BIOLOGY
Chapter 17: pp. 299 - 316
10th Edition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ensatina eschscholtzi picta
Parents
1
Members of a northern ancestral
population migrated southward.
Ensatina eschscholtzi
oregonensis
horse
donkey
mating
2
Subspecies are separated by
California’s Central Valley .Some
interbreeding between populations
does occur.
Central
Valley
Barrier
fertilization
Ensatina eschscholtzi platensis
Ensatina eschscholtzi
xanthoptica
Sylvia S. Mader
Speciation and
Macroevolution
Ensatina eschscholtzi
croceater
Usually
mules cannot
reproduce.
If an
offspring
does result,
it cannot
reproduce.
mule (hybrid)
Offspring
(Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo
Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals
Animals/Earth Scenes;
Ensatina eschscholtzi
eschscholtzii
3
Evolution has occurred, and in
the south, subspecies do not
interbreed even though they
live in the same environment.
Ensatina eschscholtzi
klauberi
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
1
Outline

Separation of the Species

Modes of Separation


Allopatic speciation

Adaptive radiation

Sympatric speciation
Macroevolution
2
Separation of the Species

Macroevolution is best observed within
the fossil record,
Requires the origin of species, also called
speciation.
 Speciation is the final result of changes in
gene pool allelic and genotypic frequencies.

3
Species Definitions
Every species has its own evolutionary
history
 Binomial nomenclature, is used to name
various species


The two-part scientific name, when translated
from the Latin, often tells you something about
the organism.

Scientific name of the dinosaur, Tyrannosaurus rex,
means “tyrant-lizard king.”
4
Species Definitions

Evolutionary species concept distinguish
species from one another based on:


Morphological (structural) traits,
Biological
species
concept
relies
primarily on reproductive isolation rather
than trait differences to define a species.
5
Species Definitions

Species Definitions

Morphological
Can be distinguished anatomically
 Specialist decides what criteria probably represent
reproductively isolated populations
 Most species described this way

6
Evolutionary Species Concept
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Orcinus orca
Hindlimbs too
reduced for walking
or swimming
Rodhocetus kasrani
Ambulocetus natans
Hindlimbs used
for both walking
on land and
paddling in water
Tetrapod with limbs
for walking
Pakicetus attocki
7
Species Definitions

Species Definitions

Biological
Populations of the same species breed only among
themselves
 Are reproductively isolated from other such
populations
 Very few actually tested for reproductive isolation

8
Biological Species Concept
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
pit-see
Acadian flycatcher , Empidonax virescens
fitz-bew
Willow flycatcher, Empidonax trailli
che-bek or che-bek
Least flycatcher, Empidonax minimus
(Acadian): © Karl Maslowski/Visuals Unlimited; (Willow): © Ralph Reinhold/Animals Animals/Earth Scenes; (Least): © Stanley Maslowski/Visuals Unlimited.
9
Human Populations
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(Left): © Sylvia S. Mader; (Right): © B & C Alexander/Photo Researchers, Inc.
10
Reproductive Isolating Mechanisms
Reproductive isolating mechanisms inhibit
gene flow between species
 Two general types:


(1) Prezygotic Mechanisms – prevents matting
attempts
Habitat Isolation - species occupy different habitats,
 Temporal Isolation - each reproduces at a different
time
 Behavioral Isolation
 Mechanical Isolation
 Gamete Isolation

11
Reproductive Barrier
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Prezygotic Isolating Mechanisms
Premating
Postzygotic Isolating Mechanisms
Mating
Habitat isolation
species 1
Fertilization
Zygote mortality
Species at same locale
occupy different habitats.
Fertilization occurs, but
zygote does not survive.
Mechanical isolation
Temporal isolation
Genitalia between
species are unsuitable
for one another.
Species reproduce at
different seasons or
different times of day.
hybrid
offspring
Hybrid sterility
Hybrid survives but is
sterile and cannot
reproduce.
species 2
Behavioral isolation
Gamete isolation
In animal species,
courtship behavior differs,
or individuals respond to
different songs, calls,
pheromones, or other
signals.
Sperm cannot reach
or fertilize egg.
F2 fitness
Hybrid is fertile, but F2 hybrid
has reduced fitness.
12
Temporal Isolation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Mating Activity
high
low
March 1 April 1
May 1
June 1
July 1
13
Prezygotic Isolating Mechanism
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Barbara Gerlach/Visuals Unlimited
14
Reproductive Isolating Mechanisms

Two general types:

(2) Postzygotic Mechanisms - Prevent hybrid
offspring from developing or breeding

Zygote Mortality

Hybrid Sterility

Reduced F2 Fitness
15
Postzygotic Isolating Mechanism
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parents
horse
donkey
mating
fertilization
Usually
mules cannot
reproduce.
If an
offspring
does result,
it cannot
reproduce.
mule (hybrid)
Offspring
(Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals Animals/Earth Scenes;
16
Modes of Speciation

Speciation:
The splitting of one species into two, or
 The transformation of one species into a new
species over time


Two modes:

(1) Allopatric Speciation
Two geographically isolated populations of one
species
 Become different species over time
 Can be due to differing selection pressures in
differing environments

17
Allopatric Speciation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ensatina eschscholtzi picta
1
Members of a northern ancestral
population migrated southward.
Ensatina eschscholtzi
oregonensis
2
Subspecies are separated by
California’s Central Valley .Some
interbreeding between populations
does occur.
Central
Valley
Barrier
Ensatina eschscholtzi platensis
Ensatina eschscholtzi
xanthoptica
Ensatina eschscholtzi
croceater
Ensatina eschscholtzi
eschscholtzii
3
Evolution has occurred, and in
the south, subspecies do not
interbreed even though they live
in the same environment.
Ensatina eschscholtzi
klauberi
18
Allopatric Speciation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lake male
River male
Lake female
River female
a. Sockeye salmon at Pleasure Point Beach, Lake Washington

b. Sockeye salmon in Cedar River .The river connects with
Lake Washington.
Salmon that matured at Pleasure Point Beach do not
reproduce with those that matured in the Cedar River.
19
Modes of Speciation

Two modes:

(2) Sympatric Speciation
One population develops into two or more
reproductively isolated groups
 No prior geographic isolation
 It involves polyploidy (a chromosome number
beyond the diploid [2n] number)


Tetraploid hybridization in plants
 Results in self fertile species
 Reproductively isolated from either parental species
20
Modes of Speciation

(2) Sympatric Speciation


A polyploid plant can reproduce with itself, but cannot
reproduce with the 2n population because not all the
chromosomes would be able to pair during meiosis.
Two types of polyploidy are known:

Autoploidy - diploid plant produces diploid gametes due to
nondisjunction during meiosis.
If diploid gamete fuses with a haploid gamete, a triploid plant
results.
A triploid (3n) plant is sterile and cannot produce offspring
because the chromosomes cannot pair during meiosis.
Alloploidy - more complicated process than autoploidy
Requires two different but related species of plants
Hybridization is followed by doubling of the chromosomes.




21
Alloploidy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
seeds
diploid
banana (2n)
no
seeds
polyploid
banana
22
Autoploidy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2n = 14
2n = 10
Clarkia concinna
Clarkia virgata
hybrid
doubling of chromosome number
2n = 24
Clarkia pulchella
(C. pulchella): © J. L. Reveal; (C. concinna): © Gerald & Buff Corsi/Visuals Unlimited; (C. virgata): ©: Dr. Dean Wm. Taylor/Jepson Herbarium, UC Berkeley
23
Adaptive Radiation


Adaptive Radiation

When members of a species invade several
new geographically separate environments

The populations become adapted to the
different environments

Many new species evolve from the single
ancestral species
This is an example of allopatric speciation
24
Adaptive Radiation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
* Lesser Koa finch
Palila
Laysan
finch
* Greater
Koa finch
Ou
* Kona
finch
Maui parrot bill
Akiapolaau
* Kauai
akialoa
Nukupuu
* Akialoa
Genus Loxops
Great
amakihi
Anianiau (green
(lesser solitaire)
amakihi)
* Extinct species or subspecies
Alauwahio
(Hawaiian
creeper)
Akepa
Amakihi
25
Principles of Macroevolution

Macroevolution
Evolution at the species or higher level of
classification
 Occurs gradually
 Evolutionists support a gradualistic model

Speciation occurs after populations become
isolated
 Each group continuing its own evolutionary pathway
 The gradualistic model suggests that it is difficult to
indicate when speciation occurred

26
Principles of Macroevolution

Macroevolution

Some paleontologists believe that
Species can appear quite suddenly
 Remain essentially unchanged phenotypically
during a period of stasis (sameness) until they
undergo extinction.
 Based on these findings, they developed a
punctuated equilibrium model to explain the pace of
evolution.

27
Gradualistic and Punctuated
Equilibrium Models
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
new
species 1
new
species 1
ancestral
species
ancestral
species
transitional link
ancestral
species
new
species 2
Time
a. Gradualistic model
stasis
new
species 2
Time
b. Punctuated equilibrium
28
Developmental Genes and
Macroevolution

Genes can bring about radical changes in
body shapes and organs.

Gene Expression Can Influence Development
A change in gene expression could stop
developmental process or continue it beyond its
normal time.
 Using modern technology researchers discovered
genes whose differential expression can bring about
changes in body shapes and organs.

29
Pax6 Gene and Eye Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(Left): © Carolina Biological Supply/Photo Researchers, Inc.; (Center): © Vol. OS02/PhotoDisc/Getty Images; (Right): © Aldo Brando/Peter Arnold, Inc.
30
Study of Pax6 Gene
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Courtesy Walter Gehring, reprinted with permission from Induction of Ectopic Eyes by Target Expression of the Eyeless Gene in Drosophila, G. Halder, P. Callaerts, Walter J. Gehring, Science Vol. 267, © 24
March 1995 American Association for the Advancement of Science
31
Hox6 Gene
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(Both): © A. C. Burke, 2000
32
Macroevolution Is Not Goal-Oriented

The evolution of the horse (Equus)
Studied since the 1870s
 Model for gradual, straight-line evolution
 Modern horse, had been achieved as a goal
 Three trends were particularly evident during
the evolution:

Increase in overall size,
 Toe reduction, and
 Change in tooth size and shape.

33
Simplified Family Tree of Equus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2 MYA
4 MYA
Equus
Neohipparion
Hipparion
12 MYA
Dinohippus
Megahippus
15 MYA
Merychippus
17 MYA
23 MYA
25 MYA
35 MYA
Miohippus
40 MYA
Palaeotherium
45 MYA
50 MYA
Hyracotherium
55 MYA
34
Review

Separation of the Species

Modes of Separation


Allopatic speciation

Adaptive radiation

Sympatric speciation
Macroevolution
35
BIOLOGY
Chapter 17: pp. 299 - 316
10th Edition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ensatina eschscholtzi picta
Parents
1
Members of a northern ancestral
population migrated southward.
Ensatina eschscholtzi
oregonensis
horse
donkey
mating
2
Subspecies are separated by
California’s Central Valley .Some
interbreeding between populations
does occur.
Central
Valley
Barrier
fertilization
Ensatina eschscholtzi platensis
Ensatina eschscholtzi
xanthoptica
Sylvia S. Mader
Speciation and
Macroevolution
Ensatina eschscholtzi
croceater
Usually
mules cannot
reproduce.
If an
offspring
does result,
it cannot
reproduce.
mule (hybrid)
Offspring
(Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo
Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals
Animals/Earth Scenes;
Ensatina eschscholtzi
eschscholtzii
3
Evolution has occurred, and in
the south, subspecies do not
interbreed even though they
live in the same environment.
Ensatina eschscholtzi
klauberi
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
36