Fig 6. 8: eukaryotic cell structure, nucleus, membrane-bound organelles, cytoskeleton, network of fibers within cell, provides support, allows shape changes, can engulf things, 10-100 um (10x larger than prokaryotes, endosymbiosis. Relationship between 2 spp in which 1 organism lives inside another organism. Connection to gb 115 origin of life. Key organelles evolved through sequence of endosymbiotic events: ancestral pro karyotic cells underwent infoldings of pm. Early eukaryote (host) ingested a prokaryote (endosymbiant: mitochondria. Anaerobic host cell (archaean) engulfed an aerobic bacteria (alpha proteobacterium) Mitochondria of all euk. descended from 1 common ancestor: plastids - group of related organelles. ---> lineage gave rise to 2 photosynthetic protists: red and green algae. Host cell from primary endosymbiosis (euk) is engulfed by another cell (euk). Occurred frequently with red and green algae: eukaryotic evolution. New data and rapidly changing hypotheses: polytomy, four supergroups. Land plants, fungi, and animal are not protists: protists.