Origin of SpeciesOrigin of Species

Ch. 14Ch. 14

Pre-AP BiologyPre-AP Biology

Ms. HautMs. Haut

The origin of species is the The origin of species is the source of biological diversitysource of biological diversity SpeciationSpeciation, the origin of new species, the origin of new species

Is at the focal point of evolutionIs at the focal point of evolution

Figure 14.1

CONCEPTS OF SPECIESCONCEPTS OF SPECIES

What is a species?What is a species? Carolus Linnaeus, a Swedish physician and Carolus Linnaeus, a Swedish physician and

botanistbotanist Used physical characteristics to distinguish speciesUsed physical characteristics to distinguish species Developed the binomial system of naming organismsDeveloped the binomial system of naming organisms

Linnaeus’ system established the basis for Linnaeus’ system established the basis for taxonomytaxonomy The branch of biology concerned with naming and The branch of biology concerned with naming and

classifying the diverse forms of lifeclassifying the diverse forms of life

SpeciesSpecies

Similarities Similarities between some between some species and species and variation within a variation within a speciesspecies Can make defining Can make defining

species difficultspecies difficult

Figure 14.2B

Figure 14.2A

What is a species?What is a species?

The Biological Species ConceptThe Biological Species Concept The biological species concept defines a The biological species concept defines a

species asspecies as A population or group of populations whose A population or group of populations whose

members can interbreed and produce fertile members can interbreed and produce fertile offspringoffspring

Reproductively isolated by various factors Reproductively isolated by various factors preventing mixing with other speciespreventing mixing with other species

Reproductive barriers Reproductive barriers keep species separatekeep species separate

Reproductive Reproductive barriersbarriers Serve to isolate Serve to isolate

a species’ gene a species’ gene pool and pool and prevent prevent interbreedinginterbreeding

Are categorized Are categorized as prezygotic or as prezygotic or postzygoticpostzygoticTable 14.3

Prevent mating or fertilization between Prevent mating or fertilization between speciesspecies Habitat isolationHabitat isolation —species live in same general —species live in same general

area but not the same placesarea but not the same places Behavioral isolationBehavioral isolation —special signals recognized —special signals recognized Temporal isolationTemporal isolation —breeding occurs at different —breeding occurs at different

timestimes Mechanical isolationMechanical isolation —anatomically incompatible —anatomically incompatible Gametic isolationGametic isolation —gamete recognition —gamete recognition

Prezygotic BarriersPrezygotic Barriers

Two species breed at different timesTwo species breed at different times

Figure 14.3A

Temporal isolationTemporal isolation

There is little or no sexual attraction There is little or no sexual attraction between species, due to specific between species, due to specific behaviorsbehaviors

Figure 14.3B

Behavioral isolationBehavioral isolation

Figure 14.3C

Female and male sex organs or gametes Female and male sex organs or gametes are not compatibleare not compatible

Mechanical isolationMechanical isolation

Operate after hybrid zygotes are formedOperate after hybrid zygotes are formedPrevent the hybrid zygote from Prevent the hybrid zygote from developing into a viable, fertile adultdeveloping into a viable, fertile adult Reduced hybrid viabilityReduced hybrid viability —embryo —embryo

abortedaborted Reduced hybrid fertilityReduced hybrid fertility —offspring sterile —offspring sterile Hybrid breakdownHybrid breakdown —offspring of hybrids —offspring of hybrids

sterilesterile

Postzygotic BarriersPostzygotic Barriers

Figure 14.3D

Offspring between two species are Offspring between two species are sterile and therefore cannot matesterile and therefore cannot mate

Hybrid sterilityHybrid sterility

MECHANISMS OF MECHANISMS OF SPECIATIONSPECIATION

Geographic isolation can lead to Geographic isolation can lead to speciationspeciation In In allopatric speciationallopatric speciation

A population is geographically A population is geographically divided, and new species often evolvedivided, and new species often evolve

A. harrisi A. leucurus

Figure 14.4

Figure 14.9

Laboratory studies of fruit flies Laboratory studies of fruit flies Have shown that changes in food Have shown that changes in food

sources can cause speciationsources can cause speciation

Figure 14.5A

Starch medium Maltose medium

Initial sampleof fruit flies

Results ofmating experiments

Female Starch Maltose

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population populations

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Mating frequenciesin experimental group

Mating frequenciesin control group

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Reproductive barriers may Reproductive barriers may evolve as populations evolve as populations

divergediverge

Geographic isolation in Death Geographic isolation in Death ValleyValleyHas led to the evolution of new Has led to the evolution of new species of pupfishspecies of pupfish

Figure 14.5B A pupfish

Allopatric SpeciationAllopatric Speciation

http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm

http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm

Male pupfish

Pupfish: Example of Speciation

http://members.aol.com/OptiquesJN/death.htm

http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm

http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm

http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm

MECHANISMS OF MECHANISMS OF SPECIATIONSPECIATION

New species can also arise within New species can also arise within the same geographic area as the the same geographic area as the parent speciesparent species In In sympatric speciationsympatric speciation

New species may arise without New species may arise without geographic isolationgeographic isolation

Many plant species have evolved by Many plant species have evolved by polyploidypolyploidy Multiplication of the chromosome Multiplication of the chromosome

number due to errors in cell division number due to errors in cell division Results in extra sets of chromosomesResults in extra sets of chromosomes

Figure 14.6B

Parent species

Meioticerror

Self-fertilization

Offspring may be viable and self-fertile

Zygote

Unreduced diploid gametes

2n = 6Diploid

4n = 12Tetraploid

O. gigas

O. lamarckiana

Figure 14.6A

Sympatric SpeciationSympatric Speciation

A Shetland pony on a UK farm has surprised its owners by giving birth to a half-zebra foal.

Horse—2n=46Zebra—2n=44

In In adaptive radiationadaptive radiation, the evolution of , the evolution of new species new species Occurs when mass extinctions or colonization Occurs when mass extinctions or colonization

provide organisms with new environmentsprovide organisms with new environments Island chainsIsland chains

Provide examples of adaptive radiationProvide examples of adaptive radiation

Adaptive radiation may Adaptive radiation may occur in new or newly occur in new or newly

vacated habitatsvacated habitats

Cactus-seed-eater(cactus finch)

Seed-eater(medium ground finch)

Tool-using insect-eater(woodpecker finch) Figure 14.8B

12

3

4

5

A B

B

B

C C

C

B

C C D

D

D

Figure 14.8A

TALKING ABOUT TALKING ABOUT SCIENCESCIENCE

Peter and Rosemary Grant study the Peter and Rosemary Grant study the evolution of Darwin’s finchesevolution of Darwin’s finches Peter and Rosemary GrantPeter and Rosemary Grant

Have documented natural selection acting Have documented natural selection acting on populations of Galápagos fincheson populations of Galápagos finches

Figure 14.9

1. Seeds blown over from mainland and form small colony

2. Gene pool isolated—evolves into new species B

3. Storms/other agents blow seeds to nearby island and evolve into species C

4. Some of species C recolonize the first island and cohabit with species B and some populate a new island

5. Speciation continues between new areas and previously colonized areas

Plant Plant speciationspeciation

Figure 14.12a

The tempo of speciation The tempo of speciation can appear steady or can appear steady or

jumpyjumpy According to the According to the

gradualism modelgradualism modelNew species New species evolve by the evolve by the gradual gradual accumulation accumulation of changes of changes brought about brought about by natural by natural selectionselection

Figure 14.12b

The tempo of speciation The tempo of speciation can appear steady or can appear steady or

jumpyjumpy The The punctuated punctuated

equilibrium modelequilibrium model draws on the fossil draws on the fossil recordrecord Species diverge Species diverge

in spurts of in spurts of relatively rapid relatively rapid change, instead change, instead of slowly and of slowly and graduallygradually

Evolutionary trends do not Evolutionary trends do not mean that evolution is goal mean that evolution is goal

directeddirected Evolutionary trends Evolutionary trends

reflect species reflect species selectionselection The unequal The unequal

speciation or speciation or unequal unequal survival of survival of species on a species on a branching branching evolutionary evolutionary treetree Figure 14.13

Hippidion and other genera

Nannippus

NeohipparionHipparion

Sinohippus Megahippus

Archaeohippus

Callippus

HypohippusAnchitherium

Miohippus

Parahippus

Paleotherium

Propalaeotherium

Pachynolophus Orohippus

Epihippus

Equus

Pliohippus

Merychippus

Mesohippus

HyracotheriumGrazersBrowsers

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Hippidion and other genera

Nannippus

NeohipparionHipparion

Sinohippus Megahippus

Archaeohippus

Callippus

HypohippusAnchitherium

Miohippus

Parahippus

Paleotherium

Propalaeotherium

Pachynolophus Orohippus

Epihippus

Equus

Pliohippus

Merychippus

Mesohippus

HyracotheriumGrazersBrowsers

Hippidion and other genera

Nannippus

NeohipparionHipparion

Sinohippus Megahippus

Archaeohippus

Callippus

HypohippusAnchitherium

Miohippus

Parahippus

Paleotherium

Propalaeotherium

Pachynolophus Orohippus

Epihippus

Equus

Pliohippus

Merychippus

Mesohippus

HyracotheriumGrazersBrowsers

EO

CE

NE

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Earth History and Earth History and MacroevolutionMacroevolution

MacroevolutionMacroevolution Is closely tied to Is closely tied to

the history of the the history of the Earth.Earth.

The fossil recordThe fossil record Is an archive of Is an archive of

macroevolution.macroevolution.

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FossilizationFossilization Most fossils are actually casts of animals or plants. Most fossils are actually casts of animals or plants. Animal dies and sinks to the sea floor. Animal dies and sinks to the sea floor. Tissue begins to decay and is buried under layers of Tissue begins to decay and is buried under layers of

sediment such as mud or sand. sediment such as mud or sand. These layers become rock. These layers become rock. The hard parts of the animal are The hard parts of the animal are

replaced with minerals such as replaced with minerals such as iron iron pyrites or silica. pyrites or silica.

These minerals form the fossil. These minerals form the fossil. Usually fossils show the hard parts of Usually fossils show the hard parts of

the animal or plant - such as the animal or plant - such as shell or bones.shell or bones.

Trace fossilsTrace fossils——evidence of living evidence of living plants or animals, such as worm plants or animals, such as worm burrows or dinosaur footprints. burrows or dinosaur footprints.

Most fossils are found in Most fossils are found in sedimentary rocks - rocks which sedimentary rocks - rocks which were created when shells or small were created when shells or small loose bits of rock are laid down in loose bits of rock are laid down in layers (limestone, sandstone, clay layers (limestone, sandstone, clay and chalk)and chalk)

http://stevekluge.com/geoscience/images/trackwayd.jpghttp://science.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecBiodiversity/Tracehelminth.jpg

Determining Age of Determining Age of FossilsFossils

Relative ageRelative age—determined by position —determined by position in sedimentary rockin sedimentary rock

Absolute ageAbsolute age—determined by —determined by radiometric dating (radioactive radiometric dating (radioactive isotopes)isotopes) Based on Based on half-lifehalf-life of an isotope—period of an isotope—period

it takes for half the radioactive material it takes for half the radioactive material to decayto decay

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Carbon-14Carbon-14

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6.254

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252

501

1000

C-14 Remaining(atoms)

Number of Half-Life

3.135

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C-14 Remaining(atoms)

Number of Half-Life Half-Life of Carbon 14

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20

40

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Number of Half-Life

Nu

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Figure 14.17a

Plate Tectonics and Plate Tectonics and MacroevolutionMacroevolution

The continents are not The continents are not locked in place.locked in place. They drift about Earth’s They drift about Earth’s

surface on plates of crust surface on plates of crust floating on a flexible floating on a flexible layer called the mantle.layer called the mantle.

California’s infamous San California’s infamous San Andreas faultAndreas fault Is at a border where two Is at a border where two

plates slide past each plates slide past each other.other.

Figure 14.18

Plate TectonicsPlate Tectonics About 250 million years agoAbout 250 million years ago

Plate movements formed Plate movements formed the supercontinent the supercontinent Pangaea.Pangaea.

Many extinctions Many extinctions occurred, allowing occurred, allowing survivors to diversify.survivors to diversify.

About 180 million years agoAbout 180 million years ago Pangaea began to break Pangaea began to break

up, causing geographic up, causing geographic isolation.isolation.

Figure 14.19

Mass Extinctions and Mass Extinctions and Explosive Explosive

Diversifications of LifeDiversifications of Life The fossil record reveals an episodic history,The fossil record reveals an episodic history,

With long, relatively stable periods punctuated by briefer With long, relatively stable periods punctuated by briefer intervals when the turnover in species composition was intervals when the turnover in species composition was much more extensive.much more extensive.

Extinction is inevitable in a changing world and occurs all Extinction is inevitable in a changing world and occurs all the time.the time. However, extinction rates have not been steady.However, extinction rates have not been steady.

Extinctions typically eliminate various species of organismsExtinctions typically eliminate various species of organisms And are followed by explosive diversifications of And are followed by explosive diversifications of

organisms.organisms.

The Process of Science: The Process of Science: Did a Meteor Kill the Did a Meteor Kill the

Dinosaurs?Dinosaurs? Scientists believe Scientists believe

that about 65 that about 65 million years ago, million years ago, at the end of the at the end of the Cretaceous period,Cretaceous period, A meteor impact A meteor impact

contributed to the contributed to the extinction of the extinction of the dinosaurs.dinosaurs.

Figure 14.20

AcknowledgementsAcknowledgements BIOLOGY: CONCEPTS AND CONNECTIONSBIOLOGY: CONCEPTS AND CONNECTIONS 5th 5th

Edition, by Campbell, Reece, Mitchell, and Taylor, Edition, by Campbell, Reece, Mitchell, and Taylor, ©2006. These images have been produced from the ©2006. These images have been produced from the originals by permission of the publisher. These originals by permission of the publisher. These illustrations may not be reproduced in any format for illustrations may not be reproduced in any format for any purpose without express written permission any purpose without express written permission from the publisher.from the publisher.

Unless otherwise noted, illustrations are credited to Unless otherwise noted, illustrations are credited to Pearson Education which have been borrowed from Pearson Education which have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONSBIOLOGY: CONCEPTS AND CONNECTIONS 3rd 3rd Edition, by Campbell, Reece, Mitchell, and Taylor, Edition, by Campbell, Reece, Mitchell, and Taylor, ©2000. These images have been produced from the ©2000. These images have been produced from the originals by permission of the publisher. These originals by permission of the publisher. These illustrations may not be reproduced in any format for illustrations may not be reproduced in any format for any purpose without express written permission any purpose without express written permission from the publisher.from the publisher.