Bio 100 Chapter 14

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


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

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


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


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.

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


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


Lake male

Lake female


River female

River male

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


*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

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


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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.T

ime

New species

Gradual changeas time passes.

ancestral species

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Figure 14.6B Punctuated equilibrium model

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.T

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.

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


(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

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

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

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Bio 100 Chapter 14