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On a sheet of paper

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  1. On a sheet of paper • Write down your thoughts on evolution: • Some things you can include: • What is the first thing you think about when you hear the word • What is your definition • When did you first hear about it • Do you agree with it (Why or why not?) • Turn into the tray when you are done • Have out the Ch. 25 reading guide

  2. “…sparked by just the right combination of physical events & chemical processes…” Origin of Life

  3. 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…

  4. History of Life Timeline • Earth formed – 4.6 bya • Earth cooled, water is present – 3.8 bya • Organic molecules form, including simple carbs, lipids, protein, and RNA – 3.7 bya • Prokaryotic cells arise – 3.5 bya • Photosynthesis arises, oxygen added to atmosphere – 2.8 bya • Eukaryotic cells arise – 2.1 bya • Sexual reproduction and multicellular organisms arise – 1.5 bya • Plants colonize land – 1.2 bya

  5. The Origin of Life is Hypothesis • Special Creation • Was life created by a supernatural or divine force? • not testable • Extra-terrestrial Origin • Was the original source of organic (carbon) materials comets & meteorites striking early Earth? • testable • Spontaneous Abiotic Origin • Did life evolve spontaneously from inorganic molecules? • testable

  6. 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?

  7. 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

  8. Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics Why was this experimentimportant??!

  9. 4 Stage Hypothesis of Origin of Life • The abiotic synthesis of small organic molecules (amino acids and nucleotides) • Joining of these monomers into polymers (proteins and nucleic acids) • The origin of self-replicating molecules that eventually made inheritance possible • Packaging of these molecules into “protobionts” – droplets that maintained an internal chemistry different than the surroundings

  10. Protobionts

  11. Key Events in Origin of Life • Origin of Cells (Protobionts) • lipid bubbles  separate inside from outside  metabolism & reproduction • Origin of Genetics • RNA is likely first genetic material • multiple functions: encodes information (self-replicating), enzyme, regulatory molecule, transport molecule (tRNA, mRNA) • makes inheritance possible • makes natural selection & evolution possible • Origin of Eukaryotes • endosymbiosis

  12. Ribozyme (RNA molecule) 3 Template Nucleotides Figure 26.5 5 5 Complementary RNA copy • RNA molecules called ribozymes have been found to catalyze many different reactions, including • Self-splicing • Making complementary copies of short stretches of their own sequence or other short pieces of RNA

  13. Early protobionts with self-replicating, catalytic RNA • Would have been more effective at using resources and would have increased in number through natural selection

  14. Concept 26.2: The fossil record chronicles life on Earth • Careful study of fossils • Opens a window into the lives of organisms that existed long ago and provides information about the evolution of life over billions of years

  15. How Rocks and Fossils Are Dated • Sedimentary strata • Reveal the relative ages of fossils

  16. Index fossils • Are similar fossils found in the same strata in different locations • Allow strata at one location to be correlated with strata at another location Figure 26.6

  17. Accumulating “daughter” isotope 1 2 Ratio of parent isotope to daughter isotope 1 4 Remaining “parent” isotope 1 8 1 16 1 2 3 4 Time (half-lives) • The absolute ages of fossils • Can be determined by radiometric dating Figure 26.7

  18. The magnetism of rocks • Can also provide dating information • Magnetic reversals of the north and south magnetic poles • Have occurred repeatedly in the past • Leave their record on rocks throughout the world

  19. The Geologic Record • By studying rocks and fossils at many different sites • Geologists have established a geologic record of Earth’s history

  20. Timeline • Key events in evolutionary history of life on Earth • 3.5–4.0 bya:life originated • 2.7 bya:free O2 = photosynthetic bacteria • 2 bya:first eukaryotes

  21. The geologic record is divided into • Three eons: the Archaean, the Proterozoic, and the Phanerozoic • Many eras and periods • Many of these time periods • Mark major changes in the composition of fossil species

  22. Key events • Photosynthesis • Eukaryotes arise (Endosymbiosis) • Multicellular Life • Move to land

  23. Concept 26.3: As prokaryotes evolved, they exploited and changed young Earth • The oldest known fossils are stromatolites • Rocklike structures composed of many layers of bacteria and sediment • Which date back 3.5 billion years ago

  24. Lynn Margulis (top right), of the University of Massachussetts, and Kenneth Nealson, of the University of Southern California, are shown collecting bacterial mats in a Baja California lagoon. The mats are produced by colonies of bacteria that live in environments inhospitable to most other life. A section through a mat (inset) shows layers of sediment that adhere to the sticky bacteria as the bacteria migrate upward. (a) Some bacterial mats form rocklike structures called stromatolites, such as these in Shark Bay, Western Australia. The Shark Bay stromatolites began forming about 3,000 years ago. The insetshows a section through a fossilized stromatolite that is about 3.5 billion years old. (b) Figure 26.11a, b

  25. The First Prokaryotes • Prokaryotes were Earth’s sole inhabitants • From 3.5 to about 2 billion years ago

  26. Electron Transport Systems • Electron transport systems of a variety of types • Were essential to early life • Have: some aspects that possibly precede life itself

  27. Photosynthesis and the Oxygen Revolution • The earliest types of photosynthesis • Did not produce oxygen

  28. Oxygenic photosynthesis • Probably evolved about 3.5 billion years ago in cyanobacteria Figure 26.12

  29. When oxygen began to accumulate in the atmosphere about 2.7 billion years ago • It posed a challenge for life • It provided an opportunity to gain abundant energy from light • It provided organisms an opportunity to exploit new ecosystems

  30. Concept 26.4: Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes • Among the most fundamental questions in biology • Is how complex eukaryotic cells evolved from much simpler prokaryotic cells

  31. ~2 bya First Eukaryotes • 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

  32. 1st 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

  33. Eukaryotic cell with mitochondrion 2nd Endosymbiosis • 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

  34. 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

  35. 10 m The Colonial Connection • The first multicellular organisms were colonies • Collections of autonomously replicating cells Figure 26.16

  36. Some cells in the colonies • Became specialized for different functions • The first cellular specializations • Had already appeared in the prokaryotic world

  37. Colonization of Land by Plants, Fungi, and Animals • Plants, fungi, and animals • Colonized land about 500 million years ago

  38. Symbiotic relationships between plants and fungi • Are common today and date from this time

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

  40. Mass Extinctions • The fossil record chronicles a number of occasions • When global environmental changes were so rapid and disruptive that a majority of species were swept away 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 Extinction rate ( ) Number of families ( ) 40 1,000 Cretaceous mass extinction 500 20 0 0 Carboniferous Neogene Cretaceous Ordovician Paleogene Devonian Cambrian Permian Jurassic Silurian Proterozoic eon Triassic Ceno- zoic Figure 26.8 Paleozoic Mesozoic

  41. Two major mass extinctions, the Permian and the Cretaceous • Have received the most attention • The Permian extinction • Claimed about 96% of marine animal species and 8 out of 27 orders of insects • Is thought to have been caused by enormous volcanic eruptions

  42. NORTH AMERICA Chicxulub crater Yucatán Peninsula • The Cretaceous extinction • Doomed many marine and terrestrial organisms, most notably the dinosaurs • Is thought to have been caused by the impact of a large meteor Figure 26.9

  43. Much remains to be learned about the causes of mass extinctions • But it is clear that they provided life with unparalleled opportunities for adaptive radiations into newly vacated ecological niches

  44. Continental Drift • Earth’s continents are not fixed • They drift across our planet’s surface on great plates of crust that float on the hot underlying mantle

  45. Eurasian Plate North American Plate Juan de Fuca Plate Caribbean Plate Philippine Plate Arabian Plate Indian Plate Cocos Plate South American Plate Pacific Plate Nazca Plate African Plate Australian Plate Scotia Plate Antarctic Plate Figure 26.18 • Often, these plates slide along the boundary of other plates • Pulling apart or pushing against each other

  46. Volcanoes and volcanic islands Oceanic ridge Trench Subduction zone Oceanic crust Seafloor spreading Figure 26.19 • Many important geological processes • Occur at plate boundaries or at weak points in the plates themselves

  47. India collided with Eurasia just 10 million years ago, forming the Himalayas, the tallest and youngest of Earth’s major mountain ranges. The continents continue to drift. 0 Cenozoic North America Eurasia By the end of the Mesozoic, Laurasia and Gondwana separated into the present-day continents. 65.5 Africa India South America Madagascar Australia Antarctica By the mid-Mesozoic, Pangaea split into northern (Laurasia) and southern (Gondwana) landmasses. Laurasia Millions of years ago 135 Gondwana Mesozoic At the end of the Paleozoic, all of Earth’s landmasses were joined in the supercontinent Pangaea. 251 Pangaea Paleozoic Figure 26.20 • The formation of the supercontinent Pangaea during the late Paleozoic era • And its breakup during the Mesozoic era explain many biogeographic puzzles

  48. Is there life elsewhere? Does it look like life on Earth? They wouldAsk Questions!