CGS NS 201 Lecture Notes - Lecture 9: Paleozoic, Multicellular Organism, Extinction Event
9 Aug 2018
School
Department
Course
Professor
Document Summary
Photosynthesis requires sunlight, carbon dioxide and hydrogen. First source of hydrogen was hydrogen sulfide gas: from volcanoes. Water + co2 sugar + o2. 2. 2 billion years ago oxygen begins to accumulate in the atmosphere. Rise of aerobic metabolism: aerobic metabolism harvests more energy per food molecule, evolution of predation. Some cells lose the rigid cell wall. Larger cells can engulf smaller cells: star enveloping other bacteria, some engulfed cells are not digested. Organelles that might have evolved from early symbionts. Endosymbiont hypothsis: anaearobic, predatory prokaryotic cell engulfs an aerobic bacterium, descendants of the engulfed bacterium evolve into the mitochondria, mitochondria-containing cell engulfs a photosynthetic bacterium, descendants of the photosynthetic bacterium evolve into chloroplasts. Mitochondrial is about the size of a modern bacteria. Mitochondria ribosomes are similar in size and structure to modern bacterial robisomes. 88% of all time that earth has existed. Evolution of multicellular life the proteozoic.
