Q: What organelles have arisen through endosymbiosis?
A: Chloroplasts and mitochondria.
To understand which organelles have arisen through endosymbiosis, we need to first understand what endosymbiosis is. Endosymbiosis is a theory that suggests certain organelles within cells, such as mitochondria and chloroplasts, were once free-living prokaryotes that were engulfed by primitive eukaryotic cells. Over time, the engulfed prokaryotes formed a symbiotic relationship with the eukaryotes, eventually becoming specialized organelles.
To answer the question, we know that both chloroplasts and mitochondria have arisen through endosymbiosis. Here's how we can arrive at this conclusion:
1. Chloroplasts: Chloroplasts are responsible for photosynthesis and are found in plants, algae, and some protists. They contain their own DNA and have a double membrane, much like prokaryotes. The endosymbiotic theory suggests that the ancestors of chloroplasts were once photosynthetic cyanobacteria that were engulfed by early eukaryotic cells. Through a process called endosymbiosis, the host eukaryotic cell and the cyanobacteria formed a mutualistic relationship, resulting in the development of the chloroplast. This theory is supported by the fact that chloroplasts have their own DNA, similar to prokaryotes, and can reproduce independently of the host cell.
2. Mitochondria: Mitochondria are known as the powerhouses of the cell and are found in almost all eukaryotic organisms. They are responsible for generating ATP, the energy currency of cells, through cellular respiration. Like chloroplasts, mitochondria have their own DNA and double membranes. The endosymbiotic theory suggests that mitochondria originated from aerobic bacteria that were engulfed by early eukaryotic cells. Through a symbiotic relationship, the host cell provided a protected environment for the bacteria, while the bacteria supplied the host cell with ATP through respiration. This theory is supported by the fact that mitochondria have features similar to bacteria, including their size, structure, and ability to reproduce independently.
In summary, both chloroplasts and mitochondria have arisen through endosymbiosis. Chloroplasts originated from photosynthetic cyanobacteria, while mitochondria originated from aerobic bacteria. The endosymbiotic theory provides a compelling explanation for the presence of these organelles within eukaryotic cells.