Evolution Dr. James R. Whitfield, Ph.D. Evolution "Nothing in Biology Makes Sense Except in the Light of Evolution” - Theodosius Dobzhansky.

EvolutionEvolutionDr. James R. Whitfield, Ph.D

EvolutionEvolution"Nothing in Biology Makes Sense

Except in the Light of Evolution”

- Theodosius Dobzhansky

What is Evolution?What is Evolution?Evolution is the process by which

different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

What is Evolution?What is Evolution?Evolution is the process by which

different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

Evolution is the story of the origin of life and the formation of the vast biodiversity on Earth

Origin of LifeOrigin of LifeThe Universe is old – about 20

billion years old!

Origin of LifeOrigin of LifeThe Universe is old – about 20

billion years old!When we look out at the stars we

are looking millions of years and trillions of miles into the past

Origin of LifeOrigin of LifeThe Universe is old – between

about 14 and 20 billion years oldWhen we look out at the stars we

are looking millions of years and trillions of miles into the past

However, no matter how long we look at those stars we are limited in how far back we can actually see – the light from the oldest stars simply has not had enough time to reach us yet!

The Big BangThe Big BangThe Big Bang theory is the

prevailing cosmological theory attempting to explain the origin of the Universe.



It describes a single huge explosion, unimaginable in physical terms resulting from tremendous heat and pressure



It describes a single huge explosion, unimaginable in physical terms resulting from tremendous heat and pressure

As the universe continued to expand it cooled down

The Big BangThe Big BangThis cooling allowed for the

formation of subatomic particles and then simple elements such as hydrogen and helium (the two most abundant elements in the Universe today)

The Big BangThe Big BangThis cooling allowed for the formation

of subatomic particles and then simple elements such as hydrogen and helium (the two most abundant elements in the Universe today)

Over the next few billions years cooling and gravity allowed for the formations of galaxies. Our galaxy – The Milky Way formed about 4.5 billion years ago

The Early EarthThe Early EarthThere was no atmosphere on the

early Earth


early EarthWater vapor (H2Ov), ammonia

(NH3), methane(CH4) , carbon monoxide (CO), and carbon dioxide (CO2)


early EarthWater vapor (H2Ov), ammonia (NH3),

methane(CH4) , carbon monoxide (CO), and carbon dioxide (CO2)

UV light broke up the water vapor into hydrogen and oxygen. The oxygen combined with ammonia and methane to form more water, carbon dioxide and ozone (O3)

The Early EarthThe Early EarthAs the planet continued to cool

the water vapor continued to condense and fall as rain



The rain eventually filled in the depressions on the Earth forming the oceans



The rain eventually filled in the depressions on the Earth forming the oceans

Life first appeared about 500 million years later or about 4 billion years ago

HOW?HOW?The previous slide said life

appeared 500 million years ago but it does not say anything about how

HOWHOW

Now that’s the big question!

Theories on the Formation of Theories on the Formation of LifeLifeSome scientists believe that life

came from outer space


came from outer spaceThe early Greeks believed that

“spores” transported life from planet to planet


came from outer spaceThe early Greeks believed that

“spores” transported life from planet to planet

This “Theory of Panspermia” is still believed by many scientists today

Theories on the Formation of Theories on the Formation of LifeLifeFor a long time people believed

in the “Theory of Spontaneous Generation” – that life appeared form nowhere

Theories on the Formation of Theories on the Formation of LifeLifeFor a long time people believed

in the “Theory of Spontaneous Generation” – that life appeared form nowhere

However Franscisco Redi and later Louis Pasteur proved that this theory was incorrect

Theories on the Formation of Theories on the Formation of LifeLifePasteur proposed the “Theory of

Biogenesis” which states that, “Omne vivum ex vivo” all life come from life

Theories on the Formation of Theories on the Formation of LifeLifePasteur proposed the “Theory of

Biogenesis” which states that, “Omne vivum ex vivo” all life come from life

If you remember one of the principle of the modern cell theory states that, “omni cellulae e cellula” all cells come from cells

Pasteur’s ExperimentPasteur’s Experiment

Theories on the Formation of Theories on the Formation of LifeLifeOparin and Haldane proposed

that the frst life could have come from pre-existing, non-living organic molecules (RNA, proteins, etc,..) and that the formation of life was preceded by chemical evolution

Theories on the Formation of Theories on the Formation of LifeLifeOparin and Haldane proposed that

the frst life could have come from pre-existing, non-living organic molecules (RNA, proteins, etc,..) and that the formation of life was preceded by chemical evolution

i.e., the formation of diverse organic molecules from inorganic components

Theories on the Formation of Theories on the Formation of LifeLifeIn 1953 Stanley Miller and Harold

Urey at the University of Chicago (Chicago, Illinois, USA) designed an experiment to recreate the conditions present on the early Earth in a laboratory setting

Theories on the Formation of Theories on the Formation of LifeLifeThey created an electric

discharge into a flask containing, methane, water vapor, ammonia, and hydrogen

Theories on the Formation of Theories on the Formation of LifeLifeThey created an electric

discharge into a flask containing, methane, water vapor, ammonia, and hydrogen

They observed the formation of amino acids – which as we know are the building blocks of proteins, which build organelles, which build cells, …

Millers FlaskMillers Flask

Theories on the Formation of Theories on the Formation of LifeLifeOther researchers performing

similar experiments have been able to produce, sugars, glycoproteins, and fats

Theories on the Formation of Theories on the Formation of LifeLifeOther researchers performing

similar experiments have been able to produce, sugars, glycoproteins, and fats

The theory that chemical evolution proceeded biological life is now generally accepted

HoweverHowever

HoweverHoweverNone of these experiments have

answered how the first self replicating metabolic life arose

HoweverHoweverNone of these experiments have

answered how the first self replicating metabolic life arose

Miller and Urey simply said, “given the conditions in the early atmosphere the building blocks of life could develop”

ButButWe do know that the first non-

cellular “life” could have originated about 3 billion years ago



That is was probably large RNA molecules, proteins and polysaccharides




The first cellular life did not appear until about 2 billion years ago




The first cellular life did not appear until about 2 billion years ago

These were unicellular, prokaryotes that lived in a watery environment

BiogenesisBiogenesisThis version of biogenesis that

the first form of life slowly arose through evolutionary forces from non-living molecules is generally accepted today

However, this is only the beginning

BiogenesisBiogenesisThis version of biogenesis that the

first form of life slowly arose through evolutionary forces from non-living molecules is generally accepted today

However, this is only the beginningWe now need to look at how these

first unicellular organisms could have evolved into the complex biodiversity of today

The Modern Theory of The Modern Theory of EvolutionEvolutionMany religious beliefs hold the

theory of “Special Creation”


theory of “Special Creation”This idea of creationism is laid

out in the Christian Bible in the Book of Genesis


theory of “Special Creation”This idea of creationism is laid out in

the Christian Bible in the Book of Genesis

Proponents of this theory believe that 1- All living this we see today were created as they are now – perfect and unchanged

2- The diversity we see now was as it was in the past and will be in the future

3- The Earth is about 6,000 years old (your book says 4,000)

The Modern Theory of The Modern Theory of EvolutionEvolutionThese ideas were strongly

challenged based on the Work of Charles Darwin and the observations he made while travelling on the H.M.S. Beagle

The Modern Theory of The Modern Theory of EvolutionEvolutionThese ideas were strongly

challenged based on the Work of Charles Darwin and the observations he made while travelling on the H.M.S. Beagle

Darwin concluded that existing life forms show similarities to varying degrees not only among themselves but with long extinct life forms

The Modern Theory of The Modern Theory of EvolutionEvolutionHe further concluded that there

had been extinctions of life forms in the past and that new life forms arose at various periods in the history of the Earth.

The Modern Theory of The Modern Theory of EvolutionEvolutionHe further concluded that there

had been extinctions of life forms in the past and that new life forms arose at various periods in the history of the Earth.

There had been a gradual evolution of life forms

Darwin’s TheoryDarwin’s TheoryDarwin theory can be

summarized as


summarized asNatural selection


summarized asNatural selectionDescent with Modification

Darwin was Influenced by Thomas Malthus

Natural SelectionNatural SelectionNatural selection states that

within any population there will be built in variation. This variation will allow some individuals to survive better than other. These organisms will outbreed the other members of the population and produce more offspring with the desired characteristics

Natural SelectionNatural SelectionNatural selection states that within

any population there will be built in variation. This variation will allow some individuals to survive better than other. These organisms will outbreed the other members of the population and produce more offspring with the desired characteristics

This is called fitness

Descent with ModificationDescent with ModificationDescent with modification simply

means that as organisms reproduce mutations will occur. Any mutation that is beneficial and increases an organisms fitness will stay in the population. Given the immensity of time the slow accumulation of mutations will lead to the formation of new species

Descent with ModificationDescent with ModificationDescent with modification simply

means that as organisms reproduce mutations will occur. Any mutation that is beneficial and increases an organisms fitness will stay in the population. Given the immensity of time the slow accumulation of mutations will lead to the formation of new species

It does not mean that the original organism will go extinct

Descent with ModificationDescent with ModificationMillion of years ago men and

monkeys shared a common ancestor. Then a branch came we went one way but the monkeys continued on the way they were

Not Accurate

The Other PlayerThe Other PlayerAlfred Wallace was a

contemporary of Darwin. He independently developed his own Theory of Evolution while working in the Malay Archipelago. Darwin was hesitant to publish his work (because of the social and political ramifications) however upon learning of Wallace’s work he felt compelled to publish first

Evolution Before DarwinEvolution Before DarwinPrior to Darwin Evolution was discussed

and tried to be explained by French Naturalist – Jean Baptiste Lamarck. Lamarck proposed that evolution was driven by use and disuse. He believed that traits could be acquired during ones lifetime and then passed on. For example, giraffes could acquire longer necks because they needed to browse high in tress. Once they got this longer neck they could pass on the trait to their offspring. This theory is no longer believed

The Evidence for EvolutionThe Evidence for EvolutionFossils – the remains (of usually

the hard parts or organisms) preserved in stone



Rocks form sediment. A cross section of the Earths crust indicates the arrangement of the sediment over very long periods of time




Different sediments contain different fossils




Different sediments contain different fossils

The Evidence for EvolutionThe Evidence for EvolutionWe can see that life forms vary

over time, that they become extinct and that new forms of life have appeared in Earth’s history

Relative vs Absolute Relative vs Absolute DatingDatingRelative dating simply states that

this is older or younger than that but gives no indications as to its actual age

Relative vs Absolute Relative vs Absolute DatingDatingRelative dating simply states that this

is older or younger than that but gives no indications as to its actual age

Absolute dating using such techniques as radioactive carbon dating, Potassium – Argon dating (K-Ar) or Uranium – Lead dating (U-Pb) uses half-life techniques to determine the absolute age of objects

The Evidence for EvolutionThe Evidence for EvolutionComparative anatomy and

morphology show similarities and differences between today’s organisms and those from the past

The Evidence for EvolutionThe Evidence for EvolutionComparative anatomy and

morphology show similarities and differences between today’s organisms and those from the past

From this we can determine the presence (or lack of) a common ancestor

The Evidence for EvolutionThe Evidence for EvolutionComparative anatomy and morphology

show similarities and differences between today’s organisms and those from the past

From this we can determine the presence (or lack of) a common ancestor

Homologous structures – The forelimb pattern of whales, bats, humans and cats all show similar bone structure but have different functions

The Evidence for EvolutionThe Evidence for EvolutionTherefore a homologous

structure is a structure that looks the same but does different things – It demonstrates a common ancestor and divergent evolution

The Evidence for EvolutionThe Evidence for EvolutionAnalogous structures represent

the opposite scenario. These are structures that look different but do the same thing. For example a bird and butterfly wing are anatomically very different but they both enable flight. This represents convergent evolution

The Evidence for EvolutionThe Evidence for EvolutionSimilar habitats often result in the

selection of similar adaptive features in different groups of organisms but toward the same function. Consider whales and sharks they have not had a similar common ancestor for tens of millions of years (or more) but because of where they live they have evolved to have similar body types

The Evidence for EvolutionThe Evidence for EvolutionSimilarities in protein and gene

function among diverse organisms give clues to common ancestry

The Evidence for EvolutionThe Evidence for EvolutionOne argument for evolution that

your book makes that most sources do not is that through artificial selection man has created new species (both plants and animals) in a few hundred years then why could it not happen in nature over a few million years

Industrial MelanismIndustrial MelanismThe peppered moth is an example of industrial

melanism. Prior to the industrial revolution in England. The white variant of the moth was most common with lesser amounts of the melanised version. The moths lived on the near-white lichens that covered the trees. As the Industrial revolution progressed the trees became black from coal-fired plants. The population of black moths increased as being this color gave them a competitive advantage (they were harder to spot) and the white moth population declined. Several years after the passage of the clean air acts as the trees returned to the normal color there was a shift once again toward white moths (Remember – no variant was totally wiped out)

Vestigial StructuresVestigial Structures

Vestigial StructuresVestigial StructuresA vestigial structure is a structure

that had a function at one time but no longer does. Some examples in humans include the wisdom teeth, pinnae cartilage of the ear and eyebrows

While most people consider the appendix to be a vestigial structure there is some controversy about this

Plica semilunaris

Adaptive RadiationAdaptive RadiationThere is an expression that says,

“Nature abhors a vacuum”


“Nature abhors a vacuum”This means that wherever life

can exist – life will exist


“Nature abhors a vacuum”This means that wherever life

can exist – life will existSome examples of this are the

plants present in the Hawaiian Islands, The finches of the Galapagos Islands and the marsupials od Australia

Adaptive RadiationAdaptive RadiationIn each of these situations you

had ancestral stock that radiated outward as various mutations allowed them to take advantage of diverse habitats – Consider how the beaks of the finches are adapted to the types of seeds found in different areas

Mechanisms of EvolutionMechanisms of EvolutionDarwin was a gradualist. He

believed that mutations were small and random but moved in one direction

Mechanisms of EvolutionMechanisms of EvolutionDarwin was a gradualist. He

believed that mutations were small and random but moved in one direction

Hugo deVries was a proponent of Saltation which states that large mutations could occur rapidly, leading to the formation of a new species in a single generation

Mechanisms of EvolutionMechanisms of EvolutionStephen J. Gould proposed a theory

called “Punctuated Equilibrium” which stated that organisms stayed stable for veru long periods of time and then for any number of reasons orgnaisms went through rapid periods of evolution (100,000s of years to a few million) and then returned to a period of stability for many millions of years

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumHardy-Weinberg can be used to

determine the frequency of a particular allele in a population

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumHardy-Weinberg can be used to

determine the frequency of a particular allele in a population

Hardy-Weinberg provides a snapshot of that population

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumHWE states that the alleles in a

population will remain constant from generation to generation in the absence of other evolutionary influences.

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumHardy-Weinberg requires a

variety of conditions to be met in order for it to be used (as you will see HWE) is more of an intellectual exercise than an actual thing. HWE requires that

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumPopulations be large

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumPopulations be largeThat there be no immigration or

emigration from the population


emigration from the populationAll mating’s be random (No mate

selection)



selection)There are no mutations



selection)There are no mutationsAll organisms are equally fit

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibriumHWE – is an algebraic formula

that states:p + q =1 wherep2 + 2pq + q2 = 1 So ifp = represents the Homozygous

dominant phenotype, pq represents the heterozygous phenotype and q represents the recessive phenotype, then

Hardy – Weinberg Hardy – Weinberg EquilibriumEquilibrium.6 + .4 = 1 and (.6)2 + 2(.6)(.4) + .42 = 1.36 + .48 + .16 = 1 Therefore36% of the population is AA48% of the population is Aa16% of the population is aaA change in the frequency of the

alleles in the population would be interpreted as evolution

Evolution Dr. James R. Whitfield, Ph.D. Evolution "Nothing in Biology Makes Sense Except in the Light of Evolution” - Theodosius Dobzhansky.

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