BIOLOGY Chapter 17: 10th Edition Speciation and Macroevolution · Scientific name of the dinosaur,...

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY 10th Edition

Speciation and Macroevolution

Chapter 17: pp. 299 - 316

(Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo

Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals

Animals/Earth Scenes;

mating

fertilization

Parents

Offspring

donkey

mule (hybrid)

Usually

mules cannot

reproduce.

offspring

does result,

it cannot

reproduce.

Ensatina eschscholtzi picta

Ensatina eschscholtzi platensis

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.

xanthoptica Ensatina eschscholtzi

croceater

eschscholtzii

klauberi Evolution has occurred, and in

the south, subspecies do not

interbreed even though they

live in the same environment.

Central

Valley

Barrier

Outline

Separation of the Species

Modes of Separation

Allopatic speciation

Adaptive radiation

Sympatric speciation

Macroevolution

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.

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.”

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.

Species Definitions

Morphological

Can be distinguished anatomically

Specialist decides what criteria probably represent

reproductively isolated populations

Most species described this way

Evolutionary Species Concept

Orcinus orca

Rodhocetus kasrani

Ambulocetus natans

Pakicetus attocki

Hindlimbs too

reduced for walking

or swimming

Hindlimbs used

for both walking

on land and

paddling in water

Tetrapod with limbs

for walking

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

Biological Species Concept

pit-see fitz-bew

Acadian flycatcher , Empidonax virescens Willow flycatcher, Empidonax trailli Least flycatcher, Empidonax minimus

(Acadian): © Karl Maslowski/Visuals Unlimited; (Willow): © Ralph Reinhold/Animals Animals/Earth Scenes; (Least): © Stanley Maslowski/Visuals Unlimited.

che-bek or che-bek

Human Populations

(Left): © Sylvia S. Mader; (Right): © B & C Alexander/Photo Researchers, Inc.

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

Reproductive Barrier

Mating Premating

Postzygotic Isolating Mechanisms Prezygotic Isolating Mechanisms

Fertilization

species 1

species 2

Habitat isolation Species at same locale

occupy different habitats.

Temporal isolation Species reproduce at

different seasons or

different times of day.

Behavioral isolation In animal species,

courtship behavior differs,

or individuals respond to

different songs, calls,

pheromones, or other

signals.

Gamete isolation Sperm cannot reach

or fertilize egg.

Mechanical isolation Genitalia between

species are unsuitable

for one another.

Zygote mortality Fertilization occurs, but

zygote does not survive.

Hybrid sterility Hybrid survives but is

sterile and cannot

reproduce.

F2 fitness Hybrid is fertile, but F2 hybrid

has reduced fitness.

hybrid

offspring

Temporal Isolation

March 1 April 1 May 1 June 1 July 1

Prezygotic Isolating Mechanism

Reproductive Isolating Mechanisms

Two general types:

(2) Postzygotic Mechanisms - Prevent hybrid

offspring from developing or breeding

Zygote Mortality

Hybrid Sterility

Reduced F2 Fitness

Postzygotic Isolating Mechanism

(Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals Animals/Earth Scenes;

mating

fertilization

Parents

Offspring

donkey

mule (hybrid)

Usually

mules cannot

reproduce.

offspring

does result,

it cannot

reproduce.

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

Allopatric Speciation

oregonensis

does occur.

croceater

eschscholtzii

interbreed even though they live

in the same environment.

Central

Valley

Barrier

Allopatric Speciation

Salmon that matured at Pleasure Point Beach do not reproduce with those that matured in the Cedar River.

Lake female

Lake male River male

River female

a. Sockeye salmon at Pleasure Point Beach, Lake Washington b. Sockeye salmon in Cedar River .The river connects with

Lake Washington.

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

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.

Alloploidy

polyploid

banana

diploid

banana (2n)

Autoploidy

Clarkia concinna Clarkia virgata

hybrid

2n = 14 2n = 10

2n = 24

doubling of chromosome number

Clarkia pulchella

(C. pulchella): © J. L. Reveal; (C. concinna): © Gerald & Buff Corsi/Visuals Unlimited; (C. virgata): ©: Dr. Dean Wm. Taylor/Jepson Herbarium, UC Berkeley

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

Adaptive Radiation

Amakihi

Akiapolaau

Nukupuu

* Akialoa

* Extinct species or subspecies

Maui parrot bill

Palila

* Lesser Koa finch

Laysan

finch * Greater

Koa finch

* Kona

* Kauai

akialoa

Alauwahio

(Hawaiian

creeper)

Anianiau

(lesser

amakihi)

amakihi

(green

solitaire)

Genus Loxops

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

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.

Gradualistic and Punctuated

transitional link

a. Gradualistic model b. Punctuated equilibrium

stasis

species 1

ancestral

species

ancestral

species

ancestral

species

species 2

Time Time

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.

Pax6 Gene and Eye Development

(Left): © Carolina Biological Supply/Photo Researchers, Inc.; (Center): © Vol. OS02/PhotoDisc/Getty Images; (Right): © Aldo Brando/Peter Arnold, Inc.

Study of Pax6 Gene

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

Hox6 Gene

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.

Simplified Family Tree of Equus

12 MYA

15 MYA

17 MYA

23 MYA

25 MYA

35 MYA

40 MYA

45 MYA

50 MYA

55 MYA

Dinohippus

Neohipparion Hipparion

Megahippus

Miohippus

Palaeotherium

Hyracotherium

Merychippus

Review

Modes of Separation

Allopatic speciation

Adaptive radiation

Sympatric speciation

Macroevolution

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY 10th Edition

Speciation and Macroevolution

Chapter 17: pp. 299 - 316

Animals/Earth Scenes;

mating

fertilization

Parents

Offspring

donkey

mule (hybrid)

Usually

mules cannot

reproduce.

offspring

does result,

it cannot

reproduce.

oregonensis

does occur.

croceater

eschscholtzii

interbreed even though they

live in the same environment.

Central

Valley

Barrier

BIOLOGY Chapter 17: 10th Edition Speciation and Macroevolution · Scientific name of the dinosaur,...

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