Evidence For The Endosymbiotic Theory

Biologist Lynn Margulis first made the case for endosymbiosis in the 1960s, but for many years other biologists were skeptical. Although Jeon watched his amoebae become infected with the x-bacteria and then evolve to depend upon them, no ane was around over a billion years ago to observe the events of endosymbiosis. Why should we call back that a mitochondrion used to be a gratuitous-living organism in its own correct? It turns out that many lines of evidence back up this idea. Most important are the many striking similarities between prokaryotes (like bacteria) and mitochondria:

When you lot expect at it this way, mitochondria really resemble tiny leaner making their livings inside eukaryotic cells! Based on decades of accumulated evidence, the scientific customs supports Margulis's ideas: endosymbiosis is the best caption for the development of the eukaryotic cell.

What'south more, the bear witness for endosymbiosis applies non but to mitochondria, but to other cellular organelles as well. Chloroplasts are like tiny dark-green factories within establish cells that help convert free energy from sunlight into sugars, and they have many similarities to mitochondria. The evidence suggests that these chloroplast organelles were also once free-living bacteria.

The endosymbiotic event that generated mitochondria must accept happened early in the history of eukaryotes, because all eukaryotes take them. Then, later on, a similar event brought chloroplasts into some eukaryotic cells, creating the lineage that led to plants.

the origins of mitochondria and chloroplasts

Despite their many similarities, mitochondria (and chloroplasts) aren't free-living bacteria anymore. The first eukaryotic cell evolved more than than a billion years ago. Since and so, these organelles have go completely dependent on their host cells. For instance, many of the fundamental proteins needed by the mitochondrion are imported from the residual of the cell. Sometime during their long-standing human 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 exist the irreversible step at which the two contained organisms get a single individual.

Grabbing take-out:Paramecium bursaria packs a lunch

Paramecium bursaria, a single-celled eukaryote that swims around in pond water, may not have its ain chloroplasts, but it does manage to "borrow" them in a rather unusual way.P. bursaria swallows photosynthetic green algae, but it stores them instead of digesting them. In fact, the ordinarily clear paramecium can pack so many algae into its body that it even looks dark-green! WhenP. bursaria swims into the light, the algae photosynthesize sugar, and both cells share luncheon on the go. ButP. bursaria doesn't exploit its algae. Not only does the agile paramecium chauffeur its algae into well-lit areas, it also shares the nutrient it finds with its algae if they are forced to live in the night.