10 Sentences 10 Words
Transcript of 10 Sentences 10 Words
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 22Chapter 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 great diversity of organisms
Figure 22.1
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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
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
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Resistance to the Idea of Evolution
• The Origin of Species
– Shook the deepest roots of Western culture
– Challenged a worldview that had been prevalent for centuries
• The Greek philosopher Aristotle
– Viewed species as fixed and unchanging
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• Carolus Linnaeus
– Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose
– Was a founder of taxonomy, classifying life’s diversity “for the greater glory of God”
– Classification system is still in use ( Binomial nomenclature)
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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
Figure 22.3
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• Paleontology, the study of fossils
– Was largely developed by French scientist Georges Cuvier
– Believed in catastrophism, speculating that each boundary between strata represents a catastrophe
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Theories of Gradualism ( James Hutton/ Charles Lyell)
• Gradualism
– Is the idea that profound change can take place through the cumulative effect of slow but continuous processes
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Lamarck’s Theory of Evolution
• Lamarck hypothesized that species evolve
– Through use and disuse and the inheritance of acquired traits
– Remember giraffe example
Figure 22.4
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Darwin’s 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 HMS Beagle, 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 many specimens of South American plants and animals
• Darwin observed various adaptations of plants and animals
– That inhabited many diverse environments
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• Darwin’s interest in the geographic distribution of species
– Was kindled by the Beagle’s stop at the Galápagos Islands near the equator west of South America
Figure 22.5
EnglandEUROPE
NORTHAMERICA
GalápagosIslands
Darwin in 1840,after his return
SOUTHAMERICA
Cape ofGood Hope
Cape Horn
Tierra del Fuego
AFRICA HMS Beagle in port
AUSTRALIA
TasmaniaNewZealand
PACIFICOCEAN
An
des
ATLANTICOCEAN
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Adaptive radiation
• From studies made years after Darwin’s voyage
– Biologists have concluded that this is indeed 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.
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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 manuscript from Alfred Russell Wallace
– Who had developed a theory of natural selection similar to Darwin’s
• Darwin quickly finished The Origin of Species
– And published it the next year
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The Origin of Species
• Darwin developed two main ideas
– Evolution explains life’s unity and diversity
– Natural selection is a cause of adaptive evolution
• The phrase descent with modification
– Summarized Darwin’s perception of the unity of life
– States that all organisms are related through 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
– With multiple branchings from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms
Figure 22.7
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)
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• Observation #1: For any species, population sizes would increase exponentially
– If all individuals that are born reproduced successfully
Figure 22.8
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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 among 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
– 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 a 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
– Will lead to a gradual change in a population, with favorable characteristics accumulating over generations
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Artificial Selection
• In the process of artificial selection
– Humans have modified other 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
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Artifical Selection Results
• Forces speed of evolutionary change to occur too quickly
• Genetically engineering organisms leads to higher prevalence of disease and disorders
( small gene pool)
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• Natural selection can produce an increase over time
– In the adaptation of organisms to their environment
Figure 22.11
(a) A flower mantidin Malaysia
(b) A stick mantidin Africa
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Differential Predation in Guppy Populations
• Researchers have observed natural selection
– Leading to adaptive evolution in guppy populations
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 priorto transplant
Experimentaltransplant ofguppiesPredator: Killifish; preys
mainly on small guppies
Guppies:Larger atsexual maturitythan those in“pike-cichlid pools”
Predator: Pike-cichlid; preys mainly on large guppies
Guppies: Smaller at sexual maturity thanthose in “killifish pools”
Figure 22.12
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RESULTS 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.
161.5185.6
67.5
Wei
ght
of g
upp
ies
at m
atur
ity (
mg)
Age
of
gupp
ies
at m
atur
ity (
days
)
92.3
48.5
Control Population: Guppiesfrom pools with pike-cichlids as predators
Experimental Population:Guppies transplanted topools with killifish aspredators
76.1
Males Females
85.7
58.2
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
– Selects for pathogens that through chance 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
– 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
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• The ability of bacteria and viruses to evolve rapidly
– Poses a challenge to our society
– Multiple resistant strains of bacteria are evolving rapidly
• MRSA ( methicillin resistant Staphylococcus aureus)- AKA flesh eating bacteria
• Mycobacterium tuberculosis
vancomycin resistant
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Homology, Biogeography, and the Fossil Record
• Evolutionary theory
– Provides a cohesive explanation for many kinds of observations
• Homology
– Is similarity resulting from common ancestry
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Anatomical Homologies
• Homologous structures between organisms
– Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor
Figure 22.14Human Cat Whale Bat
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• Comparative embryology
– Reveals additional anatomical homologies early in development
Figure 22.15
Pharyngealpouches
Post-analtail
Chick embryo Human embryo
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• Vestigial organs
– Are some of the most intriguing homologous structures
– Are remnants of structures that served important functions in the organism’s ancestors
Human examples: appendix, coccyx
Whales: hip bones
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Molecular Homologies
• Biologists also observe homologies among organisms at the molecular level
– 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, 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
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Biogeography
• Darwin’s observations of the geographic distribution of species, biogeography
– Formed an important part of his theory of evolution
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Sugarglider
AUSTRALIA
NORTHAMERICA
Flyingsquirrel
Figure 22.17
Convergent Evolution
• Some similar mammals that have adapted to similar environments
– Have evolved independently from different ancestors
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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
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• The Darwinian view of life
– Predicts that evolutionary transitions should leave signs in the fossil record
• Paleontologists
– Have discovered fossils of many such transitional forms
Figure 22.18