The first
eukaryotic cells were thought to be amoeba-like cells that received their
nutrients by phagocytosis and had a nucleus that was formed when it was
pinched off and surrounded by the chromosomes. Specifically, the
mitochondria formed bacteria that had aerobic respiration were ingested
and chloroplasts were formed when photosynthetic bacteria were
ingested. Some proof is that mitochondria and chloroplasts have their
own circular DNA like bacteria. They also have their own ribosomes that
are like bacterial ribosomes. Lastly, the mitochondria and chloroplasts
are the same size as prokaryotic cells and divide by binary fission.
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Ashley Burris (https://canvas.fscj.edu/courses/71848/users/142506)
Jun 19, 2023
Hi Robin!
I also found it intriguing that mitochondria and chloroplasts have
their own DNA. I found it very insightful how you elaborated further
and included ribosomes. Fun fact about ribosomes, they are known as
the protein factory of the cell! I always found this easy to remember
due to “rib” which is clearly a protein that most of us eat on occasion,
it just seems perfectly fitting.
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Ashley Burris (https://canvas.fscj.edu/courses/71848/users/142506)
Jun 19, 2023
In ∼900 Mya endosymbiosis was discovered. It is defined as one
organism living within another organism. The name is derived from two
Greek root words: endo, meaning within, and symbios, meaning living
together. Without endosymbiosis, many life forms would not exist, such
as plants, fungi, and animals. I found the most intriguing evidence to be
mitochondria and chloroplast having their own DNA. Mitochondrial DNA
can resist degrading and is an expert at duplicating/copying itself.
Chloroplasts also play a major part in our world as they produce energy
through photosynthesis. Without photosynthesis, there would be no
oxygen, lack of oxygen means almost no living thing could survive. It is
so intriguing how things are intertwined, working together, to supply the
only life that we know.
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Heidi Street (She/Her)
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Jun 19, 2023
The theory of endosymbiosis proposes that mitochondria and
chloroplasts were once independent prokaryotic organisms that were
engulfed by another ancestral cell. It is believed that hosts cells ingested
aerobic bacteria. Rather than being destroyed, these prokaryotes formed
a mutually beneficial relationship with the host cell, eventually becoming
essential components of the eukaryotic cell’s functioning.
through evolution, the aerobic bacteria becoming mitochondria and the
photosynthetic bacteria becoming chloroplasts.
The similarities between mitochondria and chloroplasts when compared
to bacteria supports the theory of endosymbiosis. Both contain double
membranes similar to prokaryotic cells and are the same size.
Additionally, mitochondria and chloroplasts have DNA, like bacteria.
Mitochondria and chloroplasts also reproduce through a process called
binary fission, which is similar to the way bacteria replicate.
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Alexis Clements
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Jun 19, 2023
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Hello Heidi,
Thanks for your response to the discussion board. This was a great
response and great supporting evidence. I appreciate the fact that
you mentioned evidence outside of DNA. I also find the evidence
provided about the double membranes very useful. Thank you for your
detailed response, I enjoyed reading it.
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Alexis Clements (https://canvas.fscj.edu/courses/71848/users/137316)
Jun 19, 2023
The theory of endosymbiosis explains the origin of certain organelles
within eukaryotic cells, such as mitochondria and chloroplasts. Some
evidence supporting this theory, includes DNA, similarities in structure,
membranes, and reproduction. Mitochondria have their own cell
membranes, just like a prokaryotic cell does. The DNA of mitochondria
and chloroplasts is more closely related to bacterial DNA than to nuclear
DNA. Mitochondria and chloroplasts exhibit striking similarities to freeliving bacteria. They have their own circular DNA, similar to bacterial
DNA, and possess ribosomes that resemble bacterial ribosomes.
https://evolution.berkeley.edu/it-takes-teamwork-howendosymbiosis-changed-life-on-earth/evidence-for-endosymbiosis/
(https://evolution.berkeley.edu/it-takes-teamwork-how-endosymbiosischanged-life-on-earth/evidence-for-endosymbiosis/)
(https://biologydictionary.net/endosymbiotic-theory/)
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Robin Patterson
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Jun 19, 2023
Hi Alexis,
I did not realize before this assignment that there were different
types of DNA. As you pointed out in your discussion there is circular
DNA which is found in bacterial DNA. These discussions truly are
helping me understand how all of this relates.
Reply
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Eliana Curry (https://canvas.fscj.edu/courses/71848/users/148561)
Jun 19, 2023
Endosymbiosis is a theory that explains how eukaryotic cells evolved from
prokaryotic cells. The theory suggests that mitochondria and chloroplasts,
the organelles that produce energy in eukaryotic cells, were once freeliving prokaryotic cells that were engulfed and then evolved a symbiotic
relationship with their host cell. Evidence for this theory includes the fact
that mitochondria and chloroplasts have their own DNA, which is circular
like that of prokaryotes, and that they replicate through binary fission, like
prokaryotes. Additionally, both organelles have a double membrane, which
is consistent with the idea that they were engulfed by a host cell.
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Claudia Pena (https://canvas.fscj.edu/courses/71848/users/70051)
Sunday
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Hello Eliana,
I like your clear and concise post. In addition, form my research I
found out that this theory is not from the past, it can also be present
in organisms like termites, which can have prokaryotes that live in
their duct and help to digest wood, without them they could not
digest it.
Claudia.
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Onix Crespo (https://canvas.fscj.edu/courses/71848/users/122748)
Jun 20, 2023
The theory of Endosymbiosis is based on the premise that chloroplasts and
mitochondria arise from Prokaryotic cells. According to this theory, the first
Eukaryotic cell was likely a amoeba-like organism that received nutrients by
phagocytosis (its the process by which a organism uses its plasma
membrane to engulf a particle, after, it compartmentalizes inside the
organism. The engulfed particle is called a phagosome while the organism
that partakes in phagocytosis is called a phagocyte.) Some of these
Amoeba-like organisms ingested prokaryotic cells who survived inside them
and developed a symbiotic relationship. A common use of phagocytosis in
the human body is our immune system, its a major mechanism used to
remove cell debris / pathogens by digesting them in the phagosome.
Reply
Evidence:
Prokaryotic cells and chloroplasts are the same size, they also divide by
binary fission.
Mitochondria and Chloroplasts have their own DNA that is circular, not
linear.
Several primitive eukaryotic microbes, such as Giardia and Trichomanas
have a nuclear membrane but no mitochondria.
Evidence against:
Although less convincing, it is possible that flagella and cilia may have come
from spirochetes.
(https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/U
nit_4%3A_Eukaryotic_Microorganisms_and_Viruses/07%3A_The_Eukaryotic
_Cell/7.8%3A_The_Endosymbiotic_Theory)
References;
https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kais
er)/Unit_4%3A_Eukaryotic_Microorganisms_and_Viruses/07%3A_The
_Eukaryotic_Cell/7.8%3A_The_Endosymbiotic_Theory
(https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/U
nit_4%3A_Eukaryotic_Microorganisms_and_Viruses/07%3A_The_Eukaryotic
_Cell/7.8%3A_The_Endosymbiotic_Theory)
https://askabiologist.asu.edu/explore/cells-living-in-cells
(https://askabiologist.asu.edu/explore/cells-living-in-cells)
https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/15-theorigin-of-cells/endosymbiosis.html
(https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/15-the-originof-cells/endosymbiosis.html)
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Claudia Pena (https://canvas.fscj.edu/courses/71848/users/70051)
Sunday
Before I start to write about the endosymbiosis theory, I have to recap
prokaryotes and eukaryotes. Then, prokaryotes have not nucleus and
membrane – bound organelles, but eukaryotes do. However, they have
common like cell membrane, cytoplasm, ribosomes, genetic material, and
finally mutualism is equal a symbiosis where both are benefit.
Therefore, the endosymbiosis theory consists with the general
evolutionary one that all organisms come from another ancestor. It could
be prokaryote or bacteria with a single DNA caused by plasma
membrane. Evidence of this theory is showed in the same bacteria which
uses oxygen to produce their own energy to evolve to mitochondria, and
also uses some energy to produce their own food considered to evolve to
chloroplast. In addition, mitochondria and chloroplasts contain their own
DNA and ribosomes, and have similar size as bacteria’s do.
Overall, this theory is not just for the past, nowadays the clear example of
this are the termites that can have prokaryotes that live in their duct to
help to digest wood, otherwise, without them they could not ingest wood
again.
