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- 1. The History of Life on Earth BIOL 102: General Biology II Chapter 25 Rob Swatski Assoc. Prof. Biology HACC-York1
- 2. Macro- evolution Changes over large time scales are seen in the fossil record Emergence of terrestrial vertebrates Origin of flight in birds Long-term impacts of mass extinctions 2
- 3. The First Cells 1. Abiotic synthesis of small organic molecules 2. Bonding small molecules into macromolecules 3. Packaging macromolecules into protocells 4. Origin of self- replicating molecules 3
- 4. Synthesis of Organic Compounds Earth formed 4.6 BYA, along with rest of solar system The early atmosphere contained water vapor & … … chemicals released by volcanic eruptions N2, NOx, CO2, CH4, NH3, H2, H2S 4
- 5. Abiotic Synthesis Hypotheses Oparin & Haldane (1920’s) Early atmosphere was a reducing environment Miller & Urey (1953) Demonstrated that Abiotic synthesis of organic molecules in a reducing atmosphere is possible 5
- 6. Water vapor “Atmosphere” Electrode Condenser Cold water Cooled water containing organic molecules Sample for chemical analysis H2O “sea” EXPERIMENT CH4 6
- 7. Massofaminoacids(mg) Numberofaminoacids 20 10 0 1953 2008 200 100 0 1953 2008 Amino acid synthesis in a simulated volcanic eruption – 2008 reanalysis of Miller study 7
- 8. 8
- 9. 9
- 10. 10
- 11. Alternative Abiotic Synthesis Hypotheses 1st organic molecules may have been synthesized near volcanoes & deep- sea hydrothermal vents Meteorites seeded the Earth with amino acids Small organic molecules (RNA monomers) polymerize when concentrated on hot sand, clay, or rock 11
- 12. 12
- 13. What is Life? List characteristics that distinguish living things from non-living things. 13
- 14. Protocells Replication & metabolism are key properties of life & may have appeared together Protocells may have been fluid- filled vesicles enclosed by a membrane-like structure Display simple replication & metabolism Also maintain an internal chemical environment 14
- 15. Protocell Evidence Protocells can be easily made in the lab; Adding clay increases their formation Form spontaneously from abiotically produced organic molecules Small membrane- bound droplets (liposomes) form when lipids are added to water Display simple metabolism 15
- 16. Liposome 16
- 17. Time (minutes) Precursor molecules plus montmorillonite clay Precursor molecules only Relativeturbidity, anindexofvesiclenumber 0 20 40 60 0 0.2 0.4 Vesicle self-assembly in montmorillonite clay17
- 18. 20 µm Vesicles dividing to produce smaller vesicles 18
- 20. 20 Which came first… RNA or DNA?
- 21. RNA & Self- Replication The 1st genetic material was probably RNA, not DNA Special RNA molecules (ribozymes) can catalyze many different reactions Ribozymes can make complementary copies of short stretches of RNA 21
- 22. 22
- 23. The “RNA World” Early protobionts with self-replicating, catalytic RNA … … would have been more effective at using resources & … … would have increased in number via natural selection RNA could have provided a template for the more stable DNA 23
- 24. Absorption of RNA Vesicle boundary 1 m 24
- 25. 25
- 26. Craig Venter : The 1st Synthetic Bacterial Cell 26
- 27. Evidence from the Fossil Record Fossils reveal changes in the history of life on Earth Sedimentary rocks are deposited into layers (strata) & are the richest source of fossils Few individuals have fossilized & even fewer have been discovered The fossil record is biased in favor of species that: existed for a long time, were abundant, widespread, & had hard parts 27
- 28. 28
- 29. Dimetrodon Stromatolites Fossilized stromatolite Coccosteus cuspidatus 4.5 cm 0.5 m 2.5cm Present Rhomaleosaurus victor Tiktaalik Hallucigenia Dickinsonia costata Tappania 1 cm 1 m 100 mya 175 200 300 375 400 500 525 565 600 1,500 3,500 270 29
- 30. Rhomaleosaurus victor, a plesiosaur (200-65.5 mya)30
- 31. 31
- 32. 32 Whitby Mudstone Formation, England
- 33. Dimetrodon, a large carnivorous synapsid more closely related to mammals than reptiles (270 mya) 33
- 34. 34
- 36. Tiktaalik (375 mya): the “fishapod” 36
- 39. 39
- 40. Coccosteus cuspidatus, a placoderm (400 mya) 40
- 42. 42
- 43. 43
- 44. 44
- 45. 45
- 46. 46 Burgess Shale, Canadian Rockies, British Columbia
- 47. Hallucigenia, Burgess Shale (525 mya) 47
- 48. 48
- 49. 49
- 50. 2.5 cm Ediacaran (565 mya) – soft-bodied inverts (?) 50 Dickinsonia costata
- 51. 51
- 53. 53 Shark Bay, Western Australia
- 58. How Rocks & Fossils Are Dated Sedimentary strata reveal the relative ages of fossils The absolute ages of fossils are determined by radiometric (radiocarbon) dating A “parent” isotope decays to a “daughter” isotope at a constant rate Each isotope has a known half-life, the time required for half the parent isotope to decay 58
- 59. Time (half-lives) Accumulating “daughter” isotope Remaining “parent” isotope 1 2 3 4 1/2 1/4 1/8 1/16 59
- 60. The Origin of Mammals Mammals belong to the Tetrapod group Mammalian evolution can be traced using anatomical evidence The common ancestor of mammals & reptiles are the Synapsids (300 mya) The more recent common mammalian ancestors are the Therapsids (280 mya) & Cynodonts (260 mya) 60
- 61. OTHER TETRAPODS †Dimetrodon †Very late (non- mammalian) cynodonts Mammals Synapsids Therapsids Cynodonts Reptiles (including dinosaurs and birds)
- 62. 62 Eothyris – early synapsid with multiple canines
- 63. 63Sail-back pelycosaurs – early synapsid temperature regulation
- 64. 64 Lystrosaurus – most common synapsid after Permian- Triassic extinction
- 65. Temporal fenestra Hinge Temporal fenestra Hinge Synapsid (300 mya) Therapsid (280 mya) Key to skull bones Articular Quadrate Squamosal Dentary
- 66. Hinge Hinge Hinges Temporal fenestra (partial view) Early cynodont (260 mya) Very late cynodont (195 mya) Later cynodont (220 mya) Key to skull bones Articular Quadrate Squamosal Dentary
- 67. 67 Cynodonts (260 mya) - Tritylodon
- 68. 68 Cynodont - Exaeretodon Herbivore – babies had deciduous teeth
- 71. Origin of solar system and Earth Prokaryotes Atmospheric oxygen Archaean 4 3 Proterozoic 2 Animals Multicellular eukaryotes Single-celled eukaryotes Colonization of land Humans Cenozoic 1
- 72. The First Unicellular Organisms The oldest known fossils are stromatolites (3.5 bya) Rock-like structures composed of many layers of bacterial mats & sediment Prokaryotes were the Earth’s only inhabitants from 3.5 to 2.1 BYA Microfossils 72
- 75. 75
- 76. 76
- 77. The First Photosynthesis Most atmospheric oxygen (O2) is of biological origin Bacteria similar to modern cyanobacteria were the likely O2 source O2 produced by photosynthesis reacted with dissolved iron Precipitated to form banded iron formations 2.7 bya 77
- 78. 78
- 79. Banded Iron Formations 79
- 80. The Oxygen Revolution Lasted from 2.7 to 2.3 BYA Oxidation posed a challenge for life & caused the extinction of many prokaryotic groups But, it provided an opportunity to gain energy from light Allowed organisms to exploit new ecosystems 80
- 81. “Oxygen revolution” Time (billions of years ago) 4 3 2 1 0 1,000 100 10 1 0.1 0.01 0.0001 AtmosphericO2 (percentofpresent-daylevels;logscale) 0.001 81
- 82. 82
- 84. 84
- 85. The First Eukaryotes The oldest eukaryotic cell fossils are 2.1 BYA old Endosymbiosis Mitochondria & plastids (chloroplasts & related organelles) were once prokaryotes living inside larger host cells Endosymbiont: a cell living within a host cell 85
- 86. Endosymbiont Theory Prokaryotic ancestors of mitochondria & plastids probably entered host cells as undigested prey or internal parasites As they became more interdependent, the host & endosymbionts became a single organism Serial endosymbiosis: mitochondria evolved before plastids through a series of endosymbiotic events Membrane invagination 86
- 87. Nucleus Cytoplasm DNA Plasma membrane Endoplasmic reticulum Nuclear envelope Ancestral prokaryote Serial Endosymbiosis 87 Infolding of plasma membrane
- 90. Key Evidence Supporting Endosymbiosis Mitochondria & plastids have similar inner membrane structures & functions as prokaryotes Their division is similar to some prokaryotes They can transcribe & translate their own DNA Their ribosomes are more like prokaryotic ribosomes 90
- 91. The Origin of Multicellularity Eukaryotic cell evolution allowed for more diverse unicellular forms A 2nd wave of diversification occurred when multicellularity evolved Gave rise to algae, plants, fungi, & animals Comparisons of DNA sequences date the common ancestor of multicellular eukaryotes to 1.5 bya 91
- 92. Oldest known multicellular eukaryote fossils – Algae (1.2 BYA) 92
- 93. 150 µm Two-Cell Stage Fossilized Animal Embryo (575 MYA) 93
- 94. Later Stage 94
- 95. 95
- 96. “Snowball Earth” Hypothesis Periods of extreme polar glaciation Life confined to the equatorial region … … or deep-sea vents 750 to 580 MYA 96
- 98. Ediacaran Biota Evolution of larger organisms More diverse forms of life Wide variety of soft- bodied animals 575 to 535 MYA 98
- 99. The Cambrian Explosion The sudden appearance of fossils resembling modern phyla in a relatively short time period Huge increase in biodiversity: soft- bodied, shelled, & segmented animals First evidence of predator-prey interactions Cambrian period: 535 to 525 MYA 99 Sanctacaris
- 100. 100 Opabinia
- 101. 101 Anomalocaridid
- 102. 102
- 103. 103
- 104. • DNA analyses suggest that many animal phyla diverged before the Cambrian explosion, perhaps as early as 700 million to 1 BYA • Fossils in China provide evidence of modern animal phyla tens of millions of years before the Cambrian explosion • The Chinese fossils suggest that “the Cambrian explosion had a long fuse”
- 105. Sponges Cnidarians Echinoderms Chordates Brachiopods Annelids Molluscs Arthropods Ediacaran Cambrian PROTEROZOIC PALEOZOIC Time (millions of years ago) 635 605 575 545 515 485 0 105
- 106. The Colonization of Land Fungi, plants, & animals began to colonize land around 500 MYA Fungi & plants likely colonized land together by 420 MYA Arthropods & tetrapods are the most widespread & diverse land animals Tetrapods evolved from lobe-finned fishes around 365 MYA 106
- 107. 107
- 108. 108
- 109. 109
- 110. 110 What are the challenges to a terrestrial lifestyle?
- 111. Factors Influencing the Rise & Fall of Biodiversity Continental drift Mass extinctions Adaptive radiations 111
- 112. Continental Drift Earth’s continents move slowly over the underlying hot mantle Oceanic & continental plates Plates collide, separate, or slide past each other Interactions result in the creation of mountains, islands, & earthquakes 112 Mantle Crust Outer core Inner core
- 113. 113
- 114. Juan de Fuca Plate North American Plate Caribbean Plate Cocos Plate Pacific Plate Nazca Plate South American Plate Eurasian Plate Philippine Plate Indian Plate African Plate Antarctic Plate Australian Plate Scotia Plate Arabian Plate 114
- 115. 115 Manam Volcano, Papua New Guinea
- 116. Pangaea (300 mya) – began breaking up 200 mya 116
- 119. Effects of the Pangaea Super-Continent (250 mya) A reduction in shallow water habitat A colder & drier inland climate Climate change as continents moved toward & away from the poles Changes in ocean circulation patterns leading to global cooling 119
- 120. Biological Impact of Pangaea Break-Up Allopatric speciation Led to the current distribution of plants, animals, & fossils Ex: similarity of fossils in areas of South America & Africa Re-shaped biodiversity via booms & busts 120 Cynognathus
- 121. 121
- 122. Mass Extinctions The fossil record reveals that most species that have ever lived are now extinct At times, the extinction rate increased dramatically Resulted in 5 mass extinctions Over 50% of Earth’s species became extinct in each event 122
- 123. Are There Any Benefits to Extinction? 123
- 124. Totalextinctionrate (familiespermillionyears): Time (millions of years ago) Numberoffamilies: CenozoicMesozoicPaleozoic E O S D C P Tr J 542 0 488 444 416 359 299 251 200 145 Era Period 5 C P N 65.5 0 0 200 100 300 400 500 600 700 800 15 10 20 124 Mass Extinction & the Diversity of Life
- 125. 125 Permian Period (299-251 MYA)
- 126. Permian Mass Extinction Between Paleozoic & Mesozoic eras (250 MYA) Occurred in < 5 MY Led to largest mass extinction: 95% of all marine species & 70% of terrestrial species May have been caused by volcanism, leading to climate change & reduced oceanic O2 126
- 127. 127 El Capitan Permian Reef -Guadalupe Mountains National Park, TX
- 128. 128 The Searchers (1956) – Monument Valley, Utah
- 129. Cretaceous Mass Extinction Between Mesozoic & Cenozoic eras (65 MYA) 50% of all marine species became extinct, along with … … many terrestrial plants & animals, including most dinosaurs The presence of iridium in sedimentary rocks suggests a meteorite impact129
- 132. The Chicxulub Crater (Yucatan Peninsula, Mexico) 132
- 133. 133 The Sixth Mass Extinction The current extinction rate is 100-1000X the normal background rate Extinction rates tend to increase when global temperatures increase Data suggest that a 6th human-caused Holocene mass extinction is currently underway
- 134. Mass extinctions Cooler Warmer Relativeextinctionrateofmarineanimalgenera 3 2 1 0 1 2 3 2 1 0 1 2 3 4 Relative temperature Fossil Extinctions & Temperature 134
- 135. Consequences of Mass Extinction Alters ecological communities & available niches It can take 5-100 MY for diversity to recover Creates potential for adaptive radiations 135
- 136. Predatorgenera (percentageofmarinegenera) Time (millions of years ago) CenozoicMesozoicPaleozoic E O S D C P Tr J 542 0 488 444 416 359 299 251 200 145 Era Period C P N 65.5 0 10 20 30 40 50 136 Mass Extinctions & Ecology
- 137. Adaptive Radiation of Mammals Underwent an adaptive radiation after the extinction of terrestrial dinosaurs Allowed increase in diversity & size of mammals Why? 137 Cynodont
- 138. Millions of years ago Monotremes (5 sp) 250 150 100200 50 ANCESTRAL CYNODONT 0 Marsupials (324 sp) Eutherians (placental mammals; 5,010 sp) Ancestral mammal 138 Adaptive Radiation of Mammals
- 139. Other Examples of Adaptive Radiations Photosynthetic prokaryotes Land plants Large Cambrian predators Insects & tetrapods 139
- 140. Close N. Amer. relative, the tarweed Carlquistia muirii Argyroxiphium sandwicense Dubautia linearis Dubautia scabra Dubautia waialealae Dubautia laxa HAWAII 0.4 MY OAHU 3.7 MY KAUAI 5.1 MY 1.3 MY MOLOKAI MAUI LANAI 140Regional Adaptive Radiation on the Hawaiian Islands
- 141. Evolutionary Effects of Developmental Genes Developmental genes control the … … rate, timing, & spatial pattern of development Major changes in body form can result Studying genetic mechanisms of change can provide insight into large-scale evolutionary change 141
- 142. 142
- 143. Chimpanzee fetus Chimpanzee adult Human fetus Human adult Heterochrony An evolutionary change in the rate or timing of developmental events Can have a significant impact on body shape Differential growth rates The contrasting shapes of human & chimpanzee skulls are due to small changes in relative growth rates 143
- 144. Paedo- morphosis The rate of reproductive development accelerates compared with somatic development The sexually mature species may retain body features that were juvenile structures in an ancestral species Ex: salamanders (Axolotl) 144
- 145. 145
- 146. 146
- 147. Changes in Spatial Pattern Evolutionary change is also due to alterations in genes controlling the placement & organization of body parts Homeotic genes: determine basic features including: Location of wing & leg development on a bird The arrangement of a flower’s parts 147
- 148. Hox Genes A class of homeotic genes providing positional info during development If Hox genes are expressed in the wrong location, body parts can be produced in the wrong location In crustaceans, a swimming appendage can be produced instead of a feeding appendage Evolution of vertebrates from invertebrates was associated with two alterations in Hox genes 148
- 149. Hox gene expression & limb development Limbless regions Snake embryo Chicken embryo 149
- 150. Changes in Genes New morphological forms likely come from gene duplication events that produce new developmental genes The evolution of 6- legged insects from a many-legged crustacean ancestor has been demonstrated in lab experiments Specific changes in the Ubx gene can “turn off” leg development Ex: Drosophila & Artemia 150
- 151. 151
- 152. Hox gene 6 Hox gene 7 Hox gene 8 About 400 mya Drosophila Artemia Ubx 152Origin of the insect body plan
- 153. Changes in Gene Regulation Changes in body form may be caused by changes in how developmental genes are regulated instead of changes in their sequence Ex: three-spine sticklebacks in lakes have fewer ventral spines than their marine relatives The gene sequence stays the same, but the regulation of gene expression is different in the two groups of fish 153
- 154. Marine stickleback embryo Close-up of ventral surface (spines) Lake stickleback embryo Close-up of mouth No spines 154 Loss of spines in lake stickleback fish: change in the regulation of Pitx1 gene expression
- 155. Evolution is Not Goal- Oriented Natural selection can only improve a structure in the context of its current use New forms arise through the slight modification of existing forms Most novel biological structures evolve in many stages from previously existing structures Complex eyes evolved independently from simple photosensitive cells many times 155
- 156. (a) Patch of pigmented cells Optic nerve Pigmented layer (retina) Pigmented cells (photoreceptors) Fluid-filled cavity Epithelium Epithelium (c) Pinhole camera-type eye Optic nerve Cornea Retina Lens (e) Complex camera lens-type eye (d) Eye with primitive lens Optic nerve CorneaCellular mass (lens) (b) Eyecup Pigmented cells Nerve fibers Nerve fibers 156