Ch 14 lecture

Copyright © 2009 Pearson Education, Inc..
Lectures by
Gregory Ahearn
University of North Florida
Chapter 14
Principles of
Evolution

Copyright © 2009 Pearson Education Inc.
14.1 How Did Evolutionary Thought
Evolve?
 Is there a connection between your wisdom
teeth and an ostrich’s wings?
 The main ideas of evolutionary biology were
only widely accepted after the publication of
Charles Darwin’s work in the late nineteenth
century.

Evolve?
 A timeline of the roots of evolutionary
thought
Fig. 14-1
Lamarck (mechanism of species change)
Wallace (evolution, natural selection)
Darwin (evolution, natural selection)
Lyell (very old Earth)
Smith (sequence of fossils)
Cuvier (catastrophism)
Hutton (gradual geologic change)
Buffon (species created, then evolve)
19001850180017501700

Evolve?
 Early biological thought did not include the
concept of evolution.
• One of the earliest scientific beliefs was called
“Creationism,” 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.

Evolve?
 Aristotle categorized all organisms into a
linear hierarchy that he called the “ladder of
Nature.”
• These ideas remained unchallenged for 2,000
years.

Fig. 14-2
Humans
Mammals
Reptiles and amphibians
Whales and porpoises
Squids and octopuses
Lobsters, crabs, etc.
Snails, clams, etc.
Insects, spiders, etc.
Jellyfishes, sponges, etc.
Higher plants
Lower plants
Inanimate matter
Birds
Fish

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.

Evolve?
 Exploration of new lands revealed a
staggering diversity of life (continued).
• 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.

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.

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.

Evolve?
 Types of fossils
Fig. 14-3
bonesfossilized feces
(coprolites)
footprinteggs in nest skin impression

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

Evolve?
 Fossils of extinct organisms
Fig. 14-4
youngest
rocks
oldest
rocks
(a) Trilobite (b) Seed ferns (c) Allosaurus

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.

Evolve?
 Some scientists devised nonevolutionary
explanations for fossils (continued).
• 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.

Evolve?
 Geology provided evidence that Earth is
exceedingly old.
• The concept of uniformitarianism, 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.

Evolve?
 Geology provided evidence that Earth is
exceedingly old (continued).
• Modern geologists estimate that Earth is
about 4.5 billion years old.
• Lyell showed that this was enough time for
evolution to occur, but he was uncertain how
evolution took place.

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.

Evolve?
mechanisms for evolution (continued).
• 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.
• Their offspring would inherit these longer
necks; eventually, this process would produce
modern giraffes with very long necks.

Evolve?
mechanisms for evolution (continued).
• 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.

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.

Evolve?
 Darwin and Wallace observed that among
all the diversity of life there were some
species that differed in only a few features.

Evolve?
 Darwin’s finches
Fig. 14-5
(a)Large ground finch, beak suited to
large seeds
(b) Small ground finch, beak suited to
small seeds
(c) Warbler finch, beak suited to insects (d) Vegetarian tree finch, beak suited to leaves

Evolve?
of evolution (continued).
• 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.

Evolve?
of evolution (continued).
• 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.
• In this book, Darwin outlined how species
evolve, and its concepts form the basis for the
modern understanding of evolution.

14.2 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.
• 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.

 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 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 natural selection.

 Postulate 1: Individuals in a population vary.
• 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.

 Postulate 2: Traits are 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.

 Postulate 3: Some individuals fail to survive
and reproduce.
• 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.

 Postulate 4: Survival and reproduction are
not determined by chance.
• 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.

 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.

 Natural selection modifies populations over
time (continued).
• 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.

14.3 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.

Occurred?
 The evolution of the whale
Fig. 14-7
Modern whales
Basilosaurus
Dorudon
Rhodocetus
Ambulocetus
Pakicetus
0
40
millionsofyearsago
45
50

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,
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.

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.

Occurred?
 Homologous structures provide evidence of
common ancestry (continued).
• 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
homologous structures and have the same
evolutionary origin.

Occurred?
 Homologous structures
Fig. 14-8
Pterodactyl
Bird
Bat
Dolphin
Seal
Dog
Sheep Shrew
humerus
ulna
metacarpals
phalanges
radius
carpals
Human
GRASPINGRUNNINGSWIMMINGFLYING

Occurred?
 Functionless structures are inherited from
ancestors.
• Evolution by natural selection helps explain
vestigial 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

Occurred?
 Functionless structures are inherited from
ancestors (continued).
• 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.

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
The bones of a
salamander’s
hindlimb function
in support and
locomotion
(c) Boa constrictor
(b) Baleen whale
(a) Salamander
Occurred?
 Vestigial structures
Fig. 14-9

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 convergent
evolution, in which natural selection causes
non-homologous structures that serve similar
functions to resemble one another.

Occurred?
 Some anatomical similarities result from
evolution in similar environments
(continued).
• 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 analogous structures,
and have very different internal anatomy.

Occurred?
 Analogous structures
Fig. 14-10

Occurred?
 Embryological similarity suggests common
ancestry.
• All vertebrate embryos look quite similar to
one another early in their development.
Fig. 14-11

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.

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 cytochrome 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.

Occurred?
 Molecular similarity shows evolutionary
relationships.
Fig. 14-12
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mouse
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mouse
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Occurred?
 Other biochemical similarities also extend to
all living cells.
• All cells have DNA.
• All cells use RNA, ribosomes, and the same
genetic code.
• All cells use the same 20 amino acids in
proteins.
• All cells use ATP 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.

14.4 What Is The Evidence That
Populations Evolve By Natural Selection?
 Controlled breeding modifies organisms.
• Artificial selection is the breeding of domestic
plants and animals to produce specific
desirable features.

 Dogs descended from wolves, and today,
the two will readily cross-breed; modern
dogs do not resemble wolves.
Fig. 14-14

 Controlled breeding modifies organisms
(continued).
• 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.

 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.

 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.

 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.
• After 14 years, the released lizards were examined
and displayed shorter and thinner legs than the
original population.

14.4 What Is the Evidence That
Populations Evolve by Natural Selection?
 Lizards grew shorter legs to allow for more
agility on narrow surfaces; long legs were at
a disadvantage on thin-branched bushes.
Fig. 14-15

 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 variation.
• 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.

 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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