Transcript No Slide Title

LifeLifeon
Earth
on Earth
Life on Earth as a 24 hour Analogy
Life is the Product of Evolution
and
Evolution is the Result of Reproduction
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
What Evolves?
Individuals or Lineages?
Individuals can not evolve
Individuals are transient …they don’t live long
Individuals are genetically fixed …they can’t change genetically
Lineages can and do evolve
Evolution
is change in genetic composition of lineages
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)
Evolution has created biodiversity:
Where does life come from
The Origin of Life
?
The Origin of Life
Cosmology, Geology, then Biological Evolution
Gravitational Collapse
of Clouds of Matter:
The Age
of Matter
The Age
of Energy
BIG
BANG
13 by bp
Formation of Galaxies,
Solar Systems, and Planets
Nebulae - Clouds of
Matter in Space
QuickTime™ and a
Video decompressor
are needed to see this picture.
A Galaxy
Stars are born within nebulae
Stars are born within nebulae
Galaxy movie
QuickTime™ and a
Video decompressor
are needed to see this picture.
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
Some stars return their ash into space
explosion
The Origin of Life
Cosmology, Geology, then Biological Evolution
Gravitational Collapse
of Clouds of Matter:
The Age
of Matter
Formation of Galaxies,
Solar Systems, and Planets
A Hospitable Planet:
Producing a variety of elements in a
REDUCING ENVIRONMENT
Spontaneous formation of macromolecules
and their polymers, including:
The Age
of Energy
proteins
nucleic acids
BIG
BANG
13 My bp
Replication
L I F E:
Evolving Lineages
Two Chemical Processes
Reduction Reactions
fewer bonds
More bonds
Oxidation Reactions
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
Reducing versus Oxydizing
Environments
Reduction
characterized pre-photosynthesis Earth
reactive
atoms
small
molecules
macromolecules
Oxidation
minimal before photosynthesis
Life on Earth:
Replicating
Nucleic Acids
Early Earth
A Reducing Environment
Reduction
characterized pre-photosynthesis Earth
reactive
atoms
small
molecules
macromolecules
Oxidation
minimal before photosynthesis
Replicating
Nucleic Acids
Miller and Urey, 1953
Earth’s Environment Today
An Oxydizing Environment
Reduction
characterized pre-photosynthesis Earth
reactive
atoms
small
molecules
Oxidation
minimal before photosynthesis
What kinds of molecules are formed?
carbohydrates
lipids
proteins
nucleic acids
Spontaneous Formation of
Proteins and RNA
Early Earth’s
Reducing Environment
produced pools of nucleotides
and amino acids by geological
processes (pre-biotic evolution)
These subunits would have
polymerized naturally, by
geological processes alone
Proteins
amino acids
RNA
nucleotides
RNA
RNA Replication
First Life
Nucleic Acids
Can Reproduce
The Transition
to Prokaryotes
Then and Now
RNA replicators
Reproduction
Info storage
DNA
Reproduction
Info storage
catalysis
catalysis
RNA
middle man
Proteins
First Life to Modern Cells
First Life:
RNA organisms
Modern Life
No
Yes
Hereditary Molecule?
RNA
DNA
Primary Catalytic Molecule?
RNA
Proteins
Cellular?
Review Capabilities:
DNA, RNA, and Proteins
Complex 3D Shapes
and Catalysis
double stranded
simple 3D shape
single stranded
complex 3D shape
single stranded
complex 3D shape
The Central Dogma of Biology
strandedness and functional versatility
double stranded
simple 3D shape
reproduction
primary structure (info storage)
no catalysis
single stranded
complex 3D shape
reproduction
primary structure (info storage)
catalysis
single stranded
complex 3D shape
no reproduction
primary structure
catalysis
Heredity and Catalysis
Replication
DNA
√
RNA
√
Proteins
Catalysis
√
√
Why Did Cellular
Compartmentalization Evolve?
Why Did Cellular
Compartmentalization Evolve?
Probable Steps
After Cellularity
First: RNA Replication
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.
Protein Synthesis
replication produced progeny molecules
ribozyme (e.g., rRNA)
ribozyme
mRNA
tRNA
Why Did Protein Replace
RNA in Catalysis?
• Complex structure is the hallmark of a catalyst
• Protein’s 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
Why Did DNA Replace
RNA in Heredity?
DNA and RNA Polymerases
proofreading requires a previous nucleotide
elongation
A
A
G
G
RNA
polymerase
C
T
A
DNA
Polymerase
C
T
elongation
A
A U
A T
A U
A T
proof-reading
DNA Proof-reading
A
A
G
G
C
C
C
T
T
A T
A T
A T
A T
A T
A T
T
G
A T
A T
G
A
A
A
G
G
G
C G
A
T
Proof-reading requires the presence of a previous nucleotide before a new one can be
added …RNA polymerase has no such requirement (primase either)
A
DNA Repair
The double strandedness of DNA enables:
• recognition of mutation sites
• replacement of excised nucleotides
with complementary nucleotides
Why Did DNA Replace
RNA in Heredity?
DNA has a much lower
mutation rate than RNA