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History of Life on Earth
Chapter 25
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Overview First Cells Major Life events Fossil Record
Geologic Time scale Mass extinctions Continental Drift
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What was Early Earth like?
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What do we really know about the first living organism??
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Can we take Darwin’s theory all the way back to the Origin of Life?
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What were the major milestones in the Evolution of Life?
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How long ago was that ?
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Getting used to the geologic time scale…
We use Millions of years (MYA) and Billions (BYA) of years ago. One Million Years: If we give 10,000 years for all of recorded human history One million years equals 100 times all human history. Enough time for 30,000 generations
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Evolutionary Clock Eras not to scale
“Our” world, with plants and animals on land is not very old Protists and Bacteria / Archae have been around longer and are more diverse.
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Ceno- zoic Meso- zoic Paleozoic Origin of solar system and Earth 1 4
Fig 25-UN11 Ceno- zoic Meso- zoic Paleozoic Origin of solar system and Earth 1 4 Proterozoic Archaean Billions of years ago 2 3
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Geologic Time Scale Table 25.1
Know : Eons Phanerozoic Proterozoic Archaean 4 eras Their dates Major Animal and Plant groups “Precambrian” Era Periods: Permian Cretaceous (K) Tertiary (T)
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The three Eras and the new groups that begin to dominate on land
Cenozoic – 65.5 MYA Mammals, birds flowering plants Mesozoic – 251 MYA Reptiles, conifers Paleozoic – 542 MYA Amphibians, insects, moss, ferns Precambrian (2 eons) – 4.6 BYA Origin of animal phyla Protists, bacteria
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The three Eons and the new groups that begin to dominate on land
Phanerozoic – Present to 542 MYA “Precambrian”: Proterozoic ,500 MYA Origins of Eukaryotes Archaean – 2,500- 4,500 MYA bacteria, and oxygen atmosphere
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Four Eras Why ? Eras do not have same amount of time
Pace of evolution quickens with each major branch or era . Recent organisms generally are more complex – older ones simpler. Why ?
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Key Events in the History of Life on Earth
4.6 BYA Formation of Earth Origins of Biomolecules Formation of Polymers Origin of Protobionts; Self replicating RNA-DNA; Metabolism; Evolution 3.5 BYA Formation of first cell – prokaryotes
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Key Events in the History of Life on Earth
2.7 BYA Origin of Oxygen generating photosynthesis 1.5 BYA Origin of Eukaryote cells 1.2 BYA – 565 MYA Multicellularity 535 MYA Cambrian Explosion 500 MYA Colonization of land
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Millions of years ago (mya)
Fig 25-UN8 1.2 bya: First multicellular eukaryotes 535–525 mya: Cambrian explosion (great increase in diversity of animal forms) 500 mya: Colonization of land by fungi, plants and animals 2.1 bya: First eukaryotes (single-celled) 3.5 billion years ago (bya): First prokaryotes (single-celled) 500 4,000 3,500 3,000 2,500 2,000 1,500 1,000 Present Millions of years ago (mya)
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Figure 25.4 Documenting the history of life
Present Rhomaleosaurus victor, a plesiosaur Dimetrodon 100 million years ago Casts of ammonites 175 200 270 300 4.5 cm Hallucigenia 375 Coccosteus cuspidatus 400 Figure 25.4 Documenting the history of life 1 cm Dickinsonia costata 500 525 2.5 cm 565 Stromatolites 600 Tappania, a unicellular eukaryote Fossilized stromatolite 3,500 1,500
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Sponges Cnidarians 500 Annelids Molluscs Chordates Arthropods
Fig 500 Sponges Cnidarians Annelids Molluscs Chordates Arthropods Echinoderms Brachiopods Early Paleozoic era (Cambrian period) Millions of years ago Figure Appearance of selected animal phyla 542 Late Proterozoic eon
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How did Life come into being ?
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Spontaneous generation ?
Life from non-living matter. Mice from wet hay makes mice Refute for animals, and plants in 1600’s. Still thought to be the case for microbes, until Pasteur.
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Louis Pasteur (1822-1895) Disproved spontaneous generation
Showed that biogenesis alone accounted for new cells Invented Pasteurization
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Biogenesis Life (whole organisms) comes from reproduction of other preexisting life. Later, the cell theory will be similar all cells come from preexisting cells.
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What about the first Cell?
Scientists think, first cell-like structures came from non living matter. What would be needed to make a cell from scratch ?
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Origin of life - Need to have biomolecules:
Complex Carbohydrates Proteins Lipids Nucleic acids To make membranes,enzymes, DNA and all the other cellular components.
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Where did biomolecules come from?
Today only living organisms make biomolecules
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“Arm Chair” science Still mostly untested hypotheses, and conjecture.
Trying to test hypotheses by making artificial cells in labs.
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Conditions on Earth 4 BYA Oparin – Haldane 1920’s chemists
No free Oxygen – No Ozone layer More uv radiation Reducing (electron rich) atmosphere More lightning Meteorite bombardment More volcanic activity H20, Methane (CH4), Ammonia (NH3)
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Energy rich early earth
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Urey & Miller Used Oparin / Haldane ideas of earth earth conditions Made an apparatus to mimic early earth conditions Let run and tested fluid for compounds Found simple sugars, amino acids, and other organic compounds.
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Stanley Miller
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Abiotic synthesis of macromolecules
Significance: Abiotic synthesis of macromolecules
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Ribozymes RNA self replication before enzymes? RNA before DNA
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Hypothetical Protobionts
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Not “facts” but working hypotheses
Lab experiments can only show what could have happened Other thoughts: Deep sea vents – constant environment, chemical energy Panspermia or microbes from meteorites Most like our understanding will change greatly in future.
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Universal Common Ancestor
Hypothetical Would be cell from which all modern life has descended Have things that ALL living organisms share: Phospholipid bilayer cell membrane Use DNA/ RNA for genes, and make proteins from the genetic code Glycolysis, ATP in their metabolism
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Fossil Record Fossil any preserved remnant or impression of an organism that lived in the past Most form in sedimentary rock, from organisms buried in deposits of sand and silt. Compressed by other layers. Also includes impressions in mud Most organic matter replaced with minerals by Petrification Some fossils may retain organic matter Encased in ice, amber, peat, or dehydrated Pollen Pollen most common fossil Some DNA has been cloned from fossilized leaves
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Fossil Formation –
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Radiometric “absolute” dating
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Dating Fossils Brachiopod index fossils
“Absolute” Radiometric dating: decay and half-life of natural isotopes. Index dating – comparing index fossils in strata Brachiopod index fossils
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Many changes in geologic history due to Plate tectonics
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Layers of the Earth Crust Asthenosphere Lithosphere
Mantle Core Crust Low-velocity zone Solid Outer core (liquid) Inner core (solid) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.) Lithosphere Asthenosphere (depth unknown)
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Plate tectonics The study of the movement of earth structures in the crust. Internal forces from the core create heat that keeps asthenosphere molten. Convection cells Mantle Plumes
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Convection Cell in Mantle
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Earth’s Layers - Crust Oceanic Crust Continental Crust
only 3 miles thick Continental Crust up to miles thick Oceans change shape much more than continents. These land movements we call Plate Tectonics, and cause earthquakes.
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Plate tectonics- Divergent Areas
Plates spread apart in Divergent (constructive) making new crust
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Convergent zones Plates move together and collide.
An Oceanic Plate sinks under Continental in a Subduction zone. Causes Earthquakes, volcanoes When Continental plates collide neither subducts, both deform, mountains
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Convergent plates
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(a) Cutaway view of Earth (b) Major continental plates
Fig North American Plate Eurasian Plate Crust Juan de Fuca Plate Caribbean Plate Philippine Plate Arabian Plate Indian Plate Mantle Cocos Plate Pacific Plate South American Plate Nazca Plate Outer core African Plate Australian Plate Figure Earth and its continental plates Inner core Scotia Plate Antarctic Plate (a) Cutaway view of Earth (b) Major continental plates
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(b) Major continental plates
Fig b North American Plate Eurasian 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 Figure Earth and its continental plates Scotia Plate Antarctic Plate (b) Major continental plates
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Present Cenozoic 65.5 Millions of years ago 135 Mesozoic 251 Paleozoic
Fig Present Cenozoic North America Eurasia 65.5 Africa South America India Madagascar Australia Antarctica Laurasia 135 Mesozoic Millions of years ago Gondwana Figure The history of continental drift during the Phanerozoic eon 251 Pangaea Paleozoic
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10 MYA India (previously an island) hits Asia
50 MYA. Australia becomes completely isolated 65.5 MYA NA and Europe still touched 135 MYA Pangea broke up into Laurasia and Gondwanaland 251 MYA Pangea all land masses touched Solves problems first posed by botanist for plant and fossil distributions. The two previously separate floras came into contact, species disperse across from one side to the other. ( SA / NA and India / Asia
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Mass extinctions Mark borders of Eras:
251 Permian (Paleo-Mesozoic) 65.5 Cretaceous (K/T boundary; Meso-Cenozoic) Caused by a major change that affects many species at once.
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(families per million years):
Fig 20 800 700 15 600 500 Number of families: (families per million years): Total extinction rate 10 400 300 5 200 100 Figure Mass extinction and the diversity of life Era Period Paleozoic Mesozoic Cenozoic E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 Time (millions of years ago)
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(percentage of marine genera)
Fig 50 40 30 (percentage of marine genera) Predator genera 20 10 Figure Mass extinctions and ecology Paleozoic Era Period Mesozoic Cenozoic E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 Time (millions of years ago)
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Permian Mass Extinction
90% marine & 80% insect species gone 251 MYA Took place in about 5 MY 2 Possible causes: Pangaea forming Extreme volcanism- Global warming, climate change. Drop in sea level, loss of shoreline & intertidal, More severe continental weather Isolated species come together and compete, causing extinctions Paleozoic to Mesozoic boundary
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Cretaceous extinctions
65.5 MYA Wiped out 50 % marine species, on land many families of plants and the Dinosaurs. Mesozoic to Cenozoic boundary. Climate cooled and shallow seas retreated. Mammals and angiosperms around earlier, but survived and radiated out to dominant now empty niches Many diverse lineages from algae to dinosaurs disappeared at once.
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NORTH AMERICA Chicxulub crater Yucatán Peninsula Fig. 25-15
Figure Trauma for Earth and its Cretaceous life For the Discovery Video Mass Extinctions, go to Animation and Video Files.
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Alvarez-Impact theory
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Chicxulub Crater- sonar image
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Impact hypothesis Anomalous Iridium layer marks boundary layer – element common in meteorites Chicxulub Crater Explains large water scarring in NA. Global winter lasting years, collapsed food chains. Ignite tremendous wildfires, acid rain. Some lineages were dying out before impact. Probably a final and sudden blow coming at a time of change, with continental drift, climate change.
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Conditions that favor fossilization:
Having Hard parts – shells, bones,cysts Get buried, trapped Marine species Marsh, flooding areas Abundant species (with many individuals) Long lived species (as a species) Avoid eroding away Get discovered
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Limitations of Fossils record
Has to die in right place under the right conditions. Most things don’t get into the fossil record Biased: Highly favors hard parts, abundant, long lived species organisms. Lots of missing organisms Hard to find, only certain areas highly researched (NA. Europe)
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Earth’s history as a clock
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Major events Origin of prokaryote cell Formation oxygen atmosphere
Origin of eukaryote cell Multi-Origins of multicellularity Cambrian explosion of animal phyla
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What we do know: Earth is old, about 4.6 BYA
Oldest fossils appear to be filamentous bacteria at about 3.5 BYA. Formed layers like today’s stromatolites Bacteria predated eukaryotes
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Early Prokaryote Fossils
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Figure 26.4
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Endosymbiosis Fig
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Endosymbiosis Theory Descendant of Archae develops eukaryote type membrane system and nucleus Eukaryote cell engulfs bacteria that survive in the cell and develop into plastids and mitochondria We’ll review evidence later in eukaryote chapter. 2.1 BYA
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Endosymbiosis – membrane layers
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Coral Living example of endosymbiotic relationships
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Earliest Multicellular organisms
1.5 MYA
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Cambrian Explosion Most animal appear at same time phyla in 20 MY
Long fuse- began earlier
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Systematics Taxonomy is naming, & organizing organisms, both living and dead, into groups. Systematics, use evolutionary relationships as the classification hierarchies.
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Systematics debates: Biggest debates, and changes will be at higher levels of classification. Shows scientists interest levels. Most lower level groups figured out. Question the origins of these groups Rely heavily on comparative gene sequences.
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Debates in Evolution Most lay people think the big debate is around the origins of humans from apes. Most scientists see this area as pretty clear, with details to be worked out by specialists. Origins of Domains, Kingdoms the big questions in evolutionary science today.
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Five Kingdoms
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A Changing View of Diversity
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Prokaryote Diversity
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Eukaryote Diversity
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Fig. 25-6 Synapsid (300 mya) Temporal fenestra Key Articular Dentary Quadrate Squamosal Therapsid (280 mya) Reptiles (including dinosaurs and birds) Temporal fenestra EARLY TETRAPODS Dimetrodon Early cynodont (260 mya) Synapsids Temporal fenestra Very late cynodonts Earlier cynodonts Therapsids Figure 25.6 The origin of mammals Later cynodont (220 mya) Mammals Very late cynodont (195 mya)
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Ceno- zoic Meso- zoic Humans Paleozoic Colonization of land Animals
Fig. 25-7 Ceno- zoic Meso- zoic Humans Paleozoic Colonization of land Animals Origin of solar system and Earth 1 4 Proterozoic Archaean Figure 25.7 Clock analogy for some key events in Earth’s history Prokaryotes Billions of years ago 2 3 Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen
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Ancestral mammal Monotremes (5 species) ANCESTRAL CYNODONT Marsupials
Fig Ancestral mammal Monotremes (5 species) ANCESTRAL CYNODONT Marsupials (324 species) Eutherians (placental mammals; 5,010 species) Figure Adaptive radiation of mammals 250 200 150 100 50 Millions of years ago
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Close North American relative, the tarweed Carlquistia muirii
Fig Close North American relative, the tarweed Carlquistia muirii KAUAI 5.1 million years MOLOKAI 1.3 million years Dubautia laxa MAUI OAHU 3.7 million years Argyroxiphium sandwicense LANAI HAWAII 0.4 million years Figure Adaptive radiation on the Hawaiian Islands Dubautia waialealae Dubautia scabra Dubautia linearis
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1.3 KAUAI MOLOKAI million 5.1 years million MAUI years OAHU 3.7
Fig a 1.3 million years KAUAI 5.1 million years MOLOKAI MAUI OAHU 3.7 million years LANAI Figure Adaptive radiation on the Hawaiian Islands HAWAII 0.4 million years
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Figure 25.19 Relative growth rates of body parts
Newborn 2 5 15 Adult Age (years) (a) Differential growth rates in a human Figure Relative growth rates of body parts Chimpanzee fetus Chimpanzee adult Human fetus Human adult (b) Comparison of chimpanzee and human skull growth
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(a) Differential growth rates in a human
Fig a Figure Relative growth rates of body parts Newborn 2 5 15 Adult Age (years) (a) Differential growth rates in a human
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(b) Comparison of chimpanzee and human skull growth
Fig b Chimpanzee fetus Chimpanzee adult Figure Relative growth rates of body parts Human fetus Human adult (b) Comparison of chimpanzee and human skull growth
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Fig Gills Figure Paedomorphosis
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Hypothetical vertebrate ancestor (invertebrate)
Fig Hypothetical vertebrate ancestor (invertebrate) with a single Hox cluster First Hox duplication Hypothetical early vertebrates (jawless) with two Hox clusters Second Hox duplication Figure Hox mutations and the origin of vertebrates Vertebrates (with jaws) with four Hox clusters
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Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Drosophila Artemia
Fig Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Figure Origin of the insect body plan Drosophila Artemia
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Ceno- Meso- zoic zoic Paleozoic Origin of solar system and Earth 1 4 2
Fig 25-UN9 Ceno- zoic Meso- zoic Paleozoic Origin of solar system and Earth 1 4 Proterozoic Archaean Billions of years ago 2 3
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Flies and fleas Caddisflies Moths and butterflies Herbivory
Fig 25-UN10 Flies and fleas Caddisflies Moths and butterflies Herbivory
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