The origin of species

publishing as Benjamin Cummings• Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species • In order to understand why Darwin

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PowerPoint Lectures for

Biology, Seventh Edition

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

Origin of Species by Means of Natural Selection

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diversity of organisms

Figure 22.1

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• Darwin made two major points in his book

of organisms presently inhabiting the Earth are descendants of ancestral species

process, natural selection

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• Concept 22.1: The Darwinian revolution

challenged traditional views of a young Earth inhabited by unchanging species

• In order to understand why Darwin’s ideas

were revolutionary

other Western ideas about Earth and its life

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• The historical context of Darwin’s 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

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.

1831–1836 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

The Origin of Species is published.

1859

Mendel publishes inheritance papers.1865

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Resistance to the Idea of Evolution

prevalent for centuries

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The Scale of Nature and Classification of Species

• The Greek philosopher Aristotle

• The Old Testament of the Bible

by God and therefore perfect

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• Carolus Linnaeus

evidence that the Creator had designed each species for a specific purpose

diversity “for the greater glory of God”

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Fossils, Cuvier, and Catastrophism

• The study of fossils

• Fossils are remains or traces of organisms

from the past

in layers or strata

Figure 22.3

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• Paleontology, the study of fossils

Georges Cuvier

• Cuvier opposed the idea of gradual

evolutionary change

speculating that each boundary between strata represents a catastrophe

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Theories of Gradualism

• Gradualism

place through the cumulative effect of slow but continuous processes

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• Geologists Hutton and Lyell

result from slow continuous actions still operating today

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Lamarck’s Theory of Evolution

• Lamarck hypothesized that species evolve

acquired traits

unsupported by evidence

Figure 22.4

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• Concept 22.2: In The Origin of Species, Darwin

proposed that species change through natural selection

• As the 19th century dawned

remained unchanged since their creation, but a major change would challenge this thinking

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Darwin’s Research

• As a boy and into adulthood, Charles Darwin

• Soon after Darwin received his B.A degree

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

specimens of South American plants and animals

• Darwin observed various adaptations of plants

and animals

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• Darwin’s interest in the geographic distribution

of species

Islands near the equator west of South America

Figure 22.5

NORTHAMERICA

GalápagosIslands

Darwin in 1840,after his return

SOUTHAMERICA

Cape ofGood Hope

Cape HornTierra del Fuego

AUSTRALIA

Tasmania

NewZealand

PACIFIC OCEAN

ATLANTIC OCEAN

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Darwin’s Focus on Adaptation

• As Darwin reassessed all that he had observed

during the voyage of the Beagle

environment and the origin of new species as closely related processes

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• From studies made years after Darwin’s

voyage

what happened to the Galápagos finches

Figure 22.6a–c

(a) Cactus eater The long,

sharp beak of the cactus

ground finch (Geospiza

scandens) helps it tear

and eat cactus flowersand pulp

(c) Seed eater The large ground

finch (Geospiza magnirostris)

has a large beak adapted forcracking seeds that fall fromplants to the ground

(b) Insect eater The green warbler

finch (Certhidea olivacea) uses its

narrow, pointed beak to grasp insects

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• In 1844, Darwin wrote a long essay on the

origin of species and natural selection

publicly, anticipating the uproar it would cause

• In June 1858 Darwin received a manuscript

from Alfred Russell Wallace

selection similar to Darwin’s

• Darwin quickly finished The Origin of Species

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The Origin of Species

• Darwin developed two main ideas

evolution

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Descent with Modification

• The phrase descent with modification

of life

descent from an ancestor that lived in the remote past

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

to the tips of the youngest twigs that represent the diversity of living organisms

Figure 22.7

Hyracoidea (Hyraxes)

Sirenia (Manatees and relatives)

(Asia)

Loxodonta africana

(Africa)

Loxodonta cyclotis

(Africa)

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Natural Selection and Adaptation

• Evolutionary biologist Ernst Mayr

three inferences based on five observations

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• Observation #1: For any species, population

sizes would increase exponentially

successfully

Figure 22.8

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• Observation #2: Nonetheless, populations tend

to be stable in size

• Observation #3: Resources are limited

• Inference #1: Production of more individuals

than the environment can support

individuals 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

Figure 22.9

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• Observation #5: Much of this variation is

heritable

• Inference #2: Survival depends in part on

inherited traits

high probability of surviving and reproducing are likely to leave more offspring than other individuals

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• Inference #3: This unequal ability of individuals

to survive and reproduce

with favorable characteristics accumulating over generations

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Artificial Selection

• In the process of artificial selection

many generations by selecting and breeding individuals that possess desired traits

Figure 22.10

Terminalbud

Lateralbuds

Brussels sproutsCabbage

Flower

Cauliflower

Flowerandstems

Stem

Kale

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Summary of Natural Selection

• Natural selection is differential success in

reproduction

individuals that vary in heritable traits and their environment

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• If an environment changes over time

these new conditions

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• Concept 22.3: Darwin’s theory explains a wide

range of observations

• Darwin’s theory of evolution

account for additional observations and experimental outcomes

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Natural Selection in Action

• Two examples

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Differential Predation in Guppy Populations

• Researchers have observed natural selection

transplant ofguppiesPredator: Killifish; preys

mainly on small guppiesGuppies:

Larger atsexual maturitythan those in

“pike-cichlid pools”

Predator: Pike-cichlid; preys mainly on large guppiesGuppies: Smaller at sexual maturity thanthose in “killifish pools”

Figure 22.12

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

populations increased compared to those of guppies in control populations.

Guppies transplanted to pools with killifish as predators

76.1

Males Females

85.758.2

Males Females

CONCLUSION

Reznick 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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The Evolution of Drug-Resistant HIV

• In humans, the use of drugs

mutations are resistant to the drugs’ effects

• Natural selection is a cause of adaptive

evolution

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• Researchers have developed numerous drugs

to combat HIV

viruses resistant to the drugs

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• The ability of bacteria and viruses to evolve

rapidly

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Homology, Biogeography, and the Fossil Record

• Evolutionary theory

kinds of observations

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Homology

• Homology

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Anatomical Homologies

• Homologous structures between organisms

variations on a structural theme that was present in a common ancestor

Figure 22.14

Human Cat Whale Bat

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• Comparative embryology

visible in adult organisms

Figure 22.15

Pharyngeal pouches

Post-anal tail

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• Vestigial organs

structures

important functions in the organism’s ancestors

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Molecular Homologies

• Biologists also observe homologies among

organisms at the molecular level

organisms inherited from a common ancestor

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Homologies and the Tree of Life

• The Darwinian concept of an evolutionary tree

of life

have observed

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• Anatomical resemblances among species

genes, and their gene products

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• Darwin’s observations of the geographic

distribution of species, biogeography

evolution

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Sugar glider

AUSTRALIA

NORTH AMERICA

Flying squirrel

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The Fossil Record

• The succession of forms observed in the fossil

record

major branches of descent in the tree of life

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• The Darwinian view of life

leave signs in the fossil record

• Paleontologists

transitional forms

Figure 22.18

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What Is Theoretical about the Darwinian View of Life?

• In science, a theory

attempts to explain and integrate a great variety of phenomena

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• Darwin’s theory of evolution by natural

selection

stimulates many new research questions

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