Download 13.1 How Did Evolutionary Thought Evolve?

Chapter 13
Principles of
Evolution
Lectures by
Gregory Ahearn
University of North Florida
Copyright © 2009 Pearson Education, Inc..
13.1 How Did Evolutionary Thought
Evolve?
• A timeline of the roots of evolutionary thought
Buffon (species created, then evolve)
Hutton (gradual geologic change)
Lamarck (mechanism of species change)
Cuvier (catastrophism)
Smith (sequence of fossils)
Lyell (very old Earth)
Darwin (evolution, natural selection)
Wallace (evolution, natural selection)
1700
1750
1800
1850
1900
Fig. 13-1
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13.1 How Did Evolutionary Thought Evolve?
 Early biological thought did not include the concept of
evolution.
• One of the earliest scientific beliefs was called
“______________,” which suggested that all organisms
were created by God simultaneously, and that each
organism remained fixed and unchanging from the
moment of its creation.
• Both Plato and Aristotle (427–347 B.C.) proposed these
ideas to students of the day.
• Aristotle categorized all organisms into a linear hierarchy
that he called the “______________________.”
• These ideas remained unchallenged for 2,000 years.
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Humans
Mammals
Birds
Reptiles and amphibians
Whales and porpoises
Fish
Squids and octopuses
Lobsters, crabs, etc.
Snails, clams, etc.
Insects, spiders, etc.
Jellyfishes, sponges, etc.
Higher plants
Lower plants
Inanimate matter
Fig. 13-2
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13.1 How Did Evolutionary Thought
Evolve?
 Exploration of new lands revealed a staggering
diversity of life.
• Discoveries of the wide diversity of life forms and how similar
to one another many were suggested that organisms were
capable of change, and that some could have been
ancestral to others.
• Early naturalists noticed that the species found in one place
were different than those found in other places.
• Others saw that in a given location, species closely
resembled one another, yet differed in some characteristics.
• These observations were inconsistent with the idea that
species were fixed and unchanging.
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13.1 How Did Evolutionary Thought
Evolve?
 A few eighteenth century scientists speculated that
species had changed over time.
 The French naturalist George Louis LeClere (1707–1788)
suggested that the original creation provided a small
number of founding species, and that some modern
species had been produced by time; that is, they
evolved through natural processes.
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13.1 How Did Evolutionary Thought
Evolve?
 Fossil discoveries showed that life has changed over time
• Developments in geology cast doubt on the idea of
permanently fixed species that remained unchanged through
time.
• Fossils—the preserved remains or traces of organisms
that had died long ago—and the layers of rock in which
they were found suggested that animals lived a long time
ago, and they were different than those of today.
• Fossils can be bones, wood, shells, tracks, burrows,
pollen grains, eggs, and feces.
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13.1 How Did Evolutionary Thought
Evolve?
 Types of fossils
eggs in nest
fossilized feces
(coprolites)
bones
footprint
skin impression
Fig. 13-3
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13.1 How Did Evolutionary Thought Evolve?
 Fossil discoveries showed that life has changed over time.
• Scientists discovered that fossil remains showed a
remarkable progression.
• Fossils from the oldest rock layers were very different
from modern organisms.
• Fossil resemblance to modern organisms gradually
increased in progressively younger rocks.
• Conclusion: different types of organisms had lived at different
times in the past
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13.1 How Did Evolutionary Thought Evolve?
 Fossils of extinct organisms
(a) Trilobite
(b) Seed ferns
(c) Allosaurus
youngest
rocks
oldest
rocks
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Fig. 13-4
13.1 How Did Evolutionary Thought Evolve?
 Some scientists devised nonevolutionary explanations for
fossils.
• Despite the growing fossil evidence, many scientists of the
eighteenth century still did not accept the idea that species
changed and new ones had arisen over time.
• Georges Cuvier (1769–1832) advanced the idea of
catastrophism.
• Catastrophism states that a vast supply of species was
created initially, and that successive catastrophes—like
the Great Flood described in the Bible—destroyed some
species.
• He theorized that organisms of the modern world are those
that survived the catastrophes.
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13.1 How Did Evolutionary Thought Evolve?
 Geology provided evidence that Earth is exceedingly old.
• The concept of _________________, proposed by geologist
Charles Lyell (1797–1875), was proposed to show that
geological processes have occurred over a long period
of time and gradually changed the landscape, implying
that the Earth is very old.
• Modern geologists estimate that Earth is about ____
__________ years old.
• Lyell showed that this was enough time for evolution to
occur, but he was uncertain how evolution took place.
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13.1 How Did Evolutionary Thought Evolve?
 Some pre-Darwin biologists proposed mechanisms for
evolution.
• Baptiste Lamark (1744–1829) hypothesized that organisms
evolved through the inheritance of acquired
characteristics.
• This idea states that the bodies of living organisms are
modified through the use or disuse of parts, and these
modifications are inherited by offspring.
• According to this concept, if giraffes tried to improve their lot
by stretching upward to feed on leaves that grew high up in
trees, their necks became longer as a result.
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13.1 How Did Evolutionary Thought Evolve?
• Their offspring would inherit these longer necks; eventually,
this process would produce modern giraffes with very long
necks.
• Today, we know that acquired characteristics are not
inherited.
• The fact that a prospective father pumps iron does not
mean that his child will look like a champion body-builder.
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13.1 How Did Evolutionary Thought Evolve?
 Darwin and Wallace proposed a mechanism of evolution.
• By the mid-1800s, many biologists had concluded that
present-day species had evolved from earlier ones; but
how?
• In 1858, Charles Darwin and Alfred Russel Wallace, working
separately, provided convincing evidence that evolution was
driven by a simple yet powerful process.
 Darwin and Wallace observed that among all the
diversity of life there were some species that differed in
only a few features.
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13.1 How Did Evolutionary Thought Evolve?
 Darwin’s finches
(a)Large ground finch, beak suited to
large seeds
(c) Warbler finch, beak suited to insects
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(b) Small ground finch, beak suited to
small seeds
(d) Vegetarian tree finch, beak suited to leaves
Fig. 13-5
13.1 How Did Evolutionary Thought Evolve?
• Both researchers found that some species differed in only a
few features.
• Both were familiar with the fossil record showing an increase
in complexity with time.
• Both knew that the Earth was extremely old.
• These facts suggested that species change over time.
• In separate but similar papers that were presented to the
Linnaean Society in London in 1858, Darwin and Wallace
each described the same mechanism for evolution.
• The next year, Darwin published his monumental book, On
the Origin of Species by Means of Natural Selection which
outlined how species evolve, and its concepts form the basis
for the modern understanding of evolution.
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13.2 How Does Natural Selection Work?
 Darwin and Wallace proposed that life’s huge
variety of excellent designs arose by a process of
descent with modification, in which individuals in
each generation differ slightly from the members
of the preceding generation.
 Over long stretches of time, these small differences
accumulate to produce major transformations.
 Darwin and Wallace’s theory rests on four
postulates.
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13.2 How Does Natural Selection Work?
 Postulate 1: Individual members of a population differ
from one another in many respects.
• People differ in size, eye color, skin color, and many
other physical features; similar variability occur in other
organisms.
• These variations occur as a result of random mutations
in DNA; differences among individuals extends to the
molecular level.
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13.2 How Does Natural Selection Work?
 Postulate 2: At least some of the differences among
members of a population are due to characteristics that
may be passed from parent to offspring.
• Although observations of people, pets, and farm animals
seemed to show that offspring generally resemble their
parents, Darwin and Wallace did not have scientific evidence
to support this postulate.
• Mendel’s work on the principles of genetics was not
published until far later, but confirmed postulate 2 through
experimentation.
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13.2 How Does Natural Selection Work?
 Postulate 3: In each generation, some individuals in a
population survive and reproduce successfully but others
do not.
• Darwin knew that organisms produce far more offspring than
are required to replace the parents.
• However, the numbers of individuals in a population tend to
remain constant; more individuals are born than survive long
enough to reproduce.
• It is clear that in a population, some individuals have more
offspring than others.
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13.2 How Does Natural Selection Work?
 Postulate 4: The fate of individuals is not determined
entirely by chance or luck; an individual’s likelihood of
survival and reproduction depends upon its characteristics;
individuals with advantageous traits survive the longest
and leave more offspring, a process known as
___________ _____________.
• Reproductive success depends upon an individual’s
characteristics.
• For example, larger male elephant seals in a California
population have more offspring than smaller males.
• These results show that in the competition to survive and
reproduce, winners are determined not by chance but by the
traits they possess.
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13.2 How Does Natural Selection Work?
 Natural selection modifies populations over time.
• Observation and experimentation suggest that the four
postulates of Darwin and Wallace are sound.
• Natural selection acts on individuals within a
population; over generations, the population changes as
the percentage of individuals inheriting favorable traits
increases; an individual cannot evolve, but a population
can.
• Although it is easier to understand how natural selection
would cause changes within a species, under the right
circumstances, the same principles might produce entirely
new species.
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13.3 How Do We Know That Evolution Has
Occurred?
 Fossils provide evidence of evolutionary change over time.
• If it is true that many fossils are the remains of species
ancestral to modern species, we ought to find a series of
fossils that start with ancient, primitive organisms and
culminate with modern species.
• Such series has been found for ancestors of modern whales,
fossil giraffes, elephants, horses, and mollusks.
• These fossil series suggest that new species evolved from,
and replaced, previous species.
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13.3 How Do We Know That Evolution Has
Occurred?
 The evolution of the whale
millions of years ago
0
Modern whales
40
Basilosaurus
45
Dorudon
Rhodocetus
Ambulocetus
50
Pakicetus
Fig. 13-7
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13.3 How Do We Know That Evolution Has
Occurred?
 ______________ anatomy gives evidence of descent with
modification.
• Comparing the bodies of organisms of different species can
reveal similarities that can be explained only by shared
ancestry, and differences that could result only from
evolutionary change during descent from a common
ancestor.
• The study of comparative anatomy has supplied strong
evidence that different species are linked by a common
evolutionary heritage.
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13.3 How Do We Know That Evolution Has
Occurred?
 Homologous structures provide evidence of common
ancestry.
• The forelimbs of birds and mammals are variously used for
flying, swimming, running, and grasping objects.
• Despite this diversity of function, the internal anatomy of all
bird and mammal forelimbs is remarkably similar.
• This similarity is what would be expected if the forelimbs
were derived from a common ancestor; each forelimb has
been modified to perform a particular function.
• Such internally similar structures are called
_______________ structures and have the same
evolutionary origin.
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13.3 How Do We Know That Evolution Has
Occurred?
 Homologous structures
humerus
ulna
radius
Pterodactyl
carpals
Dolphin
metacarpals
Dog
phalanges
Human
Bird
Bat
FLYING
Seal
SWIMMING
Sheep
Shrew
RUNNING
GRASPING
Fig. 13-8
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13.3 How Do We Know That Evolution Has
Occurred?
 Functionless structures are inherited from ancestors.
• Evolution by natural selection helps explain
______________ structures that serve no apparent purpose.
• Examples: molar teeth in vampire bats (which live on blood
and thus don’t chew their food) and pelvic bones in whales
and some snakes
• These are homologous structures to those found in, and
used by, other vertebrates; ancestors of whales had four
legs with well-developed pelvic bones.
• During whale evolution, losing the hind legs provided a
streamlining advantage; therefore, modern whales only have
small, useless pelvic bones.
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13.3 How Do We Know That Evolution Has
Occurred?
 Vestigial structures
The bones of a
salamander’s
hindlimb function
in support and
locomotion
(a) Salamander
(b) Baleen whale
These vestigial bones are
similar in structure to
those of the salamander
but serve no function; all
three animals inherited
the bones from a
common ancestor
(c) Boa constrictor
Fig. 13-9
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13.3 How Do We Know That Evolution Has Occurred?
 Some anatomical similarities result from evolution in
similar environments.
• There are many anatomical similarities that do not stem from
common ancestry.
• Such similarities stem from ___________ evolution, in
which natural selection causes non-homologous
structures that serve similar functions to resemble one
another.
• Both birds and insects have wings, but this similarity did not
arise from evolutionary modification of a structure that both
birds and insects inherited from a common ancestor.
• Such outwardly similar, but non-homologous, structures are
called ______________ structures, and have very different
internal anatomy.
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13.3 How Do We Know That Evolution Has
Occurred?
 Analogous structures
Fig. 13-10
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13.3 How Do We Know That Evolution Has
Occurred?
 Embryological similarity suggests common ancestry.
• All vertebrate embryos look quite similar to one another early
in their development.
Fig. 13-11
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13.3 How Do We Know That Evolution Has
Occurred?
• In early embryonic development, fish, turtles, chickens,
mice, and humans all develop tails and gill slits.
• Only fish retain gills as adults, and only fish, turtles, and
mice retain tails.
• Ancestral vertebrates possessed genes that directed the
development of gills and tails; all their descendents still
have these genes.
• In fish, these genes are active throughout development; in
humans, these genes are active only during early
development, and the structures are lost as adults.
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13.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms.
• Biochemical similarities among organisms provide
perhaps the most striking evidence of their evolutionary
relatedness.
• The protein _______________ c is present in all plants
and animals, and performs the same function in all of
them.
• The DNA sequence of nucleotides is similar in all these
diverse species; this provides evidence that a common
ancestor of plants and animals had cytochrome c in its
cells.
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13.3 How Do We Know That Evolution Has
Occurred?
 Molecular similarity shows evolutionary relationships.
human A T G G G T G A T G T T G A G A A A G G C A A G A A G A T T T T T A T T A T G A A G
mouse A T G G G T G A T G T T G A A A A A G G C A A G A A G A T T T T T G T T C A G A A G
human T G T T C C C A G T G C C A C A C C G T T G A A A A G G G A G G C A A G C A C A A G
mouse T G T G C C C A G T G C C A C A C T G T G G A A A A G G G A G G C A A G C A T A A G
human A C T G G G C C A A A T C T C C A T G G T C T C T T T G G G C G G A A G A C A G G T
mouse A C T G G A C C A A A T C T C C A C G G T C T G T T C G G G C G G A A G A C A G G C
human C A G G C C C C T G G A T A C T C T T A C A C A G C C G C C A A T A A G A A C A A A
mouse C A G G C T G C T G G A T T C T C T T A C A C A G A T G C C A A C A A G A A C A A A
human G G C A T C A T C T G G G G A G A G G A T A C A C T G A T G G A G T A T T T G G A G
mouse G G C A T C A C C T G G G G A G A G G A T A C C C T G A T G G A G T A T T T G G A G
human A A T C C C A A G A A G T A C A T C C C T G G A A C A A A A A T G A T C T T T G T C
mouse A A T C C C A A A A A G T A C A T C C C T G G A A C A A A A A T G A T C T T C G C T
human G G C A T T A A G A A G A A G G A A G A A A G G G C A G A C T T A A T A G C T T A T
mouse G G A A T T A A G A A G A A G G G A G A A A G G G C A G A C C T A A T A G C T T A T
human C T C A A A A A A G T A C T A A T G A G
mouse C T T A A A A A G G T A C T A A T G A G
Fig. 13-12
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13.3 How Do We Know That Evolution Has
Occurred?
 Other biochemical similarities also extend to all living cells.
• All cells have _______.
• All cells use RNA, ribosomes, and the same ________ code.
• All cells use the same 20 __________ ________ in proteins.
• All cells use ______ as a cellular energy carrier.
• The explanation for such widespread sharing of these
complex and specific biochemical traits is that they are
homologous, arising from a common ancestor.
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13.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Controlled breeding modifies organisms.
• ____________ ____________ is the breeding of domestic
plants and animals to produce specific desirable features.
• Humans produced radically different dogs in a few thousand
years by repeatedly selecting individuals with desirable
traits.
• Therefore, it is plausible that natural selection by an
analogous process acting over hundreds of millions of years
produce the spectrum of living organisms.
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13.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Dogs descended from wolves, and today, the two will
readily cross-breed; modern dogs do not resemble
wolves.
Fig. 13-13
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13.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Evolution by natural selection occurs today.
• Brighter coloration can evolve when fewer predators are
present.
• In Trinidad, guppies live in streams with larger predators that
eat them.
• In the shallow upstream waters, the guppies are free of
predators and are more brightly colored than the
downstream guppies.
• Thus, where predators are common, they act as agents of
natural selection by eliminating the bright-colored guppies.
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13.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Natural selection can lead to pesticide resistance.
• Insect pests can evolve resistance to pesticides through
natural selection.
• In Florida, a pesticide called Combat was used to control the
number of roaches; roaches that liked it were killed.
• Those that survived inherited a rare mutation that caused
them to dislike the sugar that was used in the Combat bait.
• Soon, all the roaches had this mutation and were immune to
Combat.
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13.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Experiments can demonstrate natural selection.
• Anolis sagrei lizards were released in small groups onto 14
small Bahamian islands that previously did not have the
lizards.
• The original lizards came from an island with tall vegetation
and many trees; the island where they were transplanted
had few or no trees, and were covered with small shrubs
and other low-growing plants.
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13.4 What Is the Evidence That
Populations Evolve by Natural Selection?
 After 14 years, the released lizards were examined and
displayed shorter and thinner legs than the original population.
 Lizards grew shorter legs to allow for more agility on
narrow surfaces; long legs were at a disadvantage on thinbranched bushes.
Fig. 13-15
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13.4 What Is the Evidence That
Populations Evolve by Natural Selection?
 Selection acts on random variation to favor the
phenotypes that work best in particular environments.
• The variations on which natural selection works are
produced by chance mutations.
• The mutations that produced bright or dark colored
Trinidadian guppies, a distaste for Combat poison in
cockroaches, and shorter legs in Bahamian lizards were
beneficial traits that arose spontaneously in each case.
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13.4 What Is the Evidence That
Populations Evolve by Natural Selection?
 Natural selection favors organisms that are best adapted
to a particular environment.
• Natural selection does not select the “best” in any
absolute sense, but only for what is best in the context
of a particular environment.
• A trait that is advantageous under one set of conditions
may become disadvantageous if conditions change.
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