The theory states that the mitochondria and chloroplast in eukaryotic cells came from bacterial cells. What are two pieces of evidence that support this theory?
There are two main pieces of evidence that support the theory that mitochondria and chloroplasts in eukaryotic cells originated from bacterial cells:
1. Endosymbiotic theory: This theory suggests that mitochondria and chloroplasts were once free-living bacteria that were engulfed by a host cell and developed a symbiotic relationship. The evidence for this theory comes from several observations. Firstly, mitochondria and chloroplasts have their own DNA, which is circular like bacterial DNA, rather than linear like eukaryotic DNA. This suggests that these organelles may have originated from bacteria. Additionally, both mitochondria and chloroplasts have their own ribosomes, which are more similar to bacterial ribosomes than eukaryotic ribosomes. This indicates that these organelles have their own protein synthesis machinery.
2. Structural similarities: Both mitochondria and chloroplasts share several structural similarities with bacteria. For example, both organelles have an outer membrane and an inner membrane, similar to the cell structure of bacteria. The inner membrane of mitochondria even has folds called cristae, which are reminiscent of the infoldings in the cell membrane of bacteria. Moreover, the size and shape of mitochondria and chloroplasts are similar to certain types of bacteria. This structural resemblance provides further evidence for the evolutionary origin of these organelles from bacterial cells.
These two pieces of evidence, along with other supporting observations, provide strong support for the theory that mitochondria and chloroplasts in eukaryotic cells originated from bacterial cells through endosymbiosis.
There are two pieces of evidence that support the theory of the endosymbiotic origin of mitochondria and chloroplasts in eukaryotic cells:
1. Similarities in structure and function: Mitochondria and chloroplasts have their own DNA, ribosomes, and similar biochemical pathways to bacteria. The structure of these organelles closely resembles that of prokaryotic cells, including a double membrane, which is consistent with the theory that they were once independent bacteria.
2. Genetic evidence: Comparative studies of mitochondrial and chloroplast DNA (mtDNA and cpDNA) have revealed striking similarities between these organelles and certain groups of bacteria. For example, the genetic sequences of genes found within mitochondria and chloroplasts closely resemble those of certain species of bacteria, suggesting a common evolutionary origin.
These lines of evidence provide strong support for the idea that mitochondria and chloroplasts were originally free-living bacteria that were engulfed by ancestral eukaryotic cells and developed into mutually beneficial symbiotic relationships.