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Chapter 14
The Origin of Species
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Mosquito Mystery
• Speciation is the emergence of new species
• In England and North America
– Two species of mosquitoes exist and spread
West Nile virus
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14.1 The origin of species is the source of
biological diversity
• Speciation, the origin of new species
– Is at the focal point of evolution
Figure 14.1
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• Earth’s incredible biological diversity is the
result of macroevolution
– Which begins with the origin of new
species
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CONCEPTS OF SPECIES
14.2 What is a species?
• Carolus Linnaeus, a Swedish physician and botanist
– Used physical characteristics to distinguish species
– Developed the binomial system of naming
organisms
• Linnaeus’ system established the basis for taxonomy
– The branch of biology concerned with naming and
classifying the diverse forms of life
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• Similarities between some species and
variation within a species
– Can make defining species difficult
Figure 14.2A
Figure 14.2B
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Speciation
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MECHANISMS OF SPECIATION
14.4 Geographic isolation can lead to speciation
• In allopatric speciation
– A population is geographically divided, and
new species often evolve
A. harrisi
A. leucurus
Figure 14.4
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Speciation in Fruit Flies
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14.5 Reproductive barriers may evolve as populations
diverge
• Laboratory studies of fruit flies
– Have shown that changes in food sources can
cause speciation
Initial sample
of fruit flies
Starch medium
Maltose medium
Figure 14.5A
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Female
Same
Different
population populations
Female
Starch
Maltose
22
9
8
20
Mating frequencies
in experimental group
Male
Different Same
Male
Maltose Starch
Results of
mating experiments
18
15
12
15
Mating frequencies
in control group
• Geographic isolation in Death Valley
– Has led to the evolution of new species of
pupfish
Figure 14.5B
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A pupfish
14.6 New species can also arise within the same
geographic area as the parent species
• In sympatric speciation
– New species may arise without geographic
isolation
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• Many plant species have evolved by polyploidy
– Multiplication of the chromosome number due
to errors in cell division
Zygote
Parent species
Meiotic
error
Offspring
may be
viable and
self-fertile
Selffertilization
4n = 12
Tetraploid
2n = 6
Diploid
O. lamarckiana
Unreduced
diploid gametes
Figure 14.6A
O. gigas
Figure 14.6B
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CONNECTION
14.7 Polyploid plants clothe and feed us
• Many plants, including food plants such as bread
wheat
– Are the result of hybridization and polyploidy
AA
Triticum monococcum
(14 chromosomes)

BB
Wild Triticum
(14 chromosomes)
AB
Sterile hybrid
(14 chromosomes)
Meiotic error and
self-fertilization

AA BB
T.turgidum
Emmer wheat
(28 chromosomes)
ABD
Sterile hybrid
(21 chromosomes)
Meiotic error and
self-fertilization
AA BB DD
Figure 14.7A
T.aestivum
Bread wheat
(42 chromosomes)
Figure 14.7B
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DD
T.tauschii
(wild)
(14 chromosomes)
Real Examples of Possible Speciation
Rhagoletis pomonella is a fly that is native to North America. Its normal host is the hawthorn tree.
Sometime during the nineteenth century it began to infest apple trees. Since then it has begun to infest
cherries, roses, pears and possibly other members of the rosaceae.
Quite a bit of work has been done on the differences between flies infesting hawthorn and flies infesting
apple. There appear to be differences in host preferences among populations. Offspring of females
collected from on of these two hosts are more likely to select that host for oviposition (Prokopy et al.
1988).
Genetic differences between flies on these two hosts have been found at 6 out of 13 allozyme loci (Feder
et al. 1988, see also McPheron et al. 1988). Laboratory studies have shown an asynchrony in emergence
time of adults between these two host races (Smith 1988). Flies from apple trees take about 40 days to
mature, whereas flies from hawthorn trees take 54-60 days to mature. This makes sense when we
consider that hawthorn fruit tends to mature later in the season that apples.
Hybridization studies show that host preferences are inherited, but give no evidence of barriers to mating.
This is a very exciting case. It may represent the early stages of a sympatric speciation event (considering
the dispersal of R. pomonella to other plants it may even represent the beginning of an adaptive radiation).
It is important to note that some of the leading researchers on this question are urging caution in
interpreting it. Feder and Bush (1989) stated
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The Biological Species Concept
• The biological species concept defines a
species as
– A population or group of populations whose
members can interbreed and produce
fertile offspring
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Other Species Concepts
• The morphological species concept
– Classifies organisms based on observable
phenotypic traits
• The ecological species concept
– Defines a species by its ecological role
• The phylogenetic species concept
– Defines a species as a set of organisms
representing a specific evolutionary lineage
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14.3
Reproductive
barriers keep
species separate
•
Reproductive barriers
–
Serve to isolate a
species’ gene pool
and prevent
interbreeding
Are categorized as
prezygotic or
postzygotic
Table 14.3
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Prezygotic Barriers
•
Prezygotic barriers
– Prevent mating or fertilization between species
In temporal isolation
Two species breed at different
times
Figure 14.3A
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• In behavioral isolation
– There is little or no sexual attraction
between species, due to specific behaviors
Figure 14.3B
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• In mechanical isolation
– Female and male sex organs or gametes
are not compatible
Figure 14.3C
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Postzygotic Barriers
• Postzygotic barriers
– Operate after hybrid zygotes are formed
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• One postzygotic barrier is hybrid sterility
– Where hybrid offspring between two
species are sterile and therefore cannot
mate
Figure 14.3D
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14.8 Adaptive radiation may occur in new or
newly vacated habitats
• In adaptive radiation, the evolution of new
species
– Occurs when mass extinctions or
colonization provide organisms with new
environments
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• Island chains
– Provide examples of adaptive radiation
Cactus-seed-eater
(cactus finch)
A
1
B
2
B
B
C
B
3
C 4
C
C
5
D
Figure 14.8B
Tool-using insect-eater
(woodpecker finch)
Seed-eater
(medium ground finch)
Figure 14.8A
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CD
D
TALKING ABOUT SCIENCE
14.9 Peter and Rosemary Grant study the
evolution of Darwin’s finches
• Peter and Rosemary Grant
– Have documented natural selection acting
on populations of Galápagos finches
Figure 14.9
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• The occasional hybridization of finch species
– May also have been important in their
adaptive radiation
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14.10 The tempo of speciation can appear steady or
jumpy
• According to the gradualism model
– New species evolve by the gradual accumulation
of changes brought about by natural selection
Time
Figure 14.10A
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• The punctuated equilibrium model draws on the
fossil record
– Where species change the most as they
arise from an ancestral species and then
change relatively little for the rest of their
existence
Time
Figure 14.10B
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MACROEVOLUTION
14.11 Evolutionary novelties may arise in several ways
• Many complex structures evolve in many stages
– From simpler versions having the same basic
function
Light-sensitive
cells
Light-sensitive
cells
Fluid-filled cavity
Transparent protective
tissue (cornea)
Cornea
Lens
Layer of
light-sensitive
cells (retina)
Optic
nerve
Eyecup
Nerve
fibers
Nerve
fibers
Patch of lightsensitive cells
Limpet
Optic
nerve
Retina
Optic
nerve
Eyecup
Simple pinhole
camera-type eye
Eye with
primitive lens
Complex
camera-type eye
Abalone
Nautilus
Marine snail
Squid
Figure 14.11
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• Other novel structures result from exaptation
– The gradual adaptation of existing
structures to new functions
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14.12 Genes that control development are
important in evolution
• “Evo-devo”
– Is a field that combines evolutionary and
developmental biology
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• Many striking evolutionary transformations
– Are the result of a change in the rate or
timing of developmental changes
Figure 14.12A
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• Changes in the timing and rate of growth
– Have also been important in human
evolution
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
Figure 14.12B
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• Stephen Jay Gould, an evolutionary biologist
– Contended that Mickey Mouse “evolved”
 Copyright Disney
Enterprises, Inc.
Figure 14.12C
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14.13 Evolutionary trends do not mean that evolution
is goal directed
• Evolutionary trends reflect species selection
PLEISTOCEN E
RECENT
– The unequal speciation or unequal survival of
species on a branching evolutionary tree
Equus
Hippidion and other genera
Nannippus
Pliohippus
PLIOCENE
Hipparion Neohipparion
Sinohippus
Megahippus
Callippus
MIOCENE
Archaeohippus
Merychippus
Anchitherium
Hypohippus
Parahippus
OLIGOCENE
Miohippus
Mesohippus
Paleotherium
Epihippus
EOCENE
Propalaeotherium
Figure 14.13
Pachynolophus
Orohippus
Hyracotherium
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Grazers
Browsers