Tree of Evolution• Conditions of Early Earth (greater radiation

and igneous activity) lead to the synthesis of abiotic (non-living) molecules– nucleic acids (RNA) & amino acids

• led to the formation of protobionts (droplets with membranes that maintained the internal environment)

• origin of self replication to produce new organisms

– Sources for the carbonaceous molecules could have come from meteorites or from the substrate. Environment in early Earth (~3.6 billion years ago) was a reducing environment (electron adding) creating the opportunity for the formation of new molecules from methane and ammonia.

Fossil record

• Prokaryotes – Stromatolites - beds of sediment containing the

byproducts of bacterial metabolism (shows blooms followed by extinctions) • oldest ~3.5 billion years - anaerobes

– halophiles – methanogens

Fossil Record

– photosynthesis and the oxygen revolution (cyanobacteria) • prokaryotes start using oxygen as a source of reducing energy

to form new molecules • photoautotrophs

Fossil Record• Eukaryotes (~2.1 billion years ago)

– arose from the symbiotic relationship and transfer of genetic material between prokaryotes

– organisms resemble simple single celled algae – Endosymbionts - mitochondria & plastids

• endosymbionts take over the role of energy making paving the path for multicellular organisms

• genetic annealing (combining of genomes) and colony formation leads to specialization and the multicellular organism

• multicellular organisms (~1.5 billion years ago) – most confined to areas of water and heat (snowball Earth hypothesis)

resembling small algae – Cambrian explosion (explosion of life ~ 700mil years ago)

Geologic time scale • eon - longest division

– Archeon - 1st eon of Earth ~3.9 to 2.5 billion years ago – Proterozoic - lasted for the next 2 billion years – Phanerozoic - most resent with evidence of life

• era - there are three eras per eon – Paleozoic - ~543 million years ago "Age of Invertebrates"

• fossils of both land and plants

– Mesozoic - ~248 million years ago "Age of Reptiles" • dinosaurs

– Cenozoic - ~most recent "Age of Mammals" • appearance of humans

Geologic time scale• periods

– Precambrian - all periods before the paleozoic era • rocks lack index fossils • fossil evidence is contained in stromatolites - layers of bacteria and algae • content is high in valuable metals - Au, Ag, Cu, ...

– Cambrian • invertebrates • trilobites is the most common index fossil ~500 million years ago

Geologic time scale

• Ordovician – invertebrates – graptolites are the most

common index fossil - lived in colonies

• Silurian - appearance of terrestrial animals

• Devonian - Age of the Fishes - 1st fossils of lungfish found

• Carboniferous - appearance of reptiles and vertebrates

Geologic time scale

• Permian - formation of Pangaea - nearly 1/2 of known fossils extinct by the end of the period – marks the end of the Paleozoic era

• Triassic - Jurassic - Cretacious are periods of the Mesozoic – rise and fall of the dinosaurs

• Paleogene, Neogene, & Quarternary are periods of the Cenozoic – formation of modern climate features and the rise of man

Geologic time scale• Epochs (part of the Cenozoic)

– Holocene… Historical time begins (.01mil yrs)– Pleistocene… Ice Ages… Humans appear (1.8mil yrs)– Pliocene… Origin of genus Homo (5.3mil yrs)– Miocene… Continued radiation of species (23mil yrs)

• Apelike ancestors of humans

– Oligocene… Origin of primate groups (33.9mil yrs)– Eocene… Angiosperms dominate (55.8mil yrs)– Paleocene… massive radiation of mammals, birds, & insects (65.5mil

yrs)