copyright © 2005 pearson education, inc. publishing as benjamin cummings ch. 22 descent with...

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

• Ch. 22

Descent with Modification


• The Origin of Species

– Focused biologists’ attention on the great diversity of organisms

Figure 22.1


• The Origin of Species

– challenged traditional views of a young Earth inhabited by unchanging species

– Shook the deepest roots of Western culture

– Challenged a worldview that had been prevalent for centuries


• Darwin

– said many species of organisms are descendants of ancestral species

– proposed natural selection as a mechanism for evolution


• 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

1800 1850 19001795 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.1837Darwin writes his essay on the origin of species.1844

Wallace sends his theory to Darwin.1858

The Origin of Species is published.1859Mendel publishes inheritance papers.1865


The Scale of Nature and Classification of Species

• The Greek philosopher Aristotle (384-322 BC)

– viewed species as fixed and unchanging

– said life forms could be arranged according to increasing complexity

• The Old Testament of the Bible

– states that species were individually designed by God


• Carolus Linnaeus (1707-1778)

– Grouped similar species into increasingly general categories reflecting what he considered the pattern of their creation

• a founder of taxonomy - the branch of biology dedicated to the naming and classifying of organisms

• Developed binomial nomenclature – a two-part naming system that includes the organism’s genus and species


Fossils, Cuvier, and Catastrophism

• The study of fossils

– Helped to lay the groundwork for Darwin’s ideas

• Fossils are remains or traces of organisms from the past

– Usually found in sedimentary rock, which appears in layers or strata


• Georges Cuvier (1769-1832)

– Developed paleontology, the study of fossils

– opposed the idea of gradual evolutionary change

– advocated catastrophism

• says that events in the past occurred suddenly and by different mechanisms than those occurring today

• This explained boundaries between strata and the location of different species


Theories of Gradualism

• Gradualism

– the idea that profound change can take place through the cumulative effect of slow but continuous processes


• Geologists Hutton and Lyell (1797-1875)

– Developed the principle of uniformitarianism, the idea that the geologic processes that have shaped the planet have not changed over the course of earth’s history

• Importance: The earth must be very old.

– Exerted a strong influence on Darwin’s thinking


Lamarck’s Theory of Evolution

• Lamarck (1744-1829) hypothesized that species evolve.

– Through use and disuse – parts of the body that are used extensively become larger and larger while those not used deteriorate.

– Acquired characteristics are inherited.


Comparison of Lamarck and Darwin

Lamarck Darwin

Use and disuse Variation

Transmission of Acquired characteristics

Inheritance

Increasing complexity Differential survival

No extinction extinction

Lamarck recognized that species evolve but his explanation of how evolution occurs was flawed.


Darwin’s Research

• Charles Darwin

– Had a strong interest in nature

– After receiving his B.A. degree, he was accepted on board the HMS Beagle, which was about to embark on a voyage around the world


The Voyage of the Beagle

• During his travels on the Beagle, Darwin

– collected many specimens of South American plants and animals

– observed adaptations of plants and animals in many diverse environments


The Beagle’s stop at the Galápagos Islands near the equator west of South America sparked Darwin’s interest in the geographic distribution of species.

EnglandEUROPE

NORTHAMERICA

GalápagosIslands

Darwin in 1840,after his return

SOUTHAMERICA

Cape ofGood Hope

Cape Horn

Tierra del Fuego

AFRICA HMS Beagle in port

AUSTRALIA

Tasmania

NewZealand

PACIFICOCEAN

An

des

ATLANTICOCEAN


Darwin’s Focus on Adaptation

• During and after the voyage of the Beagle,

– Darwin began to see a link between adaptation to different environments and the origin of new species


• From studies made years after Darwin’s voyage, biologists concluded that this is what happened to the Galápagos finches

Figure 22.6a–c

(a) Cactus eater. The long,sharp beak of the cactusground finch (Geospizascandens) helps it tearand eat cactus flowersand pulp.

(c) Seed eater. The large groundfinch (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 itsnarrow, pointed beak to grasp insects.


• 1844: Darwin wrote an essay on the origin of species and natural selection

– reluctant to introduce his theory publicly, anticipating the uproar it would cause

• 1858: Darwin received a manuscript from Alfred Russell Wallace who had developed a theory of natural selection similar to Darwin’s

• 1859: Darwin quickly finished The Origin of Species And published it the next year


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

– With multiple branchings from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms

Hyracoidea(Hyraxes)

Sirenia(Manatees

and relatives)

Yea

rs a

goM

illio

ns

of y

ea

rs a

go

Dei

no

ther

ium

Ma

mm

ut

Ste

go

don

Ma

mm

uth

us

Pla

tyb

elo

don

Bar

yth

eriu

m

Mo

eri

ther

ium

Elephasmaximus

(Asia)

Loxodontaafricana(Africa)

Loxodontacyclotis(Africa)


Natural Selection

• Adaptations– Heritable characteristics that enhance

organisms’ ability to survive and reproduce in specific environments.

Desert fox: large ears radiate heat. Arctic fox: small ears conserve heat.


For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully.


Overproduction

• Production of more individuals than the environment can support

• Leads to a competition for resources


Variations in traits occur

Members of a population vary extensively in their characteristics. No two individuals are exactly alike

Figure 22.9


Survival depends on inherited traits and the resources available in the environment.

• Individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

• This leads to a gradual change in a population, with favorable characteristics accumulating over generations


Summary of Natural Selection

• Natural selection is differential success in reproduction

– results from the interaction between individuals that vary in heritable traits and their environment


• Natural selection can produce an increase over time in the adaptation of organisms to their environment.


Artificial Selection

– Humans have modified species over many generations by selecting and breeding individuals that possess desired traits

Figure 22.10

Terminalbud

Lateralbuds

Brussels sproutsCabbage

Flowercluster

Leaves

Cauliflower

Flowerandstems

Broccoli Wild mustard Kohlrabi

Stem

Kale


Artificial Selection - breeding


• If an environment changes over time

– Natural selection may result in populations adapting to these new conditions.

• Populations adapt NOT individual organisms.


The Evolution of Drug-Resistant HIV

• In humans, the use of drugs

– Selects for pathogens that through chance mutations are resistant to the drugs’ effects

• Natural selection is a cause of adaptive evolution


• 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

Per

cen

t of

HIV

res

ista

nt

to 3

TC

Weeks


• The ability of bacteria and viruses to evolve rapidly

– Poses a challenge to our society


Homology, Biogeography, and the Fossil Record

• Evolutionary theory

– Provides a cohesive explanation for many kinds of observations


Homology

• Homology

– Is similarity resulting from common ancestry


Anatomical Homologies

• Homologous structures between organisms

– variations on a structure that was present in a common ancestor

Figure 22.14Human Cat Whale Bat


Comparative embryology

– Reveals anatomical homologies not visible in adult organisms

Figure 22.15

Pharyngealpouches

Post-analtail

Chick embryo Human embryo


Vestigial organs

remnants of structures that served important functions in the organism’s ancestors


Molecular Homologies

• Biologists can observe homologies among organisms at the molecular level

– Such as genes that are shared among organisms inherited from a common ancestor


Homologies and the Tree of Life

• The Darwinian concept of an evolutionary tree of life

– Can explain the homologies that researchers have observed


• Anatomical resemblances among species

– Are generally reflected in their molecules, their genes, 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 AreIdentical to the Amino Acids in aHuman Hemoglobin Polypeptide


Biogeography

• Darwin’s observations of the geographic distribution of species, biogeography

– Formed an important part of his theory of evolution


Sugarglider

AUSTRALIA

NORTHAMERICA

Flyingsquirrel

Figure 22.17

• Some similar mammals that have adapted to similar environments

– Have evolved independently from different ancestors

https://www.youtube.com/watch?v=1-FHzf4xnWw

https://www.youtube.com/watch?v=cHa8jrxdF_4


The Fossil Record• The Darwinian view of life

– Predicts that evolutionary transitions should be found in the fossil record

• Paleontologists have discovered fossils of many such transitional forms.


Theory of Evolution

• In science, a theory

– Accounts for many observations and data and attempts to explain and integrate a great variety of phenomena


• Darwin’s theory of evolution by natural selection

– Integrates diverse areas of biological study and stimulates many new research questions

copyright © 2005 pearson education, inc. publishing as benjamin cummings ch. 22 descent with...

Documents