CHAPTER 13

anoxygenic

the earliest phototrophs did not produce O2 or __________

cyanobacteria

the earliest O2-producing phototrophs

stromatolites

fossilized microbial mats “layered rocks” formed by the deposition of carbonate or silicate minerals.

reduced iron

as cyanobacteria produced O2, it initially could not accumulate in the atmosphere because it reacted with ____________ dissolved in earth’s oceans

banded iron formations

striped, laminated sedimentary rock formations

o2 to o3

conversion for ozone shield

ozone shield

a barrier that protects the surface of earth from much of the uv radiation from the sun

genome, ribosomes, antibiotic sensitivity, nuclear gene transfers

mitochondria and chloroplasts originated as free-living bacteria based on four key lines of evidence

genomes

they contain their own circular DNA genomes that encode essential proteins, tRNAs/rRNAs

ribosomes
16s rRNA

they possess bacterial-sized ________ with __________ sequences that group them within proteobacteria and cyanobacteria

antibiotic sensitivity

they are inhibited by the same antibiotics that target bacterial ribosomes

nuclear gene transfer

many organellar genes were translocated to the host nucleus during early endosymbiosis

serial endosymbiotic hypothesis

a complex, nucleus-bearing cell line, first evolved a cytoskeleton and nucleus, then subsequently acquired mitochondria and later chloroplasts via endosymbiosis

symbiogenesis hypothesis

proposes that the eukaryotic cell arose directly from a metabolic symbiosis between an H2-producing bacterium and H2-consuming archaeal partner, where the bacterium eventually evolved into the mitochondrion

lokiarchaeota

newly discovered archaea contain eukaryotic-like genes, suggesting close evolutionary links to the host lineage that gave rise to eukarya

microbial clocks

this allows the scientists to estimate the time since microbial species diverged from their closest relatives based on gene sequence dissimilarity.