Evidence for evolution In the early 1800’s prevailing belief was that: organisms were specially...

Evidence for evolutionEvidence for evolution

In the early 1800’s prevailing belief was In the early 1800’s prevailing belief was that:that: organisms were specially created and organisms were specially created and

unchanged since their creationunchanged since their creation Species created independently of each other Species created independently of each other Earth not old. Ussher’s estimate: for Earth’s Earth not old. Ussher’s estimate: for Earth’s

creation 4004 BCcreation 4004 BC

LamarckLamarck

Fact of evolution proposed in late 1700’s Fact of evolution proposed in late 1700’s early 1800’s.early 1800’s.

Jean Baptiste Lamarck 1809, 1815 Jean Baptiste Lamarck 1809, 1815 proposed that all species were derived by proposed that all species were derived by gradual evolution from other species.gradual evolution from other species.

Lamarck’s idea was that evolution was Lamarck’s idea was that evolution was driven by an innate tendency of organisms driven by an innate tendency of organisms to become more complex over time.to become more complex over time.

Inheritance of Acquired Inheritance of Acquired CharacteristicsCharacteristics

Lamarck’s proposed mechanism of Lamarck’s proposed mechanism of evolution was called the evolution was called the Inheritance of Inheritance of Acquired CharacteristicsAcquired Characteristics (IAC) (IAC)

IAC suggested that modifications to IAC suggested that modifications to organisms during their life could be organisms during their life could be passed on to their offspring (e.g., a giraffe passed on to their offspring (e.g., a giraffe stretching its neck during its life passes stretching its neck during its life passes slightly longer neck to offspring).slightly longer neck to offspring).

Inheritance of Acquired Inheritance of Acquired CharacteristicsCharacteristics

Obviously, Lamarck’s ideas about the Obviously, Lamarck’s ideas about the mechanism of evolution largely contradict mechanism of evolution largely contradict current biological knowledge.current biological knowledge.

The information required to build a body is The information required to build a body is stored in DNA and that information (influenced stored in DNA and that information (influenced by the environment) determines the phenotype. by the environment) determines the phenotype. Changes to the phenotype during life however Changes to the phenotype during life however do not affect the DNA sequence. Information do not affect the DNA sequence. Information flow is thus only in one direction from DNA flow is thus only in one direction from DNA phenotype, not in the reverse direction.phenotype, not in the reverse direction.

EpigeneticsEpigenetics

However, recent research in the emerging However, recent research in the emerging field of epigenetics shows that Lamarckian field of epigenetics shows that Lamarckian effects may occur through changes in the effects may occur through changes in the control of gene expression caused by control of gene expression caused by environmental effects e.g. food shortage environmental effects e.g. food shortage during development. during development.


Epigenetics is the study of heritable changes in Epigenetics is the study of heritable changes in gene expression caused by mechanisms other gene expression caused by mechanisms other than changes in the DNA sequence.than changes in the DNA sequence.

The DNA nucleotide sequence is not changed The DNA nucleotide sequence is not changed but whether and how much genes are expressed but whether and how much genes are expressed can be altered and some of these changes may can be altered and some of these changes may be passed from one generation to another.be passed from one generation to another.


One way in which epigenetic effects have been One way in which epigenetic effects have been shown to occur is through environmentally shown to occur is through environmentally induced methylation in which a methyl group induced methylation in which a methyl group (CH(CH33) is added to cytosine nucleotides ) is added to cytosine nucleotides

converting them to 5-methyl-cytosine.converting them to 5-methyl-cytosine.

More heavily methylated regions are translated More heavily methylated regions are translated and transcribed less frequently than non-and transcribed less frequently than non-methylated regions.methylated regions.


One well documented example of epigenetic effects One well documented example of epigenetic effects resulted from the Dutch winter famine of 1944/45 at the resulted from the Dutch winter famine of 1944/45 at the end of WWII.end of WWII.

The children of women pregnant during the famine were The children of women pregnant during the famine were born smaller than normal (which was to be expected). born smaller than normal (which was to be expected).

However, the children of those children were also born However, the children of those children were also born smaller than average. This suggests the famine induced smaller than average. This suggests the famine induced epigenetic changes in mothers pregnant during the epigenetic changes in mothers pregnant during the famine that were passed to their offspring. famine that were passed to their offspring.

Charles Darwinpublished“On the origin of species”in 1859.

Charles Darwin (1809-1882)Charles Darwin (1809-1882)

Son of a wealthy doctor. Son of a wealthy doctor. Dropped out of medical school.Dropped out of medical school. Studied theology, but was much more Studied theology, but was much more

interested in natural history (e.g. he had a interested in natural history (e.g. he had a large insect collection).large insect collection).

After college signed on as captain’s After college signed on as captain’s companion on companion on TheThe BeagleBeagle. .

Voyage of the Voyage of the BeagleBeagle

Darwin companion for Captain Fitzroy on

Voyage of The Beagle (1831-1836). The Beagle’s mission was to map the

coast of South America, but the ship traveled around the World.

Sites visited included Galapagos Islands a group of volcanic islands (hence of recent origin) off the coast of Ecuador.

Galapagos Giant Tortoise

Unique animals on Galapagos includegiant tortoises, marine iguanas, and Darwin’s finches.

Sharp-beakedGround Finch

Influence of geological thinking on Influence of geological thinking on DarwinDarwin

By the time of “The Beagle” voyage the By the time of “The Beagle” voyage the idea that Earth was young was being idea that Earth was young was being challenged.challenged.

Opposition based on principle of Opposition based on principle of Uniformitarianism. Uniformitarianism.

This is the idea that geological processes This is the idea that geological processes happening today are the same as have happening today are the same as have operated in the past.operated in the past.


Uniformitarianism contrasted with Uniformitarianism contrasted with CatastrophismCatastrophism which proposed that which proposed that current geological formations had resulted current geological formations had resulted from catastrophic events (such as the from catastrophic events (such as the biblical flood) which occurred on scale biblical flood) which occurred on scale unknown today.unknown today.

Uniformitarianism first proposed by James Uniformitarianism first proposed by James Hutton and championed by Charles Lyell.Hutton and championed by Charles Lyell.


During the voyage Darwin read Lyell’s new book During the voyage Darwin read Lyell’s new book “Principles of Geology.”“Principles of Geology.”

Lyell emphasized two points:Lyell emphasized two points: 1. 1. GradualismGradualism: Geological features can be : Geological features can be

explained by the slow gradual action of explained by the slow gradual action of processes we observe every day e.g. erosion processes we observe every day e.g. erosion by wind and water, deposition of sediments in by wind and water, deposition of sediments in rivers.rivers.

2. 2. The Earth is very oldThe Earth is very old: there has been lots of : there has been lots of time for change to occur. time for change to occur.


Hutton and Lyell inferred Earth must be Hutton and Lyell inferred Earth must be very old based on measurements of rate very old based on measurements of rate of ongoing rock forming processes (e.g. of ongoing rock forming processes (e.g. deposition of mud and sand).deposition of mud and sand).

These developments in geology focused These developments in geology focused Darwin on the potential importance of Darwin on the potential importance of gradual changegradual change in shaping structures. in shaping structures.

What Darwin observedWhat Darwin observed

On the voyage Darwin noted many things On the voyage Darwin noted many things that were puzzling from the point of view of that were puzzling from the point of view of a creationist explanation for the diversity of a creationist explanation for the diversity of life.life.

What Darwin observedWhat Darwin observed 1. South American fossils resembled living 1. South American fossils resembled living

South American animals. South American animals. 2. Parts of the world with similar habitats and 2. Parts of the world with similar habitats and

climates (e.g. Australia and South America) are climates (e.g. Australia and South America) are populated by very different animals.populated by very different animals.

3. Plants and animals on each continent are 3. Plants and animals on each continent are different from those on other continents.different from those on other continents.

4. Many species on remote oceanic islands are 4. Many species on remote oceanic islands are found only there (endemic).found only there (endemic).

5. Endemic species on islands closely resemble 5. Endemic species on islands closely resemble species found on adjacent mainland.species found on adjacent mainland.

What Darwin observedWhat Darwin observed

These observations taken together don’t make These observations taken together don’t make sense if organisms were specially created. sense if organisms were specially created. Why should similar habitats in different parts of the Why should similar habitats in different parts of the

world have different faunas?world have different faunas? Why should remote islands have unique faunas that Why should remote islands have unique faunas that

differ from but resemble those on adjacent land differ from but resemble those on adjacent land masses?masses?

Together these observations suggested to Together these observations suggested to Darwin that species Darwin that species change over timechange over time i.e., that i.e., that evolution occurs.evolution occurs.

Darwin and WallaceDarwin and Wallace

After returning from the voyage Darwin spent more than After returning from the voyage Darwin spent more than 20 years developing his ideas and gathering the evidence 20 years developing his ideas and gathering the evidence to support them. to support them.

In 1858 Charles Darwin and Alfred Russel Wallace jointly In 1858 Charles Darwin and Alfred Russel Wallace jointly proposed natural selection as the proposed natural selection as the primaryprimary mechanismmechanism by by which evolution takes place.which evolution takes place.

In 1859 Darwin published his book On the Origin of In 1859 Darwin published his book On the Origin of Species, which summarized his ideas about evolution and Species, which summarized his ideas about evolution and presented the evidence to support them.presented the evidence to support them.

The “modern synthesis”The “modern synthesis”

Idea of evolution was accepted rapidly by Idea of evolution was accepted rapidly by scientists.scientists.

Lack of understanding of heredity and Lack of understanding of heredity and population genetics, however, prevented natural population genetics, however, prevented natural selection being accepted as the principal selection being accepted as the principal mechanism of evolution until 1930’s.mechanism of evolution until 1930’s.

The “Modern Synthesis” in the 1930’s of The “Modern Synthesis” in the 1930’s of combined the ideas of population genetics and combined the ideas of population genetics and natural selection to explain gradual evolution, natural selection to explain gradual evolution, speciation, and macroevolution. speciation, and macroevolution.

Evidence for EvolutionEvidence for Evolution

Evidence of change in organisms over Evidence of change in organisms over timetime

An example in a living species:An example in a living species: evolution of beak length in soapberry bugs.evolution of beak length in soapberry bugs. Soapberry bugs use long beak to penetrate Soapberry bugs use long beak to penetrate

seeds in fruits and eat them.seeds in fruits and eat them. Native host plant is balloon vine which has Native host plant is balloon vine which has

thick fruits.thick fruits.

Evolution of Soapberry BugsEvolution of Soapberry Bugs

In 1926 flat-podded Golden rain tree In 1926 flat-podded Golden rain tree introduced to Florida. Has thin fruits.introduced to Florida. Has thin fruits.

Today soapberry bugs feeding on Golden Today soapberry bugs feeding on Golden rain trees have much shorter beaks than rain trees have much shorter beaks than those living on balloon vines.those living on balloon vines.

Comparison of beaklengths in areaswith and withoutgolden rain trees

Data from museumspecimens documents change in beak lengthover time.

Antibiotic resistance in bacteriaAntibiotic resistance in bacteria

In 1947 only four years after the mass In 1947 only four years after the mass production of penicillin began resistant strains of production of penicillin began resistant strains of StaphylococcusStaphylococcus aureus aureus began to be reported.began to be reported.

Antibiotic resistance is now widespread and in Antibiotic resistance is now widespread and in the US half of all the US half of all S. aureusS. aureus infections are infections are resistant to multiple antibiotics including resistant to multiple antibiotics including penicillin, tetracycline, erythromicin and penicillin, tetracycline, erythromicin and methicillin. methicillin.

Antibiotic resistanceAntibiotic resistance

Bacteria have evolved resistance quickly Bacteria have evolved resistance quickly in part because of their rapid reproduction, in part because of their rapid reproduction, but also because antibiotics were misused but also because antibiotics were misused (e.g. by being overprescribed or (e.g. by being overprescribed or prescribed for non-bacterial infections and prescribed for non-bacterial infections and by people not completing their course of by people not completing their course of antibiotics)antibiotics)

The evidence for evolutionThe evidence for evolution

Fossil evidenceFossil evidence Vestigial structuresVestigial structures Homologous structuresHomologous structures Atavistic structuresAtavistic structures Other evidenceOther evidence

Jerry-rigged structuresJerry-rigged structures Adaptive radiationAdaptive radiation Artificial selectionArtificial selection

Fossil evidenceFossil evidence

Fossils are mineralized copies of the Fossils are mineralized copies of the remains of organisms preserved in remains of organisms preserved in sedimentary rocks.sedimentary rocks.

In the process of fossilization a dead In the process of fossilization a dead organism is covered by sediment and the organism is covered by sediment and the organic matter is replaced by minerals organic matter is replaced by minerals leaving behind an impression of the leaving behind an impression of the organism.organism.

Fossil evidence of evolutionFossil evidence of evolution

Millions of fossils have been collected and Millions of fossils have been collected and it is clear from fossil evidence that many it is clear from fossil evidence that many species (in fact almost all that have ever species (in fact almost all that have ever existed) have become extinct. existed) have become extinct.

Equally clearly the faunas of different Equally clearly the faunas of different geological eras are very different and have geological eras are very different and have changed over time.changed over time.


Law of Succession: Fossil and living Law of Succession: Fossil and living organisms in same area are related to organisms in same area are related to each other and differ from organisms in each other and differ from organisms in other areas.other areas.

South America contains both fossil and South America contains both fossil and living armadillosliving armadillos

Extinct glyptodont (2,000 kg) resembles themodern-day South American armadillo (2 kg).


Similarly modern Australia is filled with Similarly modern Australia is filled with marsupials and fossils in Australia are of marsupials and fossils in Australia are of similar marsupial forms.similar marsupial forms.

Extinct short-faced kangaroo.Extinct short-faced kangaroo.

http://msnbcmedia2.msn.com/j/msnbc/Components/Photos/061226/061226_kangaroo_vmed_1p.widec.jpg


Transitional formsTransitional forms If fossil organisms are ancestral to modern If fossil organisms are ancestral to modern

organisms then there should be organisms then there should be transitional fossils that show transitional fossils that show characteristics intermediate between the characteristics intermediate between the older and more recent groups. older and more recent groups.

ArchaeopteryxArchaeopteryx

ArchaeopteryxArchaeopteryx the oldest known fossil bird the oldest known fossil bird (name means “ancient wing) has mix of (name means “ancient wing) has mix of reptilian and avian features.reptilian and avian features.

Reptilian: long tail, teeth, long clawed Reptilian: long tail, teeth, long clawed fingersfingers

Avian: feathers, ribs with uncinate Avian: feathers, ribs with uncinate processes, avian shoulder girdle.processes, avian shoulder girdle.

Archaeopteryx(oldest knownfossil bird)Jurassic 150mya

Evolution of mammalsEvolution of mammals There are numerous excellent fossil series that There are numerous excellent fossil series that

document the transitions from ancestral species document the transitions from ancestral species to later species.to later species.

For example: the evolution of mammals from For example: the evolution of mammals from synapsid reptiles. synapsid reptiles.

An extensive series of fossils documents the An extensive series of fossils documents the changes in the synapsid lower jaw from a jaw changes in the synapsid lower jaw from a jaw made of multiple bones to the modern mammals made of multiple bones to the modern mammals single dentary and the incorporation of some single dentary and the incorporation of some synapsid jaw bones into the inner ear.synapsid jaw bones into the inner ear.

www.mun.ca/biology/scarr/142019_QA_to_DS_jaws.jpg

http://www.talkorigins.org/faqs/comdesc/images/jaws2.gif

Tiktaalik roseaeTiktaalik roseae

Another example is the evolution of the first Another example is the evolution of the first amphibians from lobe finned fishes. amphibians from lobe finned fishes.

The transitional fossil The transitional fossil Tiktaalik roseaeTiktaalik roseae possesses an intermediate suites of characters.possesses an intermediate suites of characters.

It has fish-like scales, palate and jaws, but an It has fish-like scales, palate and jaws, but an amphibian-like mobile neck and head, an ear amphibian-like mobile neck and head, an ear that could hear in air, and the bones in its fins that could hear in air, and the bones in its fins are intermediate between those of fish such as are intermediate between those of fish such as EusthenopteronEusthenopteron and and PanderichthysPanderichthys and early and early amphibians such as amphibians such as AcanthostegaAcanthostega..

Tiktaalik roseae 375 mya

Figure 25.01a

http://images.google.com/imgres?imgurl=http://www.bringyou.to/apologetics/SynapsidReptileMammal.jpg&imgrefurl=http://www.bringyou.to/apologetics/p15.htm&usg=__xL62Y1igePmktGVlxKZ_0QKqfxo=&h=617&w=489&sz=118&hl=en&start=3&um=1&itbs=1&tbnid=pvmoIlV49CGugM:&tbnh=136&tbnw=108&prev=/images%3Fq%3Dsynapsid%2Bto%2Bmammals%2Bjaw%2Bevolution%26hl%3Den%26sa%3DG%26um%3D1

Vestigial structuresVestigial structures

Many organisms possess rudimentary or Many organisms possess rudimentary or functionless versions of body parts that functionless versions of body parts that function in close relatives/ancestors.function in close relatives/ancestors.

The fact that structures are rudimentary The fact that structures are rudimentary implies they had ancestors in which these implies they had ancestors in which these structures were functional. This suggests structures were functional. This suggests an evolutionary history.an evolutionary history.

Examples of Vestigial structures Examples of Vestigial structures

Cave populations of Mexican tetra fish Cave populations of Mexican tetra fish have eye sockets, but no eyes.have eye sockets, but no eyes.

Kiwis have tiny, stubby wingsKiwis have tiny, stubby wings Boas have tiny remnant hind limbsBoas have tiny remnant hind limbs

http://news.nationalgeographic.com/news/2006/02/images/060217_kiwi.jpg

Mexican Tetra

Human vestigial structuresHuman vestigial structures

Coccyx: vestigial tailbone at base of spine.Coccyx: vestigial tailbone at base of spine. Arrector pili muscle at base of hair follicles Arrector pili muscle at base of hair follicles

makes hair stand up.makes hair stand up. Appendix: reduced in size. Used in Appendix: reduced in size. Used in

digestion of cellulose in herbivores e.g. digestion of cellulose in herbivores e.g. rabbits.rabbits.

Vestigial developmental traitsVestigial developmental traits

Adult chickens: three bones in forefoot Adult chickens: three bones in forefoot (wing), four in hindfoot. (wing), four in hindfoot.

However, digit 5 appears briefly during However, digit 5 appears briefly during embryonic development before embryonic development before disappearing.disappearing.

Molecular vestigial traitsMolecular vestigial traits

Human genome contains large numbers of Human genome contains large numbers of pseudogenes that do not code for pseudogenes that do not code for functional RNA or proteins. These are functional RNA or proteins. These are leftovers from evolutionary history once leftovers from evolutionary history once functional genes that have been turned off.functional genes that have been turned off.

E.g. there are several pseudogenes of E.g. there are several pseudogenes of hemoglobin. May be as many as 6,000 hemoglobin. May be as many as 6,000 pseudogenes in human genome.pseudogenes in human genome.

Homologous structuresHomologous structures

Homologous structures are those constructed Homologous structures are those constructed from the same basic components which have from the same basic components which have been inherited from a common ancestor and been inherited from a common ancestor and then modified for different purposes.then modified for different purposes.

E.g. The forelimbs of a human, mole, horse, E.g. The forelimbs of a human, mole, horse, dolphin and bat are constructed from the same dolphin and bat are constructed from the same bones, but the bones differ in size and shape bones, but the bones differ in size and shape and the structures made from the bones are and the structures made from the bones are used in radically different ways.used in radically different ways.

Homologous structuresHomologous structures

Homologous structures make no sense if Homologous structures make no sense if organisms were specially created, but they organisms were specially created, but they do if a set of organisms share a common do if a set of organisms share a common ancestor and all inherited the same basic ancestor and all inherited the same basic bone structure from that ancestor.bone structure from that ancestor.

Homologous structures imply an Homologous structures imply an evolutionary history and common evolutionary history and common ancestry.ancestry.

FIG 2.11

Homologous structures (i.e. derived from a common ancestor). Even though the forelimbs have evolved to carry out very different tasks they are all constructedfrom the same bones.

Homology vs. Convergent Homology vs. Convergent EvolutionEvolution

Not all similarities between different species are due to Not all similarities between different species are due to homology.homology.

The streamlined shapes of sharks and whales are not a due to The streamlined shapes of sharks and whales are not a due to common ancestry but to common ancestry but to convergent evolutionconvergent evolution. .

The same selection pressures to be able to swim efficiently in The same selection pressures to be able to swim efficiently in water have independently produced similarly shaped bodies water have independently produced similarly shaped bodies instead of the traits being inherited from a recent common instead of the traits being inherited from a recent common ancestor.ancestor.

Homology vs. Convergent Homology vs. Convergent EvolutionEvolution

Whales and dolphins evolved from Whales and dolphins evolved from terrestrialterrestrial ancestors about 50 million years ago, whereas ancestors about 50 million years ago, whereas shark fossils as much as 350 million years old shark fossils as much as 350 million years old are known.are known.

The whales are most closely related to The whales are most closely related to artiodactyls (hoofed mammals that include deer artiodactyls (hoofed mammals that include deer and hippos) and both whales and deer evolved and hippos) and both whales and deer evolved from hoofed, carnivorous ancestors.from hoofed, carnivorous ancestors.

http://static.howstuffworks.com/gif/great-white-shark-1.jpg

www.seaworld.org/.../images/killer-whale.jpg

Homologous vs. Analagous Homologous vs. Analagous structuresstructures

Similarly, the wings of butterflies and birds Similarly, the wings of butterflies and birds are not homologous (because their are not homologous (because their structural components were not derived structural components were not derived from a recent common ancestor) but from a recent common ancestor) but perform the same function. perform the same function.

Such structures are analagous. They carry Such structures are analagous. They carry out the same function.out the same function.

Molecular HomologyMolecular Homology

All organisms (with a few minor exceptions) use All organisms (with a few minor exceptions) use the same genetic code to specify which the same genetic code to specify which sequences of bases specify which amino acids sequences of bases specify which amino acids when assembling proteins.when assembling proteins.

The reason the code is essentially universal is The reason the code is essentially universal is that a mutation that altered the code would alter that a mutation that altered the code would alter almost every protein produced and so would be almost every protein produced and so would be lethal.lethal.

Figure 1.1.1. The standard genetic code and known variant nuclear codes. (1) Candida, a unicellular yeast. (2) Micrococcus. (3) ciliated protozoans and green algae. (4) Mycoplasma. (5) suppressor codon in bacteria. (6) Euplotes. (7) the selenocysteine codon (8) Spiroplasma. (9) Micrococcus. (10) resume codon in ssrA RNA (Lehman 2001).

http://www.talkorigins.org/faqs/comdesc/section1.html

Molecular Homology: Genetic flaws Molecular Homology: Genetic flaws shared by different speciesshared by different species

Chromosome 17 in humans PMP22 gene Chromosome 17 in humans PMP22 gene has duplicate sequence of DNA (CMT1A has duplicate sequence of DNA (CMT1A repeat) on either side of it.repeat) on either side of it.

It is the result of duplication and insertion It is the result of duplication and insertion of DNA and occasionally causes of DNA and occasionally causes inaccurate crossing over during meiosis.inaccurate crossing over during meiosis.

Molecular HomologyMolecular Homology

Humans share CMT1A repeat with Humans share CMT1A repeat with bonobos and chimpanzees, but not bonobos and chimpanzees, but not gorillas, orang-utans or other primates.gorillas, orang-utans or other primates.

Suggests CMT1A derived from common Suggests CMT1A derived from common ancestor of bonobos, chimps and humans.ancestor of bonobos, chimps and humans.

Atavistic traitsAtavistic traits

Atavistic traits are anatomical Atavistic traits are anatomical “throwbacks” that occasionally occur when “throwbacks” that occasionally occur when a feature present in an ancestor reappears a feature present in an ancestor reappears in a modern organism.in a modern organism.

For example, occasionally horses are born For example, occasionally horses are born that have additional toes either side of that have additional toes either side of their hoof. Similarly, sometimes people their hoof. Similarly, sometimes people are born with a short tail.are born with a short tail.

http://atheistzoo.blogspot.com/2010/10/atavisms-blast-from-past.html


Such oddities are due to errors in Such oddities are due to errors in development that cause ancestral traits development that cause ancestral traits normally suppressed in the genome to be normally suppressed in the genome to be expressed.expressed.

The presence of genes for such traits The presence of genes for such traits indicate an evolutionary history.indicate an evolutionary history.


The embryos of a diverse array of The embryos of a diverse array of vertebrates are very similar in early vertebrates are very similar in early development.development.

Atavistic traits such as gill slits and a Atavistic traits such as gill slits and a postanal tail, which are not present in the postanal tail, which are not present in the adult appear briefly before disappearing adult appear briefly before disappearing later in development.later in development.

Other evidence for evolution: jerry-Other evidence for evolution: jerry-rigged structuresrigged structures

Jerry-rigged structures e.g. the Panda’s Jerry-rigged structures e.g. the Panda’s thumb.thumb.

In pandas, a wrist bone has been modified In pandas, a wrist bone has been modified into a “thumb” that is used to grip bamboo into a “thumb” that is used to grip bamboo stalks and assist in stripping leaves.stalks and assist in stripping leaves.

The “thumb” is not a very efficient solution The “thumb” is not a very efficient solution to the problem of bamboo stripping.to the problem of bamboo stripping.

http://www.athro.com/evo/pthumb.html

Panda’s ThumbPanda’s Thumb

Natural selection must work with the materialavailable to it. Process is more like someonetinkering in their workshop and assembling an object from spare parts than an engineer building a structure from scratch.

The jerry-rigged nature of the panda’s “thumb” implies pandas were not designed, but evolved.

Other evidence for evolution: Other evidence for evolution: adaptive radiationadaptive radiation

Adaptive radiation and clusters of species.Adaptive radiation and clusters of species.

Many remote islands are populated by Many remote islands are populated by morphologically diverse clusters of closely morphologically diverse clusters of closely related species.related species.

This pattern is difficult to explain without This pattern is difficult to explain without evolution.evolution.

Process of adaptive radiationProcess of adaptive radiation

Ancestral colonists arrive on island.Ancestral colonists arrive on island.

Shortage of resident species means many Shortage of resident species means many niches are unfilled.niches are unfilled.

Ancestral colonizing species gives rise to Ancestral colonizing species gives rise to many species that occupy unfilled niches.many species that occupy unfilled niches.

Adaptive radiationAdaptive radiation

Examples: Darwin’s finches on Examples: Darwin’s finches on Galapagos Island, Drosophila on Hawaiian Galapagos Island, Drosophila on Hawaiian Islands.Islands.

Darwin’s FinchesDarwin’s Finches

On Galapagos Islands there are 13 On Galapagos Islands there are 13 species of anatomically very different, but species of anatomically very different, but closely related species of finch.closely related species of finch.

They differ greatly in beak size and diet They differ greatly in beak size and diet having evolved very different lifestyles.having evolved very different lifestyles.

Hawaiian DrosophilaHawaiian Drosophila

More than 25% of the world’s 1,250 species of Drosophila fruit flies found on Hawaiian Islands.

Few insect competitors so Drosophila have diversified to fill large number of niches.

If faunas were created why are If faunas were created why are there woodpecker finches, but no there woodpecker finches, but no woodpeckers on the Galapagos woodpeckers on the Galapagos

Islands?Islands?

Artificial SelectionArtificial Selection

Artificial Selection. Humans as the agents of Artificial Selection. Humans as the agents of selection have selectively bred for desirable selection have selectively bred for desirable traits in domestic animals and plants for traits in domestic animals and plants for thousands of years.thousands of years.

The tremendous diversity of body forms that The tremendous diversity of body forms that have been produced in domestic dogs in very have been produced in domestic dogs in very few generations show how quickly organisms few generations show how quickly organisms can change in response to selection.can change in response to selection.

Tameness in silver foxesTameness in silver foxes

One excellent example of artificial selection is One excellent example of artificial selection is Dimitri Belyaev’s work to breed tame Silver Dimitri Belyaev’s work to breed tame Silver foxes.foxes.

In each generation he bred only from the tamest In each generation he bred only from the tamest individuals and in only six generations was able individuals and in only six generations was able to produce foxes that were eager for human to produce foxes that were eager for human contact and behaved like domestic dogs rather contact and behaved like domestic dogs rather than foxes.than foxes.

Tameness in silver foxesTameness in silver foxes

After about 30 generations 70-80% of the After about 30 generations 70-80% of the experimental population displayed extreme experimental population displayed extreme tameness.tameness.

In addition many foxes lots their fox-like look, In addition many foxes lots their fox-like look, became piebald and resembled Welsh collies. became piebald and resembled Welsh collies. These were side-effects of selection for These were side-effects of selection for tameness (an example of pleiotropy: genes tameness (an example of pleiotropy: genes having more than one effect).having more than one effect).

Silver fox after multiple generations of selection for tameness (upper left)

http://www.nature.com/scitable/nated/content/42740/Belyaev_foxes_MED.jpg

Creationism and “Intelligent Creationism and “Intelligent Design”Design”

The idea of evolution has been harshly criticized The idea of evolution has been harshly criticized by religious fundamentalists since the by religious fundamentalists since the publication of the Origin in 1859. publication of the Origin in 1859.

This has been especially true in the U.S. This has been especially true in the U.S.

Repeatedly, believers in the literal truth of the Repeatedly, believers in the literal truth of the Bible have attempted to have alternatives to Bible have attempted to have alternatives to evolution (i.e., creationism) taught in the public evolution (i.e., creationism) taught in the public schools and to have the teaching of evolution schools and to have the teaching of evolution either banned or restricted.either banned or restricted.


The U.S. Supreme Court has prohibited The U.S. Supreme Court has prohibited the teaching of creationism in public the teaching of creationism in public schools as a violation of the establishment schools as a violation of the establishment of religion clause of the Constitution.of religion clause of the Constitution.

Latest attempt to insert creationism into Latest attempt to insert creationism into schools is the idea of “Intelligent Design.”schools is the idea of “Intelligent Design.”


The concept of “intelligent design” is outlined The concept of “intelligent design” is outlined most clearly in Michael Behe’s book “Darwin’s most clearly in Michael Behe’s book “Darwin’s Black Box.”Black Box.”

The central idea in “intelligent design” is that The central idea in “intelligent design” is that some structures in the body are so complex that some structures in the body are so complex that they could not possibly have evolved by a they could not possibly have evolved by a gradual process of natural selection. These gradual process of natural selection. These structures are said to “irreducibly complex.”structures are said to “irreducibly complex.”


By “irreducibly complex” Behe means that By “irreducibly complex” Behe means that a complex structure cannot be broken a complex structure cannot be broken down into components that are down into components that are themselves functional and that the themselves functional and that the structure must have come into existence in structure must have come into existence in its complete form.its complete form.


If structures are “irreducibly complex” If structures are “irreducibly complex” Behe claims that they cannot have Behe claims that they cannot have evolved. Thus, their existence implies evolved. Thus, their existence implies they must have been created by a they must have been created by a designer (i.e. God, although the designer designer (i.e. God, although the designer is not explicitly referred to as such).is not explicitly referred to as such).


Behe’s main examples are various Behe’s main examples are various biochemical pathways in the body, the biochemical pathways in the body, the blood clotting system, and structures such blood clotting system, and structures such as the bacterial flagellum.as the bacterial flagellum.


Since the publication of Behe’s book, it Since the publication of Behe’s book, it has been demonstrated repeatedly that has been demonstrated repeatedly that things he has claimed to be irreducibly things he has claimed to be irreducibly complex are not in fact so.complex are not in fact so.

E.g. the flagellum in eel sperm lacks E.g. the flagellum in eel sperm lacks several of the components found in other several of the components found in other flagella, yet the flagellum functions well.flagella, yet the flagellum functions well.


The blood clotting system in dolphins lacks The blood clotting system in dolphins lacks at least one component that the human at least one component that the human system has, yet it too is functional.system has, yet it too is functional.

In addition, plausible gradual scenarios for In addition, plausible gradual scenarios for the evolution of biochemical pathways the evolution of biochemical pathways including the Kreb’s cycle have been including the Kreb’s cycle have been documented.documented.

Evolution of complex structuresEvolution of complex structures

The evolution of complex structures, such The evolution of complex structures, such as the eye, appears difficult, but natural as the eye, appears difficult, but natural selection achieves this by the slow selection achieves this by the slow accumulation of minor improvements from accumulation of minor improvements from one generation to the next.one generation to the next.


Each step on the evolutionary pathway from a Each step on the evolutionary pathway from a simple light sensing cell to a complex eye simple light sensing cell to a complex eye capable of focusing and producing color vision, capable of focusing and producing color vision, must be beneficial to the organism that possess must be beneficial to the organism that possess it and a slight improvement on earlier versions.it and a slight improvement on earlier versions.

It is not necessary for a structure to be perfect or It is not necessary for a structure to be perfect or even very good, it just needs to be better than even very good, it just needs to be better than the alternatives to be favored by selection.the alternatives to be favored by selection.

Variation in mollusc eyes from (a) pigment spot to (b) pigment cup to (c) simple optic cup in abalone to (d) complex lensed eyes in a marine snail and octopus.


Computer simulations suggest that eyes Computer simulations suggest that eyes can evolve easily and in nature eyes have can evolve easily and in nature eyes have evolved independently more than 40 evolved independently more than 40 times.times.

Evidence for evolution In the early 1800’s prevailing belief was that: organisms were specially...

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Transcript of Evidence for evolution In the early 1800’s prevailing belief was that: organisms were specially...