biology in focus - chapter 23

CAMPBELL BIOLOGY IN FOCUS

© 2014 Pearson Education, Inc.

Urry • Cain • Wasserman • Minorsky • Jackson • Reece

Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge

23Broad Patterns of Evolution


Overview: Lost Worlds

Past organisms were very different from those now alive

The fossil record shows evidence of macroevolution, broad changes above the species level; for example The emergence of terrestrial vertebrates The impact of mass extinctions The origin of flight in birds


Figure 23.1


Figure 23.UN01

Cryolophosaurus skull


Concept 23.1: The fossil record documents life’s history

The fossil record reveals changes in the history of life on Earth

Video: Grand Canyon


Figure 23.2

Dimetrodon

Coccosteus cuspidatus

Stromatolites

Tappania

Tiktaalik

Hallucigenia

Dickinsoniacostata

3,500

1,500600560

510500

400375

300270

200175

100mya

0.5 m

4.5 cm

1 cm

1 m

2.5 cm

Rhomaleosaurusvictor


Figure 23.2a

Stromatolite crosssection


Figure 23.2b

Stromatolites


Figure 23.2c

Tappania


Figure 23.2d

Dickinsonia costata

2.5 cm


Figure 23.2e

Hallucigenia1 cm


Figure 23.2f

Coccosteus cuspidatus4.5 cm


Figure 23.2g

Tiktaalik


Figure 23.2h

Dimetrodon0.5 m


Figure 23.2i

Rhomaleosaurus victor1 m


The Fossil Record

Sedimentary rocks are deposited into layers called strata and are the richest source of fossils

The fossil record indicates that there have been great changes in the kinds of organisms on Earth at different points in time


Few individuals have fossilized, and even fewer have been discovered

The fossil record is biased in favor of species that Existed for a long time Were abundant and widespread Had hard parts


How Rocks and Fossils Are Dated

Sedimentary strata reveal the relative ages of fossils The absolute ages of fossils can be determined by

radiometric dating A “parent” isotope decays to a “daughter” isotope at

a constant rate Each isotope has a known half-life, the time

required for half the parent isotope to decay


Figure 23.3

½

¼⅛

Time (half-lives)

Frac

tion

of p

aren

tis

otop

e re

mai

ning

Remaining“parent”isotope

Accumulating“daughter”

isotope

1 2 4

1 16

3


Radiocarbon dating can be used to date fossils up to 75,000 years old

For older fossils, some isotopes can be used to date volcanic rock layers above and below the fossil


The geologic record is a standard time scale dividing Earth’s history into the Hadean, Archaean, Proterozoic, and Phanerozoic eons

The Phanerozoic encompasses most of the time that animals have existed on Earth

The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic

Major boundaries between geological divisions correspond to extinction events in the fossil record

The Geologic Record

Animation: The Geologic Record


Table 23.1


Table 23.1a


Table 23.1b


The oldest known fossils are stromatolites, rocks formed by the accumulation of sedimentary layers on bacterial mats

Stromatolites date back 3.5 billion years ago Prokaryotes were Earth’s sole inhabitants for more

than 1.5 billion years


Early prokaryotes released oxygen into the atmosphere through the process of photosynthesis

The increase in atmospheric oxygen that began 2.4 billion years ago led to the extinction of many organisms

The eukaryotes flourished in the oxygen-rich atmosphere and gave rise to multicellular organisms


The Origin of New Groups of Organisms

Mammals belong to the group of animals called tetrapods

The evolution of unique mammalian features can be traced through gradual changes over time


Figure 23.4

OTHERTETRA-PODS

Synapsid (300 mya)

Reptiles(includingdinosaurs and birds)

†Very late (non-mammalian)cynodonts

†Dimetrodon

Mammals

Synapsids

Therapsids

Cynodonts

Key to skull bonesArticular DentaryQuadrate Squamosal

Early cynodont (260 mya)

Temporalfenestra(partial view)

Hinge

Temporalfenestra

Hinge

Temporalfenestra

Hinge Hinge

Therapsid (280 mya)New hinge

Very late cynodont (195 mya)

Original hinge

Later cynodont (220 mya)


Figure 23.4a

OTHERTETRAPODS

Reptiles(includingdinosaurs and birds)

Mammals

†Very late (non-mammalian)cynodonts

†Dimetrodon

Cynodonts

Therapsids

Synapsids


Synapsids (300 mya) had single-pointed teeth, large temporal fenestra, and a jaw hinge between the articular and quadrate bones


Therapsids (280 mya) had large dentary bones, long faces, and specialized teeth, including large canines


Figure 23.4b

Synapsid (300 mya)

Therapsid (280 mya)

Key to skull bonesArticularQuadrateDentarySquamosal

Temporalfenestra

Temporalfenestra

Hinge

Hinge


Early cynodonts (260 mya) had large dentary bones in the lower jaw, large temporal fenestra in front of the jaw hinge, and teeth with several cusps


Later cynodonts (220 mya) had teeth with complex cusp patterns and an additional jaw hinge between the dentary and squamosal bones


Very late cynodonts (195 mya) lost the original articular-quadrate jaw hinge

The articular and quadrate bones formed inner ear bones that functioned in transmitting sound

In mammals, these bones became the hammer (malleus) and anvil (incus) bones of the ear


Figure 23.4c

Key to skull bonesArticularQuadrateDentarySquamosal

Hinge

New hinge

Original hinge

Hinge

Temporalfenestra(partial view)

Early cynodont (260 mya)

Later cynodont (220 mya)

Very late cynodont (195 mya)


The history of life on Earth has seen the rise and fall of many groups of organisms

The rise and fall of groups depend on speciation and extinction rates within the group

Concept 23.2: The rise and fall of groups of organisms reflect differences in speciation and extinction rates


Figure 23.5

Commonancestor oflineages Aand B

Millions of years ago

Lineage BLineage A

†

†

†

†

†

†

4 3 2 1 0


Plate Tectonics

At three points in time, the landmasses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago

According to the theory of plate tectonics, Earth’s crust is composed of plates floating on Earth’s mantle


Figure 23.6

Crust

Mantle

Outercore

Innercore


Tectonic plates move slowly through the process of continental drift

Oceanic and continental plates can separate, slide past each other, or collide

Interactions between plates cause the formation of mountains and islands and earthquakes

Video: Lava Flow

Video: Volcanic Eruption


Figure 23.7

Eurasian Plate

PhilippinePlate

AustralianPlate

IndianPlate

ArabianPlate

AfricanPlate

AntarcticPlate

ScotiaPlate

NazcaPlate

SouthAmericanPlate

PacificPlate

CaribbeanPlate

NorthAmericanPlateJuan

de FucaPlate

Cocos Plate


Consequences of Continental Drift

Formation of the supercontinent Pangaea about 250 million years ago had many effects A deepening of ocean basins A reduction in shallow water habitat A colder and drier climate inland


Figure 23.8

Collision ofIndia withEurasia

Present-daycontinents

Laurasia andGondwanalandmasses

The supercontinentPangaeaPangaea

Gondwana

Laurasia

Antarctica

Eurasia

AfricaIndia

Australia

North America

SouthAmerica Madagascar

Cen

ozoi

cM

esoz

oic

Pale

ozoi

c251 mya

135 mya

65.5 mya

45 mya

Present


Figure 23.8a

Laurasia andGondwanalandmasses

The supercontinentPangaeaPangaea

Gondwana

Laurasia

Mes

ozoi

cPa

leoz

oic251 mya

135 mya


Figure 23.8b

Collision ofIndia withEurasia

Present-daycontinents

Antarctica

Eurasia

AfricaIndia

Australia

North America

SouthAmerica Madagascar

Cen

ozoi

c

65.5 mya

45 mya

Present


Continental drift can cause a continent’s climate to change as it moves north or south

Separation of landmasses can lead to allopatric speciation For example, frog species in the subfamilies

Mantellinae and Rhacophorinae began to diverge when Madagascar separated from India


Figure 23.9

Millions of years ago (mya)

Mantellinae(Madagascar only):100 speciesRhacophorinae(India/southeastAsia): 310 species

India

Madagascar

56 mya88 mya

1

1

2

280 60 40 20 0


The distribution of fossils and living groups reflects the historic movement of continents For example, the similarity of fossils in parts of South

America and Africa is consistent with the idea that these continents were formerly attached


Mass Extinctions

The fossil record shows that most species that have ever lived are now extinct

Extinction can be caused by changes to a species’ environment

At times, the rate of extinction has increased dramatically and caused a mass extinction

Mass extinction is the result of disruptive global environmental changes


The “Big Five” Mass Extinction Events

In each of the five mass extinction events, more than 50% of Earth’s species became extinct


Figure 23.10

Time (mya)

Paleozoic Mesozoic Cenozoic

542 488 444 416 359 299 251 200 145 65.5 0E O S D C P Tr J PC N Q

0

100

200

300

400

500

600

700

800

900

1,000

1,100

EraPeriod

To

tal e

xtin

ctio

n ra

te(fa

mili

es p

er m

illio

n ye

ars)

:

Num

ber o

f fam

ilies

:

0

5

10

15

20

25


The Permian extinction defines the boundary between the Paleozoic and Mesozoic eras 251 million years ago

This mass extinction occurred in less than 500,000 years and caused the extinction of about 96% of marine animal species


A number of factors might have contributed to these extinctions Intense volcanism in what is now Siberia Global warming resulting from the emission of large

amounts of CO2 from the volcanoes

Reduced temperature gradient from equator to poles Oceanic anoxia from reduced mixing of ocean waters


The Cretaceous mass extinction 65.5 million years ago separates the Mesozoic from the Cenozoic

Organisms that went extinct include about half of all marine species and many terrestrial plants and animals, including most dinosaurs


The presence of iridium in sedimentary rocks suggests a meteorite impact about 65 million years ago

Dust clouds caused by the impact would have blocked sunlight and disturbed global climate

The Chicxulub crater off the coast of Mexico is evidence of a meteorite collision that dates to the same time


Figure 23.11

NORTHAMERICA

YucatánPeninsula

Chicxulubcrater


Is a Sixth Mass Extinction Under Way?

Scientists estimate that the current rate of extinction is 100 to 1,000 times the typical background rate

Extinction rates tend to increase when global temperatures increase

Data suggest that a sixth, human-caused mass extinction is likely to occur unless dramatic action is taken


Figure 23.12

Mass extinctions

Cooler WarmerRelative temperature

0 1 2−2 −1−3−2

−1

0

1

2

3R

elat

ive

extin

ctio

n ra

te o

fm

arin

e an

imal

gen

era

3 4


Consequences of Mass Extinctions

Mass extinction can alter ecological communities and the niches available to organisms

It can take 5–100 million years for diversity to recover following a mass extinction

The type of organisms residing in a community can change with mass extinction For example, the percentage of marine predators

increased after the Permian and Cretaceous mass extinctions

Mass extinction can pave the way for adaptive radiations


Figure 23.13

Time (mya)

Paleozoic Mesozoic Cenozoic

542 488 444 416 359 299 251 200 145 65.5 0E O S D C P Tr J PC N

Q

EraPeriod

0

10

20

30

40

50

Pred

ator

gen

era

(%)

Permian massextinction

Cretaceousmass extinction


Adaptive Radiations

Adaptive radiation is the evolution of many diversely adapted species from a common ancestor

Adaptive radiations may follow Mass extinctions The evolution of novel characteristics The colonization of new regions


Worldwide Adaptive Radiations

Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs

The disappearance of dinosaurs (except birds) allowed for the expansion of mammals in diversity and size

Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods


Figure 23.14

Ancestralmammal

ANCESTRALCYNODONT

Time (millions of years ago)250 200 150 100 50 0

Eutherians(5,010species)

Marsupials(324species)

Monotremes(5 species)


Regional Adaptive Radiations

Adaptive radiations can occur when organisms colonize new environments with little competition

The Hawaiian Islands are one of the world’s great showcases of adaptive radiation

Animation: Allometric Growth


Figure 23.15

Close North Americanrelative, the tarweedCarlquistia muirii

Argyroxiphiumsandwicense

Dubautia linearisDubautia scabra

Dubautia waialealae

Dubautia laxa KAUAI5.1

millionyears OAHU

3.7millionyears

HAWAII0.4

millionyears

1.3millionyearsMAUI

MOLOKAI

LANAI

N


Figure 23.15a

KAUAI5.1

millionyears

OAHU3.7

millionyears

HAWAII0.4

millionyears

1.3 million years MAUI

MOLOKAI

LANAI

N


Figure 23.15b

Close North Americanrelative, the tarweedCarlquistia muirii


Figure 23.15c

Dubautia waialealae


Figure 23.15d

Dubautia laxa


Figure 23.15e

Dubautia scabra


Figure 23.15f

Argyroxiphiumsandwicense


Figure 23.15g

Dubautia linearis


Studying genetic mechanisms of change can provide insight into large-scale evolutionary change

Concept 23.3: Major changes in body form can result from changes in the sequences and regulation of developmental genes


Effects of Development Genes

Genes that program development influence the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult


Changes in Rate and Timing

Heterochrony is an evolutionary change in the rate or timing of developmental events

It can have a significant impact on body shape The contrasting shapes of human and chimpanzee

skulls are the result of small changes in relative growth rates


Figure 23.16

Chimpanzee infant Chimpanzee adult

Chimpanzee adultChimpanzee fetus

Human adultHuman fetus


Figure 23.16a

Chimpanzee infant Chimpanzee adult


Another example of heterochrony can be seen in the skeletal structure of bat wings, which resulted from increased growth rates of the finger bones


Figure 23.17

Hand andfinger bones


Heterochrony can alter the timing of reproductive development relative to the development of nonreproductive organs

In paedomorphosis, the rate of reproductive development accelerates compared with somatic development

The sexually mature species may retain body features that were juvenile structures in an ancestral species


Figure 23.18

Gills


Changes in Spatial Pattern

Substantial evolutionary change can also result from alterations in genes that control the placement and organization of body parts

Homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged


Hox genes are a class of homeotic genes that provide positional information during animal development

If Hox genes are expressed in the wrong location, body parts can be produced in the wrong location

For example, in crustaceans, a swimming appendage can be produced instead of a feeding appendage


The Evolution of Development

Adaptive evolution of both new and existing genes may have played a key role in shaping the diversity of life

Developmental genes may have been particularly important in this process


Changes in Gene Sequence

New morphological forms likely come from gene duplication events that produce new developmental genes

A possible mechanism for the evolution of six-legged insects from a many-legged crustacean ancestor has been demonstrated in lab experiments

Specific changes in the Ubx gene have been identified that can “turn off” leg development


Figure 23.19

Hox gene 6 Hox gene 7 Hox gene 8

About 400 mya

Drosophila Artemia

Ubx


Changes in Gene Regulation

Changes in morphology likely result from changes in the regulation of developmental genes rather than changes in the sequence of developmental genes For example, threespine sticklebacks in lakes have

fewer spines than their marine relatives The gene sequence remains the same, but the

regulation of gene expression is different in the two groups of fish


Figure 23.UN03

Threespine stickleback(Gasterosteus aculeatus)

Ventral spines


Figure 23.20

Hypothesis A: Differences insequence

Hypothesis B: Differences inexpression

Results

Marine stickleback embryo:expression in ventral spine andmouth regions

Lake stickleback embryo:expression only in mouthregions

Result: NoThe 283 amino acids of the Pitx1protein are identical.Result: Yes

Red arrows indicate regions of Pitx1expression.


Figure 23.20a

Marine stickleback embryo:expression in ventral spine andmouth regions



Figure 23.20b

Lake stickleback embryo:expression only in mouthregions



Concept 23.4: Evolution is not goal oriented

Evolution is like tinkering—it is a process in which new forms arise by the slight modification of existing forms


Evolutionary Novelties

Most novel biological structures evolve in many stages from previously existing structures

Complex eyes have evolved from simple photosensitive cells independently many times

Exaptations are structures that evolve in one context but become co-opted for a different function

Natural selection can only improve a structure in the context of its current utility


Figure 23.21

(a) Patch of pigmented cellsPigmented cells(photoreceptors)

Nervefibers

Epithelium

Example: Patella, a limpet

(b) Eyecup

Nerve fibers

Pigmentedcells

Example: Pleurotomaria, aslit shell mollusc

(c) Pinhole camera-type eye

EpitheliumFluid-filledcavity

Opticnerve Pigmented

layer (retina)Example: Nautilus

(d) Eye with primitive lens

Cellularmass(lens)

Cornea

Optic nerve

Example: Murex, a marinesnail

Cornea

Lens

RetinaOpticnerve

(e) Complex camera lens-type eye

Example: Loligo, a squid


Figure 23.21a

(a) Patch of pigmented cellsPigmented cells(photoreceptors)

Nervefibers

Epithelium

Example: Patella, a limpet


Figure 23.21b

(b) Eyecup

Nerve fibers

Pigmentedcells

Example: Pleurotomaria, aslit shell mollusc


Figure 23.21c

(c) Pinhole camera-type eye

EpitheliumFluid-filledcavity

Opticnerve Pigmented

layer (retina)Example: Nautilus


Figure 23.21d

(d) Eye with primitive lens

Cellularmass(lens)

Cornea

Optic nerve

Example: Murex, a marinesnail


Figure 23.21e

Cornea

Lens

RetinaOpticnerve

(e) Complex camera lens-type eye

Example: Loligo, a squid


Evolutionary Trends

Extracting a single evolutionary progression from the fossil record can be misleading

Apparent trends should be examined in a broader context

The species selection model suggests that differential speciation success may determine evolutionary trends

Evolutionary trends do not imply an intrinsic drive toward a particular phenotype


Figure 23.22

Holocene

Pleistocene

Pliocene

Mio

cene

Equus

Sino

hipp

us

Meg

ahip

pus

Hyp

ohip

pus

Arc

haeo

hipp

us

Anchitherium

0

5

10

15

20

25

30

35

40

45

50

55

Olig

ocen

eEo

cene

Para

hipp

us

Pliohippus

Merychippus

Mesohippus

Mio

hipp

us

Hap

lohi

ppus

Pala

eoth

eriu

m

Pach

ynol

ophu

s

Prop

alae

othe

rium

Epih

ippu

s

Oro

hipp

us

Hyracotherium

Hyracotheriumrelatives

KeyGrazersBrowsers

Hip

pario

n

Neo

hipp

ario

n

Nan

nipp

us

Cal

lippu

s

Hip

pidi

on a

ndcl

ose

rela

tives

Mill

ions

of y

ears

ago


Figure 23.22a

25

30

35

40

45

50

55

Olig

ocen

eEo

cene

Mesohippus

Mio

hipp

us

Hap

lohi

ppus

Pala

eoth

eriu

m

Pach

ynol

ophu

s

Prop

alae

othe

rium

Epih

ippu

s

Oro

hipp

us

Hyracotherium

Hyracotheriumrelatives

GrazersBrowsers

Mill

ions

of y

ears

ago


Figure 23.22b

GrazersBrowsers

Mill

ions

of y

ears

ago

Holocene

Pleistocene

Pliocene

Mio

cene

Equus

Sino

hipp

us

Meg

ahip

pus

Hyp

ohip

pus

Arc

haeo

hipp

us

Anchitherium

0

5

10

15

20

Para

hipp

us

Pliohippus

Merychippus

Hip

pario

n

Neo

hipp

ario

n

Mio

-hi

ppus


Figure 23.UN02

Paleocene Eocene

Millions of years ago (mya)

Species withplanktonic larvae

Species withnonplanktonic

larvae

65 60 55 50 45 40 35


Figure 23.UN04

Flies andfleas

Caddisflies

Moths andbutterfliesHerbivory

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