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Evolution III
Evolution notes III• Organic Compounds• Three hypotheses• 1. Extra-terrestrial Origin• 2. Random Chance Events• 3. Pre-biotic Evolution — most accepted
idea
Evolution Notes III• Earth’s age is estimated to be around• 4.6 billion years old.• Oldest sedimentary rocks, 3.8 billion years
contain no fossils.• Oldest evidence is molecules of fossil
organic material, 3.4 billion• Oldest candidate for possible organic
microfossils, 3.5 billion• Oldest definitely living 2.5 billion—
Bluwago formation, remains of Blue-green algae (prokaryotic cells).
• Pre-biotic evolution took approximately one-half to a billion years
Evolution Notes III
Earth’s earlyatmosphereconsisted of :
Carbon Dioxide Methane Gas
Nitrogen Hydrogen Sulfide
Carbon Monoxide
Ammonia (NH3)
Water
Evolution Notes III
• These came from out-gassing from earth’s inside
• Note: there was no free oxygen nor ozone found in the stratosphere
• Remember Ozone is needed to block UV light from the sun
Evolution IIIPre-biotic evolution:• Slow evolution of chemical
into organic molecules using external energy:
1. Heata. Sunb.Internal radiation from
earth
Evolution Notes III
Pre-biotic evolution:
2. Lighta. UV
lightb. Visible
light
Evolution Notes III
Pre-biotic evolution:
3. Electrical discharge (lightning)
Evolution Notes IIISome
Experiments:
• In 1953 Stanley Miller mixed the molecules of primitive earth’s atmosphere and subjected them to electrical sparks to simulate lightning, resulting in the formation of amino acids.
Evolution Notes IIIDetails of the
Miller Experiment:
• The apparatus was built from glass tubes and containers.
• Boiling water, ammonia, methane, and Hydrogen were passed through an electrical spark.
• A glass trap caught any molecules created by the reaction.
• (The trap kept the products from being destroyed by the spark.)
Tar 85%
Carboxlic Acids 13.0%
Glycine 1.05%
Alanine 0.85%
Glutamic Acid Trace
Glutamic Acid Trace
Aspartic Acid Trace
Valine Trace
Leucine Trace
Serine Trace
Proline Trace
Treonine Trace
Evolution IIIIn a second experiment, hydrogen was bubbled through the molecule mix and let out of the flask resulting in the formation of amino acids, ATP, ribose and deoxyribose sugars, urea, and other basic building blocks of life. The most common amino acids that were found in this mixture are the ones most commonly found in living organisms today.
Evolution IIIIn lab experiments preformed by Sidney Walter Fox (b. March 24, 1912. d. Aug. 10, 1998), these amino acids produced thermalproteinoids under dry and gentle forms of heating, such as those found in tidepools gradually drying out.
Evolution Notes IIIIt is felt that proteins were developed before nucleic acids.Proteins are attracted to clay particles. The clay particles actually absorb the proteins along their surface and aid in the formation of macro –molecules. These molecules can form into more complex ones. There are several different combinations.
Evolution Notes IIIIt is felt that proteins were developed before nucleic acids.When DNA first appeared it could out compete all other forms of macro-molecules because it can replicate. This had to happen once, because then replication system would take over and divergence could occur.
Evolution Notes III
First bacteria cells were strictly anaerobic, living in carbon dioxide and methane gasses.
Evolution Notes III• Photosynthesis first
appeared in cyanobacteria (blue-green algae).
• This process began the release of O2 into the atmosphere and also allowed for more efficient respiration to occur.
Evolution Notes III
• True early forms of bacteria came about around 2.5 million years ago. First eukarotic cells occurred 1,300,000,000 (1.3x109) years ago. Oldest multicellular animals are approximately one billion to 7,000,000 years old.
Evolution Notes III
Hardy / Weinberg Law of Equilibrium
Determines the expected statistical results from a mathematical equation of genes (alleles) in a population (a group of interbreeding species).
Evolution Notes III
Works only under these conditions:
1.Random and equal mating2.Very large population size
(infinite number ∞, several 1,000s)
3.No net mutations4.No selection (natural or artificial)5.No gene flow (in or out of population)
Evolution Notes III
Equation: p2 + 2pq + q2 = 1
Where: p = frequency of dominant allele
q = frequency of recessive allele
It is (p+q)2 factored
Evolution III
• Results in:
= p2
= 2pq
= q2
Evolution III
• Results in:
BB = p2
Bb = 2pq
bb = q2
Evolution III
Class Eye Color: p2 + 2pq + q2 = 1
Brown — pq + p2
Blue — q2
Total
q2 = #/@
q= square root of q2 = ?
p= 1-(square root of q2) = ?
This results in the percent of BB, Bb, and bb alleles
If you are not brown-eye, then you have blue eyes
Evolution III
Class Eye Color:p2 + 2pq + q2 = 1Example
11 Brown — pq + p2
6 Blue — q2
17 Total
q2 = #/@
q= square root of q2 =
p= 1-(square root of q2) =
This results in the percent of BB, Bb, and bb alleles
.412 + 2(.41 *.59)+ .592
.17 + 2(.24) + .35.17 + .48 + .35
17% BB 48% Bb 35% bb6/17 = .35
.59 1-.59=
.41
Evolution IIIUsually doesn’t happen in nature, but
used because:1.Nature approximates these conditions
by/becausea)Most mutations cancel each otherb)Probability of selection (death) having an
effect is lowc) Some populations have little movement
2.Can use to make predictions3.Can alter equation mathematically4.Use as a tool to measure change
Evolution Notes III
Selection:
• It is the differential survival or reproduction of individuals of different genotypes.
• Natural selection works only on heritable traits — genes.
Evolution Notes IIINatural Selection:• Controlled by large numbers of genes• Natural selection acts on phenotypes, not genotypes.
• The phenotypic trait must be heritable, however, in order for evolution to occur.
• Natural selection acts faster against dominant alleles than recessive alleles.
• Evolution does not produce perfectly adapted organisms.
• Evolution generally causes the modification of existing structures, not the creation of brand new ones and the results are often compromises between various needs of the organism.
Evolution Notes III
Three types of selection:1. Directional — pushes values
toward one extreme2. Normalizing — selection
against extremes (stabilizing)
3. Disruptive — two or more favored at same time
Evolution Notes III
• Directional Selection:– Eliminates one
extreme variation from an array of possible phenotypes. Results in a shift towards the other extreme.
Evolution Notes III
• Stabilizing Selection:– Selection acts to
eliminate both extremes of an array of phenotypes. Results in an increase in individuals exhibiting an intermediate phenotype.
Evolution Notes III
• Disruptive Selection– Selection acts
to remove the intermediate phenotypes favoring the extreme phenotypes:
Evolution Notes III
Other types of selection:
1. Genetic Drift the random loss of fixing of genes because of a small gene pool
2. Gene Flow the loss of alleles through immigration or emigration
3. Neutral Alleles
Evolution Notes III
SpeciationIncomplete
speciation
1. Sub-species — interbreed
2. Semi-species — mate less often
Evolution Notes III
SpeciationHow speciation
occurs
1. Reproductively Isolated
2. Evolutionally Divergent1. Mutations2. Environment
Evolution Notes III
Classic Examples of speciation:
1. Allopatric – geographic
a) Separate species adapt to own area / climate
b) If they can meet and if cannot mate then allopatric
c) Must be separated a long time — 10,000 to 50,00 years
Evolution Notes III
Examples:
1. Squirrels of the Grand Canyon were at one time the same species
North Rim South Rim
Kaibab Albert’s
Higher elevation Lower elevation
Eats pine nuts Eats seeds
Darker fur Golden yellow fur
White tail Not white tail
• Now they are separate species
Evolution Notes III1. Habitat preference — Apple
Maggot Fly originally on Hawthorne trees
2. Chromosomal Mutationa) Different ploidy (N)b)Extremely commonn in plantsc) Instance speciationd)Parthoenogenetic reproduction
i. Females only, no mating, no male needed
ii. Some species of lizards in the Southwest
Evolution Notes IIIII Parpatric — cline
• Cline — 1. Character gradient in
morphological geographic variable sup-species
2. Continuing change from one geographical area to another
Examples: 1. Frogs along the Atlantic
Coast
2. Gulls around Arctic Circle (circumpolary)
Evolution Notes III
III Catastropic — environmental disaster
Isolation of small groups of population members and to which genetic drift occurs
Reasons:
1.Reproductive isolation
2.Divergency
Evolution Notes IIIIV Convergent evolution:– This occurs when species evolve into a common phentoypic form due to a common need.
Example the diagram portrays a shark, icthyosaurus, and a dolphin. These are fish, reptile ands mammal respectively (very different families of animals). Yet they all have a torpedo body shape, pectoral, caudal and dorsal fins. This is based on their common need to swim rapidly in an aquatic environment.
Evolution Notes III
Divergent evolution.• Occurs when species evolve in several directions away from a common ancestor.
• This happens usually to fill a vacant ecological niche. Also known as adaptive radiation.
End