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BIOLOGY Life on Earth
WITH PHYSIOLOGY Tenth Edition
Audesirk Audesirk Byers
14
Principles of
Evolution
Lecture Presentations by
Carol R. Anderson
Westwood College, River Oaks Campus
© 2014 Pearson Education, Inc.
Chapter 14 At a Glance
 14.1 How Did Evolutionary Thought Develop?
 14.2 How Does Natural Selection Work?
 14.3 How Do We Know That Evolution Has
Occurred?
 14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Evolution is the change over time in the
characteristics of a population
– Population is all the individuals of one species in a
particular area
 Modern biology is based on our understanding that
life has evolved, a principle unrealized by early
scientists
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Early biological thought did not include the concept
of evolution
– Pre-Darwinian science was heavily influenced by
theological ideas, maintaining that all organisms were
created simultaneously by God, and that each distinct
life-form was permanently fixed and did not change
over time
– Plato (427–347 B.C.) proposed that each object on
Earth was merely a temporary reflection of its divinely
inspired “ideal form”
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Early biological thought did not include the concept
of evolution (continued)
– Pre-Darwinian science was heavily influenced by
theological ideas, maintaining that all organisms were
created simultaneously by God, and that each distinct
life-form was permanently fixed and did not change
over time (continued)
– Aristotle (384–322 B.C.) arranged all organisms on a
linear scale of increasing complexity (the “ladder of
Nature”)
© 2014 Pearson Education, Inc.
Figure 14-1 Aristotle’s Ladder of Nature
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
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Exploration of new lands revealed a staggering
diversity of life
– Europeans were often accompanied by naturalists
who observed and collected plants and animals of
previously unknown lands
– By the 1700s observations and collections
accumulated by naturalists revealed the true scope of
life’s variety
– The number of species was far greater than expected
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Exploration of new lands revealed a staggering
diversity of life (continued)
– Revelation of the discoveries led 18th-century
naturalists to take note of fascinating patterns
– Geographic areas possessed their own sets of species
– Some species closely resembled one another yet
differed in some characteristics
– To some naturalists, these patterns seemed
inconsistent with the idea that species were fixed and
unchanging
© 2014 Pearson Education, Inc.
Figure 14-2 A timeline of the roots of evolutionary thought
Buffon
(species created, than evolve)
Hutton
(gradual geologic change)
Lamarck
(mechanism of species change)
Cuvier
(successive catastrophes)
Smith (sequence of fossils)
Lyell (very old Earth)
Darwin
(evolution, natural selection)
Wallace (evolution, natural selection)
1700
© 2014 Pearson Education, Inc.
1750
1800
1850
1900
14.1 How Did Evolutionary Thought Develop?
 A few scientists speculated that life had evolved
– George Louis LeClerc (Comte de Buffon; 1707–1788)
– Suggested that the original creation provided a
relatively small number of founding species
– Species changed over time through natural processes
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Fossil discoveries showed that life has changed over
time
– Fossils are the preserved remains or traces of
organisms that had died long ago
– Fossils were the petrified remains of bones, wood,
shells, or their impressions left in mud
– Other fossils included preserved traces such as tracks,
burrows, pollen, eggs, and feces
© 2014 Pearson Education, Inc.
Figure 14-3 Types of fossils
eggs in nest
© 2014 Pearson Education, Inc.
fossilized feces
(coprolites)
bones
footprint
skin
impression
14.1 How Did Evolutionary Thought Develop?
 Fossil discoveries showed that life has changed over
time (continued)
– Significance of fossil distribution
– The British surveyor William Smith (1769–1839), who
studied rock layers and the fossils embedded in them,
recognized that certain fossils were always found in the
same layers of rock
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Fossil discoveries showed that life has changed over
time (continued)
– Significance of fossil distribution (continued)
– The organization of fossils and rock layers was
consistent with fossils across different areas
– Fossil type A always found in a rock layer resting
beneath a younger layer containing fossil type B, which
is found rested beneath an even younger layer
containing fossil type C, and so on
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Fossil discoveries showed that life has changed over
time (continued)
– Scientists of the period discovered that fossil remains
showed remarkable progression
– Most fossils found in the oldest layers were very
different from modern organisms
– The resemblance to modern organisms gradually
increased in progressively younger rocks
– Many of the fossilized species were extinct, which means
no members of the species still lived on Earth
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Fossil discoveries showed that life has changed over
time (continued)
– Scientists concluded that
– Different types of organisms had lived at different times
in the past
– This countered the view that species were created at
one time and did not change afterward
© 2014 Pearson Education, Inc.
Figure 14-4 Different fossils are found in different rock layers
youngest
rocks
oldest
rocks
© 2014 Pearson Education, Inc.
Trilobite
Seed ferns
Allosaurus
14.1 How Did Evolutionary Thought Develop?
 Some scientists devised non-evolutionary
explanations for fossils
– To account for the existence of extinct species while
preserving the notion of a single creation by God,
Georges Cuvier (1769–1832) proposed the theory of
catastrophism
– The Great Flood described in the Bible produced layers
of rock and destroyed many species, fossilizing some of
their remains in the process
– The organisms of the modern-day species are the
survivors of these catastrophes
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Geology provided evidence that the Earth is
exceedingly old
– Charles Lyell (1797–1875) challenged Cuvier’s
hypothesis of a world shaped by successive
catastrophes
– Lyell, building on the earlier thinking of Hutton,
considered the forces involved in catastrophes and
concluded no need to invoke catastrophes to explain
the finding of geology
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Geology provided evidence that the Earth is
exceedingly old (continued)
– Lyell presented the idea of uniformitarianism to
explain that Earth’s landscape was produced by past
action of the same geological processes observed
today
– The acceptance of uniformitarianism by scientists
implied that Earth is ancient
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Evolve?
 Some pre-Darwin biologists proposed mechanisms
for evolution
– Jean Baptiste Lamarck (1744–1829) was one of the
first scientists to propose a mechanism for evolution
– Observed that older fossils tend to be less like existing
organisms than are more recent fossils
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Some pre-Darwin biologists proposed mechanisms
for evolution (continued)
– In 1809, Lamarck published a book in which he
hypothesized that organisms evolved through the
inheritance of acquired characteristics
– Acquired characteristics is a process in which the
bodies of living organisms are modified during their
lifetime through use or disuse of different parts inherited
by the offspring
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Some pre-Darwin biologists proposed mechanisms
for evolution (continued)
– Understanding how inheritance works refutes
Lamarck’s evolutionary mechanism
– Gregor Mendel, geneticist, began to understand how
traits are passed on and that acquired characteristics
are not heritable
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Darwin and Wallace proposed a mechanism of
evolution
– Charles Darwin (1809–1882) and Alfred Wallace
(1823–1913) provided convincing evidence that
evolution was driven by a simple yet powerful process
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Darwin and Wallace proposed a mechanism of
evolution (continued)
– Although Darwin and Wallace had different
educational backgrounds, they possessed similar
qualities
– They traveled extensively in the tropics and studied
plants and animals
– Darwin and Wallace found that some species differ in
only a few features
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Evolve?
 Darwin and Wallace proposed a mechanism of
evolution (continued)
– Although Darwin and Wallace had different
educational backgrounds, they possessed similar
qualities (continued)
– Both were familiar with fossils previously discovered
– Both were aware of the studies of Hutton and Lyell, who
proposed Earth was ancient
– Both men sought a mechanism that might cause
evolutionary change
© 2014 Pearson Education, Inc.
14.1 How Did Evolutionary Thought Develop?
 Darwin and Wallace proposed a mechanism of
evolution (continued)
– Darwin was the first to propose a mechanism for
evolution, sketched in 1842 and described more fully
in his 1844 essay
– Wallace authored a paper outlining similar ideas 16
years after Darwin’s essay
© 2014 Pearson Education, Inc.
Figure 14-5 Darwin’s finches, residents of the Galápagos Islands
Large ground finch, beak
suited to large seeds
Warbler finch, beak suited
© 2014 Pearson Education, Inc.to insects
Small ground finch, beak
suited to small seeds
Vegetarian tree finch, beak
suited to leaves
14.1 How Did Evolutionary Thought Develop?
 Darwin and Wallace proposed a mechanism of
evolution
– Darwin and Wallace independently proposed that
organisms evolved by natural selection
– Both presented papers to the Linnaean Society in
London in 1858
– Darwin published On the Origin of Species by Means
of Natural Selection in 1859
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace proposed that life’s diverse
forms arose through the process of descent with
modification
– Individuals in each generation differ slightly from the
members of the preceding generation
– Over long time periods, small differences accumulate
to produce major transformations
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
– Postulate 1: Individual members of a population differ
from one another in many respects
– 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
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
(continued)
– Postulate 3: In each generation, some individuals in
a population survive and reproduce successfully but
others do not
– Postulate 4: The face of individuals is not determined
entirely by luck or chance; instead, an individual’s
likelihood of survival and reproduction depends on its
characteristics
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
(continued)
– Postulate 1: Individuals in a population vary
– People differ in size, eye color, skin color, and other
physical features
– Variability is present in populations of other organisms
© 2014 Pearson Education, Inc.
Figure 14-6 Variation in a population of snails
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
(continued)
– Postulate 2: Traits are passed from parent to
offspring
– The principles of genetics were unknown when Darwin
published On the Origin of Species
– The later work by Mendel demonstrated conclusively
that particular traits can be passed to offspring
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
(continued)
– Postulate 3: Some individuals fail to survive and
reproduce
– Essay on the Principle of Population (Thomas Malthus)
influenced Darwin’s formulation of Postulate 3
– More organisms must be born than survive long enough
to reproduce
© 2014 Pearson Education, Inc.
14.2 How Does Natural Selection Work?
 Darwin and Wallace’s theory rests on four postulates
(continued)
– Postulate 4: Survival and reproduction are not
determined by chance
– Reproductive success depends on an individual’s
characteristics
– In the competition to survive and reproduce, winners
are determined not by chance but by the traits they
possess
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Animation: Natural Selection for Antibiotic Resistance
14.2 How Does Natural Selection Work?
 Natural selection modifies populations over time
– Natural selection acts on individuals within a
population
– The population changes over time
– Over generations, the population changes, as the
percentage of individuals inheriting favorable traits
increases
– An individual cannot evolve, but a population can
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Evolution is an accepted scientific theory today
– A scientific theory is a general explanation of
important natural phenomena, developed through
extensive, reproducible observations
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 An overwhelming body of evidence supports the
theory of evolution
– Fossils
– Comparative anatomy (the study of how body
structures differ among species)
– Embryology (the study of developing organisms in the
period from fertilization to birth)
– Biochemistry
– Genetics
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Fossils provide evidence of evolutionary change
over time
– If fossils are remains of species ancestral to modern
species, fossils begin with the ancient organism,
progress through intermediate stages, and culminate
in a modern species
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Fossils provide evidence of evolutionary change
over time (continued)
– Several series of fossils have been found that exhibit
the evolution of body structures over time
– These fossil series suggest that new species evolved
from, and replaced, previous species
– One series reveals that modern whales evolved from
land-dwelling ancestors
© 2014 Pearson Education, Inc.
Figure 14-7 The evolution of the whale
Millions of years ago
0
Modern whales
40
Basilosaurus
45
Dorudon
Rhodocetus
Ambulocetus
50
Pakicetus
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative 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
– Comparing the bodies of organisms of different
species can reveal differences that could result only
from evolutionary change during descent from a
common ancestor
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Homologous structures provide evidence of common
ancestry
– A body structure may be modified by evolution to
serve different functions in different species
– Homologous structures are structures that have the
same evolutionary origin despite their current
appearance or function
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Homologous structures provide evidence of common
ancestry (continued)
– Bird and mammalian forelimbs are homologous
structures
– The forelimbs are used for flying, swimming, running,
and grasping objects
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Homologous structures provide evidence of common
ancestry (continued)
– Despite their different uses, they have strong
anatomical similarities
– Such similarity is exactly what we would expect if bird
and mammal forelimbs were derived from a common
ancestor
© 2014 Pearson Education, Inc.
Figure14-8 Homologous structures
humerus
Pterodactyl
Dolphin
Dog
ulna
radius
carpals
metacarpals
phalanges
Human
Bird
Bat
FLYING
© 2014 Pearson Education, Inc.
Seal
SWIMMING
Sheep
RUNNING
Shrew
GRASPING
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Functionless structures are inherited from ancestors
– Evolution by natural selection helps explain the
curious circumstance of vestigial structures
– Vestigial structures have no apparent essential
function
– Molar teeth in vampire bats (which live on a diet of blood
and, therefore, don’t chew their food) are vestigial
structures
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Pelvic bones in whales and in certain snakes also
serve no function in modern species
– Both vestigial structures are homologous to structures
found in and used by other vertebrates
– Evolutionary theory suggests that as the animals
evolved into new habitats, some of their structures
that made them less fit were reduced to the point of
insignificance
© 2014 Pearson Education, Inc.
Figure 14-9 Vestigial structures
Salamander
Baleen whale
Boa constrictor
© 2014 Pearson Education, Inc.
The bones of a
salamander’s hind
limb function in
support and
locomotion
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
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Some anatomical similarities result from evolution in
similar environments
– Some anatomical similarities do not stem from
common ancestry
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Some anatomical similarities result from evolution in
similar environments (continued)
– Convergent evolution is a process in which natural
selection causes non-homologous structures that serve
similar functions to resemble one another
– The similarity of the wings of insects and birds did not
arise from evolutionary modification of a structure
inherited from an ancestor
– The similarity arose from parallel modification of two
different, non-homologous structures
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Some anatomical similarities result from evolution in
similar environments (continued)
– Because natural selection favored flight in both birds
and insects, they evolved wings of similar appearance
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Comparative anatomy gives evidence of descent
with modification (continued)
– Analogous structures are structures that are
outwardly similar in appearance, but differ in their
evolutionary origin
– Analogous structures are typically very different in
internal anatomy because the parts are not derived
from common ancestral structures
© 2014 Pearson Education, Inc.
Figure 14-10 Analogous structures
Damselfly
Swallow
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Embryological similarity suggests common ancestry
– Karl von Baer, in the early 1800s, noted that all
vertebrate embryos resemble one another in their
early development
– Fish, turtles, chickens, mice, and humans develop a
tail and gill slits (gill grooves) during their early
embryonic stage
– Only adult fish retain gills and tail because the genes
are active throughout their embryonic development
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Figure 14-11 Embryological stages reveal evolutionary relationships
Lemur
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Pig
Human
14.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms
– Modern technology revealed molecular similarities
among organisms
– Biochemical similarities among organisms provide
perhaps the most striking evidence of their
evolutionary relatedness
– Relatedness is revealed by homologous molecules
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms (continued)
– DNA sequencing is a powerful tool for revealing
molecular homologies
– The sequence of nucleotides in DNA molecules can be
quickly determined
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms (continued)
– The sequences in DNA molecules of one organism
can be compared a different organism
– The gene that encodes the protein cytochrome c is
found in all plants and animals and performs the same
function in both
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms (continued)
– The biochemical similarities are so fundamental that
they extend to all living cells
– All cells use DNA as the carrier of genetic information
– All use RNA, ribosomes, and approximately the same
genetic code to translate that genetic information into
proteins
© 2014 Pearson Education, Inc.
14.3 How Do We Know That Evolution Has
Occurred?
 Modern biochemical and genetic analyses reveal
relatedness among diverse organisms (continued)
– The biochemical similarities are so fundamental that
they extend to all living cells (continued)
– All use roughly the same set of 20 amino acids to build
proteins
– All use ATP as a cellular energy carrier
© 2014 Pearson Education, Inc.
Figure 14-12 Molecular similarity shows evolutionary relationships
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Controlled breeding modifies organisms
– Artificial selection is selective breeding of domestic
plants and animals to produce specific desirable
features
– Modern dogs are descended from wolves and readily
crossbreed today
– In only a few thousand years, humans artificially
selected for all breeds of modern dogs
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Figure 14-13 Dog diversity illustrates artificial selection
Gray wolf
© 2014 Pearson Education, Inc.
Diverse dogs
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Controlled breeding modifies organisms (continued)
– Humans have created tremendous variation in several
species over relatively short periods of time through
artificial selection
– Isn’t it plausible that much larger changes could result
from hundreds of millions of years of natural selection?
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
– Scientific observation and experimentation provide
additional evidence of natural selection
– Brighter coloration
– Herbicide and pesticide resistance
– Experimental introductions of Anolis sagrei lizards
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Brighter coloration can evolve when fewer predators
are present
– Trinidad guppy experiment
– Female guppies prefer to mate with brightly colored
males; however, brightly colored males are more likely to
be eaten by predators
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Brighter coloration can evolve when fewer predators
are present (continued)
– Trinidad guppy experiment (continued)
– Males found in areas lacking predators were brightly
colored
– Males found in areas with predators were duller by
comparison (predators eliminated brightly colored males
before they could reproduce)
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Brighter coloration can evolve when fewer predators
are present (continued)
– The conclusion was that when fewer predators are
present, brighter coloration can evolve
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Brighter coloration can evolve when fewer predators
are present (continued)
– An experiment confirmed the conclusion
– Predators were introduced to previously predator-free
areas (where males were brightly colored)
– Within a few generations, male guppies in those areas
evolved to become less colorful
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Figure 14-14 Guppies evolve to become more colorful in predator-free environments
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance
– Natural selection is evident in weed species that have
evolved resistance to the herbicides with which we try
to control them
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance (continued)
– Successful agriculture depends on farmers’ ability to kill
weeds that compete with crop plants, but glyphosate,
active ingredient found in Roundup, can no longer be
used
– The glyphosate inactivates an enzyme essential to
plants’ survival
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance (continued)
– Ragweed survivors of the glyphosate carry a mutation
that causes them to produce a tremendous amount of
enzyme that glyphosate attacks, more enzyme than
glyphosate can destroy
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance (continued)
– The evolution of glyphosate-resistant superweeds was
a direct result of changes in agriculture practice
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance (continued)
– Just as weeds have evolved to resist herbicides, many
of the insects that attack crops have also evolved
resistance to the pesticides that farmers use to control
them
– More than 500 species of crop-damaging insects have
been documented
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Natural selection can lead to herbicide and pesticide
resistance (continued)
– Just as weeds have evolved to resist herbicides, many
of the insects that attack crops have also evolved
resistance to the pesticides that farmers use to control
them (continued)
– Virtually every pesticide has fostered the evolution of
resistance in at least one important species
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
– Small groups of Anolis sagrei lizards were introduced
onto 14 small Bahamian islands with thinly branched
bushes and no trees
– Lizards were originally from Staniel Cay, an island with
thickly branched trees
– Their long legs were adaptive for maneuvering on the
thick branches of these trees
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
(continued)
– After 14 years, comparisons were made between lizards
on the Bahamian islands and those of Staniel Cay
– The original small groups of lizards had given rise to
thriving populations of hundreds of individuals
– Lizards on all 14 Bahamian islands had shorter, thinner
legs
– The lizard populations changed in response to new
environments
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
(continued)
– Natural selection appeared to favor individuals with
shorter, thinner legs because they were able to move
more agilely along the thinner vegetation of their new
islands
– Because they could move more agilely, they were able to
escape predators better than their longer-legged
ancestors in the new environment
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
(continued)
– Natural selection appeared to favor individuals with
shorter, thinner legs because they were able to move
more agilely along the thinner vegetation of their new
islands (continued)
– More of the shorter-legged lizards survived to pass their
genes for shorter legs on
© 2014 Pearson Education, Inc.
Figure 14-15 Anole leg size evolves in response to a changed environment
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
(continued)
– The variations on which natural selection works are
produced by chance mutations that arose
spontaneously
– Trinidadian guppies
– Extra enzyme in giant ragweed plants
– Shorter legs in Bahamian lizards
© 2014 Pearson Education, Inc.
14.4 What Is the Evidence That Populations Evolve
by Natural Selection?
 Evolution by natural selection occurs today
(continued)
– Experiments can demonstrate natural selection
(continued)
– Natural selection selects for organisms that are best
adapted to a particular environment
– Natural selection does not select for the “best” in any
absolute sense, but only for what is best in the context of
a particular environment
© 2014 Pearson Education, Inc.