Chapter 14 The Origin of Species

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Chapter 14Chapter 14

The Origin of Species


Mosquito Mystery

• Speciation is the emergence of new species

• In England and North America

– Two species of mosquitoes exist and spread West Nile virus


14.1 The origin of species is the source of biological diversity

• Speciation, the origin of new species

– Is at the focal point of evolution

Figure 14.1


• Earth’s incredible biological diversity is the result of macroevolution

– Which begins with the origin of new species


CONCEPTS OF SPECIES

14.2 What is a species?

• Carolus Linnaeus, a Swedish physician and botanist

– Used physical characteristics to distinguish species

– Developed the binomial system of naming organisms

• Linnaeus’ system established the basis for taxonomy

– The branch of biology concerned with naming and classifying the diverse forms of life


• Similarities between some species and variation within a species

– Can make defining species difficult

Figure 14.2B

Figure 14.2A


The Biological Species Concept

• The biological species concept defines a species as

– A population or group of populations whose members can interbreed and produce fertile offspring


Other Species Concepts

• The morphological species concept

– Classifies organisms based on observable phenotypic traits

• The ecological species concept

– Defines a species by its ecological role

• The phylogenetic species concept

– Defines a species as a set of organisms representing a specific evolutionary lineage


14.3 Reproductive barriers keep species separate

• Reproductive barriers

– Serve to isolate a species’ gene pool and prevent interbreeding

– Are categorized as prezygotic or postzygotic

Table 14.3


Prezygotic Barriers

• Prezygotic barriers

– Prevent mating or fertilization between species


• In temporal isolation

– Two species breed at different times

Figure 14.3A


• In behavioral isolation

– There is little or no sexual attraction between species, due to specific behaviors

Figure 14.3B


Figure 14.3C

• In mechanical isolation

– Female and male sex organs or gametes are not compatible


Postzygotic Barriers

• Postzygotic barriers

– Operate after hybrid zygotes are formed


Figure 14.3D

• One postzygotic barrier is hybrid sterility

– Where hybrid offspring between two species are sterile and therefore cannot mate


MECHANISMS OF SPECIATION

14.4 Geographic isolation can lead to speciation

• In allopatric speciation

– A population is geographically divided, and new species often evolve

A. harrisi A. leucurus

Figure 14.4


14.5 Reproductive barriers may evolve as populations diverge

• Laboratory studies of fruit flies

– Have shown that changes in food sources can cause speciation

Figure 14.5A

Starch medium Maltose medium

Initial sampleof fruit flies

Results ofmating experiments

Female Starch Maltose

Female Same Different

population populations

Mal

e M

alto

se S

tarc

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Mal

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iffer

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ame

Mating frequenciesin experimental group

Mating frequenciesin control group

22 9

208 12

18 15

15


• Geographic isolation in Death Valley

– Has led to the evolution of new species of pupfish

Figure 14.5B A pupfish


14.6 New species can also arise within the same geographic area as the parent species

• In sympatric speciation

– New species may arise without geographic isolation


• Many plant species have evolved by polyploidy

– Multiplication of the chromosome number due to errors in cell division

Figure 14.6B

Parent species

Meioticerror

Self-fertilization

Offspring may be viable and self-fertile

Zygote

Unreduced diploid gametes

2n = 6Diploid

4n = 12Tetraploid

O. gigas

O. lamarckiana

Figure 14.6A


AA BB

AB

AA BB DD

ABD

AA BB DD

Triticum monococcum(14 chromosomes)

Wild Triticum(14 chromosomes)

Sterile hybrid(14 chromosomes)

Meiotic error andself-fertilization

T.turgidumEmmer wheat(28 chromosomes)

T.tauschii(wild)(14 chromosomes)

Sterile hybrid(21 chromosomes)

Meiotic error andself-fertilization

T.aestivumBread wheat(42 chromosomes)

Figure 14.7A

CONNECTION

14.7 Polyploid plants clothe and feed us

• Many plants, including food plants such as bread wheat

– Are the result of hybridization and polyploidy

Figure 14.7B


14.8 Adaptive radiation may occur in new or newly vacated habitats

• In adaptive radiation, the evolution of new species

– Occurs when mass extinctions or colonization provide organisms with new environments


• Island chains

– Provide examples of adaptive radiation

Cactus-seed-eater(cactus finch)

Seed-eater(medium ground finch)

Tool-using insect-eater(woodpecker finch)

Figure 14.8B

1 23

4

5

A B

B

B

C C

C

B

C CD

DD

Figure 14.8A


TALKING ABOUT SCIENCE

14.9 Peter and Rosemary Grant study the evolution of Darwin’s finches

• Peter and Rosemary Grant

– Have documented natural selection acting on populations of Galápagos finches

Figure 14.9


• The occasional hybridization of finch species

– May also have been important in their adaptive radiation


14.10 The tempo of speciation can appear steady or jumpy

• According to the gradualism model

– New species evolve by the gradual accumulation of changes brought about by natural selection

Time

Figure 14.10A


• The punctuated equilibrium model draws on the fossil record

– Where species change the most as they arise from an ancestral species and then change relatively little for the rest of their existence

Time

Figure 14.10B


MACROEVOLUTION

14.11 Evolutionary novelties may arise in several ways

• Many complex structures evolve in many stages

– From simpler versions having the same basic function

Figure 14.11

Light-sensitivecells

Light-sensitivecells

Fluid-filled cavity Transparent protectivetissue (cornea)

Cornea

Layer of light-sensitivecells (retina)

Nervefibers

Nervefibers

Opticnerve

Opticnerve

Opticnerve

Eyecup Retina

Lens

Patch of light-sensitive cells Eyecup

Simple pinholecamera-type eye

Eye withprimitive lens

Complexcamera-type eye

Limpet Abalone Nautilus Marine snail Squid


• Other novel structures result from exaptation

– The gradual adaptation of existing structures to new functions


14.12 Genes that control development are important in evolution

• “Evo-devo”

– Is a field that combines evolutionary and developmental biology


Figure 14.12A

• Many striking evolutionary transformations

– Are the result of a change in the rate or timing of developmental changes


Figure 14.12B

Chimpanzee fetus Chimpanzee adult

Human fetus Human adult

• Changes in the timing and rate of growth

– Have also been important in human evolution


• Stephen Jay Gould, an evolutionary biologist

– Contended that Mickey Mouse “evolved”

Figure 14.12C

Copyright DisneyEnterprises, Inc.


14.13 Evolutionary trends do not mean that evolution is goal directed

• Evolutionary trends reflect species selection

– The unequal speciation or unequal survival of species on a branching evolutionary tree

Figure 14.13

Hippidion and other genera

Nannippus

NeohipparionHipparion

Sinohippus Megahippus

Archaeohippus

Callippus

HypohippusAnchitherium

Miohippus

Parahippus

Paleotherium

Propalaeotherium

Pachynolophus Orohippus

Epihippus

Equus

Pliohippus

Merychippus

Mesohippus

HyracotheriumGrazersBrowsers

EO

CE

NE

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CE

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TP

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Chapter 14 The Origin of Species

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