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

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