chapter 3 darwinian natural selection. the mechanism of natural selection in the last chapter we...

Chapter 3Chapter 3Darwinian Natural SelectionDarwinian Natural Selection

The Mechanism of Natural SelectionThe Mechanism of Natural Selection

In the last chapter we discussed the evidence that evolution occurs

Now we examine HOW it occurs Darwin tied together pattern with

process Why his argument was so elegant...

In the last chapter we discussed the evidence that evolution occurs

Now we examine HOW it occurs Darwin tied together pattern with

process Why his argument was so elegant...

Darwin’s Four PostulatesDarwin’s Four Postulates

1. Individual species are variable

2. Some variation is passed on to offspring

3. More young are born than can survive

4. Survival and reproduction are not random Individuals with most favorable variations

survive to reproduce more Natural selection, or survival of the fittest







HIV There is variation among virions in their

resistance to AZT The ability to distinguish between AZT and

thymidine is inherited Not all virions are able to infect T cells and

reproduce The virions that distinguish AZT the best

produce more offspring and are naturally selected for

HIV There is variation among virions in their

resistance to AZT The ability to distinguish between AZT and

thymidine is inherited Not all virions are able to infect T cells and

reproduce The virions that distinguish AZT the best

produce more offspring and are naturally selected for

Fitness and AdaptationFitness and Adaptation

Individuals who win the competition and survive to reproduce are more fit

Darwinian fitness is the ability of an individual to survive and reproduce in its environment

An adaptation is a trait that increases an individual’s fitness in its environment

Adaptations are enhanced and favored by natural selection

Individuals who win the competition and survive to reproduce are more fit

Darwinian fitness is the ability of an individual to survive and reproduce in its environment

An adaptation is a trait that increases an individual’s fitness in its environment

Adaptations are enhanced and favored by natural selection


Alfred Russel Wallace had independently developed the theory of natural selection before Darwin published his book

Wallace is not as famous because Darwin’s argument was more complete and he eventually published it first

The four postulates can be independently verified Natural selection is testable

Alfred Russel Wallace had independently developed the theory of natural selection before Darwin published his book

Wallace is not as famous because Darwin’s argument was more complete and he eventually published it first

The four postulates can be independently verified Natural selection is testable

Finch Beak Evolution in the Galápagos IslandsFinch Beak Evolution in the Galápagos Islands

Peter and Rosemary Grant Studying Darwin’s finches since 1973 14 finch species Species differ in overall size, beak

dimensions, and other characters Variation in beak morphology tied to

feeding habits Insects, seeds, nectar, parasites, leaves, fruit

Peter and Rosemary Grant Studying Darwin’s finches since 1973 14 finch species Species differ in overall size, beak

dimensions, and other characters Variation in beak morphology tied to

feeding habits Insects, seeds, nectar, parasites, leaves, fruit


Study of ground finches on Daphne Major Very small island Distant from others Good natural laboratory Finches cannot easily disperse to or from

Daphne Major

Study of ground finches on Daphne Major Very small island Distant from others Good natural laboratory Finches cannot easily disperse to or from

Daphne Major


Geospiza fortis, medium ground finch 1200 finch individuals on island

All marked Eats seeds

Crack by grasping at base of bill and applying force Beak size is variable within species

Bigger beaks eat bigger seed species Smaller beaks eat smaller seed species

Geospiza fortis, medium ground finch 1200 finch individuals on island

All marked Eats seeds

Crack by grasping at base of bill and applying force Beak size is variable within species

Bigger beaks eat bigger seed species Smaller beaks eat smaller seed species

Evolutionof GalapagosFinches

Evolutionof GalapagosFinches


Testing Postulate 1: Are Populations Variable? Because each finch is marked, each can be

measured Weight, wing length, beak width, beak depth,

beak length, etc. Beak depth is variable within this species

Testing Postulate 1: Are Populations Variable? Because each finch is marked, each can be

measured Weight, wing length, beak width, beak depth,

beak length, etc. Beak depth is variable within this species

Beak depth in medium ground finches on Daphne Major in 1976.

VARIATION

Beak depth in medium ground finches on Daphne Major in 1976.

VARIATION


Testing Postulate 2: Is Variation Heritable? Beak depth variation could be genetic or

environmental Must estimate heritability

Proportion of variation observed in a population due to variation in the effects of genes

Compare parents and offspring Beak depth is heritable

Testing Postulate 2: Is Variation Heritable? Beak depth variation could be genetic or

environmental Must estimate heritability

Proportion of variation observed in a population due to variation in the effects of genes

Compare parents and offspring Beak depth is heritable

Heritability of beak depth in G. fortis. VARIATION IS HERITABLE

Heritability of beak depth in G. fortis. VARIATION IS HERITABLE


Testing Postulate 3: Is There an Excess of Offspring so that Only Some Individuals Live to Reproduce? In 1977 there was a severe drought

84% of finch population died

In normal times 89% of finches die before they reproduce

Clearly, more individuals are born than can survive and reproduce

Testing Postulate 3: Is There an Excess of Offspring so that Only Some Individuals Live to Reproduce? In 1977 there was a severe drought

84% of finch population died

In normal times 89% of finches die before they reproduce

Clearly, more individuals are born than can survive and reproduce

Ex. of Exponential Growth and Its Potential Role in Selection…Ex. of Exponential Growth and Its Potential Role in Selection…

Wallace: 1 pair birds produces 4 young per year each pair produce 4 times in a life 15 years each pair produces 10 million birds

Darwin: Elephant lives 100 yrs, produces about 6 progeny between 30-90 1 pr produces 19 million in 750 yrs if all offsp.

reproduce

Wallace: 1 pair birds produces 4 young per year each pair produce 4 times in a life 15 years each pair produces 10 million birds

Darwin: Elephant lives 100 yrs, produces about 6 progeny between 30-90 1 pr produces 19 million in 750 yrs if all offsp.

reproduce

Brodie: 2 Bullfrogs-----50,000 eggs/life (frog = .5 lb; egg mass=25 cm2)

if 10 survive (.02%)...........250,000 eggs

if .02% surv. (50 frogs).......1,250,100 eggs

250 frogs.......6,250,000 eggs (4th generation)

by 10th gen. 19,531,250......~500 billion eggs

which is about 2 sq km of eggs and about 10,000 (9,866 tons) of frog

Brodie: 2 Bullfrogs-----50,000 eggs/life (frog = .5 lb; egg mass=25 cm2)

if 10 survive (.02%)...........250,000 eggs

if .02% surv. (50 frogs).......1,250,100 eggs

250 frogs.......6,250,000 eggs (4th generation)

by 10th gen. 19,531,250......~500 billion eggs

which is about 2 sq km of eggs and about 10,000 (9,866 tons) of frog


Testing Postulate 4: Are Survival and Reproduction Nonrandom? After drought, the Grants measured the surviving

birds again Found that finches with deepest beaks survived

more than others Deep beaks were favorable during drought

because only one plant produced a lot of fruit Tribulus cistoides has large, hard fruits Only birds with deep, narrow beaks can crack them

Testing Postulate 4: Are Survival and Reproduction Nonrandom? After drought, the Grants measured the surviving

birds again Found that finches with deepest beaks survived

more than others Deep beaks were favorable during drought

because only one plant produced a lot of fruit Tribulus cistoides has large, hard fruits Only birds with deep, narrow beaks can crack them

Result of 1977 DroughtResult of 1977 Drought

Seed abundance droppedSeed abundance dropped

Bird abundance droppedBird abundance dropped

Average type of seeds available for food on Daphne Major

Average type of seeds available for food on Daphne Major


Testing Postulate 4: Are Survival and Reproduction Nonrandom? Natural selection caused deep beaks to be

favored during the drought Other birds died out Other droughts produced similar effects El Niño produced the opposite

A very wet year caused the production of small, soft seeds Small birds with shallow beaks were selected for

Natural Selection is dynamic

Testing Postulate 4: Are Survival and Reproduction Nonrandom? Natural selection caused deep beaks to be

favored during the drought Other birds died out Other droughts produced similar effects El Niño produced the opposite

A very wet year caused the production of small, soft seeds Small birds with shallow beaks were selected for

Natural Selection is dynamic

Natural selection caused deep beaks to be favored during the drought



LOOK HOW PRONOUNCED TREND IS IN NEXT YEAR’S OFFSPRING!


LOOK HOW PRONOUNCED TREND IS IN NEXT YEAR’S OFFSPRING!


Did evolution occur? Natural selection acted on finch

population Evolution is a response to selection A change in populations over generations To know if evolution occurred, must see if

characteristics changed over time ....Evolution did occur

Did evolution occur? Natural selection acted on finch

population Evolution is a response to selection A change in populations over generations To know if evolution occurred, must see if

characteristics changed over time ....Evolution did occur

30 Years of evolution in Daphne Major finches30 Years of evolution in Daphne Major finches

The Nature of Natural SelectionThe Nature of Natural Selection

Even though the process is quite simple, it is sometimes difficult to think statistically to understand natural selection

Will discuss popular ideas about natural selection that are incorrect

Show how natural selection does and does not operate

Even though the process is quite simple, it is sometimes difficult to think statistically to understand natural selection

Will discuss popular ideas about natural selection that are incorrect

Show how natural selection does and does not operate


Natural selection acts on individuals but evolution occurs in populations When HIV virions are exposed to AZT or finches

are exposed to changes in seed availability, those selected individuals are not changed

They just live through selection event and produce more offspring than others

The populations of finches or virions then change, not the individuals

Natural selection acts on individuals but evolution occurs in populations When HIV virions are exposed to AZT or finches

are exposed to changes in seed availability, those selected individuals are not changed

They just live through selection event and produce more offspring than others

The populations of finches or virions then change, not the individuals


Natural selection acts on phenotypes, but evolution changes allele frequencies If deep beaks had not been heritable, the deep

beaked individuals would have survived the drought, but evolution could not have occurred because the trait would not be passed on to the offspring

The next generation would still have a wide range of beak depths

Natural selection can only act on traits that have a genetic basis

Natural selection acts on phenotypes, but evolution changes allele frequencies If deep beaks had not been heritable, the deep

beaked individuals would have survived the drought, but evolution could not have occurred because the trait would not be passed on to the offspring

The next generation would still have a wide range of beak depths

Natural selection can only act on traits that have a genetic basis


Natural selection is backward looking, not forward looking Each generation is a product of selection by the

environmental conditions from the generation before

AZT resistant virions and deep beaked finches are well adapted to the situations introduced in their parent’s generation

If there is a new environmental change, they may not be well adapted to it

Organisms cannot adapt to future conditions, only those in the past

Natural selection is backward looking, not forward looking Each generation is a product of selection by the

environmental conditions from the generation before

AZT resistant virions and deep beaked finches are well adapted to the situations introduced in their parent’s generation

If there is a new environmental change, they may not be well adapted to it

Organisms cannot adapt to future conditions, only those in the past


Natural selection can produce new traits, even though it acts on existing traits Can select from variation present

Cannot instantly create a new beak for cracking a certain fruit

Over time, natural selection can produce new traits

New mutations every generation for natural selection to act upon

Natural selection can produce new traits, even though it acts on existing traits Can select from variation present

Cannot instantly create a new beak for cracking a certain fruit

Over time, natural selection can produce new traits

New mutations every generation for natural selection to act upon


Artificial selection experiment Started with 163 ears of corn Found variation of 4–6% oil content Selected 24 ears with highest oil content per

generation for 60 years Now those ears have 16% oil No overlap with original population Evolution produced a new trait

Artificial selection experiment Started with 163 ears of corn Found variation of 4–6% oil content Selected 24 ears with highest oil content per

generation for 60 years Now those ears have 16% oil No overlap with original population Evolution produced a new trait


Natural selection can also lead to novel traits Selection can repurpose traits for new

functions Giant panda’s thumb

Used to strip bamboo stalks “thumb” is actually a wrist bone modified to act as a

thumb Must have been variation in size of wrist bone and

selection for elongation Preadaptation, or exaptation

Natural selection can also lead to novel traits Selection can repurpose traits for new

functions Giant panda’s thumb

Used to strip bamboo stalks “thumb” is actually a wrist bone modified to act as a

thumb Must have been variation in size of wrist bone and

selection for elongation Preadaptation, or exaptation

Giant Panda’s ThumbGiant Panda’s Thumb


Natural selection is not perfect Can only work with variation present Finches with deep, narrow beaks can break hard

seeds the best Most of the selected birds had wide beaks

Genes for wide beaks and deeps beaks must be linked

Natural selection could not make the perfect beak because the genes for it were not present

Adaptation, not perfection

Natural selection is not perfect Can only work with variation present Finches with deep, narrow beaks can break hard

seeds the best Most of the selected birds had wide beaks

Genes for wide beaks and deeps beaks must be linked

Natural selection could not make the perfect beak because the genes for it were not present

Adaptation, not perfection


Natural selection is nonrandom, but not progressive Natural selection increases adaptation

but is not directional We see trend to increased complexity but

some organisms decrease in complexity Tapeworm Snake Cave fish

Natural selection is nonrandom, but not progressive Natural selection increases adaptation

but is not directional We see trend to increased complexity but

some organisms decrease in complexity Tapeworm Snake Cave fish


Natural selection acts on individuals, not groups Organisms are never self-sacrificing or

altruistic Only endanger themselves for selfish gain

Prairie dog alarm calls Lions nursing other cubs

Do so because of relatedness or reciprocity

Natural selection acts on individuals, not groups Organisms are never self-sacrificing or

altruistic Only endanger themselves for selfish gain

Prairie dog alarm calls Lions nursing other cubs

Do so because of relatedness or reciprocity

The Evolution of DarwinismThe Evolution of Darwinism

Since Darwin did not know about mutation, he had no idea how variation was generated in populations

Since Darwin did not know about genetics, he did not understand how variations were passed to offspring The Idea of blending inheritance

Since Darwin did not know about mutation, he had no idea how variation was generated in populations

Since Darwin did not know about genetics, he did not understand how variations were passed to offspring The Idea of blending inheritance

The (Wrong) Idea of Blending InheritanceThe (Wrong) Idea of Blending Inheritance

Genes are like pigments in paint... Mixing two colors of paint (i.e., the mixing

of genes from parents) would result in an even blend of traits (in offspring)...

We know this is not the case... although some phenotypes of offspring may be

intermediate between those of parents GENOTYPES ARE DISTINCT, DISCRETE

CHARACTERS! E.g. Mammalian Hair Color...

Genes are like pigments in paint... Mixing two colors of paint (i.e., the mixing

of genes from parents) would result in an even blend of traits (in offspring)...

We know this is not the case... although some phenotypes of offspring may be

intermediate between those of parents GENOTYPES ARE DISTINCT, DISCRETE

CHARACTERS! E.g. Mammalian Hair Color...

Evolution of DarwinismEvolution of Darwinism

Evolution is the unifying theory of biology

Was not the standard in biology until 70 years after Darwin’s publication

Darwin’s ideas had three problems that had to be solved before full acceptance on evolution by natural selection

Evolution is the unifying theory of biology

Was not the standard in biology until 70 years after Darwin’s publication

Darwin’s ideas had three problems that had to be solved before full acceptance on evolution by natural selection

History of Evolutionary Thought History of Evolutionary Thought

I. Early Ideas of Change the Greeks

II. Darwinian Revolution Intellectual environment pre-Darwin Change as

a concept Darwin and contemporaries III. Post Darwin

Blending Inheritance Mendel Biometrics IV. The Modern Synthesis

Hardy-Weinberg Dobzhansky Haldane, Fisher, Wright Recent innovations

I. Early Ideas of Change the Greeks

II. Darwinian Revolution Intellectual environment pre-Darwin Change as

a concept Darwin and contemporaries III. Post Darwin

Blending Inheritance Mendel Biometrics IV. The Modern Synthesis

Hardy-Weinberg Dobzhansky Haldane, Fisher, Wright Recent innovations

Natural Selection (by Darwin and Wallace)Natural Selection (by Darwin and Wallace)

Did not incorporate any element of inheritance, taken for granted

that parents produce like offspring

Did not incorporate any element of inheritance, taken for granted

that parents produce like offspring


Darwin did not know how variability was created Thought that variation in organisms would

be used up eventually New variation created continuously by

mutation

Darwin did not know how variability was created Thought that variation in organisms would

be used up eventually New variation created continuously by

mutation


Darwin did not know how traits were inherited Believed in blending inheritance

Individual traits would be lost by merging with other traits

After Mendel was re-discovered we know that alleles are inherited independently

Darwin did not know how traits were inherited Believed in blending inheritance

Individual traits would be lost by merging with other traits

After Mendel was re-discovered we know that alleles are inherited independently

Mendelian inheritanceMendelian inheritance

Gregor Mendel (Czech Monk) performed experiments demonstrating particulate inheritance in mid 1800's but they were unknown until "rediscovered" by De Vries and Tschermak

Initially a great blow, because characters that are controlled by one or a few loci exhibit discrete variation -- differences between genotypes was too big to fit into Darwin's theory

Gregor Mendel (Czech Monk) performed experiments demonstrating particulate inheritance in mid 1800's but they were unknown until "rediscovered" by De Vries and Tschermak

Initially a great blow, because characters that are controlled by one or a few loci exhibit discrete variation -- differences between genotypes was too big to fit into Darwin's theory

The Modern SynthesisThe Modern Synthesis

For first 70 years after Origin of Species was published, biology was in turmoil

Between 1932 and 1953 the Modern Synthesis answered Darwin’s original problems with new data

For first 70 years after Origin of Species was published, biology was in turmoil

Between 1932 and 1953 the Modern Synthesis answered Darwin’s original problems with new data

Biometricians Biometricians

Karl Pearson, August Weismann, Francis Galton were demonstrating that most genes have only small effect, and that most variation is continuous

(eg, body size, speed, vs eye color) this fit fine into Darwinian theory

Karl Pearson, August Weismann, Francis Galton were demonstrating that most genes have only small effect, and that most variation is continuous

(eg, body size, speed, vs eye color) this fit fine into Darwinian theory


Again around the 1930's, Natural Selection and gradual evolution started to come back, primarily through the efforts of a few geneticists responsible for what is now called the New Synthesis or Neo-Darwinian theory.

Primarily combines genetics, mathematics and evolutionary theory into a set of ideas called population genetics

Again around the 1930's, Natural Selection and gradual evolution started to come back, primarily through the efforts of a few geneticists responsible for what is now called the New Synthesis or Neo-Darwinian theory.

Primarily combines genetics, mathematics and evolutionary theory into a set of ideas called population genetics


Grounded in two propositions Gradual evolution results from small

genetic changes that are acted upon by natural selection

The origin of species and higher taxa, macroevolution, can be explained in terms of natural selection acting on individuals, microevolution

Grounded in two propositions Gradual evolution results from small

genetic changes that are acted upon by natural selection

The origin of species and higher taxa, macroevolution, can be explained in terms of natural selection acting on individuals, microevolution

Hardy-Weinberg (-Castle) theorem Hardy-Weinberg (-Castle) theorem

A demonstration that frequencies of genes do not change from one generation to the next if all members mate at random and there is no advantage to any gene. This is the foundation of all population genetics, because by adding terms for selection and migration, it can be shown that gene frequencies do change in the face of very weak forces.

A demonstration that frequencies of genes do not change from one generation to the next if all members mate at random and there is no advantage to any gene. This is the foundation of all population genetics, because by adding terms for selection and migration, it can be shown that gene frequencies do change in the face of very weak forces.

The MODERN SYNTHESIS The MODERN SYNTHESIS

Theodosius Dobzhansky (1900-1975)Theodosius Dobzhansky (1900-1975)

With fruitflies, revealed hidden genetic variation and demonstrated that the differences between races and species were genetic --- led to the understanding that species are not "morpho-types" but variable populations that are reproductively isolated from one another

One of the main fathers of the New Synthesis, by combining genetics with the more established views of evolutionary process

With fruitflies, revealed hidden genetic variation and demonstrated that the differences between races and species were genetic --- led to the understanding that species are not "morpho-types" but variable populations that are reproductively isolated from one another

One of the main fathers of the New Synthesis, by combining genetics with the more established views of evolutionary process


Other Major PlayersOther Major Players

Sewall Wright: used Guinea pig as eraser, worked on polydactyly and coat color in guinea pigs. He was an intimidating mathematician, pioneer in multivariate approaches to evolution. Developed shifting balance theory of maintenance of variation

R. A. Fisher: Competing mathematician and father of linear statistics (Regression); "The Genetical Theory of Natural Selection"

Sewall Wright: used Guinea pig as eraser, worked on polydactyly and coat color in guinea pigs. He was an intimidating mathematician, pioneer in multivariate approaches to evolution. Developed shifting balance theory of maintenance of variation

R. A. Fisher: Competing mathematician and father of linear statistics (Regression); "The Genetical Theory of Natural Selection"


Recent Innovations Recent Innovations

Cladistics -- Willi Hennig, a new and more rigorous means of approaching questions of relationship founded on a specific model of evolution including parsimony

Neutral Theory -- Mootoo Kimura, suggested that most evolution is neutral and has no effect on the phenotype, based on the idea that most changes to DNA do not have noticeable effects on phenotype

Cladistics -- Willi Hennig, a new and more rigorous means of approaching questions of relationship founded on a specific model of evolution including parsimony

Neutral Theory -- Mootoo Kimura, suggested that most evolution is neutral and has no effect on the phenotype, based on the idea that most changes to DNA do not have noticeable effects on phenotype

Recent Challenges or InnovationsRecent Challenges or Innovations

Punctuated equilibrium -- Stephen Jay Gould & Niles Eldridge, later Stephen Stanley; motivated by observation that fossil record tends to reflect a less continuous change than expected by gradual change. Referred to by some as “evolution by jerks”. Non-constant mode and rate of evolution, at times suggested that most evolutionary change occurs at level of species-selection

Punctuated equilibrium -- Stephen Jay Gould & Niles Eldridge, later Stephen Stanley; motivated by observation that fossil record tends to reflect a less continuous change than expected by gradual change. Referred to by some as “evolution by jerks”. Non-constant mode and rate of evolution, at times suggested that most evolutionary change occurs at level of species-selection


Can re-state Darwin’s postulates As a result of mutation creating new

alleles, and segregation and independent assortment shuffling alleles into new combinations, individuals within populations are variable for nearly all traits

Individuals pass their alleles on to their offspring

Can re-state Darwin’s postulates As a result of mutation creating new




Can re-state Darwin’s postulates In most generations, more offspring are

produced than can survive

Individuals that survive and reproduce, or who reproduce the most, are those with alleles and allelic combinations that best adapt them to their environment

Can re-state Darwin’s postulates In most generations, more offspring are




We also now know, as Darwin suspected, that natural selection is not the only cause of evolution

It is usually the primary cause

Will examine other mechanisms for evolution later in the course

We also now know, as Darwin suspected, that natural selection is not the only cause of evolution

It is usually the primary cause

Will examine other mechanisms for evolution later in the course

Scientific Creationism DebateScientific Creationism Debate

Evolution totally accepted by biologists since Modern Synthesis

Political and philosophical controversy still exists in U.S.

Scopes Monkey Trial of 1925 John Scopes taught evolution to his

students despite a Tennessee law preventing the teaching of Darwinism

Evolution totally accepted by biologists since Modern Synthesis

Political and philosophical controversy still exists in U.S.

Scopes Monkey Trial of 1925 John Scopes taught evolution to his

students despite a Tennessee law preventing the teaching of Darwinism


Scopes Monkey Trial of 1925 A widely publicized trial William Jennings Bryan prosecutor Clarence Darrow defense attorney The prosecution won but Scopes was only

fined $100 and the prosecution looked ridiculous in their arguments

Considered a win for Darwinism

Scopes Monkey Trial of 1925 A widely publicized trial William Jennings Bryan prosecutor Clarence Darrow defense attorney The prosecution won but Scopes was only

fined $100 and the prosecution looked ridiculous in their arguments

Considered a win for Darwinism


In 1967 U.S. Supreme Court struck down state laws prohibiting teaching of evolution

Fundamentalists reformed argument to be called Creation Science Wanted equal time in schools

In 1987 Supreme Court declared a religious idea could not be taught in public schools Violates first amendment

In 1967 U.S. Supreme Court struck down state laws prohibiting teaching of evolution

Fundamentalists reformed argument to be called Creation Science Wanted equal time in schools

In 1987 Supreme Court declared a religious idea could not be taught in public schools Violates first amendment


Recently, a new name (with similar ideas) has been used for the creationist viewpoint: Intelligent Design Theory Discuss “organs of extreme perfection” The vertebrate eye example... William Paley in 1802 stated that if you found

a watch you would assume that it had to be made by an intelligent creator

He said it is the same for the vertebrate eye It is too intricate and complex to arise from

random events

Recently, a new name (with similar ideas) has been used for the creationist viewpoint: Intelligent Design Theory Discuss “organs of extreme perfection” The vertebrate eye example... William Paley in 1802 stated that if you found

a watch you would assume that it had to be made by an intelligent creator

He said it is the same for the vertebrate eye It is too intricate and complex to arise from

random events


Of course, natural selection is not random

According to Darwin, the vertebrate eye must have arisen from simpler eyes that evolved in grades

Found examples of intermediate eyes from other living organisms that probably mimic the evolutionary pathway of the vertebrate eye

Of course, natural selection is not random

According to Darwin, the vertebrate eye must have arisen from simpler eyes that evolved in grades

Found examples of intermediate eyes from other living organisms that probably mimic the evolutionary pathway of the vertebrate eye

Variation in mollusc eyesVariation in mollusc eyes

Simple pigmented spot

Simple pigmented cup

Optic cup in Abalone

Complex lensed eyes of marine snail Littorina

Complex lensed eyes of an octopus

Simple pigmented spot

Simple pigmented cup

Optic cup in Abalone

Complex lensed eyes of marine snail Littorina

Complex lensed eyes of an octopus

Another arguement that has been used to discount evolution..:

Irreducibility complex – single system in which all of its multiple parts are required for function

Eukaryotic flagella example

Is it reasonable to think that multiple complex parts can be derived evolutionarily through the mechanisms we know operate in nature??

Co-option of Crystalline genes example...

Another arguement that has been used to discount evolution..:

Irreducibility complex – single system in which all of its multiple parts are required for function

Eukaryotic flagella example

Is it reasonable to think that multiple complex parts can be derived evolutionarily through the mechanisms we know operate in nature??

Co-option of Crystalline genes example...


Gene co-option crystallins of animal eye lensesGene co-option crystallins of animal eye lenses


“Because organisms progress from simpler to more complex forms evolution violates the second law of thermodynamics” Organisms do not necessarily evolve to

be more complex The second law, entropy, only applies to

closed systems The earth is an open system with plants

capturing light from the sun

“Because organisms progress from simpler to more complex forms evolution violates the second law of thermodynamics” Organisms do not necessarily evolve to

be more complex The second law, entropy, only applies to

closed systems The earth is an open system with plants

capturing light from the sun

SummarySummary

For our purposes, we need to remember that if we are discussing science, evidence must be allowed to make scientific decisions

The evidence for evolution is compelling and, single handedly, explains essentially all facets of patterns in biology

It is important to recognize the simplistic requirements for evolution, upon which we will continue to build details and examples for the next several months...

For our purposes, we need to remember that if we are discussing science, evidence must be allowed to make scientific decisions

The evidence for evolution is compelling and, single handedly, explains essentially all facets of patterns in biology

It is important to recognize the simplistic requirements for evolution, upon which we will continue to build details and examples for the next several months...


Restating Darwin’s postulates As a result of mutation creating new



Restating Darwin’s postulates As a result of mutation creating new




Restating Darwin’s postulates In most generations, more offspring are



Restating Darwin’s postulates In most generations, more offspring are



chapter 3 darwinian natural selection. the mechanism of natural selection in the last chapter we...

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