The Origin and Evolution of Life

1. The Origin and Evolution of Life Chapter 20

2. The Big Bang • 12-15 billion years ago all matter was compressed into a space the size of our sun • Sudden instantaneous distribution of matter and energy throughout the known universe

3. Archeon Eon and Earlier • 4,600 mya: Origin of Earth • 4,600 - 3,800 mya • Formation of Earth’s crust, atmosphere • Chemical and molecular evolution • First cells (anaerobic bacteria)

4. Earth Forms • About 4.6 and 4.5 billion years ago • Minerals and ice orbiting the sun started clumping together • Heavy metals moved to Earth’s interior, lighter ones floated to surface • Produced outer crust and inner mantle

5. Earth Is “Just Right” for Life • Smaller in diameter, gravity would not be great enough to hold onto atmosphere • Closer to sun, water would have evaporated • Farther from sun, water would have been locked up as ice

6. First Atmosphere • Hydrogen gas • Nitrogen • Carbon monoxide • Carbon dioxide • No gaseous oxygen

7. Origin of Organic Compounds • Amino acids, other organic compounds can form spontaneously under conditions like those on early Earth • Clay may have served as template for complex compounds • Compounds may have formed near hydrothermal vents

8. Stanley Miller’s Experiment electrodes to vacuum pump spark discharge CH4 NH3 H2O H2 gases water out condenser water in water droplets water containing organic compounds boiling water Figure 20.3 b Page 326 liquid water in trap

9. Chemical Evolution chlorophyll a • Spontaneous formation of porphyrin rings from formaldehyde • Components of chlorophylls and cytochromes formaldehyde porphyrin ring system Figure 20.4  Page 720

10. RNA World • DNA is genetic material now • DNA-to-RNA-to-protein system is complicated • RNA may have been first genetic material • RNA can assemble spontaneously • How switch from RNA to DNA might have occurred is not known

11. Proto-Cells • Microscopic spheres of proteins or lipids can self assemble • Tiny sacs like cell membranes can form under laboratory conditions that simulate conditions in evaporating tidepools

12. living cells enzymes and other proteins DNA RNA formation of protein-RNA systems, evolution of DNA formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions Possible Sequence membrane-bound proto-cells self-replicating system enclosed in a selectively permeable, protective lipid sphere Figure 20.5  Page 331

13. Proterozoic Eon • Origin of photosynthetic Eubacteria • Noncyclic pathway first • Cyclic pathway next • Oxygen accumulates in atmosphere • Origin of aerobic respiration

14. The First Cells • Originated in Archeon Eon • Were prokaryotic heterotrophs • Secured energy through anaerobic pathways • No oxygen present • Relied on glycolysis and fermentation

15. History of Life ARCHAEBACTERIAL LINEAGE ANCESTORS OF EUKARYOTES Noncyclic pathway of photosynthesis Cyclic pathway of photosynthesis ORIGIN OF PROKARYOTES Aerobic respiration Figure 20.6  Page 332 3.8 bya 3.2 bya 2.5 bya

16. History of Life ARCHAEBACTERIA Extreme halophiles Methanogens Extreme thermophiles ORIGINS OF ANIMALS EUKARYOTES ORIGINS OF EUKARYOTES Animals Heterotrophic protistans ORIGINS OF FUNGI Fungi Photosynthetic protistans ORIGINS OF MITOCHONDRIA Plants ORIGINS OF PLANTS ORIGINS OF CHLOROPLASTS EUBACTERIA Photosynthetic oxygen producers Other photosynthetic bacteria Chemotrophs, heterotrophs Figure 20.6  Page 332 1.2 bya 900 mya 435 mya present

17. Advantages of Organelles • Nuclear envelope may have helped to protect genes from competition with foreign DNA • ER channels may have protected vital proteins DNA infolding of plasma membrane Figure 20.10  Page 335

18. Theory of Endosymbiosis • Lynn Margulis • Mitochondria and chloroplasts are the descendents of free-living prokaryotic organisms • Prokaryotes were engulfed by early eukaryotes and became permanent internal symbionts

19. Paleozoic Era (570-240 mya) • Six periods • Cambrian • Ordovician • Silurian • Devonian • Carboniferous • Permian

20. Paleozoic Era • By early Paleozoic, diverse organisms of all six kingdoms lived in seas • During the Silurian and Devonian, plants and animals invaded the land • Ended with the greatest known mass extinction and the formation of Pangea

21. Cambrian Period • Explosive radiation of marine organisms • Mass extinction near end of period • May have resulted from cooling of seas Gondwana Page 336

22. Ordovician Period • Adaptive radiation of new reef organisms in warm, shallow seas • Increase in diversity of shelled animals • Ended with glaciation and mass extinction as Gondwana straddled South Pole

23. Silurian into Devonian Reef communities recover Do not post on Internet Do not post on Internet First land plants Figure 20.13 Page 337

24. Devonian Vertebrates • Jawed fishes arise, diversify • Ancestors of amphibians onto land • Radiation of amphibians begins • Period ends with another mass extinction

25. Carboniferous Period • Sea levels swing widely • Amphibians diversify • First reptiles • Seedless vascular plants and gymnosperms thrive

26. Permian Period • Insects, amphibians, and early reptiles in swamp forests • Ends with greatest known mass extinction Do not post on Internet Figure 20.13 Page 337

27. The Mesozoic Era • Divided into three periods • Triassic • Jurassic • Cretaceous • The “Age of the Reptiles” • Major geologic event was breakup of Pangea

28. Triassic Period • Seas repopulated after Permian extinction • First dinosaurs and mammals • Ends with a mass extinction Do not post on Internet A therapsid Figure 20.15  Page 339

29. Jurassic Period Do not post on Internet • Radiation of the dinosaurs • Ended with a mass extinction that ended many dinosaur lineages ichthyosaur Figure 20.15  Page 339

30. Cretaceous Period • Surviving dinosaurs diversify • Seedless plants and gymnosperms begin to decline Do not post on Internet Figure 20.15  Page 339

31. Rise of Flowering Plants • Conifers and other gymnosperms were dominant in early Mesozoic • Angiosperms arose during the late Jurassic or the early Cretaceous • In less than 40 million years, they displaced conifers and related plants in most environments

32. Rise of the Angiosperms 250 200 • Angiosperms arose during the late Jurassic or early Cretaceous • In less than 40 million years, they displaced conifers and related plants in most environments angiosperms 150 number of genera 100 ferns cycads 50 conifers ginkgos other genera 0 Figure 20.14Page 338 160 140 120 100 80 60 millions of years ago

33. K-T Asteroid Impact Theory • An asteroid impact caused mass extinction Cretaceous–Tertiary (K–T) boundary • Iridium • Impact crater in present Gulf of Mexico

34. Global Broiling Hypothesis • Energy released at the K–T impact site was equivalent to detonating 100 million nuclear bombs • Most animals and plants in open were destroyed • Provided opportunity for the mammalian adaptive radiation

35. Cenozoic Era • Continents collided and mountain ranges arose • Mammals underwent adaptive radiation • Tropical forests gave way to woodlands and grasslands • Most recent Ice Age occurred • Humans set stage for possible mass extinction

36. Paleocene to Eocene • Tropical forests and subtropical forests extended as climates warmed • Mammalian lineage diversified

37. Later Cenozoic • Climates became cooler and drier • Grasslands and woodlands dominated • Grazing and browsing animals thrived Do not post on Internet Dry woodland of Pleistocene Figure 20.17bPage 341

38. At Present • Distribution of land masses favors high biodiversity • Tropical forests are richest ecosystems • In midst of what may be a great mass extinction • Human hunters and human activities have increased the pace of extinction