A Brief History of Life on Earth

1. A Brief History of Life on Earth Geology Today Chapter 15 Barbara W. Murck and Brian J. Skinner Horned dinosaurs, 70 m.y. ago Mark Marcuson; Nebraska State Museum N. Lindsley-Griffin, 1999

2. Organization of Life Amino acidsare the basic building blocks of proteins. Biosynthesis is the linking together (or polymerization) of small organic molecules (like amino acids) to form larger ones, called biopolymers (like proteins). N. Lindsley-Griffin, 1999

3. Organization of Life DNA - Deoxyribonucleic acid - is a double-chain biopolymer that consists of two twisted chain-like molecules held together by organic molecules. DNA contains all the genetic information needed for organisms to grow and reproduce. DNA stores genetic information. Fig. 15.7, p. 443 N. Lindsley-Griffin, 1999

4. Organization of Life RNA - Ribonucleic acid - is a single-strand molecule similar to one-half of a DNA strand. RNA contains the information needed to construct an exact duplicate of the protein molecule. RNA transmits the genetic information that DNA stores. Fig. 15.7, p. 443 N. Lindsley-Griffin, 1999

5. Organization of Life Short chain of fossil cyanobacteria cells, 1.0 b.y. Bitter Springs Chert, N. Australia Metabolism is the set of biochemical reactions by which organisms produce and extract food energy. Fermentation is anaerobic metabolism - without oxygen. Respiration is aerobic metabolism - with oxygen. Living cyanobacterium Oscillatoria N. Lindsley-Griffin, 1999

6. Oxygen in Atmosphere Photosynthesis - process whereby plants use light energy to cause carbon dioxide to react with water. Byproducts are: Organic substances - carbohydrates and free oxygen All free oxygen now in the atmosphere originated by photosynthesis. Fig. 15.3, p. 439 N. Lindsley-Griffin, 1999

7. Early Earth Major events and trends in Earth’s surface environment during the first 4.0 b.y.: Ocean forms, 4.4 b.y. Oldest bacteria, 3.8 b.y. Blue-green algae, 3.0 b.y. Iron formations, 2.2 b.y. Oxygen buildup, 2.0 b.y. Eukaryotes, 2.0 b.y. Abundant multicelled fossils, 0.6 b.y. Fig. 15.1, p. 437 N. Lindsley-Griffin, 1999

8. Early Earth 4.6 b.y. The solar system coalesced 4.6 b.y. ago from a cloud of cosmic dust and gas. Gravitational compaction caused nuclear fusion to begin in the sun. Planetesimalsgathered into larger clusters to make planets; leftover material formed asteroids and comets. Asteroid Ida Nebula M16 N. Lindsley-Griffin, 1999

9. Early Earth4.5 b.y. Probably molten at first, Earth was battered by repeated impacts of planetesimals. The first atmosphere was stripped away by solar wind or impacts, but was replenished by volcanic eruptions. It was too hot for water to exist on the surface. John Drummond; Time-Life Books N. Lindsley-Griffin, 1999

10. Early Earth4.4 b.y. As Earth cooled, water vapor in the atmosphere condensed and rained out to form oceans - maybe as early as 4.4 b.y. ago. Don Davis; Time-Life Books N. Lindsley-Griffin, 1999

11. Early Life3.8 b.y. Near the end of the intense bombardment period, about 3.8 b.y. ago, Earth still was wracked by meteorite impacts and volcanic eruptions. It was a tough place to make a living. Don Davis; Time-Life Books N. Lindsley-Griffin, 1999

12. Origin of Life The first life required chemosynthesis of organic compounds - such as amino acids - from inorganic materials like atmospheric gases, to make proteins. Lightening bolts discharge through volcanic gases, Mt. Pinatubo, Philippines Fig. 15.4, p. 441 N. Lindsley-Griffin, 1999

13. Origin of Life One hypothesis suggests simple microbes first formed in aerosols - tiny liquid droplets or solid particles suspended in the atmosphere. Could lightening discharges have provided the energy? Lightening bolts discharge through volcanic gases, Mt. Pinatubo, Philippines Fig. 15.4, p. 441 N. Lindsley-Griffin, 1999

14. Origin of Life Black smoker Galapagos Is. Fig. 15.6, p. 443 Because of the adverse surface conditions, the most likely place for life to develop might have been at deep ocean thermal springs, protected from meteorite bombardment. Both the raw materials and the heat needed for chemosynthesis would have been available here. N. Lindsley-Griffin, 1999

15. Origin of Life3.5 b.y. +? Short chain of fossil cyanobacteria cells, 1.0 b.y. Bitter Springs Chert, N. Australia The first life was microbial. Oldest fossils of microbes found on Earth (so far) are nearly 3.5 b.y. old. Rocks in Greenland thought to have formed as byproducts of microbial activity are 3.8 b.y. Living cyanobacterium Oscillatoria N. Lindsley-Griffin, 1999

16. Mars Life?4.5-3.6 b.y. Meteorite ALH84001 was found in Antarctica in 1984. It is 4.5 b.y. old. Its chemistry is unlike Earth rocks - instead, it is like Mars rocks analyzed by remote landers. It is thought to have originated on Mars, but was “splashed” into space by an impact near the end of the heavy bombardment period. It remained in space until about 16,000 years ago, when it was attracted by Earth’s mass and fell onto Antarctica. Fig. 15.5, p. 442 N. Lindsley-Griffin, 1999

17. Mars Life?4.5-3.6 b.y. Fig. 15.5, p. 442 In 1996, tiny tube-like structures were discovered inside the meteorite. Some scientists have interpreted these structures as fossils of microbes - if so, they would be at least 3.6 b.y. old. The debate is raging hotly - stay tuned for further developments. N. Lindsley-Griffin, 1999

18. Oxygen Atmosphere1.8 b.y. Chemical sediments from 2.0 to 1.8 b.y. consist of oxygen-poor iron minerals plus oxygen-rich iron minerals Interlayering reflects a transition from oxygen-poor atmosphere to oxygen-rich atmosphere during this time. Brockman Formation, 2.0 b.y., W. Australia (Fig. 8.10, p. 227) N. Lindsley-Griffin, 1999

19. Early Life All organisms are composed of cells, a complex grouping of chemical compounds enclosed in a membrane, or porous wall. Prokaryotic cells store their DNA in a poorly defined part of the cell, not separated from the cytoplasm - the main body of the cell - by a membrane. Prokaryotic cell lacks a well-defined nucleus Fig. 15.8, p. 445 N. Lindsley-Griffin, 1999

20. Early Life Eukaryotic cell has a well-defined, membrane-bound nucleus Fig. 15.8, p. 445 Eukaryotic cells include a distinct nucleus surrounded by a membrane, as well as other membrane-bounded organelles - well defined parts that each have a specific function. N. Lindsley-Griffin, 1999

21. Early Life Prokaryotic cells are the earliest and simplest cell forms; many are anaerobic. Modern bacteria are prokaryotes. Eukaryotic cells are larger and more complex; most require oxygen. Most advanced life forms are Eukaryotes. Fig. 15.8, p. 445 N. Lindsley-Griffin, 1999

22. How Fossils Form Mineralization - bones and other hard parts are replaced by minerals carried in solution by groundwater. Petrified wood has been replaced by mineralization. Even though its original woody texture is preserved, it consists entirely of minerals like crystalline quartz, chalcedony, or agate. Petrified Forest Natl. Park, Arizona Fig. 15.16, p. 455 N. Lindsley-Griffin, 1999

23. How Fossils Form Trace fossils are indirect evidence of organisms: tracks and trails wormholes and burrows nests feces (coprolites) calcite mounds (stromatolites) Dinosaur tracks, 65 m.y.a. Fig. 15.18, p. 455 N. Lindsley-Griffin, 1999

24. How Fossils Form Some organisms are frozen in permafrost,likethis wooly mammoth. Some organisms are trapped and preserved whole in amber or tar, like this Eocene to Oligocene age mosquito. (Fig. 15.15, p. 454). N. Lindsley-Griffin, 1999

25. Evolution Darwin’s Finches Fig. 15.13 p. 451 Charles Darwin visited the Galapagos Islands in 1832. He observed many species of finches on the islands, whereas only one lives on the nearby continent of South America. Each finch species occupies a different environment, and eats different food. Their beaks and their feeding behavior vary to exploit the sparse resources as effectively as possible. N. Lindsley-Griffin, 1999

26. Evolution Darwin’s Finches Fig. 15.13 p. 451 To explain his observations, Darwin hypothesized that species can adapt to new conditions through natural selection. Individuals who are well-adapted are more likely to pass on their characteristics to the next generation. Individuals who are poorly adapted tend to be eliminated and are less likely to produce offspring to perpetuate their genes. N. Lindsley-Griffin, 1999

27. Evolution Darwin’s Finches Fig. 15.13 p. 451 All natural populations have individuals with different characteristics. In any setting, some features work better than others, and these individuals will tend to reproduce more successfully. Over time, the entire population will evolve towards a better adaptation. N. Lindsley-Griffin, 1999

28. Evolution Darwin’s Finches Fig. 15.13 p. 451 Back to Darwin’s Finches -- A study of DNA released in mid-1999 showed that all the Galapagos finches are closely related to each other. They probably were derived from the South American finch that Darwin hypothesized was their common ancestor. N. Lindsley-Griffin, 1999

29. Evolution The iguana problem: Galapagos Islands are only 3 m.y. old. DNA from Galapagos iguanas shows that they have evolved about 7 m.y. since splitting off from their South American cousins. BUT -- The islands did not even exist when the iguanas left South America 7 m.y. ago. Galapagos Iguana Fig. B15.1, p. 452 N. Lindsley-Griffin, 1999

30. Evolution The iguana problem (Cont.): The Galapagos Islands are a hot spot chain like Hawaii, in which the older volcanoes have subsided below sea level. Hypothesis: the ancestral iguanas swam from South America to the easternmost island. As time passed and each island in the chain subsided, they moved west to the next one. It took them 7 m.y. to make the trip. Galapagos Iguana Fig. B15.1, p. 452 N. Lindsley-Griffin, 1999

31. Fossil Record - Archean 3.5 b.y.: The oldest known fossils are chains of prokaryotic cells from a chert in W. Australia. Notice how similar they are to the possible microbes in Mars meteorite ALH84001 N. Lindsley-Griffin, 1999

32. Fossil Record - Precambrian Stromatolites are layers of calcium carbonate that form in warm, shallow seas by the activities of photosynthetic bacteria. Fossil stromatolites > 1.5 b.y. are evidence of microbial activity during the Proterozoic and Archean (as far back as 3.0 b.y. or earlier). Stromatolites, Shark’s Bay, W. Australia (Fig. 15.10, p. 447) N. Lindsley-Griffin, 1999

33. Fossil Record - Proterozoic About 1.4 b.y.a. - oldest eukaryotes By 1.0 b.y.a. - eukaryotes common 600 m.y. - Ediacara fauna: oldest fossils of larger, multicellular, soft-bodied marine animals. Named for Ediacara Hills, Australia. Dickinsonia costata - worm-like, 7.5 cm across Fig. 15.11 p. 448 Mawsonia spriggi - a floating, disc-shaped animal like a jellyfish, 13 cm across. N. Lindsley-Griffin, 1999

34. Fossil Record - Late Proterozoic Ediacaran Fauna are still poorly understood. Some are simple blobs, others are like jellyfish, worms, or soft-bodied relatives of the arthropods. They appear worldwide in strata about 600 m.y. old, suggesting a relatively sudden explosion of soft multicelled forms. N. Lindsley-Griffin, 1999

35. Fossil Record - Late Proterozoic Plants: Land plants probably evolved from green algae about 600 m.y. ago. Life on land may have looked like this. In the seas, bacteria and green algae were common at the end of the Precambrian. Green algae (Fig. 15.22, p. 458) N. Lindsley-Griffin, 1999

36. Fossil Record - Cambrian Trilobite, Utah (Fig. 15.20) 545-505 m.y.a. - beginning of period of great diversification: Higher atmospheric oxygen affected skeletal biochemistry and supported larger organisms. Ozone developed to level where it blocked ultraviolet radiation. Eukaryotes invented sexual reproduction. Hard parts appeared. Soft-bodied arthropod, B.C. (Fig. 15.21, p. 457) N. Lindsley-Griffin, 1999

37. Fossil Record - Cambrian Trilobite, Utah (Fig. 15.20) 545-505 m.y.a.: Hard external skeletons protected trilobites, clams, snails, and sea urchins from predators. Soft-bodied animals diversified from Ediacaran fauna into the Burgess Shale fauna. Gills, filters, efficient guts, circulatory systems, and other features of more advanced life forms developed. Soft-bodied arthropod, B.C. (Fig. 15.21, p. 457) N. Lindsley-Griffin, 1999

38. Fossil Record - Cambrian 545-505 m.y.a.: reconstruction of Burgess Shale fauna J. Wiley & Sons, The Blue Planet N. Lindsley-Griffin, 1999

39. Fossil Record - Ordovician 490-443 m.y.a.: Seas held abundant marine invertebrates with sophisticated adaptations to different conditions. Straight-shelled cephalopods, trilobites, snails, brachiopods, and corals in a shallow inland sea. The Field Museum, Chicago N. Lindsley-Griffin, 1999

40. Fossil Record - Silurian 438-408 m.y.a.: This was the “Golden Age” of cephalopods and brachiopods (a clam-like shellfish). The first land plants developed, and the first arthropods (scorpion-like invertebrates) ventured onto land. The Milwaukee Museum N. Lindsley-Griffin, 1999

41. Fossil Record - Devonian Lutgens and Tarbuck, 1999 408-360 m.y.a.: The “Golden Age” of fishes American Museum of Natural History, New York N. Lindsley-Griffin, 1999

42. Fossil Record - Devonian Modern fern leaf with dark spores on underside 408-360 m.y.a.: Land plants became common. Vascular plants developed - club mosses and ferns. These plants had structural support from stems and limbs and a vascular system providing an internal plumbing system for water. Fossil fern in shale, 350 m.y. (Fig. 15.23, p. 459) N. Lindsley-Griffin, 1999

43. Fossil Record - Late Devonian 380-360 m.y.a. - First seed plants - the naked-seedplants - developed. Gymnosperms like Glossopteris developed. Ginkgos are long-lived relics of the ancient family of naked-seed plants, so are conifers. Modern and fossil ginkgo leaves (Fig. 15.24, p. 459) N. Lindsley-Griffin, 1999

44. Fossil Record - Carboniferous 360-286 m.y.a.: Age of amphibians; first winged reptiles and first winged insects. Widespread forests and swamps. Ichthyostega had features like a tail that it inherited from fish; and legs that allowed it to move around on land. Fig. 3.9, p. 65 Michael Rothman; John Wiley & Sons N. Lindsley-Griffin, 1999

45. Fossil Record - Pennsylvanian 320-290 m.y.a.: peat swamps common, with scale trees, seed ferns, scouring rushes, and large dragonflies The Field Museum, Chicago N. Lindsley-Griffin, 1999

46. Fossil Record - Permian 286-248 m.y.a.: Amphibians decline; reptiles and insects increase; first mammal-like reptiles appear. Nonseed plants decline. Eryops, a carnivorous amphibian -The Field Museum, Chicago N. Lindsley-Griffin, 1999

47. Fossil Record - Triassic 225 m.y.a.: First dinosaurs and mammals; explosive radiation of dinosaurs. (Primitive Ornithischia, an early dinosaur) National Museum of Natural Sciences, Canada N. Lindsley-Griffin, 1999

48. Fossil Record - Jurassic 213-144 m.y.a.: The Age of dinosaurs; forests of gymnosperms and ferns cover most of Earth Smithsonian Natural History Museum J.R. Griffin, 1999

49. Fossil Record - Jurassic 213-144 m.y.a.: Age of dinosaurs American Museum of Natural History, New York, N.Y. N. Lindsley-Griffin, 1999

50. Fossil Record - Jurassic and Cretaceous 213-65 m.y.a.: Age of dinosaurs. Birds appear. Dragonfly, Brazil 7 cm (3 in.) long Fig. 15.26, p. 460 Fig. 3.9, p. 65 Breck Kent; John Wiley & Sons N. Lindsley-Griffin, 1999