Early Earth

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Early Earth the Origin of Life (Ch. 26)
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• The history of living organisms and the history
  of Earth are inextricably linked
•  
•   Formation and subsequent breakup of Pangaea
  affected biotic diversity

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•  The first photosynthetic organism released
  oxygen into the air and altered Earths
  atmosphere

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Endosymbiotic Theory

• certain organelles originated as free-living
  bacteria that were taken inside another cell as
  endosymbionts through endocytosis

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Evidence

• structural
• mitochondria chloroplasts resemble bacterial
  structure
• both have double membranes
• genetic
• mitochondria chloroplasts have their own
  circular DNA, like bacteria
• Mitochondria and chloroplasts have bacteria-like
  RNA and ribosomes (70S as opposed to 80S in
  eukaryote cytoplasms) that enable them to make
  their own proteins and divide independently of
  the host cell
• functional
• mitochondria chloroplasts move freely within
  the cell
• mitochondria chloroplasts reproduce
  independently from the cell

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• Homo sapiens have changed the land, water, and
  air on a scale and at a rate unprecedented for a
  single species

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Figure 2. Sea level is changing. Observing
stations from around the world report
year-to-year changes in sea level. The reports
are combined to produce a global average time
series. The year 1976 is arbitrarily chosen as
zero for display purpose.
Figure 1. Global warming revealed. Air
temperature measured at weather stations on
continents and sea temperature measured along
ship tracks on the oceans are combined to produce
a global mean temperature each year. This
150-year time series constitutes the direct,
instrumental record of global warming.
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• History of Life on Earth
•   Life on Earth originated between 3.5 and 4.0
  billion years ago
•   Because of the relatively simple structure of
  prokaryotes, it is assumed that the earliest
  organism were prokaryotes
• this is supported by
• fossil evidence
• (spherical filamentous
• prokaryotes recovered
• from 3.5 billion year
• old stromatolites in
• Australia and Africa)

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Layers of blue-green algae
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•  Major Episodes in the History of Life
•  
•   first prokaryotes- 3.5 to 4.0 billion years
  ago
•   photosynthetic bacteria- 2.5 billion years
  ago

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•   first eukaryotes- 2 billion years ago
•  
•  

The oldest unequivocal remains of a diversity of
microorganisms occur in the 2.0 BYO Gunflint
Chert of the Canadian Shield This fauna
includes not only bacteria and cyanobacteria but
also ammonia consuming Kakabekia and some things
that resemble green algae and fungus-like
organisms
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•   plants evolved from green algae
•   fungi and animals arose from different groups
  of heterotrophic unicellular organisms

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•    first animals (soft-bodied invertebrates)-
  700 million years ago
•  
•   first terrestrial colonization by plants and
  fungi- 475 million years ago
• -plants transformed the landscape
• and created new opportunities for all forms of
  life

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• Prebiotic Chemical Evolution 
•   Earths ancient environment was different from
  today
• -very little atmospheric oxygen
• -lightning, volcanic activity, meteorite,
  bombardment, UV radiation all more intense

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• Oparin / Haldane hypothesis (1920s) the
  reducing atmosphere and greater UV radiation on
  primitive Earth favored reactions that built
  complex organic molecules from simple monomers as
  building blocks

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Miller / Urey experiment (1953)

• Simulated atmospheric conditions hypothesized to
  be on early Earth by constructing an apparatus
  containing H2O, H2, CH4, and NH3.
• Results
• They produced amino acids and other organic
  molecules.
• Additional follow-up experiments have produced
  all 20 amino acids, ATP, some sugars, lipids and
  purine and pyrimidine bases of RNA and DNA.

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• Origin of Life - Different Hypotheses
•  
• No one knows how life actually began on Earth
  experiments indicate key steps that could have
  occurred.
•   Panspermia some organic compounds may have
  reached Earth by way of meteorites and comets

meteorite
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•   Sea floor / Deep-sea vents hot water and
  minerals emitted from deep sea vents may have
  provided energy and chemicals needed for early
  protobionts
•  
•   Simpler hereditary systems (self-replicating
  molecules) may have preceded nucleic acid genes.

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•   Chemical evolution may have occurred in four
  stages
• 1)   abiotic synthesis of monomers
• 2)  joining of monomers into polymers (e.g.
  proteins, nucleic acid)
• 3)  formation of protobionts (droplets
• formed from clusters of molecules)
• 4)  origin of heredity (likely that RNA
  was first)
•  

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Abiotic Synthesis of Polymers

• Researchers have produced amino acid polymers by
  dripping amino acid solutions onto hot sand,
  clay, or rock
• Form spontaneously without enzymes or ribosomes
• Polymers are all different (dont get the same
  one each time)
• May have acted as weak catalysts for reactions on
  early Earth???

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•   Protobionts collections of abiotically
  produced molecules (membrane bound) able to
  maintain an internal environment different from
  their surroundings and exhibiting some life
  properties such as metabolism and excitability
• (experimental evidence
• suggests spontaneous
• formation of
• Protobionts some have
• membrane potential/
• excitability)
•  

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RNA

• RNA can carry out enzyme-like functions
  (ribozymes)
• Some can make up short segments of RNA
• Some can remove segments of themselves
• Some can act on different molecules (tRNA)
• Reactions are slow

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possible formation of protobionts self-repliating
RNA as early genes
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• The Major Lineages of Life the old 5 Kingdom
  System
• Living organisms
•  
• Prokaryotic Eukaryotic
•  
• Simple/unicells Multicellular
• Autotrophic Heterotrophic
•  
• Absorptive Ingestive
• nutrition nutrition

(Monera)
(Protista)
(Plantae)
(Animalia)
(Fungi)
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How was the atmosphere of the early earth
different than it is today?

1. The early earths atmosphere contained mostly
   carbon monoxide
2. The early earths atmosphere had more oxygen than
   it has today
3. The early earths atmosphere contained more
   single celled organisms than it does today
4. The early earths atmosphere did not contain
   oxygen

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In the 4-stage hypothesis for the chemical
evolution of life, which of the following is the
correct sequence?

1. Synthesize monomers join monomers form
   protobionts system of heredity
2. Form protobionts synthesize monomers join
   monomers system of heredity
3. System of heredity join monomers synthesize
   monomers form protobionts
4. Synthesize monomers join monomers system of
   heredity form protobionts

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What is a protobiont?

1. A self-replicating early life form that uses RNA
   for heredity
2. A group of monomers that join/bond when
   temporarily bonded to materials such as clay or
   volcanic rock
3. Early enzymes that were able to join basic amino
   acids together
4. Collection of abiotically produced molecules that
   can maintain an internal environment and exhibit
   some life properties

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What is the name of the alternate hypothesis for
the seeding of organic compounds on earth by
meteorites comets?

1. Deep Sea Vent Hypothesis
2. Panspermia
3. Impact Hypothesis
4. Early Earth Seeding Hypothesis

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In the old 5 Kingdom system used to classify all
life, what are the names of the Kingdoms?

1. Bacteria Plantae Animalia Fungi Protista
2. Bacteria Plantae Animalia Fungi Monera
3. Plantae Animalia Bacteria Monera Protista
4. Plantae Animalia Fungi Monera Protista