Concepts of Biology 2nd Edition

1. Chapter 14
Speciation and
Evolution
Lecture Outline
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2. 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
14-2

3.  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
14-3

4. 14-4
Figure 14.1A Evolution
of modern toothed
whales
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Orcinus orca
No hind limbs.
Rodhocetus
kasrani
Hind limbs too reduced
for walking or swimming.
Hind limbs used for
walking and paddling.
Ambulocetus
natans
Pakicetus
attocki
Hind limbs used
for walking.

5. 14-5
Figure 14.1B Three species of flycatchers. The call of each bird is
given on the photograph

6. 14-6
Figure 14.1C The Massai of East Africa (left) and the Eskimos of
Alaska (right) belong to the same species

7. 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
14-7

8. 14-8
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
hybrid
off spring
Zygote mortality
Fertilization occurs, but
zygote does not survive.
F2 fitness
Hybrid is fertile, but F2 hybrid
has reduced fitness.
Gamete isolation
Sperm cannot reach
or fertilize egg.Behavioral isolation
In animal species,
courtship behavior differs,
or individuals respond to
different songs,calls,
pheromones,or other
signals.
Temporal isolation
Species reproduce at
different seasons or
different times of day.
Habitatisolation
Species at same locale
occupy different habitats. Mechanical isolation
Genitalia between
species are unsuitable
for one another. Hybrid sterility
Hybrid survives but is
sterile and cannot
reproduce.

9. 14-9
Figure 14.2B Mating activity peaks at different times of the year for
these species of frogs
woodfrogleopardfrogpickerelfrog
greenfrog
bullfrog
high
low
March 1 April 1 May 1 June 1 July 1
MatingActivity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. 14-10
Figure 14.2C Male blue-footed boobie doing a courtship dance for
a female

11. 14-11
Figure 14.2D Mules
cannot reproduce
due to chromosome
noncompatibility
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parents
horse
64 chromosomes
donkey
62 chromosomes
mating
mule (hybrid)
63 chromosomes
fertilization
Offspring
(donkey): © Robert J. Erwin/Photo Researchers, Inc.; (offspring): © Jorg & Petra Wegner/AnimalsAnimals
Usually
mules cannot
reproduce.
If an offspring
does result,
it cannot
reproduce.

12. 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
14-12

13. 14-13
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
Central
Valley
Members of a northern ancestral
population migrated southward.
Ensatina eschscholtzi
oregonensis
Subspecies are separated by
California’s Central Valley. Some
interbreeding between populations
does occur.
Ensatina eschscholtzi
xanthoptica
Ensatina eschscholtzi
croceater
Ensatina eschscholtzi
klauberi
Ensatina eschscholtzi
eschscholtzii
Evolution has occurred, and in the
south, subspecies do not interbreed
even though they live in the same
environment.

14. 14-14
Figure 14.3
B: Sockeye salmon at Pleasure Point Beach, Lake Washington
C: Sockeye salmon in Cedar River. The river connects with Lake Washington
B C
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Lake male
Lake female
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
River female
River male

15. 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
14-15

16. 14-16
Figure 14.4 Adaptive
radiation in Hawaiian
honeycreepers
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
*Lesser Koa finch Palila
*Greater
Koa finch
Laysan
finch
Maui parrot bill
Genus Psittirostra
Akiapolaau
*Kauai
akialoa
*Akialoa
*Extinct species or subspecies
Nukupuu
Alauwahio
(Hawaiian
creeper)
Anianiau
(lesser
amakihi)
amakihi
(green
solitaire)
Akepa
Amakihi
Genus Hemignathus
Ou
*Kona
finch

17.  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
14-17

18. 14-18
Figure 14.5A Autoploidy: The small, diploid-seeded banana is contrasted
with the large, polyploid banana that produces no seeds
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
seeds
diploid
banana (2n)
polyploid
banana
no
seeds
(diploid): © Randy C. Ploetz

19. 14-19
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

20. 14-20
Macroevolution Involves Changes at the
Species Level and Beyond

21. 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
14-21

22. 14-22
Figure 14.6A
Gradualistic model
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Time
New species
Gradual change
as time passes.
ancestral species

23. 14-23
Figure 14.6B
Punctuated
equilibrium model
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Time
no change no change no change
new
species
no change
new
species
ancestral species

24. 14-24
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

25. 14-25
Figure 14B
Burgess Shale quarry where many ancient fossils have been found

26. 14-26
Figure 14B cont’d
An artist’s depiction of the variety of fossils is accompanied by photos of the
actual fossilized remains

27. 14-27
Figure 14B cont’d
An artist’s depiction of the variety of fossils is accompanied by photos of the
actual fossilized remains.

28. 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
14-28

29. 14-29
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.

30. 14-30
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

31. 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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32. 14-32
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
Hipparion
Neohipparion
Merychippus
Dinohippus
Equus
2 MYA
4 MYA
12 MYA
15 MYA
17 MYA
23 MYA
25 MYA
35 MYA
40 MYA
45 MYA
50 MYA
55 MYA

33. 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-oriented
14-33