The theory of endosymbiosis provides a possible explanation for how eukaryotic cells came into existence. the presence of chloroplasts in photosynthetic organisms is one phenomenon explained by this theory. based on the theory of endosymbiosis, what was the significance of the development of chloroplasts?

The correct answer is -

Chloroplasts is a double membrane bound specialised organelle that is present in the photosynthetic organsisms (such as plants and algae).

The inner membrane is similar to membrane of ancient prokaryotes that could perform photosynthesis.

In other words, it helps in the synthesis of food (glucose) using carbon dioxide and water in the presence of sunlight.  

In the process of photosynthesis, Oxygen is released as a waste product (when photolysis of water takes place to provide electrons, required in the photosynthesis) in the atmosphere.

Due to this, oxygen rich environment is produced, which allowed the formation of more complex, aerobic life forms (that is oxygen breathing organisms) on the planet Earth.