Evolution of Earth and Life: From Early Beginnings to Diverse Present

1. Learning Objectives To understand: I. the history of our planet • Non-living periods • Periods with life II. that the Earth and the diversity of life has changed over time III. trends in diversity over time

2. Early Earth • Earth began forming ~ 4.5 bya • Evidence: • 1st atmosphere = N2, H2, CO and CO2 • no O2 or ozone, high UV & winds • H2O was present

3. Experiments mimicking conditions on early earth demonstrate that organic compounds can form from inorganic compounds • Amino acids, nucleotides, carbs, ATP, NAD(P) • Phospholipid ‘bubbles’ provide structure for a cell

4. First Life Prokaryotes originated ~ 3.8 bya in Archean & proliferated through Proterozoic Chemoautotrophs made carbohydrates using chemicals in environment - non-oxygen releasing; released sulfur Oxygen releasing photosyn. arose later (=photoautotrophs) Breakdown of carbohydrates to ATP did not req’ oxygen at first (=fermentation), but later organisms use O2

5. Photosynthesis ~ 3.2 bya • Effects of oxygen: • Mass extinction of many organisms • Prokaryotic diversity of a different kind starts to diversify • ozone layer develops ~2 bya

6. Origin of eukaryotic cells • ~ 1 bya • Endosymbiosis • partnerships between prokaryotic ancestors • chloroplasts and mitochondria • Evidence?

7. youngest oldest Archean • prokarys. only Proterozoic Paleozoic Mesozoic Cenozoic youngest oldest

8. Paleozoic • Started with mass extinction, then adaptive radiation of multicellular organisms • Life proliferated in seas • Cambrian explosion of inverts • Armored fish follow • Then land invasion: plants, insects, amphibians

9. Mesozoic Adaptive radiation of seed bearing plants and reptiles followed by mass extinction

10. Cenozoic • Adaptive radiation of mammals • H. sapiens evolved in last 40,000 yrs. Agriculture arose 10,000 yrs. • Average extinction rates • 1 spp./1 million spp./year • 20th century extinction rates • 1,000 -10,000 spp. / 1 million spp. / year

11. Biodiversity • Millions of species now on earth (~2 million) • Diversity has changed radically over time • Observations - Many species look like other species • Broad similarities = lineages with similar phenotypes & life histories • Reptiles = snakes, lizards, crocs • Gymnosperms = pines, spruce, fir, larch • Primates = great apes, chimps, humans • Within a very closely related group, the different species of the group tend to live in different habitats • White Pine and Jack Pine and tamarack live in different habitats • Great apes (baboons, gorillas, orangutans) live in different habitats

12. Conclusions • Broad similarities in life histories are present because lineages are related • Supported by initially by studies of anatomy, development, and now by molecular data • Similar species in different habitats exist b/c each habitat ‘selects’ for traits in slightly different ways

13. Taxonomy classifies organisms to reflect relatedness. Taxon - a group of organisms with similar form(s) that are related. Reptiles are a taxonomic group Gymnosperms are a taxonomic group Then, all of the pines (white, red, limber, lodgepole, etc) are another more specific taxonomic group. All pines are closely related.

14. Classification system • developed by Linnaeus (~1758) • hierarchial organization • binomial species name genus and epithet = species • Used to identify organisms

15. Species belong to a genus (1st part of name) • Genera grouped into families • Families grouped into orders • Orders --> classes • Classes --> Phyla • Phyla • Kingdoms – 6 kingdoms • Domains are the largest unit • Eukarya, Bacteria, Archaea Eukarya Domain