According to the endosymbiotic theory, what is the relationship between prokaryotes and eukaryotes?

• A. Eukaryotic cells originated when ancestral prokaryotic cells engulfed other prokaryotes, which became organelles such as mitochondria and chloroplasts.
• B. Prokaryotes evolved from eukaryotes by losing their organelles.
• C. Eukaryotes are simply larger versions of prokaryotes with no internal compartmentalization.
• D. Eukaryotes and prokaryotes evolved independently with no shared ancestry.

Answer: (A)

Verified step by step guidance

1. Understand the endosymbiotic theory: This theory explains the origin of eukaryotic cells as a result of a symbiotic relationship between ancestral prokaryotic cells. Specifically, it suggests that certain prokaryotes were engulfed by larger prokaryotic cells and eventually evolved into organelles such as mitochondria and chloroplasts.
2. Analyze the options provided: The correct answer should align with the idea that eukaryotic cells originated through the engulfment and symbiosis of prokaryotic cells, leading to the development of specialized organelles.
3. Eliminate incorrect options: For example, the statement 'Prokaryotes evolved from eukaryotes by losing their organelles' contradicts the theory, as prokaryotes existed before eukaryotes. Similarly, 'Eukaryotes are simply larger versions of prokaryotes with no internal compartmentalization' ignores the presence of organelles in eukaryotic cells. Lastly, 'Eukaryotes and prokaryotes evolved independently with no shared ancestry' is inconsistent with the shared evolutionary history implied by the theory.
4. Focus on the correct interpretation: The correct answer should reflect the idea that eukaryotic cells originated when ancestral prokaryotic cells engulfed other prokaryotes, which then became organelles such as mitochondria and chloroplasts.
5. Conclude by connecting the theory to modern evidence: Highlight that the endosymbiotic theory is supported by evidence such as the presence of double membranes in mitochondria and chloroplasts, their own DNA, and their ability to replicate independently within eukaryotic cells.