Understanding the Endosymbiosis Theory: How Eukaryotic Cells Evolved from Prokaryotic Cells

What is the endosymbiosis theory?

an explanation for how modern eukaryotes evolved from prokaryotes- that mitochondria and chloroplasts were free living organisms.

The endosymbiosis theory is a scientific theory that suggests how eukaryotic cells (cells with a nucleus and other membrane-bound organelles) evolved from simpler prokaryotic cells (cells without a nucleus or membrane-bound organelles).

According to the endosymbiosis theory, mitochondria, which are organelles that produce energy for cells, and chloroplasts, which are organelles that carry out photosynthesis in plants, are believed to have originated from bacteria that were engulfed by larger cells and evolved over time to form a symbiotic relationship. The theory suggests that a larger cell engulfed a smaller bacterial cell but instead of digesting it, it formed a symbiotic relationship in which the larger cell provided protection and nutrients for the smaller cell, and in turn, the smaller cell provided energy through cellular respiration (in the case of mitochondria) or photosynthesis (in the case of chloroplasts).

Over time, the smaller bacterial cells became specialized organelles within the larger cell, with their own DNA and ability to divide independently of the host cell. The evolutionary advantage of this symbiotic relationship was that the host cell could produce more energy and nutrients, allowing it to grow and develop new functions.

The endosymbiosis theory is supported by several lines of evidence, including the similarity of mitochondrial and chloroplast DNA to that of bacteria, the presence of a double membrane surrounding these organelles similar to that of bacteria, and the fact that these organelles can reproduce independently within a cell.

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