Life on Earth

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Life on Earth
Life on Earth
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Life on Earth as a 24 hour Analogy
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Life is the Product of EvolutionandEvolution
is the Result of Reproduction
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Life is Based on Reproduction

• Each INDIVIDUAL ORGANISM is dualistic
• We are each a REPLICATOR
• We are each an ecological INTERACTOR, the role
  of which is to command access to those
  environmental resources required to reproduce
• Because we reproduce, we are each
• MEMBERS OF LINEAGES

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What Evolves?Individuals or Lineages?

• Individuals can not evolve
• Individuals are transient they dont live long
• Individuals are genetically fixed they cant
  change genetically
• Lineages can and do evolve

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Evolution is change in genetic composition of
lineages
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How is evolution based on reproduction?

• Reproduction produces LINEAGES
• successive generations sharing genetic
  continuity potentially immortal
• Reproductive fidelity is imperfect mutations
  occur, producing GENETIC VARIATION
• genetic novelties arise routinely. These
  represent genetic experiments
• Reproduction has a multiplicative effect on
  population growth that results in NATURAL
  SELECTION
• populations grow exponentially, but the
  resources they need do not. This results in a
  struggle for existence in which the individuals
  that are best suited to their environments tend
  to leave more offspring. Which causes the
  population to evolve (change in its genetic
  composition)

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Evolution has created biodiversity
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The Origin of Life

• Where does life come from ?

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The Origin of LifeCosmology, Geology, then
Biological Evolution
Gravitational Collapse of Clouds of
Matter Formation of Galaxies, Solar Systems,
and Planets
The Age of Matter
The Age of Energy
B I G B A N G 13 by bp
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Nebulae - Clouds of Matter in Space
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A Galaxy
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Stars are born within nebulae
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Stars are born within nebulae
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Galaxy movie
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Why Did Life Originate on Earth?

• Temperature
• Gravity
• Large elements
• Atoms have an natural tendency to interact,
  forming molecules made of atoms bonded to one
  another

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Some stars return their ash into space
explosion
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The Origin of LifeCosmology, Geology, then
Biological Evolution
Gravitational Collapse of Clouds of
Matter Formation of Galaxies, Solar Systems,
and Planets
A Hospitable Planet Producing a variety of
elements in a REDUCING ENVIRONMENT
The Age of Matter
Spontaneous formation of macromolecules and their
polymers, including proteins nucleic acids
The Age of Energy
B I G B A N G 13 My bp
Replication
L I F E Evolving Lineages
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Two Chemical Processes
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Chemical Processes

• Reduction Environments (early Earth)
• more bonds are made than broken, resulting in
  a net accumulation of molecules
• Oxidation Environments (since photosynthesis,
  because of O2)
• fewer bonds are made than broken, resulting in
  a net accumulation of molecules

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Reducing versus Oxydizing Environments
Reduction characterized pre-photosynthesis Earth
Life on Earth Replicating Nucleic Acids
reactive atoms
small molecules
macromolecules
Oxidation minimal before photosynthesis
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Early EarthA Reducing Environment
Reduction characterized pre-photosynthesis Earth
reactive atoms
small molecules
Replicating Nucleic Acids
macromolecules
Oxidation minimal before photosynthesis
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Miller and Urey, 1953
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Earths Environment TodayAn Oxydizing Environment
Reduction characterized pre-photosynthesis Earth
reactive atoms
small molecules
Oxidation minimal before photosynthesis
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What kinds of molecules are formed?
carbohydrates
lipids
proteins
nucleic acids
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Spontaneous Formation of Proteins and RNA
These subunits would have polymerized naturally,
by geological processes alone
Early Earths Reducing Environment produced pools
of nucleotides and amino acids by geological
processes (pre-biotic evolution)
Proteins RNA
amino acids RNA nucleotides
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RNA Replication First Life
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Nucleic Acids Can Reproduce
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The Transition to Prokaryotes
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Then and Now
Reproduction Info storage catalysis
RNA replicators
Reproduction Info storage
catalysis
DNA
RNA
Proteins
middle man
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First Life to Modern Cells
First Life RNA organisms No RNA RNA
Modern Life Yes DNA Proteins
Cellular? Hereditary Molecule? Primary
Catalytic Molecule?
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Review Capabilities DNA, RNA, and Proteins
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Complex 3D Shapesand Catalysis
double stranded simple 3D shape
single stranded complex 3D shape
single stranded complex 3D shape
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The Central Dogma of Biologystrandedness and
functional versatility
reproduction primary structure (info storage) no
catalysis
double stranded simple 3D shape
reproduction primary structure (info storage)
catalysis
single stranded complex 3D shape
no reproduction primary structure catalysis
single stranded complex 3D shape
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Heredity and Catalysis
Replication
Catalysis
v
DNA RNA Proteins
v
v
v
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Why Did Cellular Compartmentalization Evolve?
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Why Did Cellular Compartmentalization Evolve?
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Probable StepsAfter Cellularity
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First RNA Replication
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The First Genes
replication produced progeny molecules complete
copies of parent molecule
ribozyme is partial copy of parent
molecule coding region of parent is a gene.
ribozyme is partial copy of parent
molecule coding region of parent is a gene.
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Protein Synthesis
replication produced progeny molecules
ribozyme (e.g., rRNA)
ribozyme
mRNA
tRNA
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Why Did Protein Replace RNA in Catalysis?

• Complex structure is the hallmark of a
  catalyst
• Proteins molecular alphabet is larger (20
  amino acids versus 4 nucleotides
• Amino acids are more chemically diverse than
  nucleotides
• Having a greater number or more diverse
  building blocks allows proteins to have more
  complex structure than RNA molecules

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Why Did DNA Replace RNA in Heredity?
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DNA and RNA Polymerasesproofreading requires a
previous nucleotide
A G C T A A
A T T
A G C T A A
A U U
DNA Polymerase
RNA polymerase
elongation
elongation
proof-reading
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DNA Proof-reading
A G C T A A
G T T
A G C T A A
T T
A G C T A A
A T T
A G C T A A
G A T T
A
G
G
Proof-reading requires the presence of a previous
nucleotide before a new one can be added RNA
polymerase has no such requirement (primase
either)
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DNA Repair
The double strandedness of DNA enables
recognition of mutation sites replacement of
excised nucleotides with complementary
nucleotides
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Why Did DNA Replace RNA in Heredity?

• DNA has a much lower
• mutation rate than RNA