chapter 16 origin of life the big bang theory big bang details galaxies are collections of stars,...
TRANSCRIPT
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Chapter 16 Chapter 16 Origin of LifeOrigin of Life
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The Big Bang The Big Bang TheoryTheory
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Big Bang DetailsBig Bang Details Galaxies are collections of stars, gas and dust bound Galaxies are collections of stars, gas and dust bound
together by their mutual gravitytogether by their mutual gravity
Galaxies comprise the basic building blocks of the Galaxies comprise the basic building blocks of the Universe Universe
When galaxies were born and how they evolved is When galaxies were born and how they evolved is currently a very active topic. currently a very active topic.
At present, the Universe is thought to have been At present, the Universe is thought to have been created in the created in the Big BangBig Bang, in which space and time , in which space and time were created in a simple hot energetic, state, about 15 were created in a simple hot energetic, state, about 15 billion (15 x 109 ) years ago. billion (15 x 109 ) years ago.
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A technique to determine the age of items on A technique to determine the age of items on our planetour planet
Carbon 14 Carbon 14 Nitrogen 14 is used to date Nitrogen 14 is used to date fossils (good up to 50 000 yrs)fossils (good up to 50 000 yrs)
Uranium 238 – Lead 236 is used to date rocks Uranium 238 – Lead 236 is used to date rocks and is good to 4.5 billion yearsand is good to 4.5 billion years
Radiometric Radiometric DatingDating
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Carbon-14 – used to date fossilsCarbon-14 – used to date fossils Carbon-14 (Carbon-14 (1414C) a rare isotope of carbon, that C) a rare isotope of carbon, that
has has 6 protons and 8 neutrons6 protons and 8 neutrons
1414C decays to C decays to 1414N at a constant rateN at a constant rate
Every 5,600 years half the Every 5,600 years half the 1414C in a sample will C in a sample will emit a beta particle (electron) and decay to emit a beta particle (electron) and decay to 1414N N
Thus 5,600 years is called the half life of Thus 5,600 years is called the half life of 1414CC
Because of Because of 1414C’s short half life, it is not useful C’s short half life, it is not useful for dating million year old fossils, it is only for dating million year old fossils, it is only accurate to about 50,000 yearsaccurate to about 50,000 years
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Half-livesHalf-lives
256 14C atoms at time 0
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Half-livesHalf-lives
128 14C and
128 14N atoms
after 5,600 years or
1 half-life
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Half-livesHalf-lives
64 14C and
192 14N atoms
after 11,200 years or
2 half-lives
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Half-livesHalf-lives
32 14C and
224 14N atoms
after 16,800 years or
3 half-lives
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Half-livesHalf-lives
16 14C and
240 14N atoms
after 22,400 years or
4 half-lives
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Half-livesHalf-lives
8 14C and
248 14N atoms
after 28,000 years or
5 half-lives
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Half-livesHalf-lives
4 14C and
252 14N atoms
after 33,600 years or
6 half-lives
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Half-livesHalf-lives
2 14C and
254 14N atoms
after 39,200 years or
7 half-lives
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Carbon-14Carbon-14 1414C is used to date organic samples C is used to date organic samples
like wood, hair, shells (CaCOlike wood, hair, shells (CaCO33) and ) and other plant and animal productsother plant and animal products
Atmospheric Atmospheric 1414C is incorporated into C is incorporated into organic molecules by plants during organic molecules by plants during photosynthesisphotosynthesis
Animals that eat the plants get Animals that eat the plants get 1414C C from the plants they eatfrom the plants they eat
The current ratio of The current ratio of 1414C to C to 1212C in the C in the atmosphere is immeasurably smallatmosphere is immeasurably small
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Carbon-14Carbon-14 With a relatively short half life and an With a relatively short half life and an
earth billions of years old, all Cearth billions of years old, all C1414 should be goneshould be gone
This would be true if not for This would be true if not for production of new production of new 1414C in the C in the atmosphere as a result of interactions atmosphere as a result of interactions between the upper atmosphere and between the upper atmosphere and neutrons in cosmic radiationneutrons in cosmic radiation
The atmospheric ratio of The atmospheric ratio of 1414C to C to 1212C C represents an equilibrium between represents an equilibrium between production and decay of production and decay of 1414CC
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Carbon-14Carbon-14Sometime in the Ancient PastSometime in the Ancient Past
CO2 fixation
Plant absorbs both C12 and C14 in the ratio they exist in the atmosphere
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Carbon-14Carbon-14A Plant Grows Absorbing COA Plant Grows Absorbing CO22
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Carbon-14Carbon-14The Plant DiesThe Plant Dies
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Carbon-14Carbon-14It Is BuriedIt Is Buried
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Carbon-14Carbon-14Over Time Over Time 1414C Decays to C Decays to 1414NN
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Carbon-14Carbon-14Over Time Over Time 1414C Decays to C Decays to 1414NN
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Other Isotopic Dating MethodsOther Isotopic Dating Methods 1414CC dating is not useful for dating dating is not useful for dating
geological strata so other methods have geological strata so other methods have been developed using isotopes with much been developed using isotopes with much longer half liveslonger half lives
Examples include:Examples include:
Uranium-235 Lead-207 0.7 x 109
emissionUranium-238 Lead-206 4.5 x 109
Thorium-232 Lead-208 14.0 x 109
Rubidium-87 Strontium-87 48.6 x 109
e- capturePotassium-40 Argon-40 1.4 x 109
MethodIsotope Product Half life
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Just How Old is EarthJust How Old is Earth
By modern estimates – about 4.5 billion By modern estimates – about 4.5 billion years oldyears old
How can we tellHow can we tell Remember Science 10 – GeologyRemember Science 10 – Geology Radiometric dating is used to measure Radiometric dating is used to measure
the RADIOACTIVE DECAY of elementsthe RADIOACTIVE DECAY of elements For example…For example…
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Aristotle (384-322 BC) proposed spontaneous generation Aristotle (384-322 BC) proposed spontaneous generation living things can arise from nonliving matterliving things can arise from nonliving matter
Leeuwenhoek presented data that seemed to support it Leeuwenhoek presented data that seemed to support it
Spallanzani’s gravy experiments refuted itSpallanzani’s gravy experiments refuted it
Francesco Redi’s ‘s experiments with covered jars refuted Francesco Redi’s ‘s experiments with covered jars refuted it it
Is Spontaneous Generation of Is Spontaneous Generation of Microbial Life Possible?Microbial Life Possible?
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Redi’s ExperimentsRedi’s Experiments
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Spallanzani’s Gravy ExperimentSpallanzani’s Gravy Experiment
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Concluded thatConcluded that Microorganisms exist in air and can Microorganisms exist in air and can
contaminate experimentscontaminate experiments
Spontaneous generation of microorganisms Spontaneous generation of microorganisms does not occurdoes not occur
Critics said sealed vials did not allow Critics said sealed vials did not allow enough air for organisms to survive and enough air for organisms to survive and that prolonged heating destroyed “life that prolonged heating destroyed “life force”force”
Spallanzani’s ExperimentsSpallanzani’s Experiments
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Pasteur’s ExperimentsPasteur’s Experiments
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Early Earth and the First Early Earth and the First Signs of LifeSigns of Life
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Some things to consider…Some things to consider…
Earth was formed ~4,500,000,000 yrs agoEarth was formed ~4,500,000,000 yrs ago
For a few hundred million years Earth was very For a few hundred million years Earth was very hot and constantly bombarded from spacehot and constantly bombarded from space
At this point there was no liquid water, life was At this point there was no liquid water, life was impossibleimpossible
About 3,900,000,000 yrs ago, Earth was About 3,900,000,000 yrs ago, Earth was solidified enough and cool enough for liquid watersolidified enough and cool enough for liquid water
Life apparently arose shortly thereafterLife apparently arose shortly thereafter
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More points to ponder…More points to ponder…
What was Earth like 3.9 billion years What was Earth like 3.9 billion years ago?ago? Are there still places on Earth that Are there still places on Earth that
resemble these conditions?resemble these conditions? How could life originally arise from non-How could life originally arise from non-
living matter?living matter? What did it take to form the first life?What did it take to form the first life? What is “life” anyway?What is “life” anyway?
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What was earth like 3.9 bya?What was earth like 3.9 bya?
http://www.space.com/scienceastronomy/planetearth/earth_archaean_010716.html
Earth was very different Earth was very different Essentially no Essentially no
atmospheric Oatmospheric O22
Highly corrosive, Highly corrosive, destroys moleculesdestroys molecules
Highly energeticHighly energetic Lightning, volcanic Lightning, volcanic
activity, UV radiation highactivity, UV radiation high Provide energy for Provide energy for
chemical reactionschemical reactions
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How could life originally arise How could life originally arise from non-living matter?from non-living matter?
The following hypothesis has been proposed:The following hypothesis has been proposed:
1.1. Non-living synthesis of small organic Non-living synthesis of small organic molecules like amino acids and nucleotidesmolecules like amino acids and nucleotides Plenty of energy availablePlenty of energy available
2.2. Joining of small moleculesJoining of small molecules Proteins and nucleic acidsProteins and nucleic acids
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The The Urey-MillerUrey-Miller experiment: experiment:
Abiotic synthesis Abiotic synthesis of organicsof organics
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Simulated early EarthSimulated early Earth AtomsphereAtomsphere
H2O, H2, CH4, NH3H2O, H2, CH4, NH3 Simple inorganic moleculesSimple inorganic molecules Electric sparks (lightning)Electric sparks (lightning)
Produced amino acids and other organic moleculesProduced amino acids and other organic molecules Couldn’t happen under modern conditionsCouldn’t happen under modern conditions
Oxidizing atmosphere attacks organic bondsOxidizing atmosphere attacks organic bonds Or: possibly Earth was contaminated with organics from Or: possibly Earth was contaminated with organics from
spacespace
Urey-MillerUrey-Miller
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Figure 26.10x LightningFigure 26.10x Lightning
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Self AssemblySelf AssemblyLiposomes can “grow” by engulfing smaller Liposomes can “grow” by engulfing smaller
liposomes or “reproduce” by splitting offliposomes or “reproduce” by splitting off
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 26.12a
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Where did life originate?Where did life originate?
Shallow water or moist sediments.Shallow water or moist sediments. Deep-sea ventsDeep-sea vents
These sites have energy, produce some These sites have energy, produce some organic compounds, and have inorganic organic compounds, and have inorganic iron and nickel sulfides that can catalyze iron and nickel sulfides that can catalyze some organic reactionssome organic reactions
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Deep sea Deep sea ventsvents
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Where are they now?Where are they now?
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Early life on earth… 3 billion years Early life on earth… 3 billion years of microbesof microbes
Bacteria were the only life for Bacteria were the only life for billionsbillions of years of years
Atmospheric OAtmospheric O22 was first made by was first made by cyanobacteriacyanobacteria Microbes still account for ~half of Microbes still account for ~half of OO22 produced globally produced globally
Plants and animals have only been here for ~600 Plants and animals have only been here for ~600 million yearsmillion years Australopithicus 4 million yrs Australopithicus 4 million yrs Homo sapiens 0.5 million yrsHomo sapiens 0.5 million yrs
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Early Earth -- volcanic activity and Early Earth -- volcanic activity and photosynthetic bacteria in dense matsphotosynthetic bacteria in dense mats
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Key events in Key events in evolutionary historyevolutionary history
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Evolutionary clock: ProkaryotesEvolutionary clock: Prokaryotes
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Prokaryotes were the first Prokaryotes were the first organisms on earthorganisms on earth3.5 billion yr old bacterial fossils3.5 billion yr old bacterial fossils Modern filamentous bacteriaModern filamentous bacteria
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Cyanobacteria – Very OldCyanobacteria – Very Old
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Bacterial mats and StromatolitesBacterial mats and Stromatolites
Fig. 26.4
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Stromatolites in Northern CanadaStromatolites in Northern Canada
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Atmospheric oxygen began Atmospheric oxygen began accumulating 2.7 billion years agoaccumulating 2.7 billion years ago
Photosynthesis probably Photosynthesis probably evolved very early in evolved very early in bacterial historybacterial history
Cyanobacteria, split water Cyanobacteria, split water and produce Oand produce O22 evolved evolved over 2.7 billion years agoover 2.7 billion years ago
This early oxygen initially This early oxygen initially reacted with dissolved iron reacted with dissolved iron to form the precipitate iron to form the precipitate iron oxide.oxide. Seen today in banded iron Seen today in banded iron
formations.formations.
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Banded iron formations -- evidence of oxygen-Banded iron formations -- evidence of oxygen-releasing photosynthesisreleasing photosynthesis
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Oxygen accumulationOxygen accumulation ““Corrosive” OCorrosive” O22 had an enormous impact on life, dooming had an enormous impact on life, dooming
many bacterial groupsmany bacterial groups
Some species survived in habitats that remained anaerobic Some species survived in habitats that remained anaerobic (these are “obligate anaerobes”)(these are “obligate anaerobes”)
Other species evolved mechanisms to use OOther species evolved mechanisms to use O22 in cellular in cellular respiration, which uses oxygen to help harvest the respiration, which uses oxygen to help harvest the energy stored in organic moleculesenergy stored in organic molecules
Thus, prokaryotes altered the planet through OThus, prokaryotes altered the planet through O2 2
evolution, making aerobic respiration possible and paving the way for other forms of life (eukaryotes)
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Evolutionary clock: EukaryotesEvolutionary clock: Eukaryotes
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Evolutionary clock: Multicellular eukaryotesEvolutionary clock: Multicellular eukaryotes
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Evolutionary clock: AnimalsEvolutionary clock: Animals
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Unnumbered Figure (page 515) Evolutionary clock: Land plantsUnnumbered Figure (page 515) Evolutionary clock: Land plants