which of these provides evidence for the origin of mitochondria and chloroplasts as prokaryotic endosymbionts?
which of these provides evidence for the origin of mitochondria and chloroplasts as prokaryotic endosymbionts?
Answer: The endosymbiotic theory provides evidence for the origin of mitochondria and chloroplasts as prokaryotic endosymbionts within eukaryotic cells. This theory suggests that these organelles, which are responsible for energy production (mitochondria) and photosynthesis (chloroplasts), were once free-living prokaryotic organisms that were engulfed by a primitive eukaryotic cell.
Several pieces of evidence support the endosymbiotic theory:
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Similarities to Bacteria: Mitochondria and chloroplasts share many structural and functional similarities with free-living bacteria. For example, they have their own DNA (circular, like bacterial DNA), ribosomes similar to bacterial ribosomes, and the ability to replicate independently within the cell.
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Reproduction: Mitochondria and chloroplasts replicate by a process similar to binary fission, which is how bacteria reproduce. This is different from the cell’s typical process of mitosis.
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Size and Shape: The size and shape of mitochondria and chloroplasts resemble those of certain types of bacteria.
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Double Membrane: Both mitochondria and chloroplasts are surrounded by a double membrane, which could have originated from the engulfing process.
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Phylogenetic Analysis: Genetic analysis shows that the DNA in mitochondria and chloroplasts is more similar to that of certain types of bacteria than to eukaryotic nuclear DNA.
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Independent DNA: The presence of their own DNA supports the idea that mitochondria and chloroplasts were once free-living organisms with their own genetic material.
These lines of evidence collectively suggest that mitochondria and chloroplasts were once prokaryotic cells that established a symbiotic relationship with eukaryotic host cells, eventually evolving into the organelles we observe in modern eukaryotic cells today.