Endosymbiotic Theory - Video Tutorials & Practice Problems

Endosymbiotic Theory

in this video, we're going to introduce the Endo Symbiotic Theory. And so the Endo symbiotic theory is a theory that suggests that today's mitochondria and chloroplasts organelles that we find inside of eukaryotic cells were once independently living bacteria. And so the Endo symbiotic theory suggests that a really, really long time ago, about 1.5 billion years ago there was an aerobic bacterium, or ah, bacteria that uses oxygen in its metabolism. And this aerobic bacterium was engulfed by an anaerobic host cell, or ah, host cell that does not use oxygen in its metabolism. And so when this aerobic bacterium was engulfed by the anaerobic host cell that created a symbiotic relationship or ah, beneficial relationship between the two organisms, since each of them had abilities that the other did not have. And so over a really, really long period of time again about 1.5 billion years, the aerobic bacterium that was engulfed by the host so lost many of its genes and abilities, and it developed and evolved into today's Mido Condra. But again, today's mitochondria, which we know is an organ l. The theory of the end of symbiotic theory suggests that the mitochondria. It was once an independently living aerobic bacteria and very similarly Theo. End of symbiotic theory suggests that ah, photosynthetic cyanobacteria or a bacterium that's capable of performing photosynthesis was also engulfed by a host cell and very similarly over a long, long period of time. It evolved into today's chloroplast, and so let's take a look at our image down below to get a better understanding of this endo symbiotic theory. So notice over here on the far left, we're showing you in blue a host cell, and this host cell is an anaerobic host cell, which means that it does not use oxygen in its metabolism. And then over here, what we have is an aerobic bacterium or a bacteria that does use oxygen in its metabolism. And so this Arabic bacterium is living separately and independently from the host cell that's over here. But then, eventually this aerobic bacterium was engulfed by the host cell, and so you can see that the aerobic bacterium over a long, long, long, long period of time eventually developed into today's mitochondria that we find inside of animal cells. And so that is what allowed for complex living organisms to arrive, such as this animal that you see over here and this Rafiki looking monkey that you see with this nice looking smile here and very similarly Ah, Long time ago, there was a cyanobacteria, MMA photosynthetic cyanobacteria that was capable of performing photosynthesis. And this cyanobacteria, um, was also engulfed. And when it was engulfed over time, it developed into today's chloroplast. And so the host cell that had both mitochondria and chloroplasts ended up developing into today's plant cell. And so you could see that plant cells. Today they have both chloroplasts and mitochondria as well, and that developed into today's plant. And so this is once again a theory and theories have lots of supporting evidence. And so some of the supporting evidence that supports the Endo symbiotic theory includes the vast amount of similarities that there are between mitochondria and chloroplasts and pro carry. It's like the aerobic bacterium and the photosynthetic cyanobacteria. And so the similarities between mitochondria, chloroplasts and pro Kerasiotes include that they both have, or Duke. They both have small circular DNA. Eso, mitochondria, chloroplasts and pro Kerasiotes all have small circular DNA. They also all have small 70 s ribosomes and they all have, Or they all replicate via a process called binary vision. And so this is a lot of similarities that mitochondria and chloroplasts have with pro carry. It's and so that suggests that supporting evidence to suggest that maybe mitochondria and chloroplasts they were once independently living pro carry its or bacteria. Now, also, in addition to these similarities, uh, mitochondria and chloroplasts, they both have two membranes. They both have an outer membrane, and they both have an inner membrane as well. And so having an outer membrane and an inner membrane is pretty consistent with this idea of being engulfed or engulf mint, where a host cell engulfs them, and that makes them acquire a second membrane. And so all of this here, these similarities and the the fact that both mitochondria, chloroplasts have two membranes. That's all consistent supporting evidence of the end of symbiotic theory. And so this here concludes our introduction to the end of symbiotic theory and how it suggests that today's mitochondria and chloroplasts they were once independently living bacteria. And so we'll be able to get some practice applying the concepts that we've learned here in our next few videos. So I'll see you guys in our next one

Endosymbiotic theory is supported by the discovery of non-nuclear DNA in the ______ and ________ organelles.

• A. Golgi apparatus and lysosomes.
• B. Mitochondria and lysosomes.
• C. Chloroplast and Golgi apparatus.
• D. Chloroplast and mitochondria.

According to the endosymbiotic theory, which of the following is likely the ancestor of the mitochondria?

• A. Aerobic eukaryotes.
• B. Aerobic bacteria.
• C. Anaerobic bacteria.
• D. Cyanobacteria.
• E. Chloroplasts.