ap bio chapter 24.pdf

8/14/2019 AP Bio Chapter 24.pdf

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LECTURE PRESENTATIONS

For CAMPBELL BIOLOGY, NINTH EDITIONJane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

2011 Pearson Education, Inc.

Lectures by

Erin Barley

Kathleen Fitzpatrick

The Origin of Species

Chapter 24


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Overview: That Mystery of Mysteries

In the Galpagos Islands Darwin discoveredplants and animals found nowhere else on Earth

Darwin referred to the origin of species as thatmystery of mysteries (1), and despite decades of

study, evolutionary biologists still cannot agree on

the underlying processes that have produced the

great diversity of life around us


Video: Galpagos Tortoise
http://localhost/var/www/apps/conversion/tmp/scratch_5/24_02Tortoise_SV.mpg


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Figure 24.1


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Speciation, the origin of new species, is at thefocal point of evolutionary theory (2)

Evolutionary theory must explain how new speciesoriginate and how populations evolve

Microevolutionconsists of changes in allelefrequency in a population over time

Macroevolution refers to broad patterns ofevolutionary change above the species level (3)


Animation: Macroevolution
http://localhost/var/www/apps/conversion/tmp/scratch_5/24_01Macroevolution_A.html


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Concept 24.1: The biological species

concept emphasizes reproductive isolation

Speciesis a Latin word meaning kind or

appearance


The biological species concept states that aspecies is a group of populations whose members

have the potential to interbreed in nature and

produce viable, fertile offspring; they do not breed

successfully with other populations (4)


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L imitations of the Biological Species Concept

The biological species concept cannot beapplied to fossils or asexual organisms

(including all prokaryotes)

The biological species concept emphasizes

absence of gene flow

However, gene flow can occur between

distinct species

For example, grizzly bears and polar bearscan mate to produce grolar bears



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Figure 24.4Grizzly bear (U. arctos )

Polar bear (U. mari t imus )

Hybrid grolar bear


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Reproductive I solation

Reproductive isolation is the existence ofbiological factors (barriers) that impede two

species from producing viable, fertile offspring

Hybrids are the offspring of crosses between

different species

Reproductive isolation can be classified by

whether factors act before or after fertilization

(5-6)



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Figure 24.3_a

Prezygotic barriers

Habitat

IsolationTemporal

Isolation

Behavioral

Isolation

Mechanical

Isolation

Gametic

IsolationReduced Hybrid

Viability

Reduced Hybrid

Fertility

Hybrid

Breakdown

Individualsof

differentspecies

MATINGATTEMPT FERTILIZATION

VIABLE,FERTILE

OFFSPRING

Postzygotic barriers

(a) (c) (e)

(d)

(b)

(g)

(k)

(h) (i)

(j)

(l)(f)

(9)


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Prezygotic barriers block fertilization from

occurring by:

Impeding different species from attempting to

mate

Preventing the successful completion of mating

Hindering fertilization if mating is successful


Postzygotic barriers prevent the hybrid zygote

from developing into a viable, fertile adult:Reduced hybrid viability

Reduced hybrid fertility

Hybrid breakdown (7)


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Habitat isolation: Two species encounter each

other rarely, or not at all, because they occupy

different habitats, even though not isolated byphysical barriers


Temporal isolation: Species that breed at

different times of the day, different seasons,

or different years cannot mix their gametes Behavioral isolation: Courtship rituals and other

behaviors unique to a species are effective

barriers Gametic Isolation: Sperm of one species may not

be able to fertilize eggs of another species Mechanical isolation: Morphological differences

can prevent successful mating (8 partial)


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Video: Blue-footed Boobies Courtship Ritual

Video: Giraffe Courtship Ritual

Video: Albatross Courtship Ritual
http://localhost/var/www/apps/conversion/tmp/scratch_5/24_03eAlbatrossCourtship_SV.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_5/24_03eGiraffeCourtship_SV.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_5/24_03eBoobiesCourtship_SV.mpg


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Reduced hybrid viability: Genes of the differentparent species may interact and impair the

hybrids development


Hybrid breakdown: Some first-generation hybrids

are fertile, but when they mate with anotherspecies or with either parent species, offspring of

the next generation are feeble or sterile (8 rest)

Reduced hybrid fertility: Even if hybrids arevigorous, they may be sterile


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Concept 24.2: Speciation can take place

with or without geographic separation

Speciation can occur in two ways:

Allopatric speciation

Sympatric speciation



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Figure 24.5

(a) (b)Allopatric speciation.

A population forms a

new species while

geographically isolated

from its parent population.

Sympatric speciation.

A subset of a population

forms a new species

without geographic

separation.

(10)


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The Process of Allopatric Speciation

The definition of barrier depends on the ability of a

population to disperse (11)

For example, a canyon may create a barrier for

small rodents, but not birds, coyotes, or pollen



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Separate populations may evolve independentlythrough mutation, natural selection, and geneticdrift

Reproductive isolation may arise as a result of

genetic divergence For example, mosquitofish in the Bahamas

comprise several isolated populations in differentponds



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Sympatric (Same Country) Speciation

In sympatric speciation, speciation takes placein geographically overlapping populations

This can occur through polyploidy, habitat

differentiation, and sexual selection. (12)



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Polyploidy

Polyploidy is the presence of extra sets ofchromosomes due to accidents during cell

division

Polyploidy is much more common in plants

than in animals

An autopolyploid is an individual with more

than two chromosome sets, derived from one

species


Fi 24 UN01


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Figure 24.UN01Cell

division

error

2n= 6 Tetraploid cell

4n= 12

2n

2nNew species

(4n)Gametes produced

by tetraploids

(13)

Figure 24 11 4


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Figure 24.11-4

Species A

2n= 6

Species B

2n= 4

Normal

gamete

n= 3

Meiotic error;

chromosome number not

reduced from 2nto n

Unreduced gamete

with 4 chromosomes

Hybrid with7 chromosomes

Unreduced gamete

with 7 chromosomes

Normal

gameten= 3

New species:

viable fertile hybrid

(allopolyploid) 2n= 10

(14)

Allopolyploids have

more than 2 haploid

sets of chromosomes

derived from 2 different

species.


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Sexual Selection

Sexual selection can drive sympatric speciation Sexual selection for mates of different colors has

likely contributed to speciation in cichlid fish in

Lake Victoria (15)



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Allopatric and Sympatric Speciation:

A Review

In allopatric speciation, geographic isolation

restricts gene flow between populations

Reproductive isolation may then arise by naturalselection, genetic drift, or sexual selection in the

isolated populations

Even if contact is restored between populations,

interbreeding is prevented



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In sympatric speciation, a reproductive barrierisolates a subset of a population without

geographic separation from the parent species

Sympatric speciation can result from polyploidy,

natural selection, or sexual selection



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Concept 24.3: Hybrid zones reveal factors

that cause reproductive isolation

A hybrid zone is a region in which members of

different species mate and produce hybrids

Hybrids are the result of mating between specieswith incomplete reproductive barriers (16)



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The fossil record includes examples of species

that appear suddenly, persist essentially

unchanged for some time, and then apparentlydisappear (17)

Niles Eldredge and Stephen Jay Gould coined the

term punctuated equilibria to describe periods of

apparent stasis punctuated by sudden change

The punctuated equilibrium model contrasts with a

model of gradual change in a species existence


Many questions remain concerning how long it

takes for new species to form, or how many genes

need to differ between species

Figure 24 17


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Figure 24.17

(a) Punctuated

pattern

Time

(b) Gradual

pattern

(18)

ap bio chapter 24.pdf

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