descent with modification – a darwinian view of life chapter 22 a.p. biology liberty senior high...
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Descent with Modification – A Darwinian View of Life
Chapter 22
A.P. Biology
Liberty Senior High School
Rick L. Knowles
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• Concept 1.4: Evolution accounts for life’s unity and diversity
• The history of life– Is a saga of a changing Earth billions of years old
Figure 1.17
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Theodosius Dobzhansky
“Nothing in biology makes sense except in the light of evolution.”
The American Biology Teacher (1973)
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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
Charles Darwin, 1831, age 22, starting his voyage on the HMS Beagle
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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– We need to examine his views in the context of other
Western ideas about Earth and its life
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• The historical context of Darwin’s life and ideas
Fig. 22.2
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The Scale of Nature and Classification of Species
• The Greek philosopher Aristotle– Viewed species as fixed and unchanging
• The Old Testament of the Bible– Holds that species were individually designed by
God and therefore perfect– “Intelligent Design”
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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”
– Viewed species similarities not as evolutionary relationship, but as patterns of creation.
Carolus Linnaeus, 1707 -1778
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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– Observed that upper strata were younger and lower strata
were older– Noticed that new species would appear in an older strata
and then disappear in a newer strata.
• Cuvier opposed the idea of gradual evolutionary change– And instead advocated catastrophism, speculating that each
boundary between strata represents a catastrophe (flood or drought).
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Theories of Gradualism• Gradualism
– Is the idea that profound change can take place through the cumulative effect of slow but continuous processes.
– 1795, James Hutton proposed that Earth’s geologic features could be explained by gradual mechanisms currently operating (ex. valleys are created by rivers)
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• Geologists Hutton and Charles Lyell– Perceived that changes in
Earth’s surface can result from slow continuous actions still operating today
– Lyell proposed uniformitarianism – same geologic processes are operating today as in the past and at the same rate.
– Exerted a strong influence on Darwin’s thinking
Charles Lyell, 1797-1875
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One of the First “Ideas” of Evolution• Lamarck compared
species today with the fossil record.
• 1809, hypothesized that species evolve through use and disuse and the inheritance of acquired traits.
• Organisms have an innate drive to become more complex.
• But the mechanisms he proposed are unsupported by evidenceJean-Baptiste de Lamarck, 1744 - 1829
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Lamarck’s View of Evolution
•Plants and animals changed over time through the use and disuse of certain characteristics.•These acquired characteristics were inherited by the next generation.•No support for this notion.
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Darwin and the HMS Beagle• During his travels
– Darwin observed and collected many specimens of South American plants and animals
• Darwin observed various adaptations of plants and animals– That inhabited many diverse
environmentsCharles Darwin, 1831, age 22, starting his voyage on the HMS Beagle
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Fig. 22.5 The Voyage of the HMS Beagle
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Name Two (2) Observations that Darwin Made Leading to His
Theory.Name One (1) Observation
We’ve Since Made About the Natural World.
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Darwin’s Observations about Evolution
• 1. Fossil Record: noticed that the fossils of South America resembled living species of that continent.
• Example: Glyptodon related to modern armadillo?
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Glyptodon
Modern Armadillo, Omaha Zoo, 2009
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Darwin’s Observations of Evolution• 2. Biogeography – plants and animals in
temperate regions of South America resemble tropical species in South America than the temperate species in Europe.
• The distribution of life across similar climates is not always the same; (climate alone is not causing diversity).
• Closely related species are found in same geographic region.
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Sugarglider
AUSTRALIA
NORTHAMERICA
Flyingsquirrel
Figure 22.17
• Different geographic regions, different mammalian “brands”– Have evolved independently from different ancestors
Marsupial Mammal
Placental Mammal
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Charles Darwin, 1835, Galapagos
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What’s so special about a bunch of islands?
National Geographic SeriesGalapagos, Tape #254
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Darwin’s Finches
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The Galapagos Archipelago
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Bartoloma Island
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Isabela Island
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• Darwin proposed that natural selection
– Could enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”
Large
ground finchSmallground
finch
Geospiza
magnirostris
Seed eater
Sharp-beaked
ground finch
Camarhynchus
psitacula
Green
warbler
finch
Large
tree finchLarge cactusground finch
Ground finches Tree finches
Insect eaters Bud eater
Warbler finches
Common ancestor fromSouth American mainland
Gray
warbler
finch
Certhidea
olivacea
Certhidea
fuscaGeospiza
difficilis
Cactus flowereater
Geospizascandens
Seed eater
Geospiza
conirostris
Geospiza
fortis
Mediumground
finch
Geospizafuliginosa
Mangrovefinch
Cactospiza
heliobates
Cactospizapallida
Woodpecker
finch
Mediumtree finch
Camarhynchuspauper
Small tree finch
Vegetarianfinch
Camarhynchusparvulus
Platyspizacrassirostris
Cactusground finch
Figure 1.23
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Large
ground finch Smallground
finch
Geospiza
magnirostris
Seed eater
Sharp-beaked
ground finch
Camarhynchus
psitaculaGreen
warbler
finch
Large
tree finchLarge cactusground finch
Ground finches Tree finches
Insect eaters Bud eater
Warbler finches
Common ancestor fromSouth American mainland
Gray
warbler
finch
Certhidea
olivacea
Certhidea
fuscaGeospiza
difficilis
Cactus flowereater
Geospizascandens
Seed eater
Geospiza
conirostris
Geospiza
fortis
Mediumground
finch
Geospizafuliginosa
Mangrovefinch
Cactospiza
heliobates
Cactospizapallida
Woodpecker
finch
Mediumtree finch
Camarhynchuspauper
Small tree finch
Vegetarianfinch
Camarhynchusparvulus
Platyspizacrassirostris
Cactusground finch
Figure 1.23
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Seen one tortoise, you’ve seen them all?
Dome-shaped Carapace Saddle-shaped Carapace
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Galapagos Tortoise Distribution
Galapagos tortoise distribution, Galapagos Islands. Redrawn from Iverson (1992).
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Galapagos Tortoise-Env. Club 2008, Omaha Zoo
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Darwin’s Focus on Adaptation• Years later, 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
Fig. 22.6
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Alfred Russel Wallace, 1823-1913
•Explored Indonesia and southeast Asia, from 1854-1861, •Observed Tigers, Orangs, and Rhinos, Oh My!
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Sumatran Rhino
Indian Rhino
Javan Rhino
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Other Observations about Evolution• 3. Artificial Selection - humans have modified
other species over many generations by selecting and breeding individuals that possess desired traits
Fig. 22.10
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• The Origin of Species articulated two main points…
– Descent with modification
– Natural selection
Figure 1.19
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Natural Selection• Darwin proposed natural selection
– As the mechanism for evolutionary adaptation of populations to their environments
Populationof organisms
Hereditaryvariations
Differences in reproductive success
Evolution of adaptationsin the population
Overproductionand struggle for
existence
Figure 1.20
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• Natural selection is the evolutionary process that occurs…– When a population’s heritable variations are exposed
to environmental factors that favor the reproductive success of some individuals over others.
1 Populations with varied inherited traits
2 Elimination of individuals with certain traits.
3 Reproduction of survivors.
4 Increasing frequency of traits that enhance survival and reproductive success. Figure 1.21
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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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Elephant Phylogeny
Fig. 22.7
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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
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• Over time natural selection can produce an increase
– In the adaptation of organisms to their environment
Fig. 22.11
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• Concept 22.3: Darwin’s theory explains a wide range of observations
• Darwin’s theory of evolution– Continues to be tested by how effectively it can account for
additional observations and experimental outcomes– Natural Selection in Action – Evolution continues today!
• Guppies• HIV• Humans
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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 o
f gu
ppie
sat
mat
urit
y (m
g)
Age
of
gupp
ies
at m
atur
ity
(day
s)
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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Anatomy of HIV
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Inside HIV
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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
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New Evidence that Darwin Did Not Have
• How old did most 19th Century people believe the Earth was?
• About 6,000 years old (Cuvier’s young Earth)
• 1. Age of the Earth- 4.5 billion year old. Better dating techniques than in Darwin’s time; more complete fossil record.
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2. Transitional Species• Have intermediate characteristics of
two groups of animals – may represent a link in evolution (missing link?).
• Changes in structures may be small – difficult to identify in fossils.
• Species replaced quickly – not common in fossil record.
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Archaeopteryx (150 million years ago)
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Archaeopteryx
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Archaeopteryx at the KU Natural History Museum
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Evolution Happens in Small Steps
Show me the frogs!
Discover- Weird Nature: Marvelous Motion, tape #55
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Other Transitional Examples?
Rodhocetus balochistanensis
Modern Whales
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A Walking Whale?
Ambulocetus natans
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Transitional Skulls
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Rodhocetus Foot
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Transitional Diatoms in Yellowstone
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3. Vestigial Structures• Existing structures that have no
apparent function, but resemble structures of presumed ancestors.
• Examples: human appendix; muscle set in humans for moving ears;
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The “Pelvis” of a Whale
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Evidence of Transitional Species Today!
Vestigial Structure- blue whales with femurs?
Life of Mammals-Return to the Water video, tape #110
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Vestigial Organs in Humans?
Structures of little or no use but may represent historical remnants of
structures that had important functions in ancestors.
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Vermiform Appendix
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Goosebumps?
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Vomeronasal or Jacobson’s Organ
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“Junk”DNA; L-gulonolactone oxidase gene
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Extra Ear Muscles – auriculares muscles
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Plantaris Muscle – 9% don’t have it
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Wisdom Teeth – mandible becoming smaller
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Third Eyelid – Plica semilunaris
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Darwin’s (Auricular) Tubercle – only 10.4% have it.
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Coccyx
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Four-Finned Dolphin; Oct, 2006
Divers hold a bottlenose dolphin which has an extra set of human palm-sized fins near its tail in Taiji, Wakayama prefecture in western Japan.
-USA Today, Nov. 6, 2006
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Four-Finned Dolphin; Oct, 2006
Divers hold a bottlenose dolphin which has an extra set of human palm-sized fins near its tail in Taiji, Wakayama prefecture in western Japan.
-USA Today, Nov. 6, 2006
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Show me more vestigial structures!
Do snakes have “feet”?
The story of boas and pythons.
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4. 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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Homology• Homologous Structures – structures in different
species that are similar because of commons ancestry.
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Sophie and a Mosasaur
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• Analogous Structures – similarity in structures due to adaptations from similar evolutionary pressures (convergent evolution) and not a common ancestor.
Analogy
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• The products of natural selection– Are often exquisite adaptations of organisms to
the special circumstances of their way of life and their environment
Figure 1.22
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5. Comparative Embryology– Reveals additional anatomical homologies not
visible in adult organisms
Figure 22.15
Pharyngealpouches
Post-analtail
Chick embryo Human embryo
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Show me an example of homologous structures!
Compare a human hand and bat wing.
Life of Mammals- Life in the Trees video, tape
#110
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6. Molecular Homologies• Biologists observe
homologies among organisms at the molecular level– Genes and proteins
that are shared among organisms inherited from a common ancestor.
Fig. 22.16
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Darwin’s Theory of Evolution
• Natural selection is the driving force of changes within species populations.
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Can we see evolution?
• Weiner, J. 1994. The Beak of the Finch. Knopf, New York.
• The video “What Darwin Never Saw”
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I want to see evolution in action!
Scientific American Frontiers-Voyage to the
Galapagos, 2000, VT 551.4 SCI