Biology Chp 22

8/12/2019 Biology Chp 22

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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures forBio logy, Seventh Edit ion

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 22

Descent with Modification: A Darwinian View of

Life


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Overview: Darwin Introduces a Revolutionary

Theory A new era of biology began on November 24,

1859

The day Charles Darwin published On the

Origin of Species by Means of Natural

Selection


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The Origin of Species

Focused biologists attention on the greatdiversity of organisms

Figure 22.1


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Darwin made two major points in his book

He presented evidence that the many speciesof organisms presently inhabiting the Earth are

descendants of ancestral species

He proposed a mechanism for the evolutionaryprocess, natural selection


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Concept 1: The Darwinian revolution

challenged traditional views of a young Earthinhabited by unchanging species

In order to understand why Darwins ideas

were revolutionary

We need to examine his views in the context of

other Western ideas about Earth and its life


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Concept 2: In The Origin of Species, Darwin

proposed that species change through naturalselection

As the 19th century dawned

It was generally believed that species had

remained unchanged since their creation, but a

major change would challenge this thinking


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The historical context of Darwins life and ideas

Figure 22.2

Linnaeus (classification)

Hutton (gradual geologic change)

Lamarck (species can change)

Malthus (population limits)

Cuvier (fossils, extinction)

Lyell (modern geology)

Darwin (evolution, nutural selection)

Mendel (inheritance)

Wallace (evolution, natural selection)

1750

American Revolution French Revolution U.S. Civil War

1800 1850 1900

1795 Hutton proposes his theory of gradualism.

1798 Malthus publishes Essay on the Principle of Population.

1809 Lamarck publishes his theory of evolution.

1830 Lyell publishes Principles of Geology.

18311836 Darwin travels around the world on HMS Beagle.

Darwin begins his notebooks on the origin of species.1837

Darwin writes his essay on the origin of species.1844

Wallace sends his theory to Darwin.1858

TheOrigin of Speciesis published.1859

Mendel publishes inheritance papers.1865



Resistance to the Idea of Evolution


Shook the deepest roots of Western culture

Challenged a worldview that had been

prevalent for centuries

Plato believed in two worlds: one real world that is

ideal and perfect and an illusory world of

imperfection that we perceive through our senses.

Aristotle believed that all living forms could bearranged on a ladder (scala naturae) of increasing

complexity with every rung taken with perfect,

permanent species.



Carolus Linnaeus

Interpreted organismal adaptations asevidence that the Creator had designed each

species for a specific purpose

Was a founder of taxonomy, classifying lifesdiversity for the greater glory of God



The Old Testament account of creation

fortified the idea that species wereindividually designed and did not evolve.

In the 1700s, the dominant philosophy,

natural theology, was dedicated to studyingthe adaptations of organisms as evidence

that the Creator had designed each species

for a purpose.

Darwins views were influenced by fossils,

the relics or impressions of organisms from

the past, mineralized in sedimentary rocks.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings



Fossils, Cuvier, and Catastrophism

The study of fossils

Helped to lay the groundwork for Darwins ideas

Fossils are remains or traces of organisms

from the past

Usually found in sedimentary rock, which appears

in layers or strata

Figure 22.3



HOW are fossils made?

Sedimentary rocks form when mud and sand

settle to the bottom of seas, lakes, and marshes.

New layers of sediment cover older ones,

creating layers of rock called strata.

Fossils within layers show that a succession of

organisms have populated Earth throughout

time.

Fig. 22.2 Fig. 22.4



Paleontology, the study of fossils, was largely

developed by Georges Cuvier, a French

anatomist.

In particular, Cuvier documented the

succession of fossil species in the Paris Basin.

Cuvier recognized that extinction had been a commonoccurrence in the history of life.

Instead of evolution, Cuvier advocated catastrophism,

that boundaries between strata were due to local flood

or drought that destroyed the species then present.

Later, this area would be repopulated by species

immigrating from other unaffected areas.



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Theories of gradualism and uniformitarianism

In contrast to Cuviers catastrophism, James

Hutton, a Scottish geologist, proposed that thediversity of landforms (e.g., canyons) could be

explained by mechanisms currentlyoperating.

Hutton proposed a theory of gradualism, thatprofound change results from slow, continuous

processes.

Later, Charles Lyell proposed a theory ofuniformitarianism, that geological processes

had not changed throughout Earths history.


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Rates of evolutionary change (Old and New concepts


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Huttons and Lyells observations and theories

had a strong influence on Darwin.

First, if geologic changes result from slow,

continuous processes, rather than sudden

events, then the Earth must be far older than

the 6,000 years assigned by theologians frombiblical inference.

Second, slow and subtle processes persisting

for long periods of time can add up tosubstantial change.



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Lamarcks Theory of Evolution

Lamarck hypothesized that species evolve

Through use and disuse and the inheritance ofacquired traits

But the mechanisms he proposed are

unsupported by evidence

Figure 22.4

L k l d f il i l i


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In 1809, Jean Baptiste Lamarck published a

theory of evolution based on his observationsof fossil invertebrates in the Natural History

Museum of Paris.

Lamarck thought that he saw what appeared tobe several lines of descent in the collected

fossils and current species.

Each was a chronological series of older to

younger fossils leading to a modern species.

Lamarck placed fossils in an evolutionary context


C f


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Central to Lamarcks mechanism of evolution

* concepts of use and disuse of parts and of

inheritance of acquired characteristics. The former proposed that body parts used extensively

to cope with the environment became larger and

stronger, while those not used deteriorated.

The latter proposed that modifications acquired during

the life of an organism could be passed to offspring.

A classic example of these is the long neck of the giraffe in

which individuals could acquire longer necks by reaching forleaves on higher branches and would pass this characteristic to

their offspring.


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Lamarcks theory was a visionary attempt to

explain both the fossil record and the current

diversity of life through its recognition of thegreat age of Earth and adaptation of organisms

to the environment.

However, there is no evidence that acquired

characteristics can be inherited.

Acquired traits (e.g., bigger biceps) do not

change the genes transmitted by gametes to

offspring.



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Darwins Research

As a boy and into adulthood, Charles Darwin

Had a consuming interest in nature

Soon after Darwin received his B.A. degree

He was accepted on board the HMSBeagle,which was about to embark on a voyage

around the world


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The Voyage of the Beagle

During his travels on the Beagle

Darwin observed and collected manyspecimens of South American plants and

animals

Darwin observed various adaptations of plantsand animals

That inhabited many diverse environments


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Darwins interest in the geographic distribution

of species

Was kindled by the Beagles stop at the Galpagos

Islands near the equator west of South America

Figure 22.5

England EUROPENORTH

AMERICA

Galpagos

Islands

Darwin in 1840,

after his return

SOUTHAMERICA

Cape of

Good Hope

Cape Horn

Tierra del Fuego

AFRICA HMS Beagle in port

AUSTRALIA

TasmaniaNew

Zealand

PACIFIC

OCEAN

Andes

ATLANTIC

OCEAN


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Darwins Focus on Adaptation

As Darwin reassessed all that he had observed

during the voyage of the Beagle

He began to perceive adaptation to the

environment and the origin of new species as

closely related processes


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From studies made years after Darwins

voyage

Biologists have concluded that this is indeed

what happened to the Galpagos finches

Figure 22.6ac

(a) Cactus eater.The long,

sharp beak of the cactusground finch (Geospiza

scandens) helps it tear

and eat cactus flowers

and pulp.

(c) Seed eater.The large ground

finch (Geospiza magnirostris)

has a large beak adapted for

cracking seeds that fall from

plants to the ground.

(b) Insect eater.The green warbler

finch (Certhidea olivacea) uses its

narrow, pointed beak to grasp insects.



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Fig. 1.17b

The finches of the Galapagos Islandsdiversified after an initial colonization from themainland to exploit different food sources on

different islands.

py g , , p g j g


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In 1844, Darwin wrote a long essay on the

origin of species and natural selection

But he was reluctant to introduce his theory

publicly, anticipating the uproar it would cause

In June 1858 Darwin received a manuscriptfrom Alfred Russell Wallace

Who had developed a theory of natural

selection similar to Darwins

Darwin quickly finished The Origin of Species

And published it the next year

Th O i i f S i


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Darwin developed two main ideas

Evolution explains lifes unity and diversity

Natural selection is a cause of adaptive

evolution

D t i th M dif i ti


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Descent wi th Modif ication

The phrase descent with modification

Summarized Darwins perception of the unityof life

States that all organisms are related through

descent from an ancestor that lived in theremote past


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In the Darwinian view, the history of life is like a tree

With multiple branchings from a common trunkto the tips of the youngest twigs that represent

the diversity of living organisms

Figure 22.7

Hyracoidea

(Hyraxes)

Sirenia(Manatees

and relatives)

Elephasmaximus

(Asia)

Loxodontaafricana

(Africa)

Loxodontacyclotis

(Africa)

N t l S l ti d Ad t ti


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Natural Selection and Adaptation

Evolutionary biologist Ernst Mayr has dissected

the logic of Darwins theory into three

inferences based on five observations

Observation #1: For any species, population

sizes would increase exponentially If all individuals that are born are able to

reproduced successfully

Birth rate is more than death rate


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Observation #2: Nonetheless, populations tend

to be stable in size

Except for seasonal fluctuations

Observation #3: Resources are limited

Inference #1: Production of more individuals

than the environment can support

Leads to a struggle for existence amongindividuals of a population, with only a fraction

of their offspring surviving


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Observation #4: Members of a population vary

extensively in their characteristics

No two individuals are exactly alike

Figure 22.9


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Observation #5: Much of this variation is

heritable

Inference #2: Survival depends in part on

inherited traits

Individuals whose inherited traits give them ahigh probability of surviving and reproducing

are likely to leave more offspring than other

individuals

Survival of the fittest? Or the luckiest?


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Survival of the fittest? Or the luckiest?

Inference #3: This unequal ability of individuals

to survive and reproduce

Will lead to a gradual change in a population,

with favorable characteristics accumulating

over generations

Affected by natural and artifical selective

pressures- predation, mate choice, diseases

Fig. 1.15


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Copyright

2002 Pearson

Education,

Inc.,

publishing as

Benjamin

Cummings

Artificial Selection


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Artificial Selection

In the process of artificial selection

Humans have modified other species overmany generations by selecting and breeding

individuals that possess desired traits

Figure 22.10

Terminalbud

Lateralbuds

Brussels sproutsCabbage

Flower

clusterLeaves

Cauliflower

Flower

and

stems

Broccoli Wild mustard Kohlrabi

Stem

Kale

Summary of Natural Selection


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Summary of Natural Selection

Natural selection is differential success in

reproduction

That results from the interaction between

individuals that vary in heritable traits and their

environment

If an environment changes over time

Natural selection may result in adaptation to

these new conditions

Mimicry and camouflage


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Mimicry and camouflage

Natural selection can produce an increase over time

In the adaptation of organisms to theirenvironment

Figure 22.11

(a) A flower mantid

in Malaysia

(b) A stick mantid

in Africa

Differential Predation in Guppy Populations


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Differential Predation in Guppy Populations

Researchers have observed natural selection

Leading to adaptive evolution in guppypopulations

Reznick and Endler transplanted guppies from pike-cichlid pools to killifish pools

and measured the average age and size of guppies at maturity over an 11-year period (30 to

60 generations).

EXPERIMENT

Pools with killifish,

but not guppies prior

to transplant

Experimental

transplant of

guppiesPredator: Killifish; preys

mainly on small guppies

Guppies:

Larger at

sexual maturity

than those in

pike-cichlid pools

Predator: Pike-cichlid; preys mainly on large guppies

Guppies: Smaller at sexual maturity than

those in killifish pools

Figure 22.12

Guppy data analysis


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Guppy data analysis

RESULTSAfter 11 years, the average size and age at maturity of guppies in the transplanted

populations increased compared to those of guppies in control populations.

161.5

185.6

67.5

92.3

48.5

Control Population: Guppies

from pools with pike-cichlids

as predators

Experimental Population:

Guppies transplanted to

pools with killifish as

predators

76.1

Males Females

85.7

58.2

Males Females

CONCLUSIONReznick and Endler concluded that the change in predator resulted in different variations

in the population (larger size and faster maturation) being favored. Over a relatively short time, this altered

selection pressure resulted in an observable evolutionary change in the experimental population.


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Example of adaptation and evolution in Drug use


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Example of adaptation and evolution in Drug use

Researchers have developed numerous drugs

to combat HIV

But using these medications selects for

viruses resistant to the drugs

Figure 22.13

PatientNo. 1

Patient No. 2

Patient No. 3

Weeks

Homology Biogeography and the Fossil Record


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Homology, Biogeography, and the Fossil Record

Evolutionary theory take into account:

Homology-- Is similarity resulting from commonancestry

Comparative embryology

Vestigial organs

Molecular homologies

Biogeography-- the geographic distribution ofspecies,

Fossil record

Anatomical Homologies


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Anatomical Homologies

Homologous structures between organisms

Are anatomical resemblances that representvariations on a structural theme that was

present in a common ancestor

Figure 22.14

Human Cat Whale Bat



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Reveals additional anatomical homologies not

visible in adult organisms

Figure 22.15

Pharyngealpouches

Post-anal

tail

Chick embryo Human embryo

Ontogeny repeats Phylogeny


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Ontogeny repeats Phylogeny


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Molecular Homologies


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Molecular Homologies

Biologists also observe

homologies among

organisms at the molecularlevel

Such as genes that

are shared among

organisms inherited

from a common

ancestor


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Anatomical resemblances among species

Are generally reflected in their molecules, theirgenes, and their gene products

Figure 22.16

Species

Human

Rhesus monkey

Mouse

Chicken

Frog

Lamprey14%

54%

69%

87%

95%

100%

Percent of Amino Acids That Are

Identical to the Amino Acids in a

Human Hemoglobin Polypeptide


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Example of the Evolutionary tree of life on Earth


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Example of the Evolutionary tree of life on Earth

The tree assumes that

all life in the planetevolved from ONE

common ancestor:1) Implies that we are all

related to each other

2) That all creatures sharesimilar characteristics

3) That life as we know it had

one sourceGod, ET or

chance?

Biogeography


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Sugar

glider

AUSTRALIA

NORTH

AMERICA

Flying

squirrel

Figure 22.17

Biogeography

Some similar mammals that have adapted to

similar environments

Have evolved independently from different ancestors

The Fossil Record


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The Fossil Record

The succession of forms observed in the fossil record

Is consistent with other inferences about the major branches of descent

in the tree of life

Transitional forms


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The Darwinian view of life

Predicts thatevolutionary

transitions should

leave signs in the

fossil record

Paleontologists

Have discovered

fossils of many such

transitional forms

Figure 22.18

lungfish


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Ancient walking fish

The Coelecanth


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Records and PROOF


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What can affect these records? What can not be recorded?

What Is Theoretical about the Darwinian View of Life?


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In science, a theory

Accounts for many observations and data andattempts to explain and integrate a great

variety of phenomena

Darwins theory of evolution by naturalselection

Integrates diverse areas of biological study

and stimulates many new research questions

Still has many unanswered questions that is

why it is still a THEORY!!!!

Documents

Biology Chp 22