Eukaryogenesis, illustration 插畫檔

Illustration of eukaryogenesis, the process of evolution from prokaryotic to eukaryotic cells. Prokaryotes are simple cells without membrane-bound organelles. Eukaryotic cells are thought to have evolved from prokaryotes approximately 1.8 to 2.7 billion years ago. One hypothesis is that infoldings of the cell wall formed organelles such as the endoplasmic reticulum, while other organelles such as mitochondria (orange) and chloroplasts (green) evolved through endosymbiosis. Endosymbiosis is the process whereby a eukaryotic cell engulfs a prokaryotic cell. During the engulfing process the prokaryote becomes surrounded by the eukaryote's membrane, forming a double membrane. Cells containing chloroplasts were the ancestors of plants and algae, while cells without chloroplasts were the ancestors of animals, fungi and protists. For this image without text see F045/9993