Origin of Life (Ch. 26)

1. “…sparked by just the right combination of physical events & chemical processes…” Origin of Life (Ch. 26)

2. Bacteria Archae- bacteria Protista Plantae Fungi Animalia 0 Cenozoic Colonization of land by animals Mesozoic Paleozoic 500 Appearance of animals and land plants First multicellular organisms 1000 PROTEROZOIC Oldest definite fossils of eukaryotes 1500 2000 Appearance of oxygen in atmosphere PRECAMBRIAN Millions of years ago Oldest definite fossils of prokaryotes 2500 3000 ARCHEAN 3500 Molten-hot surface of earth becomes cooler 4000 4500 Formation of earth The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story…

3. What is Life? • First we have to define LIFE… • organized as cells • respond to stimuli • regulateinternal processes • homeostasis • use energy to grow • metabolism • develop • change & mature within lifetime • reproduce • heredity • DNA / RNA • adaptation & evolution

4. Life comes from Non-Life Where is the line between living and non-living? “A vehicle (organism) built by design information (DNA) for the purpose of replicating that information” Good– but too inclusive??? (computer viruses, etc.) Terrestrial life is cellular (sorry viruses). No worries— Alive or Not, I exist!!!

5. The Origin of Life is Hypothesis • Special Creation • Life was created by a supernatural or divine force. • not testable • Extraterrestrial Origin (Panspermia) • The original source of organic (carbon) materials was comets & meteorites striking early Earth. • testable • Spontaneous Abiotic Origin • Life evolved spontaneously from inorganic molecules. • testable

7. Conditions on early Earth • Reducing atmosphere • water vapor (H2O), CO2, N2, NOx, H2,NH3, CH4, H2S • lots of available H & its electron • no free oxygen • Energy source • lightning, UV radiation, volcanic low O2 = organic molecules do not breakdown as quickly What’s missingfrom thatatmosphere?

8. 5 Steps to go from Non-Life to Life • Formation (or presence) of Biological Molecules • Isolation of Biological Molecules from Surroundings (aka “Cells”) • Development of Metabolism. • Development of Information Molecules. • Reproduction.

9. Electrodes discharge sparks (lightning simulation) Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") Origin of Organic Molecules • Abiotic synthesis • 1920Oparin & Haldane propose reducing atmosphere hypothesis • 1953Miller & Ureytest hypothesis • formed organic compounds • amino acids • adenine CH4 H2 NH3

10. It’s ALIVE! Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics

11. Glucose-phosphate 20 m Glucose-phosphate Phosphorylase Starch Amylase Phosphate Bubbles…Tiny bubbles… Maltose Maltose (a) Simple reproduction. This liposome is “giving birth” to smallerliposomes (LM). (b) Simple metabolism. If enzymes—in this case,phosphorylaseand amylase—are included in the solution from which the droplets self-assemble, some liposomes can carry out simple metabolic reactions and export the products. Origin of Cells (Protobionts) • Bubbles separate inside from outside metabolism & reproduction

12. Origin of Genetics Dawn of natural selection • RNA is likely first genetic material • multi-functional • codes information • self-replicating molecule • makes inheritance possible • natural selection & evolution • enzyme functions • ribozymes • replication • regulatory molecule • transport molecule • tRNA & mRNA

13. Ribozyme (RNA molecule) 3 Template Nucleotides Complementary RNA copy 5 5 A ribozyme capable of replicating RNA

14. Key Events in Origin of Life • Key events in evolutionary history of life on Earth • life originated 3.5–4.0 bya • “Heterotroph Hypothesis”: cells eating other cells for ~700 million years.

15. Prokaryotes • Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteria modern bacteria chains of one-celledcyanobacteria

16. Stromatolites Lynn Margulis Fossilized mats of prokaryotes resemble modern microbial colonies

17. Oxygen atmosphere • Oxygen begins to accumulate 2.7 bya • reducing oxidizing atmosphere • evidence in banded iron in rocks = rusting • makes aerobic respiration possible • photosynthetic bacteria (blue-green algae)

18. First Eukaryotes ~2 bya • Development of internal membranes • create internal micro-environments • advantage: specialization = increase efficiency • natural selection! nuclear envelope endoplasmicreticulum (ER) plasma membrane infolding of theplasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell

19. Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell

20. Endosymbiosis Eukaryotic cell with mitochondrion • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

21. Lynn Margulis Theory of Endosymbiosis • Evidence • structural • mitochondria & chloroplasts resemble bacterial structure • genetic • mitochondria & chloroplasts have their own circular DNA, like bacteria • functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell

22. Cambrian explosion • Diversification of Animals • within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya

25. Millions of years ago 600 400 300 200 500 100 0 2,500 100 Number of taxonomic families 80 2,000 Permian mass extinction Extinction rate 60 1,500 Number of families ( ) Extinction rate ( ) 40 1,000 Cretaceous mass extinction 500 20 0 0 Carboniferous Neogene Cretaceous Ordovician Paleogene Cambrian Devonian Jurassic Permian Triassic Proterozoic eon Silurian Ceno- zoic Paleozoic Mesozoic Diversity of life & periods of mass extinction Cambrian explosion

26. Cretaceous extinction The Chicxulub impact crater in the Caribbean Sea near the Yucatan Peninsula of Mexico indicates an asteroid or comet struck the earth and changed conditions 65 million years ago

27. Early mammal evolution • 125 mya mammals began to radiateout & fill niches

28. Classifying Life • Molecular datachallenges 5 Kingdoms • Monera was too diverse • 2 distinct lineages of prokaryotes • Protists are still too diverse • not yet sorted out

29. 3 Domain system • Domains = “Super” Kingdoms • Bacteria • Archaea • extremophiles = live in extreme environments • methanogens • halogens • thermophiles • Eukarya • eukaryotes • protists • fungi • plants • animals

30. Eukaryote Prokaryote Archaebacteria&Bacteria Classification • Old 5 Kingdom system • New3 Domain system • reflects a greater understanding of evolution & molecular evidence • Bacteria • Archaebacteria • Eukaryotes • Protists • Plants • Fungi • Animals

31. KingdomBacteria KingdomArchaebacteria KingdomProtist KingdomFungi KingdomPlant KingdomAnimal

32. Is there life elsewhere? Does it look like life on Earth? Any Questions??

33. Have Humans Created Life? Certainly not cellular life. “Synthia” – Created in 2010 by the Venter Institute Very simple bacterium with a completely synthesized chromosome Some computer programs sure behave a lot like life does...

34. 0 Review Questions

35. 1. What is (are) the drawback(s) associated with the hypothesized abiogenetic formation of organic monomers in early Earth's atmosphere? * the relatively short time between intense meteor bombardment and appearance of the first life forms the lack of experimental evidence that organic monomers can form abiogenetically uncertainty about which gases comprised early Earth's atmosphere 1 only 2 only 3 only 1 and 3 2 and 3 0

36. In the Miller- Urey experiment, application of electric sparks to simple gasses resulted in the formation of • Steroids • Oxygen • Cellulose • Simple amino acids • DNA

37. The following questions refer to the following choices: 1. aerobic autotrophs 2. aerobic heterotrophs 3. anaerobic heterotrophs 4. anaerobic autotrophs What is the most likely order in which the choices above evolved on Earth? Give two pieces of evidence to support your order for #3.