Download Evolution 2

Abiogenesis

The spontaneous generation of life from nonliving matter.

It was widely held that maggots arose
spontaneously in rotting meat or broth.
Francesco Redi (Italian 1668)
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One of the first to disprove spontaneous
generation. An Italian doctor who proved
maggots came from flies.
Lazzaro Spallanzani
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Some scientists
believed that there
was a life force in the
air
He tried to disprove
the life force theory
He was unsuccessful
 There are
microorganism in
the air
Louis Pasteur
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
Successful in proving there was no life force
The curved neck allowed air to pass but trapped
microorganisms
Biogenesis

All living things arise from other living things
But how did life first form?
RNA Theory
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The first molecules of life were
RNA
RNA
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Carried genetic information
Can be replicated
Can make proteins
Is a catalyst
Similar in form to ATP
RNA evolved into DNA
Oparin (1930)
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Spontaneous generation did occur once at the
beginning of life
Believed that at high temperatures and with electrical
charge the early gases could combine to form simple
organic compounds
As the Earth cooled the organic compounds
collected in the oceans = Primordial soup
Miller & Urey (1953)

Tested Oparin’s Hypothesis under laboratory
conditions and produced some amino acids and
sugars
Alternative Theory

Metorites may have brought organic compounds
(amino acids) to Earth
First Cells
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They were:
Prokaryotic
 Anaerobic
 Herterotrophic
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Endosymbiotic Theory
Lynn Margulis
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Evolution of
eukaryotic cells
Eukaryotic cells
evolved from large
prokaryotic cells that
were invaded by small
aerobic and small
photosynthetic
prokaryotes
LaMarck
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Lamark said
organisms acquired
traits by using their
bodies in new ways

These new
characteristics were
passed to offspring

Lamark was totally
wrong!
Evolution
Decent with Modification
(Change in Species Over Time)
Mechanisms for Evolution

Natural Selection
Environmental Pressures
 Variation
 Competition
 Isolation
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Sexual Selection
Sexual Selection
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Sexual Selection
 Variation
 Competition for
mates
 Choice
Charles Darwin
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
1.
2.
As a result of his travels to the Galapagos islands
and extensive studies of various organisms
He developed 2 major theories
Decent with modification
Modification by natural selection
Rules for Natural Selection
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than
survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass
those advantages to their children
5. Species alive today are descended with
modifications from common ancestors
Natural Selection
Methods of Natural Selection
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Stabilizing – Favors the average form of a trait
Directional – Favors the extreme form of a trait
Disruptive – Favors both extremes
Antibiotic Resistance
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
How natural selection works
How natural selection works
Resistance to antibacterial soap
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
Generation 1: 1.00 not resistant
0.00 resistant
Generation 2: 0.96 not resistant
0.04 resistant
mutation!
How natural selection works
How natural selection works
Resistance to antibacterial soap
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
Generation 1: 1.00 not resistant
0.00 resistant
Generation 2: 0.96 not resistant
0.04 resistant
Generation 2: 0.96 not resistant
0.04 resistant
Generation 3: 0.76 not resistant
0.24 resistant
Generation 3: 0.76 not resistant
0.24 resistant
Generation 4: 0.12 not resistant
0.88 resistant
Speciation
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Geographic isolation
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Geographic barrier between populations
Reproductive isolation
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Pre-zygote – No breeding
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Different mating seasons
Not recognizing an organism as a potential mate
Post-zygote – Fertilization
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Offspring are sterile or no zygote is formed
Evidence for Evolution
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Fossil record
Homologous body structures
Embryology
Geographic distribution
Biochemical evidence (Genetic)
Fossil Record
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The fossil record infers the
history of the Earth
Shows new life forms have arisen
during the Earth’s history
Shows diversity in the life forms
Relative Dating Vs. Radioactivity
Where fossils are
located in the strata
 Not as accurate
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Uses the
degradation of
radioactive
elements
 Example: Carbon
Dating
 More accurate
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Homologous Body Structures
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Structures look
similar but
function
differently
Vestigial Organs
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Organ that serves no useful function
e.g. Appendix, tailbone, Wisdom teeth
Embryology
Similarities in Embryology
 In their early stages of
development, chickens,
turtles and rats look
similar, providing
evidence that they
shared a common
ancestry.
Geographic Distribution
Biochemical Evidence

Genetic material in all organisms is similar
Shows a common ancestor for all living things
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DNA
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Pace of Evolution
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Gradualism – Slow and steady change over time
Punctuated Equilibrium – abrupt change
followed by little or no change