The theory would be endosymbiont theory. It was developed on the idea that some eukaryotic organelles come from prokaryotic organisms. It is also known as symbiogenesis. This theory says that these organelles were first from prokaryotic cells that is living inside a host cell.
Connective tissue connects or separates other tissues and organs, and usually has little or no cells embedded with collagen or other fibers, Like cartilaginous, fatty, and elastic tissues.
