bio 100 chapter 14
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Chapter 14Speciation and
EvolutionLecture Outline
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14.1 The Definition of a Species
Macroevolution Requires the origin of species Observed best within the fossil record
Speciation Splitting of one species into two or more or the
transformation of one species into a new species
over time
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Evolutionary Species Concept Members of a species share the same distinct
evolutionary pathway and that species can be recognized by diagnostic trait differences
Diagnostic traits distinguish one species from another Assumes that the members of a species are
reproductively isolated
Biological Species Concept relies primarily on reproductive isolation rather than trait differences to define a species
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Figure 14.1A Evolution of modern toothed whales
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Orcinus orca
No hind limbs.
Rodhocetuskasrani
Hind limbs too reducedfor walking or swimming.
Hind limbs used forwalking and paddling.
Ambulocetusnatans
Pakicetusattocki
Hind limbs usedfor walking.
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Figure 14.1B Three species of flycatchers. The call of each bird is given on the photograph
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Figure 14.1C The Massai of East Africa (left) and the Eskimos of Alaska (right) belong to the same species
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14.2 Reproductive barriers maintain genetic differences between species
Reproductive isolating mechanisms Prezygotic isolating mechanisms
Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gamete isolation
Postzygotic isolating mechanisms Zygote mortality Hybrid sterility F2 fitness
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Figure 14.2A Reproductive barriers
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
PrezygoticIsolating Mechanisms Postzygotic Isolating Mechanisms
FertilizationMatingPremating
species 1
species 2
hybridoff spring
Zygote mortalityFertilization occurs, butzygote does not survive.
F2 fitnessHybrid is fertile, but F2 hybridhas reduced fitness.
Gamete isolationSperm cannot reachor fertilize egg.Behavioral isolation
In animal species,courtship behavior differs,or individuals respond todifferent songs,calls,pheromones,or othersignals.
Temporal isolationSpecies reproduce atdifferent seasons ordifferent times of day.
HabitatisolationSpecies at same localeoccupy different habitats. Mechanical isolation
Genitalia betweenspecies are unsuitablefor one another. Hybrid sterility
Hybrid survives but issterile and cannotreproduce.
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Figure 14.2B Mating activity peaks at different times of the year for these species of frogs
woo
d fr
ogle
opar
d fr
ogpi
cker
el fr
og
gree
n fr
og
bull
frog
high
low
March 1 April 1 May 1 June 1 July 1
Mat
ing
Act
ivit
yCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Figure 14.2C Male blue-footed boobie doing a courtship dance for a female
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Figure 14.2D Mules cannot reproduce due to chromosome noncompatibility
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parents
horse64 chromosomes
donkey62 chromosomes
mating
mule (hybrid)63 chromosomes
fertilization
Offspring
(donkey): © Robert J. Erwin/Photo Researchers, Inc.; (offspring): © Jorg & Petra Wegner/AnimalsAnimals
Usuallymules cannotreproduce.If an offspringdoes result,it cannotreproduce.
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14.3 Allopatric speciation utilizes a geographic barrier
Allopatric speciation Requires that the subpopulations be separated by a
geographic barrier
Ex: Ensantina salamanders in California Distinct forms no longer interbreed
Ex: Sockeye Salmon in Washington State Some introduced to Lake Washington Colonized different habitats and different traits favored
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Figure 14.3A Allopatric speciation among Ensatina salamanders
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ensatina eschscholtzi picta
Ensatina eschscholtzi platensis
1
2
3
CentralValley
Members of a northern ancestral population migrated southward.
Ensatina eschscholtzioregonensis
Subspecies are separated by California’s Central Valley. Some interbreeding between populations does occur.
Ensatina eschscholtzixanthoptica
Ensatina eschscholtzicroceater
Ensatina eschscholtziklauberi
Ensatina eschscholtzieschscholtzii
Evolution has occurred, and in the south, subspecies do not interbreed even though they live in the same environment.
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Figure 14.3B: Sockeye salmon at Pleasure Point Beach, Lake WashingtonC: Sockeye salmon in Cedar River. The river connects with Lake Washington
B C
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Lake male
Lake female
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River female
River male
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14.4 Adaptive radiation produces many related species
Adaptive radiation Single ancestral species gives rise to a variety of
species, each adapted to a specific environment An ecological niche is where a species lives and how
it interacts with other species
Ex: Common goldfinch-like ancestor arrived in Hawaii from Asia or North America about 5 mya Today honeycreepers have a range of beak sizes and
shapes for feeding on various food sources, including seeds, fruits, flowers, and insects
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Figure 14.4 Adaptive radiation in Hawaiian honeycreepers
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*Lesser Koa finch Palila
*GreaterKoa finch
Laysanfinch
Maui parrot bill
Genus Psittirostra
Akiapolaau
*Kauaiakialoa
*Akialoa
*Extinct species or subspecies
Nukupuu
Alauwahio(Hawaiiancreeper)
Anianiau(lesseramakihi)
amakihi(greensolitaire)
Akepa
Amakihi
Genus Hemignathus
Ou
*Konafinch
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Sympatric speciation Speciation without the presence of a geographic
barrier More common in flowering plants than in animals due
to self-pollination
Polyploidy – chromosome number beyond the diploid (2n) number
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Figure 14.5A Autoploidy: The small, diploid-seeded banana is contrasted with the large, polyploid banana that produces no seeds
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seeds
diploidbanana (2n)
polyploidbanana
noseeds
(diploid): © Randy C. Ploetz
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HOW BIOLOGY IMOPACTS OUR LIVES
14A The Many Uses of Corn, an Allotetraploid
Modern corn’s (Zea mays) ancient ancestor was teosinte from southern Mexico
Between 4000 and 3000 B.C., the hand of artificial selection began to shape the evolution of corn
Corn is an allotetraploid – it is 4n Hybridization between 2 related species followed by
doubling of the chromosomes
Corn is America’s number-one field crop, yielding 9.5 billion bushels yearly
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Macroevolution Involves Changes at the Species Level and Beyond
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14.6 Speciation occurs at different tempos
Many evolutionists accept a gradualistic model evolution which proposes that speciation occurs after populations become isolated
Some paleontologists think that species appear suddenly, and then they remain essentially unchanged phenotypically until they undergo extinction Based on these findings, other evolutionists
developed a punctuated equilibrium model to explain the pace of evolution
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Figure 14.6A Gradualistic model
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ime
New species
Gradual changeas time passes.
ancestral species
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Figure 14.6B Punctuated equilibrium model
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ime
no change no change no change
newspecies
no change
newspecies
ancestral species
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HOW SCIENCE PROGRESSES
14B The Burgess Shale Hosts a Diversity of Life
Burgess Shale contains fossils of marine life some 540 mya
Many of the fossils are remains of soft-bodied invertebrates
Fossils tell us that the ancient seas were teeming with weird-looking, mostly invertebrate animals
All of today’s groups of animals can trace their ancestry to one of these strange-looking forms
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Figure 14BBurgess Shale quarry where many ancient fossils have been found
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Figure 14B cont’dAn artist’s depiction of the variety of fossils is accompanied by photos of the actual fossilized remains
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Figure 14B cont’dAn artist’s depiction of the variety of fossils is accompanied by photos of the actual fossilized remains.
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14.7 Development plays a role in speciation
Investigators have discovered genes whose differential expression can bring about changes in body shapes
These regulatory genes found in all organisms Genes must date back to a common ancestor
that lived more than 600 MYA
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Figure 14.7A Differential expression of regulatory genes during development can account for differences in vertebrate limbs
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(boy, dog, bird): © Corbis RF
The limbs of these ferrestrial mammals are shaped for running (or walking). The limbs of birds are shaped for flight.
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Figure 14.7B Differential expression of a Hox genes causes (a) a chick to have fewer vertebrae than (b) a snake in a particular region (colored pink) of the spine
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14.8 Speciation is not goal-oriented
Modern horses evolved about 4 mya Have features adaptive for living on an open plain:
large size long legs, hoofed feet, and strong teeth
Family tree of Equus tells us once more that speciation, diversification, and extinction are common occurrences in the fossil record
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Figure 14.8 Simplified family tree of Equus. Every dot is a genus.Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Miohippus
Palaeotherium
Hyracotherium
Megahippus
HipparionNeohipparion
Merychippus
Dinohippus
Equus2 MYA
4 MYA
12 MYA
15 MYA
17 MYA
23 MYA25 MYA
35 MYA
40 MYA
45 MYA
50 MYA
55 MYA
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Connecting the Concepts:Chapter 14
Macroevolution is the study of the origin and history of species on Earth
Speciation usually occurs by allopatric speciation but can occur after sympatric speciation
Gradualistic vs punctuated equilibrium model for speed of speciation
Ancient regulatory genes can bring about changes in body shape and organs
Evolution is not goal-oriented14-33