Question

Some aspects of eukaryotes are more similar to Archaea, while other aspects of eukaryotic cell composition appear more closely related to Bacteria. Explain how endosymbiosis could resolve this paradox.

a) Endosymbiosis implies that eukaryotes evolved from both Archaea and Bacteria.
b) Endosymbiosis suggests that eukaryotes obtained mitochondria from Archaea and chloroplasts from Bacteria.
c) Endosymbiosis indicates that eukaryotes have a common ancestor with both Archaea and Bacteria.
d) Endosymbiosis demonstrates that Archaea and Bacteria evolved from eukaryotic cells.

Answer 1

The endosymbiotic theory explains eukaryotic evolution by suggesting a symbiotic merger between an archaean host cell and a bacterial cell, leading to the formation of complex cells with organelles like mitochondria and chloroplasts.

Step-by-step explanation:

One of the key concepts in understanding the evolution of eukaryotic cells is the notion of endosymbiosis. This hypothesis resolves the paradox of how eukaryotes have features similar to both Archaea and Bacteria. According to the endosymbiotic theory, proposed by Lynn Margulis, eukaryotic cells originated from the fusion of an archaean host cell with a bacterial cell, leading to a symbiotic relationship where one cell lived inside another. Over time, this intimate association led to the two cells evolving into a single complex cell with a nucleus (derived from the archaean host) and organelles such as mitochondria and chloroplasts (originating from the engulfed bacteria).

Genome fusion by endosymbiosis, as suggested by researchers like James Lake, implies that eukaryotic cells are a product of an ancient merger between different domains of life, reconciling why some eukaryotic genes resemble those of Archaea while others are closer to bacterial DNA. Furthermore, this theory is supported by the evidence that mitochondria and chloroplasts have their own prokaryote-like DNA. The endosymbiotic event is considered the ultimate event in eukaryotic evolution, giving rise to the complex cells that characterize plants, animals, fungi, and protists today.

James Lake's hypothesis that eukaryotic cells developed from an endosymbiotic gene fusion between an Archaea and a Bacteria has further strengthened the endosymbiotic theory, although further evidence and validation of the conditioned reconstruction (CR) algorithm are needed. Nevertheless, modern DNA analysis has shifted the consensus towards endosymbiosis as a pivotal process in the emergence of eukaryotic life, signifying a revolutionary change in our understanding of the tree of life.