Select All The Organelles That Are Thought To Have Arisen By Endosymbiosis.

Endosymbiosis, the process by which one organism engulfs and lives inside another, has played a crucial role in shaping the evolution of life on Earth. It is through endosymbiosis that some of the most important organelles in our cells have originated. These organelles were once independent organisms that formed a symbiotic relationship with the host cell, eventually becoming an essential part of it. In this article, we will explore the organelles that are thought to have arisen by endosymbiosis and delve into the fascinating processes that led to their formation.


One of the most well-known examples of endosymbiosis is the origin of mitochondria. Mitochondria are responsible for generating energy in cells through the process of cellular respiration. They have their own DNA and ribosomes, which suggests that they were once free-living bacteria. The theory proposes that early eukaryotic cells engulfed these bacteria, establishing a mutually beneficial relationship. The host provided protection and nutrients, while the bacteria produced energy-rich ATP molecules. Over time, the bacteria lost their ability to survive independently and became fully integrated into the host cell.


Chloroplasts, the organelles responsible for photosynthesis in plants and algae, are believed to have originated from a similar endosymbiotic event. It is thought that a eukaryotic cell engulfed a photosynthetic bacterium, such as a cyanobacterium, and established a symbiotic relationship. The host cell provided protection and nutrients, while the bacterium performed photosynthesis, converting sunlight into energy. This endosymbiotic event not only gave rise to chloroplasts but also transformed the Earth’s atmosphere by producing oxygen as a byproduct of photosynthesis.


In addition to chloroplasts, endosymbiosis has also given rise to other types of plastids, such as chromoplasts and leucoplasts. Chromoplasts are responsible for synthesizing and storing pigments, giving fruits and flowers their vibrant colors. Leucoplasts, on the other hand, are involved in the synthesis of starch and other storage compounds. These organelles are believed to have originated from ancient cyanobacteria that were engulfed by eukaryotic cells and underwent a similar process of endosymbiosis.


Apicoplasts are organelles found in apicomplexan parasites, such as malaria-causing Plasmodium. These organelles are thought to have originated from a secondary endosymbiotic event. It is believed that an ancient eukaryotic cell engulfed a red alga, which already contained a chloroplast derived from primary endosymbiosis. Over time, the engulfed alga lost its photosynthetic ability but retained some essential metabolic functions. Today, apicoplasts play a crucial role in the survival of apicomplexan parasites and are a target for antimalarial drugs.

Golgi Apparatus

While not all organelles thought to have arisen through endosymbiosis are directly involved in energy production or metabolism, they still play vital roles in cell function. The Golgi apparatus, for example, is responsible for modifying, sorting, and packaging proteins for transport within the cell or secretion to the outside. Although the exact origin of the Golgi apparatus is still debated, some theories propose that it might have evolved through the endosymbiotic integration of an ancient microorganism.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a complex network of membranous sacs and tubules involved in the synthesis of lipids and proteins and the transportation of these molecules within the cell. The origin of the ER is still not well understood, but some scientists propose that it could have emerged through the endosymbiotic acquisition of a bacterial cell membrane by an ancestral eukaryotic cell. This acquisition would have provided the host cell with a selective advantage by increasing its capacity for protein synthesis and lipid metabolism.

Frequently Asked Questions

Q: Which organelle is the best example of endosymbiosis?

A: The mitochondrion is considered the best example of endosymbiosis. It has its own DNA and ribosomes, similar to bacteria, and is believed to have originated from the engulfment of a free-living bacterium by an ancestral eukaryotic cell.

Q: How does endosymbiosis contribute to the evolution of organisms?

A: Endosymbiosis has played a crucial role in the evolution of organisms by providing them with new capabilities and functions. Through endosymbiosis, symbiotic organisms have merged to form a single, more complex organism, allowing for greater specialization and diversity.

Q: Are there any other organelles that might have originated from endosymbiosis?

A: While the organelles mentioned in this article are the most well-known examples, there is still ongoing research and debate about the origin of other organelles, such as lysosomes and peroxisomes. The endosymbiotic origin of these organelles is still a topic of investigation and discovery.

Final Thoughts

The concept of endosymbiosis has revolutionized our understanding of how cells and organisms have evolved over time. The origin of organelles through endosymbiosis provides compelling evidence for the interconnectedness of all living things and the immense adaptive potential of symbiotic relationships. By studying these ancient events, scientists continue to uncover the intricate mechanisms of life’s complexity, unlocking the secrets of our shared evolutionary history.

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