Which definition describes endosymbiosis best?

• A. A relationship in which two organisms live together but do not affect each other.
• B. A process by which organisms compete for the same resources in an environment.
• C. A type of reproduction where offspring are produced without fertilization.
• D. A symbiotic relationship in which one organism lives inside the cells of another organism, often leading to mutual benefit.

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the term 'endosymbiosis.' It refers to a specific type of symbiotic relationship where one organism lives inside the cells of another organism. This relationship often results in mutual benefits for both organisms.
2. Step 2: Analyze the provided options. The first option describes a neutral relationship where two organisms coexist without affecting each other, which is not endosymbiosis. The second option refers to competition, which is unrelated to symbiosis. The third option describes a type of reproduction, which is also not relevant to endosymbiosis.
3. Step 3: Focus on the fourth option, which correctly defines endosymbiosis as a symbiotic relationship where one organism resides inside the cells of another organism, often leading to mutual benefits. This aligns with the biological concept of endosymbiosis.
4. Step 4: Recall examples of endosymbiosis in biology, such as the origin of mitochondria and chloroplasts in eukaryotic cells. These organelles are believed to have originated from free-living bacteria that entered into an endosymbiotic relationship with ancestral eukaryotic cells.
5. Step 5: Conclude that the correct definition of endosymbiosis is the fourth option, as it accurately describes the biological phenomenon and its implications.