Mitochondria and chloroplasts are thought to have evolved...

Key Concepts

Binary Fission and Replication Mechanisms

The way mitochondria and chloroplasts replicate—by a process analogous to binary fission seen in bacteria—provides a significant piece of experimental evidence for the endosymbiotic hypothesis. This replication method suggests an evolutionary link between these organelles and free-living bacteria, indicating that they might have once been independent organisms.

Organelle Genomes

Mitochondria and chloroplasts each have their own DNA that is distinct from the nuclear genome, mirroring the circular chromosomes found in bacteria. This genomic evidence supports the idea that these organelles descended from bacteria, as their genetic material encodes proteins and RNAs that are similar to those found in prokaryotic cells.

Endosymbiotic Theory

This theory proposes that organelles such as mitochondria and chloroplasts originated from free-living bacteria that formed a symbiotic relationship with ancestral eukaryotic cells. Experimental evidence supporting this theory includes observations that these organelles contain their own circular DNA, replicate independently by binary fission, and feature membranes consistent with engulfment, all of which are characteristics of prokaryotic organisms.

Transcript

00:01 This question asks, mitochondria and chloroplasts are thought to have evolved from symbiotic bacteria present in nucleated cells.

00:08 What is the experimental evidence from this chapter that supports this hypothesis? so as we know, there are going to be these key similarities between the bacteria, mitochondria, and chloroplasts that will kind of serve as evidence of the endosymbiotic hypothesis.

00:26 So remember, there is the endosymbion.

00:32 Hypothesis which basically states that these membrane bound organelle containing cells or just more generally referred to as eukaryotes this hypothesis states that these eukaryotes originated or were given rise to from the symbiosis of some sort of bacteria and a nucleated cell.

01:31 And what is the evidence supporting this? well, if we are to look at the mitochondrial and bacterial ribosomes, we find that they are going to differ from the eukaryotic cytosalic ribosomes.

01:44 So that would be the first thing.

01:47 So you can say bacterial and mitochondrial, because remember the mitochondria as well as the chloroplast, all have their own ribosomes, and they also have their own rna and dna sequences as well.

02:04 So bacterial and mitochondrial ribosomes differ from eukaryotic ribosomes, both in their rna and protein composition.

02:32 So that's the first piece of evidence.

02:33 The second piece of evidence is the fact that, well, to go along with this kind of.

02:40 We won't write it down, but just to further emphasize at this point...

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