Question

Some scientists think that complex eukaryotic cells formed from the union of two separate prokaryotic cells. The engulfing of one prokaryotic cell by another is a plausible explanation of why a eukaryotic cells lack the defense mechanisms of prokaryotic cells. b organelles in a eukaryotic cell work cooperatively. c eukaryotic cells don't share any similarities with prokaryotic cells. d organelles in a eukaryotic cell would attack other cells.

Answer 1

The best explanation for why some scientists think that complex eukaryotic cells formed from the union of two separate prokaryotic cells is:

**b. organelles in a eukaryotic cell work cooperatively.**

This idea is part of the endosymbiotic theory, which suggests that certain organelles in eukaryotic cells, such as mitochondria and chloroplasts, originated from free-living prokaryotic cells that were engulfed by ancestral eukaryotic cells. These organelles have retained their own DNA and can perform essential functions in collaboration with the host cell, supporting the idea of cooperation between once-independent organisms.