AP Biology Ch 23 24.pdf - North Lamar ISD

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Bellringer: Grade FRQ’s

• Grade the writing examples (Scale 0-3 pts)

• Discuss with shoulder partner

• Now grade with a rubric

• Discuss with shoulder partner

This should give you ideas on how to write

for AP Biology Tests


Chapter 23 Notes


Fig. 23-13

Original population

(c) Stabilizing

selection

(b) Disruptive selection(a) Directional selection

Phenotypes (fur color)Originalpopulation

Evolvedpopulation


The Key Role of Natural Selection in Adaptive Evolution

• Natural selection increases the frequencies of

alleles that enhance survival and reproduction

• Adaptive evolution occurs as the match

between an organism and its environment

increases


Fig. 23-14

(a) Color-changing ability in cuttlefish

(b) Movable jawbones insnakes

Movable bones


• Because the environment can change,

adaptive evolution is a continuous process

• Genetic drift and gene flow do not consistently

lead to adaptive evolution as they can increase

or decrease the match between an organism

and its environment


Sexual Selection

• Sexual selection is natural selection for

mating success

• It can result in sexual dimorphism, marked

differences between the sexes in secondary

sexual characteristics


Fig. 23-15


• Intrasexual selection is competition among individuals of one sex (often males) for mates of the opposite sex

• Intersexual selection, often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates

• Male showiness due to mate choice can increase a male’s chances of attracting a female, while decreasing his chances of survival


• How do female preferences evolve?

• The good genes hypothesis suggests that if a

trait is related to male health, both the male

trait and female preference for that trait should

be selected for


Fig. 23-16

SC male graytree frog

Female graytree frog

LC male graytree frog

EXPERIMENT

SC sperm Eggs LC sperm

Offspring ofLC father

Offspring ofSC father

Fitness of these half-sibling offspring compared

RESULTS

1995Fitness Measure 1996

Larval growth

Larval survival

Time to metamorphosis

LC better

NSD

LC better(shorter)

LC better(shorter)

NSD

LC better

NSD = no significant difference; LC better = offspring of LC males

superior to offspring of SC males.


The Preservation of Genetic Variation

• Various mechanisms help to preserve genetic

variation in a population


Diploidy

• Diploidy maintains genetic variation in the form

of hidden recessive alleles


Balancing Selection

• Balancing selection occurs when natural

selection maintains stable frequencies of two or

more phenotypic forms in a population


• Heterozygote advantage occurs when

heterozygotes have a higher fitness than do

both homozygotes

• Natural selection will tend to maintain two or

more alleles at that locus

• The sickle-cell allele causes mutations in

hemoglobin but also confers malaria resistance

Heterozygote Advantage


Fig. 23-17

0–2.5%

Distribution ofmalaria caused byPlasmodium falciparum(a parasitic unicellular eukaryote)

Frequencies of thesickle-cell allele

2.5–5.0%

7.5–10.0%

5.0–7.5%

>12.5%

10.0–12.5%


• In frequency-dependent selection, the

fitness of a phenotype declines if it becomes

too common in the population

• Selection can favor whichever phenotype is

less common in a population

Frequency-Dependent Selection


Fig. 23-18

“Right-mouthed”

1981

“Left-mouthed”

Sample year

1.0

0.5

0’82 ’83 ’84 ’85 ’86 ’87 ’88 ’89 ’90


Neutral Variation

• Neutral variation is genetic variation that

appears to confer no selective advantage or

disadvantage

• For example,

– Variation in noncoding regions of DNA

– Variation in proteins that have little effect on

protein function or reproductive fitness


Why Natural Selection Cannot Fashion Perfect Organisms

1. Selection can act only on existing variations

2. Evolution is limited by historical constraints

3. Adaptations are often compromises

4. Chance, natural selection, and the

environment interact


You should now be able to:

1. Explain why the majority of point mutations

are harmless

2. Explain how sexual recombination generates

genetic variability

3. Define the terms population, species, gene

pool, relative fitness, and neutral variation

4. List the five conditions of Hardy-Weinberg

equilibrium


5. Apply the Hardy-Weinberg equation to a

population genetics problem

6. Explain why natural selection is the only

mechanism that consistently produces

adaptive change

7. Explain the role of population size in genetic

drift


8. Distinguish among the following sets of terms:

directional, disruptive, and stabilizing

selection; intrasexual and intersexual

selection

9. List four reasons why natural selection cannot

produce perfect organisms


PowerPoint® Lecture Presentations for

BiologyEighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Chapter 24

The Origin of Species


What you need to know…

• The difference between microevolution and

macroevolution.

• The biological concept of species.

• Prezygotic and postzygotic barriers that maintain

reproductive isolation in natural populations.

• How allopatric and sympatric speciation are similar

and different.

• How an autopolyploid or an allopolypoloid

chromsomal change can lead to sympatric speciation.

• How punctuated equilibrium and gradualism describe

2 different tempos of speciation.


Overview: That “Mystery of Mysteries”

• In the Galápagos Islands Darwin discovered

plants and animals found nowhere else on

Earth

Video: Galápagos Tortoise

24_01Tortoise_SV.mpg

24_01Tortoise_SV.mpg

../DVD_2_Chs_22-39 (E)/Chapter_24/A_PowerPoint_Lectures/24_Lecture_Presentation/24_01Tortoise_SV.mpg


• Speciation, the origin of new species, is at the focal point of evolutionary theory

• Evolutionary theory must explain how new species originate and how populations evolve

• Microevolution consists of adaptations that evolve within a population, confined to one gene pool

• Macroevolution refers to evolutionary change above the species level

Animation: Macroevolution

24_17Macroevolution_A.html

24_17Macroevolution_A.html

../DVD_2_Chs_22-39 (E)/Chapter_24/A_PowerPoint_Lectures/24_Lecture_Presentation/24_17Macroevolution_A.swf


Concept 24.1: The biological species concept emphasizes reproductive isolation

• Species is a Latin word meaning “kind” or

“appearance”

• Biologists compare morphology, physiology,

biochemistry, and DNA sequences when

grouping organisms


The Biological Species Concept

• biological species concept - states that a

species 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

• Gene flow between populations holds the

phenotype of a population together

Fig. 24-2

(a) Similarity between different species

(b) Diversity within a species


Reproductive Isolation

• Reproductive isolation is the existence of

biological 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

Fig. 24-4

Prezygotic barriers

Habitat Isolation

Individuals

of differentspecies

Temporal Isolation Behavioral Isolation

Matingattempt

Mechanical Isolation Gametic Isolation

Fertilization

Reduced Hybrid Viability Reduced Hybrid Fertility

Postzygotic barriers

Hybrid Breakdown

Viable,fertile

offspring

(a)

(b)

(d)

(c) (e) (f) (g) (h) (i)

(j)

(l)

(k)

Fig. 24-4a

Habitat Isolation Temporal Isolation

Prezygotic barriers

Behavioral Isolation

Matingattempt

Mechanical Isolation

(f)(e)(c)(a)

(b)

(d)

Individualsof

differentspecies

Fig. 24-4i

Prezygotic barriers

Gametic Isolation

Fertilization

Reduced Hybrid Viability


Reduced Hybrid Fertility Hybrid Breakdown

Viable,fertile

offspring

(g) (h) (i)

(j)

(l)

(k)

Fig. 24-4b

Prezygotic barriers

Habitat Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation

Individualsof

differentspecies

Matingattempt

Prezygotic barriers

Fig. 24-4j

Gametic Isolation

Fertilization

Reduced Hybrid Viability Reduced Hybrid Fertility


Hybrid Breakdown

Viable,fertile

offspring


• 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

– Include: Habitat isolation, behavioral

isolation, temporal isolation, mechanical

isolation, gametic isolation


• Habitat isolation: Two species encounter each

other rarely, or not at all, because they occupy

different habitats, even though not isolated by

physical barriers


•Temporal isolation: Species that breed at

different times of the day, different seasons,

or different years cannot mix their gametes

Eastern spotted skunk(Spilogale putorius)

Western spotted skunk(Spilogale gracilis)


•Behavioral isolation:

Courtship rituals and other

behaviors unique to a

species are effective

barriers

Video: Blue-footed Boobies Courtship Ritual

Video: Giraffe Courtship Ritual

Video: Albatross Courtship Ritual

Courtship ritual of blue-footed boobies

24_04eBoobiesCourtship_SV.mpg

24_04eBoobiesCourtship_SV.mpg

24_04eGiraffeCourtship_SV.mpg

24_04eGiraffeCourtship_SV.mpg

24_04eAlbatrossCourtship_SV.mpg

24_04eAlbatrossCourtship_SV.mpg

../DVD_2_Chs_22-39 (E)/Chapter_24/A_PowerPoint_Lectures/24_Lecture_Presentation/24_04eBoobiesCourtship_SV.mpg

../DVD_2_Chs_22-39 (E)/Chapter_24/A_PowerPoint_Lectures/24_Lecture_Presentation/24_04eGiraffeCourtship_SV.mpg

../DVD_2_Chs_22-39 (E)/Chapter_24/A_PowerPoint_Lectures/24_Lecture_Presentation/24_04eAlbatrossCourtship_SV.mpg


•Mechanical isolation:

Morphological

differences can prevent

successful mating

Bradybaena with shellsspiraling in oppositedirections


•Gametic isolation:

Sperm of one species

may not be able to

fertilize eggs of another

species

Sea urchins


• Postzygotic barriers prevent the hybrid

zygote from developing into a viable, fertile

adult:

– Reduced hybrid viability

– Reduced hybrid fertility

– Hybrid breakdown


•Reduced hybrid

viability: Genes of the

different parent species

may interact and impair

the hybrid’s

development

Ensatina hybrid


•Reduced hybrid fertility: Even if hybrids are

vigorous, they may be sterile

+ =

Donkey Horse Mule (sterile hybrid)


•Hybrid breakdown:

Some first-generation

hybrids are fertile, but

when they mate with

another species or with

either parent species,

offspring of the next

generation are feeble

or sterile Hybrid cultivated rice plants with

stunted offspring (center)


Limitations of the Biological Species Concept

• The biological species concept cannot be

applied to fossils or asexual organisms

(including all prokaryotes)


Other Definitions of Species

• Other species concepts emphasize the unity

within a species rather than the separateness

of different species

• The morphological species concept defines

a species by structural features

– It applies to sexual and asexual species but

relies on subjective criteria


• The ecological species concept views a

species in terms of its ecological niche

– It applies to sexual and asexual species and

emphasizes the role of disruptive selection

• The phylogenetic species concept: defines a

species as the smallest group of individuals on

a phylogenetic tree

– It applies to sexual and asexual species, but it

can be difficult to determine the degree of

difference required for separate species


Concept 24.2: Speciation can take place with or without geographic separation

• Speciation can occur in two ways:

– Allopatric speciation

– Sympatric speciation

Fig. 24-5

(a) Allopatric speciation (b) Sympatric speciation


Allopatric (“Other Country”) Speciation

• In allopatric speciation, gene flow is

interrupted or reduced when a population is

divided into geographically isolated

subpopulations


The Process of Allopatric Speciation

• The definition of barrier depends on the ability

of a population to disperse

• Separate populations may evolve

independently through mutation, natural

selection, and genetic drift

Fig. 24-6

A. harrisi A. leucurus


Evidence of Allopatric Speciation

• Regions with many geographic barriers

typically have more species than do regions

with fewer barriers

Fig. 24-7

Mantellinae(Madagascar only):100 species

Rhacophorinae(India/SoutheastAsia): 310 species

Other Indian/

Southeast Asianfrogs

Millions of years ago (mya)

1 2 3

1 2 3

100 80 60 40 20 0

88 mya 65 mya 56 mya

India

Madagascar


• Reproductive isolation between populations

generally increases as the distance between

them increases

Fig. 24-8

Geographic distance (km)

Deg

ree

of

rep

rod

ucti

ve i

so

lati

on

00

50 100 150 250200 300

0.5

1.0

1.5

2.0


• Barriers to reproduction are intrinsic;

separation itself is not a biological barrier


Sympatric (“Same Country”) Speciation

• In sympatric speciation, speciation takes

place in geographically overlapping populations


Polyploidy

• Polyploidy is the presence of extra sets of

chromosomes due to accidents during cell

division

• An autopolyploid is an individual with more

than two chromosome sets, derived from one

species

Fig. 24-10-1

2n = 6 4n = 12

Failure of celldivision afterchromosomeduplication givesrise to tetraploid

tissue.

Fig. 24-10-2

2n = 6 4n = 12


tissue.

2n

Gametesproducedare diploid..

Fig. 24-10-3

2n = 6 4n = 12


tissue.

2n

Gametesproducedare diploid..

4n

Offspring withtetraploidkaryotypes maybe viable andfertile.


• An allopolyploid is a species with multiple

sets of chromosomes derived from different

species

Fig. 24-11-1

Species A2n = 6

Normalgameten = 3

Meioticerror

Species B2n = 4

Unreducedgametewith 4chromosomes

Fig. 24-11-2

Species A2n = 6

Normalgameten = 3

Meioticerror

Species B2n = 4


Hybridwith 7chromosomes

Fig. 24-11-3

Species A2n = 6

Normalgameten = 3

Meioticerror

Species B2n = 4




Normalgameten = 3

Fig. 24-11-4

Species A2n = 6

Normalgameten = 3

Meioticerror

Species B2n = 4




Normalgameten = 3

Viable fertilehybrid(allopolyploid)2n = 10


• Polyploidy is much more common in plants

than in animals

• Many important crops (oats, cotton, potatoes,

tobacco, and wheat) are polyploids


Habitat Differentiation

• Sympatric speciation can also result from the

appearance of new ecological niches

• For example, the North American maggot fly

can live on native hawthorn trees as well as

more recently introduced apple trees


Sexual Selection

• Sexual selection can drive sympatric speciation

• Sexual selection for mates of different colors

has likely contributed to the speciation in cichlid

fish in Lake Victoria

Fig. 24-12

EXPERIMENT

Normal lightMonochromatic

orange light

P.pundamilia

P. nyererei


Allopatric and Sympatric Speciation: A Review

• In allopatric speciation, geographic isolation

restricts gene flow between populations

• Reproductive isolation may then arise by

natural selection, genetic drift, or sexual

selection in the isolated populations

• Even if contact is restored between

populations, interbreeding is prevented


• In sympatric speciation, a reproductive barrier

isolates a subset of a population without

geographic separation from the parent species

• Sympatric speciation can result from

polyploidy, natural selection, or sexual

selection


Concept 24.3: Hybrid zones provide opportunities to study factors that cause reproductive isolation

• A hybrid zone is a region in which members of

different species mate and produce hybrids


Patterns Within Hybrid Zones

• A hybrid zone can occur in a single band where

adjacent species meet

• Hybrids often have reduced fitness compared

with parent species

• The distribution of hybrid zones can be more

complex if parent species are found in multiple

habitats within the same region

Fig. 24-13

EUROPE

Fire-belliedtoad range

Hybrid zone

Yellow-belliedtoad range

Yellow-bellied toad,

Bombina variegata

Fire-bellied toad,

Bombina bombina

Allele

fre

qu

en

cy (

log

scale

)

Distance from hybrid zone center (km)

40 30 20 2010 100

0.01

0.1

0.5

0.9

0.99


Hybrid Zones over Time

• When closely related species meet in a hybrid

zone, there are three possible outcomes:

– Strengthening of reproductive barriers

– Weakening of reproductive barriers

– Continued formation of hybrid individuals


Reinforcement: Strengthening Reproductive Barriers

• The reinforcement of barriers occurs when

hybrids are less fit than the parent species

• Over time, the rate of hybridization decreases

• Where reinforcement occurs, reproductive

barriers should be stronger for sympatric than

allopatric species

Fig. 24-15

Sympatric malepied flycatcher

Allopatric malepied flycatcher

Pied flycatchers

Collared flycatchers

Nu

mb

er

of

fem

ale

s

(none)

Females mating

with males from:Ownspecies

Other

species

Sympatric males

Own

speciesOther

species

Allopatric males

0

4

8

12

16

20

24

28


Fusion: Weakening Reproductive Barriers

• If hybrids are as fit as parents, there can be

substantial gene flow between species

• If gene flow is great enough, the parent species

can fuse into a single species

Fig. 24-16

Pundamilia nyererei Pundamilia pundamilia

Pundamilia “turbid water,”hybrid offspring from a location

with turbid water


Concept 24.4: Speciation can occur rapidly or slowly and can result from changes in few or many genes

• Many questions remain concerning how long it

takes for new species to form, or how many

genes need to differ between species


The Time Course of Speciation

• Broad patterns in speciation can be studied

using the fossil record, morphological data, or

molecular data


Patterns in the Fossil Record

• The fossil record includes examples of species that appear suddenly, persist essentially unchanged for some time, and then apparently disappear

• Niles Eldredge and Stephen Jay Gould coined the term punctuated equilibrium 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

Fig. 24-17

(a) Punctuated pattern

(b) Gradual pattern

Time


Speciation Rates

• The punctuated pattern in the fossil record and

evidence from lab studies suggests that

speciation can be rapid

• The interval between speciation events can

range from 4,000 years (some cichlids) to

40,000,000 years (some beetles), with an

average of 6,500,000 years

Fig. 24-18

(a) The wild sunflower Helianthus anomalus

H. anomalus

H. anomalus

H. anomalus

(b) The genetic composition of three chromosomes in H.anomalus and in experimental hybrids

Chromosome 1

Chromosome 2

Chromosome 3

Experimental hybrid

Experimental hybrid

Experimental hybrid

Key

Region diagnostic forparent species H. petiolaris

Region diagnostic forparent species H. annuus

Region lacking information on parental origin

Fig. 24-18a

(a) The wild sunflower Helianthus anomalus

Fig. 24-18b

(b) The genetic composition of three chromosomes in H.

anomalus and in experimental hybrids

Region lacking information on parental origin

Region diagnostic for

parent species H. petiolarisRegion diagnostic for

parent species H. annuus

Key

Experimental hybrid

Experimental hybrid

Experimental hybrid

Chromosome 3

Chromosome 2

Chromosome 1

H. anomalus

H. anomalus

H. anomalus


Studying the Genetics of Speciation

• The explosion of genomics is enabling

researchers to identify specific genes involved

in some cases of speciation

• Depending on the species in question,

speciation might require the change of only a

single allele or many alleles

Fig. 24-19

Fig. 24-20

(a) Typical Mimulus lewisii (b) M. lewisii with an M. cardinalis flower-color allele

(c) Typical Mimulus cardinalis (d) M. cardinalis with an M. lewisii flower-color allele


You should now be able to:

1. Define and discuss the limitations of the four species concepts

2. Describe and provide examples of prezygotic and postzygotic reproductive barriers

3. Distinguish between and provide examples of allopatric and sympatric speciation

4. Explain how polyploidy can cause reproductive isolation

5. Define the term hybrid zone and describe three outcomes for hybrid zones over time

AP Biology Ch 23 24.pdf - North Lamar ISD

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