Transcript Early Earth
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 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 • 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 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 • 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 Origin of eukaryotic cells • ~ 1 bya • Endosymbiosis – partnerships between prokaryotic ancestors – chloroplasts and mitochondria – Evidence? Archean oldest youngest – prokarys. only Proterozoic Paleozoic Mesozoic Cenozoic youngest oldest 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 Mesozoic Adaptive radiation of seed bearing plants and reptiles followed by mass extinction 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 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 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 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. Classification system • developed by Linnaeus (~1758) • hierarchial organization • binomial species name genus and epithet = species • Used to identify organisms •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