Lecture Set 4b: Bacteria, Archae, and Protists Chpt 16

Early Earth (3.5 BYA) Atmosphere of carbon dioxide, hydrogen, sulfuric acid, water, ammonium and methane –No oxygen. –You would die in seconds –No FOOD!?! Kinda. Chemicals to eat… –Miller-Urey Experiment

The Earliest Organisms Bacteria and Archae capable of surviving without oxygen –Used chemical energy from H-S bonds or C-H bonds.

Then came cyanobacteria… A real game-changer! –Started doing photosynthesis, and creating oxygen Lots, and lots and lots of cyanobacteria creating lots and lots and lots of oxygen Whole oceans of just bacterial mats Enough to change the whole world’s atmosphere and chemistry!

Diversification of Prokaryotes Prokaryotes ruled the world for 2.5 billion years, or so. –Became different, diverse, and successful. Some evolved cell walls with peptioglycan –Eubacteria Some evolved histones and introns –Archae

Eubacteria Such as cyanobacteria, staphylococcus, streptococcus, E. coli, etc. –Have a cell wall with peptidoglycan –The most successful organisms on Earth! –Have endospores Allows them to survive in stasis until better conditions come along

Plasmids Small rings of DNA not part of the chromosome Can be exchanged to other bacteria via pilli

Archae No peptidoglycan, but histones (in some species), introns, a more complex RNA polymerase –Shares traits with Eukaryotes –Believed to evolved into Eukaryotes Most are extremophiles –Like environments with high heat, methane, salt, etc. Eu

The origin of Eukaryotes The first Eukaryotes appeared –~2 BYA –Descended from Archae –Protists Single celled, then colonies of single-celled, then multicellular

Protists Protozoans –“Animal-like” before animals Algae –“plant-like” –Kelp, sea weed, etc A large assortment of other things not plants, animals, or fungi

Protists Slime Molds Kelp Amoebas Sea Weed Dinoflagellates Radialarians Etc..