Classification & History of Life Today & next time Taxonomy Modes of Life Origin of Life Traditional new History of life Taxonomy: Organize life into related groups Traditional Taxonomy Grouped by shared traits & separated by differences (presumed evolutionary divergence) e.g. Put Birds into own Class - distinct from dinosaurs New method: Cladistics Organized by relatedness of organisms (evolutionary divergence), using DNA when possible. e.g. birds are now a subgroup in dinasauria Normally Taxonomy & Cladistics agree 1
Major divisions: Kingdoms SIX Kingdoms! New one = Archea Thanks C. Woese Prokaryotes = no discrete nucleus containing genetic material This bush of life accurately shows Archea, Eubacteria and Eukaryotes diverging x from single point (x). What is not accurate is that it is now believed that Archea are evolutionarily closer to Eukaryotes than to Eubacteria Prokaryote Some are extremophiles Live in hot springs, hydrothermal vents, glacial ice Some are Chemotrophic S- or CH 4 - reducing Archaeobacterea 2
Eubacteria Prokaryote true bacteria Includes Cyanobacteria (blue - green algae) = pond scum Euacteria & Archea = 50% of all organic matter! 1 x 10 6 bacteria per cc water! 3
Protista Eukaryotes - have nucleus with genetic material Unicellular to simple multicellular Most Algae are protist phytoplankton are protist (diatoms & foraminifera) Plantae Eukaryote Multicellular Reproduce sexually Photosynthetic 4
Plants & Protists Only 0.3 x 10 6 species 96% terrestrial 4% (~11,000) marine Mostly protists (algae/plankton) Marine plants are way DIFFERENT than land plants large algae (Brown, Red etc. Kelp) Fungi/Mycota Eukaryotes Feed on decaying organic mater (dead organisms) Genetically closer to Animalia than Plantae 5
Animalia Eukaryotes Multicellular Consume other organisms 1.2 x 10 6 species 80% terrestrial 20% marine 10,000 pelagic 190,000 benthic Division of Kingdoms: Kingdom divided -> phylum -> class etc. to species Each division has a number of subdivisions Species is the final division - all members share diagnostic traits and can breed. 6
Strategies of life: All organisms eat, survive and reproduce How do they eat and survive? Autotrophs - synthesize own food Photosynthetic - combine solar energy with nutrients to grow tissue Chemotrophic - extract energy from chemical reactions. These form the base of food web!!! 7
Heterotrophs - eat other organisms Herbivores, carnivores, omnivores Detrivores = filter organic matter from sediment = deposit feeders (worms) from water = filter feeders (coral, spunges) Mode and mobility Pelagic organisms live in water column Planktonic = float Nektonic = swim Benthic organisms live on substrate Epifaunal = live on surface Enfaunal = live in substrate (burrow) 8
Origin of Life on Earth: Traditional Concept Oldest fossils are 3.5 b.y. Life began 1 b.y. after planet condensation Early atmosphere Reducing environment (No O 2 ) No ozone, UV-B radiation! Rich in CH 4, NH 3, CO 2, N 2 Primordial Soup... Not this one Origin of Life: Traditional Concept Miller & Urey, 1953 Simulated a reducing atmosphere and primordial ocean added energy Lightening, volcanic, solar radiation, etc. Results: Formed 12 of 20 amino acids in life Other organic molecules too (HCN, Formaldehyde) Conclusion: Not hard to make simple organic molecules Note: 74 amino acids found in Chondritic meteorites. 9
Origin of Life: Traditional Concept Later experiments (Fox) Created polymers of amino acids Proteins RNA! Fatty acids & lipids - required for cells Note: also in chondritic meteorites! No replication of these polymers in the lab, NOT Life Origin of Life: Traditional Concept Conclusion of Experiments Early atmosphere + energy results in amino acids - and maybe life Or: (not traditional concept) meteorites add amino acids and lipids to early Earth (extraterrestrial life) Problem: that nasty UV-B! Turn to new discoveries for origin of life... 10
New discovery Vent Communities Discovered 1976 on the Galapagos Spreading Center Now known on all midocean ridge systems What are all these heterotrophs eating? Chemotrophic Bacteria Get energy from reducing methane and sulfur Do not rely on sunlight! Base of vent food web Origin of Life: New hypothesis Amino acids Extraterrestrial, or Generated at vent (heat Energy) as in Miller-Urey experiments Why at vent and not surface? Deep sea is shielded from UV-B! Pyrite (FeS 2 ) is abundant in this environment and can serve as catalyst for replicating RNA Gunter Wächtershäuser s new idea 11
Origin of Life: New Hypothesis Carl Woese: new discovery DNA of chemotrophic bacteria indicate they are different than eubacteria Why are they called Archeabacteria (old bacteria)? They diverged from the bush of life long ago Possibly back when life evolved on earth in the deep oceans. Question: when did Earth first have oceans? 4.3 b.y. Maybe life started long before first fossil (3.5 b.y.) 12