Download Ch 22 Evidences for Evolution 2016

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 22
Descent with Modification:
A Darwinian View of Life
Lectures by
Erin Barley
Kathleen Fitzpatrick
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Overview: Endless Forms Most Beautiful
• A new era of biology began in 1859 when
Charles Darwin published The Origin of
Species
• The Origin of Species focused biologists’
attention on the great diversity of
organisms
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• Darwin noted that current species are
descendants of ancestral species
• Evolution can be defined by Darwin’s
phrase descent with modification
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Figure 22.2
1809
Lamarck publishes his
hypothesis of evolution.
1798
Malthus publishes
“Essay on the Principle
of Population.”
1812
1858
Cuvier publishes his extensive
studies of vertebrate fossils.
1795
Hutton proposes
his principle of
gradualism.
1830
Lyell publishes
Principles of Geology.
While studying species in
the Malay Archipelago,
Wallace (shown in 1848)
sends Darwin his hypothesis
of natural selection.
1790
1870
1809
183136
Charles Darwin
is born.
Darwin travels around
the world on HMS
Beagle.
1859
On the Origin of
Species is published.
1844
Darwin writes his
essay on descent
with modification.
The Galápagos Islands
Scala Naturae and Classification of Species
• The Greek philosopher Aristotle viewed
species as fixed and arranged them on a
scala naturae
• He thought since the Old Testament held that
species were individually designed by God
they were therefore perfect.
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• Carolus Linnaeus interpreted organismal
adaptations as evidence that the Creator had
designed each species for a specific purpose
• Linnaeus was the founder of taxonomy, the
branch of biology concerned with classifying
organisms
• He developed the binomial format for naming
species (for example, Homo sapiens)
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Qur’an, Surahs: The Light and The Bee
• “And Allah has created every animal from
water: of them there are some that creep on
their bellies; some that walk on two legs; and
some that walk on four.” 24 Light, 45
“Do they not look at the birds, held poised in
the midst of…the sky? Nothing holds them up
but (the power of) Allah.” 16 The Bee, 79
Bible/Torah, Book of Genesis, Chapt. 1
God said, “Let the waters swarm with swarms of living
creatures, and let birds[g] fly above the earth across the expanse
of the heavens.” 21 So God created the great sea creatures and
every living creature that moves, with which the waters swarm,
according to their kinds, and every winged bird according to its
kind. And God saw that it was good. 22 And God blessed them,
saying, “Be fruitful and multiply and fill the waters in the seas,
and let birds multiply on the earth.” 23 And there was evening
and there was morning, the fifth day.
• 24 And God said, “Let the earth bring forth living creatures
according to their kinds—livestock and creeping things and
beasts of the earth according to their kinds.” And it was
so. 25 And God made the beasts of the earth according to their
kinds and the livestock according to their kinds, and everything
that creeps on the ground according to its kind. And God saw
that it was good.
•
20 And
Ideas About Change over Time
• 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
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Figure 22.3
Sedimentary rock
layers (strata)
Younger stratum
with more recent
fossils
Older stratum
with older fossils
• Paleontology, the study of fossils, was largely
developed by French scientist Georges Cuvier
• Cuvier, who also believed in God, advocated
catastrophism, speculating that each
boundary between strata represents a
catastrophe
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• Gradualism- principle that profound change is
the cumulative product of slow, continuous
processes
• Gradualism challenged Charles Lyell’s principle
of uniformitarianism states that the
mechanisms of change are constant over time
• Although Darwin rejected this view, it strongly
influenced his thinking
• He concluded the Earth must be ancient
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Lamarck’s Hypothesis of Evolution
• Lamarck hypothesized that species evolve
through use and disuse of body parts and the
inheritance of acquired characteristics
• The mechanisms he proposed are unsupported
by evidence
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Acquired Traits cannot be inherited
Lamarkian Evolution
• Cheetahs can run faster than 60 miles per
hour when in pursuit of prey. How would an
evolutionary biologist explain how this ability
evolved, assuming their ancestors could only
run 20 miles per hour?
Concept 22.2: Descent with modification by
natural selection explains the adaptations of
organisms and the unity and diversity of life
• Some doubt about the permanence of species
preceded Darwin’s ideas
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Darwin’s Research
• As a boy and into adulthood, Charles Darwin
had a consuming interest in nature
• Darwin first studied medicine (unsuccessfully),
and then theology at Cambridge University
• After graduating, he took an unpaid position as
naturalist and companion to Captain Robert
FitzRoy for a 5-year around the world voyage
on the Beagle
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The Voyage of the Beagle
• During his travels on the Beagle, Darwin collected
specimens of South American plants and animals
• He observed that fossils resembled living species
from the same region, and living species
resembled other species from nearby regions
• He experienced an earthquake in Chile and
observed the uplift of rocks
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Figure 22.5
Darwin in 1840,
after his return
from the
voyage
HMS Beagle in port
Great
Britain
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
PACIFIC
OCEAN
Pinta
Genovesa
Santiago
Fernandina
Isabela
0
20
40
Kilometers
Daphne
Islands
Pinzón
Santa Santa
Cruz
Fe
Florenza
Equator
SOUTH
AMERICA
Equator
Chile
PACIFIC
OCEAN
San
Cristobal
Española
Andes Mtns.
Marchena
Brazil
Malay Archipelago
PACIFIC
OCEAN
AUSTRALIA
Cape of
Argentina Good Hope
Cape Horn
Tasmania
New
Zealand
Darwin’s Focus on Adaptation
• In reassessing his observations, Darwin
perceived adaptation to the environment and
the origin of new species as closely related
processes
• From studies made years after Darwin’s
voyage, biologists have concluded that this is
what happened to the Galápagos finches
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Figure 22.6
(b) Insect-eater
(a) Cactus-eater
(c) Seed-eater
Descent with Modification
• Darwin never used the word evolution in the
first edition of The Origin of Species
• The phrase descent with modification
summarized Darwin’s perception of the unity
of life
• The phrase refers to the view that all
organisms are related through descent from
an ancestor that lived in the remote past
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• In 1844, Darwin wrote an essay on natural
selection as the mechanism of descent with
modification, but did not introduce his theory
publicly
• Natural selection is a process in which individuals
with favorable inherited traits are more likely to
survive and reproduce
• Is natural selection driven by the
“Survival of the Fittest”???
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The Origin of Species
• Darwin explained three broad observations:
– The unity of life
– The diversity of life
– The match between organisms and their
environment
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• In the Darwinian view, the history of life is
like a tree with branches representing life’s
diversity
• Darwin’s theory meshed well with the
hierarchy of Linnaeus
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Figure 22.7
Figure 22.8
Hyracoidea
(Hyraxes)
Sirenia
(Manatees
and relatives)
†Moeritherium
†Barytherium
†Deinotherium
†Mammut
†Platybelodon
†Stegodon
†Mammuthus
Elephas maximus
(Asia)
Loxodonta africana
(Africa)
Loxodonta cyclotis
(Africa)
60
34
24
Millions of years ago
5.5 2 104 0
Years ago
Darwin’s take on Malthus’ book
• Observation #1:
Species have such
great fertility that
their population
would increase
exponentially if they
all reproduce
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Figure 22.11
Spore
cloud
• Observation #2: Most populations are stable in
size
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Observation #3: Natural resources
are limited
Inference: Production of more
individuals than the environment can
support leads to struggle for existence
among individuals of a population
Observation #4: Individuals vary
extensively in their characteristics
Observation #5: Much of this
variation is heritable
• Inference: Survival in the struggle for existence
is not random, but depends on the hereditary
constitution of the surviving individual
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• Inference: This unequal ability of individuals
to survive and reproduce will lead to the
accumulation of favorable traits in the
population over generations
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Artificial Selection, Natural Selection, and
Adaptation
• Darwin noted that humans have modified
other species by selecting and breeding
individuals with desired traits, a process
called artificial selection
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Figure 22.9
Cabbage
Selection for
apical (tip) bud
Brussels
sprouts Selection for
axillary (side)
buds
Broccoli
Selection
for flowers
and stems
Selection
for stems
Selection
for leaves
Kale
Wild mustard
Kohlrabi
• Darwin was influenced by Thomas Malthus,
who noted the potential for human population
to increase faster than food supplies and
other resources
• If some heritable traits are advantageous,
these will accumulate in a population over
time, and this will increase the frequency of
individuals with these traits
• This process explains the match between
organisms and their environment
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Natural Selection: A Summary
• Individuals with certain heritable characteristics
survive and reproduce at a higher rate than
other individuals
• Natural selection increases the adaptation of
organisms to their environment over time
• If an environment changes over time, natural
selection may result in adaptation to these new
conditions and may give rise to new species
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How would Lamarck and
Darwin explain the mantids?
(a) A flower mantid in Malaysia
(b) A leaf mantid in Borneo
• Note that individuals do not evolve;
populations evolve over time
• Natural selection can only increase or
decrease heritable traits that vary in a
population
• Adaptations vary with different environments
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Is Natural Selection able to occur?
Concept 22.3: Evolution is supported by an
overwhelming amount of scientific evidence
• New discoveries continue to fill the gaps
identified by Darwin in The Origin of Species
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Direct Observations of Evolutionary Change
• Two examples provide evidence for natural
selection: natural selection in response to
introduced plant species, and the evolution
of drug-resistant bacteria
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Explain the theory of evolution by natural
selection as presented by Darwin. (5 points)
•
•
•
•
•
•
•
variation in populations
adaptations: differences may enable some individuals to outcompete others
differential survival: individuals with more favorable traits will be
“selected”
competition for food, nesting sites, mates, escape predators,
survive
disease/parasites
survivors are then able to reproduce more and pass on favorable
traits to (“survival of the fittest”) their offspring.
individuals with favorable traits will make up a greater percentage
of the population in the next generation.
Natural Selection in Response to Introduced
Plant Species
• Soapberry bugs use their “beak” to feed on
seeds within fruits
• In southern Florida soapberry bugs feed on
balloon vine with larger fruit; they have longer
beaks
• In central Florida they feed on goldenrain tree
with smaller fruit; they have shorter beaks
• Correlation between fruit size and beak size has
also been observed in Louisiana, Oklahoma, and
Australia
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• In all cases, beak size has evolved in
populations that feed on introduced plants
with fruits that are smaller or larger than the
native fruits
• These cases are examples of evolution by
natural selection
• In Florida this evolution in beak size occurred
in less than 35 years
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Figure 22.13a
FIELD STUDY
Soapberry bug with beak
inserted in balloon vine fruit
Figure 22.13b
RESULTS
Beak
10
On native species,
southern Florida
8
Number of individuals
6
4
2
0
Museum-specimen average
10
On introduced species,
central Florida
8
6
4
2
0
6
7
8
9
Beak length (mm)
10
11
The Evolution of Drug-Resistant Bacteria
• The bacterium Staphylococcus aureus is
commonly found on people
• One strain, methicillin-resistant S. aureus
(MRSA) is a dangerous pathogen
• S. aureus became resistant to penicillin in
1945, two years after it was first widely used
• S. aureus became resistant to methicillin in
1961, two years after it was first widely used
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• Methicillin works by inhibiting a protein used by
bacteria in their cell walls
• MRSA bacteria use a different protein in their
cell walls
• When exposed to methicillin, MRSA strains are
more likely to survive and reproduce than
nonresistant S. aureus strains
• MRSA strains are now resistant to many
antibiotics
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Figure 22.14
2,750,000
1
250,000 base pairs
2,500,000
Chromosome map
of S. aureus clone USA300
500,000
Key to adaptations
2,250,000
Methicillin resistance
Ability to colonize hosts
750,000
Increased disease severity
2,000,000
Increased gene exchange
(within species) and
toxin production
1,750,000
1,500,000
1,250,000
1,000,000
Explain how evolution by natural selection can
explain emergence of MRSA.
• Antibiotic gene already present
• Environmental pressure (antibiotics) present
• Bacteria with antibiotic resistance will be
selected for, those without will be selected
against
• Bacteria with resistance will have a higher
fitness (reproductive success)
• Time- generations of bacteria will see MRSA
become more prevalent
• Natural selection does not create new traits, but
edits or selects for traits already present in the
population
• The local environment determines which traits will
be selected for or selected against in any specific
population
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Lamarkian or Darwinian?
Population of individuals all of the same kind
(identical characteristics in all members).
Individuals capable of transformation
Darwinian
Population of interbreeding individuals with
similar characteristics, though variation is
common among all of them at all times.
Individuals fixed and unchanging. Population
capable of transformation.
Lamarkian or Darwinian?
• Keen eyesight of the hawk: “In a population of hawks, the
power of their vision and the color of their feathers are
necessary to successfully catch food. Since nature pressured
hawks to possess keen eyesight and camouflaging coloration,
individual hawks began to develop the ability of keen eyesight
and camouflage. Those who adapted with the necessary traits
could more easily spot their prey (small voles and mice) and
thus were successful in securing food to eat. The hawks that
failed to adapt, due to poor eyesight had difficulty spotting prey
and died for lack of food. The hawks with the keen eyesight
passed on this trait to their offspring. The hawks that died were
not able to produce any offspring. Over a number of
generations, the population of hawks all came to possess
extremely powerful vision."
Darwinian
Keen eyesight of the hawk: “In a population of hawks,
individual variation existed in the power of their vision, just as
variation exists in the color of their feathers. In their competition
for food, the individuals with keener eyesight could more easily
spot their prey (small voles and mice) and thus were successful in
securing food to eat. The hawks with poor eyesight had difficulty
spotting prey and died for lack of food. The hawks with the keen
eyesight passed on this trait to their offspring. The hawks that died
were not able to produce any offspring. Over a number of
generations, the population of hawks all came to possess
extremely powerful vision."
Which takes less
faith?
1. Naturalism
2. Theistic Evolution
3. Supernaturalism
Evidence from many fields of Biology
for Evolution
•
•
•
•
•
Biogeography
Fossil Record
Comparative Anatomy
Comparative embryology
Molecular Biology
Biogeography
• Biogeography, the geographic distribution of
species, provides evidence of evolution
• Earth’s continents were formerly united in a
single large continent called Pangaea, but have
since separated by continental drift
• An understanding of continent movement and
modern distribution of species allows us to
predict when and where different groups
evolved
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Biogeography
The Fossil Record
• The fossil record provides evidence of the
extinction of species, the origin of new groups,
and changes within groups over time
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Coelocanth
Anything Into Oil
Technological savvy could turn 600 million tons of turkey
guts and other waste into 4 billion barrels of light Texas
crude each year.
http://discovermagazine.com/2003/may/featoil/
Trilobites
“Why then is not every geological formation and every
stratum full of such intermediate links? Geology assuredly
does not reveal any such finely graduated organic chain;
and this, perhaps, is the most obvious and gravest
objection which can be urged against my theory. The
explanation lies, as I believe, in the extreme imperfection of
the geological record.”
-Charles Darwin (1859), The Origin of Species, p. 280.
Figure 22.20
Other
even-toed
ungulates
Hippopotamuses
†Pakicetus
†Rodhocetus
Common
ancestor
of cetaceans
†Dorudon
Living
cetaceans
70
60
50
40
30
20
Millions of years ago
10
0
Key
Pelvis
Femur
Tibia
Foot
Ambulocetus
Rodhocetus
Homology
• Homology is similarity resulting from recent
common ancestry
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Anatomical and Molecular Homologies
• Homologous structures are anatomical
resemblances that represent variations on a
structural theme present in a common ancestor
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Figure 22.15
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
• ‘If you look at a 1953 Corvette and
compare it to the latest model, only the
most general resemblances are evident,
but if you compare a 1953 and a 1954
Corvette, side by side, then a 1954 and
a 1955 model, and so on, the descent
with modification is overwhelmingly
obvious. This is what paleontologists do
with fossils, and the evidence is so solid
and comprehensive that it cannot be
denied by reasonable people’
-Dr. Tim Berra, professor of Zoology, Ohio State
University
Question to ponder at the biochemical
level…
• If so many homologies exist today due to
millions of years of evolution, why do we not
see more of a difference at the biochemical
level?
• We still observe the same genetic code, the
same 20 amino acids, the same process of
transcription and translation, etc.
Homologies and “Tree Thinking”
• Evolutionary trees are hypotheses about the
relationships among different groups
• Homologies form nested patterns in
evolutionary trees
• Evolutionary trees can be made using different
types of data, for example, anatomical and
DNA sequence data
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Figure 22.17
Branch point
Lungfishes
Amniotes
2
Digitbearing
limbs
Amnion
Mammals
Lizards
and snakes
3
4
Homologous
characteristic
Crocodiles
Ostriches
6
Feathers
Hawks and
other birds
Birds
5
Tetrapods
Amphibians
1
A Different Cause of Resemblance:
Convergent Evolution
• Convergent evolution is the evolution of
similar, or analogous, features in distantly
related groups
• Analogous traits arise when groups
independently adapt to similar environments
in similar ways
• Convergent evolution does not provide
information about ancestry
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Convergent Evolution?
“Wings” homologous or
analogous?
NORTH
AMERICA
Sugar
glider
AUSTRALIA
Flying
squirrel
Homologous or Analogous?
• Vestigial structures are remnants of features
that served important functions in the
organism’s ancestors
• Examples of homologies at the molecular level
are genes shared among organisms inherited
from a common ancestor
• 180 vestigial structures named in 1890
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Problem with Vestigial structures
There were once over hundred parts of the
human anatomy that were considered vestigial,
or useless. Here are a few that over the past
couple decades have been deemed “useful”:
1. Spleen
2. Tonsils
3. Appendix
4. Coccyx (Tailbone)
http://news.nationalgeographic.com/news/2009/
07/090730-spleen-vestigial-organs.html
“Ontogeny Recapitulates Phylogeny”
Ontogeny- growth and development
Recapitulates- summarizes
Phylogeny- evolutionary history
Figure 22.16
Pharyngeal
arches
Post-anal
tail
Chick embryo (LM)
Human embryo
Molecular Biology
How much difference overall?
• Humans and chimps are 96% identical in our DNA
sequence.
• That 4% represents a total number of DNA
differences of about 125 million
• “To put this number into perspective, a typical 8½ x
11-inch page of text might have 4,000 letters and
spaces. It would take 10,000 such pages full of text to
equal 40 million letters! So the difference between
humans and chimpanzees includes about 35 million
DNA bases that are different, about 45 million in the
human that are absent from the chimp, and about 45
million in the chimp that are absent from the human”
-Dr. David DeWitt
What Is Theoretical About Darwin’s View
of Life?
• 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
• Ongoing research adds to our understanding of
evolution
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