Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host.

Mitochondria and chloroplasts are considered semi-autonomous organelles, as they resemble bacteria. They have DNA, RNA and ribosomes, and are capable of synthesizing proteins. They reproduce by binary division. Each organelle has several copies of circular DNA, but its genetic information is not enough to classify the organelle's proteins. For this reason, mitochondria and chloroplasts are divided by two genetic systems, that of the organelle and that of the cell nucleus.

Explanation:

Endosymbiotic theory suggests that mitochondria and chloroplasts evolved when bacteria were phagocyted by an ancestral eukaryotic cell. Acquiring mitochondria is a very important stage for eukaryotes, because thanks to them the ability to aerobic respiration was achieved. On the other hand, chloroplasts arose when some eukaryotes phagocytized photosynthetic bacteria and the symbiotic relationship between them was established.

the oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf, but operationally is often referred to as beginning where the water depths drop to below 100 meters (328 feet), seaward from the coast to the open ocean.

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