A theory by which prokaryotes gave rise to the first eukaryotic cells. Chloroplasts in plants and mitochondrion in other eukaryotes are believed to have once been prokaryotic organisms engulfed by larger prokaryotic cells.

Trees with light brown bark dominate an ecosystem the ecosystem has populations of insects that thrive on the tree bark over time some insect species developed certain physical characteristics that them thrive on the tree bark these physical characteristics also the insects defend themselves from predators which insect species is probaly the species with the new physical characteristics?