Origin of Life

Primordial Earth

- Atmosphere contained CO2, CO, ammonia, methane, hydrogen, nitrogen, and water vapour but no oxygen

Earth formed a solid crust _____ later

600 million years

Abiogenesis

the theory that organic molecules arose from non-living material

Protocells

May have been fluid-filled vesicles with a membrane-like structure
- Adding clay can increase the rate of vesicle formation

First replicating genetic material

RNA
- Natural selection produced self-replicating RNA molecules

Strata

Layers of sedimentary rocks and are the richest source of fossils

Fossil record biased in favor of species that:

- Existed for a long time
- Were abundant and widespread
- Had hard parts

Phanerozoic eon (541 mil-now)

- Paleozoic
- Mesozoic
- Cenozoic

Archaean Eon (4.6-2.5 billion years ago)

- Origin of Earth
- Oldest known rocks on Earth's surface
- Oldest fossils of cells (prokaryotes) appear
- Concentration of atmospheric oxygen begins to increase

Proterozoic (2.5 bil - 542 mil years ago)

- Eukaryotic cells appear
- Diverse algae and soft-bodied invertebrate animals appear

Paleozoic (542-251 million years ago)

- Cambrian explosion (542 mil years ago)
- Coniferous period - extensive forests of vascular plants form, seed plants appear (359-299 mil years ago)

Stromatolites

Oldest known fossils formed by accumulation of sedimentary layers on bacterial mats
- Date back to 3.5 billion years ago
- Prokaryotes were Earth's sole inhabitants 3.5 to 2.1 bil years ago

Oxygen revolution

2.7 billion years ago, O2 began accumulating and rusting iron-rich terrestrial rocks, causing many prokaryotes to go extinct

- some groups survived and started using cellular respiration to harvest energy

Cyanobacteria

Caused early rise in O2 levels

Miller-Urey experiment

Experiment designed to simulate primordial Earth's atmosphere

Colonization of land

What happened 500 million years ago

Heterochrony

an evolutionary change in the rate or timing of developmental events
- Can have a significant impact on body shape

Paedomorphosis

the rate of reproductive development accelerates compared with somatic development

Homeotic genes

determine such basic features as where wings and legs will develop on a bird or how a flower's parts are arranged

Hox genes

genes that provide positional information during development

endosymbiont theory

theory that proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells

serial endosymbiosis

supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events