Download Fig. 22-6 - Geneva Area City Schools

Chapter 22
Descent with Modification:
A Darwinian View of Life
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
1. What is our current working definition of
evolution?
• A new era of biology began in 1859 when
Charles Darwin published The Origin of
Species
• Evolution can be defined by Darwin’s phrase
descent with modification
• It is also considered a change in allele
frequencies.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-1
Examples of evolution.
Squirrel!
• Carolus Linnaeus (1707-1778) was a Swedish physician
and botanist who sought to classify life’s diversity “for the
greater glory of God.”
• He developed the two-part, or binomial, system of naming
species
• iInterpreted organismal adaptations as evidence that the
Creator had designed each species for a specific purpose
(clearly he did not support evolution)
• Linnaeus was the founder of taxonomy, the branch of
biology concerned with classifying organisms
• He was not a proponent of evolution.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
A little fossil background.
• 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
Video: Grand Canyon
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-3
Layers of deposited
sediment
Younger stratum
with more recent
fossils
Older stratum
with older fossils
Briefly describe the beliefs of the following individuals:
• Georges Cuvier (1769-1832) observed that the
older the stratum, the more dissimilar its fossils
were to current life forms.
• Also noted that from one layer to the next, some
new species appeared while others disappeared.
• He staunchly opposed evolution, but advocated
catastrophism
– Periodic catastrophes destroyed many of the
species living in an area, and the area was
repopulated by species immigrating in from
other areas.
• In contrast, other scientists suggested that
profound change could take place through the
cumulative effect of slow but continuous
processes.
• In 1795, Geologists James Hutton and Charles
Lyell perceived that changes in Earth’s surface
can result from slow continuous actions still
operating today
• Lyell’s principle of uniformitarianism states
that the mechanisms of change are constant
over time
• This view strongly influenced Darwin’s thinking
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Lamarck’s Hypothesis of Evolution
• Lamarck published his hypothesis in 1809, the
year Darwin was born.
• He proposed two ideas:
– use and disuse
– inheritance of acquired characteristics
• The mechanisms he proposed are unsupported
by evidence
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-4
Inheritance of Acquired Traits
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Voyage of the Beagle
• During his travels on the Beagle, Darwin collected
specimens of South American plants and animals
• He observed adaptations of plants and animals
that inhabited many diverse environments
• Darwin was influenced by Lyell’s Principles of
Geology and thought that the earth was more than
6000 years old
• His interest in geographic distribution of species
was kindled by a stop at the Galápagos Islands
near the equator west of South America
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
His interest in geographic distribution of species
was kindled by a stop at the Galápagos Islands near
the equator west of South America
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Genovesa
Equator
Marchena
Santiago
Fernandina
Isabela
Daphne
Islands
Pinzón
Santa
Santa
Cruz
Fe
Florenza
SOUTH
AMERICA
AUSTRALIA
PACIFIC
OCEAN
San
Cristobal
Cape of
Good Hope
Tasmania
Española
Cape Horn
Tierra del Fuego
New
Zealand
• Darwin observed geological phenomena that
challenged the current idea that the Earth was
only 6000 years old
• He also observed finches that had very similar
traits, but also differed in ways that made them
more suitable for their environment.
• He hypothesized that the Galapagos had been
colonized by organisms that had strayed from
South America and then diversified, giving rise to
new species on various islands
Fig. 22-6
(a) Cactus-eater
(c) Seed-eater
(b) Insect-eater
Darwin’s Focus on Adaptation
• An adaptation is an inherited characteristic of
an organism that enhances its survival and
reproduction in specific environments.
• From studies made years after Darwin’s
voyage, biologists have concluded that this is
indeed what happened to the Galápagos
finches
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• In 1844, Darwin wrote an essay on the origin of
species and natural selection but did not
introduce his theory publicly, anticipating an
uproar
• In June 1858, Darwin received a manuscript
from Alfred Russell Wallace, who had
developed a theory of natural selection similar
to Darwin’s
• Darwin quickly finished The Origin of Species
and published it the next year
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Origin of Species
• Darwin developed two main ideas:
– Descent with modification
– Natural selection
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Descent with Modification
• Darwin never used the word evolution in the
first edition of The Origin of Species
• The phrase refers to the view that all
organisms are related through descent from an
ancestor that lived in the remote past
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-8a
Platybelodon
Stegodon
Mammuthus
Elephas maximus
(Asia)
Loxodonta
africana
(Africa)
Loxodonta cyclotis
(Africa)
34
24
Millions of years ago
5.5
2 104 0
Years ago
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
• Darwin then described four observations of
nature and from these drew two inferences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-9
Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi
Fig. 22-10
Observation #1: Members
of a population often vary
greatly in their traits
• Observation #2: Traits are inherited from
parents to offspring
• Observation #3: All species are capable of
producing more offspring than the environment
can support
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Observation #4: Owing to lack of food or other
resources, many of these offspring do not
survive
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Therefore: Individuals whose inherited traits
give them a higher probability of surviving and
reproducing in a given environment tend to
leave more offspring than other individuals
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Darwin was influenced by Thomas Malthus
who noted the potential for human population
to increase faster than food supplies and other
resources
• Cornucopians vs. Malthusians
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Video: Seahorse Camouflage
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
• Note that individuals do not evolve;
populations evolve over time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Direct Observations of Evolutionary Change
• Two examples provide evidence for natural
selection: the effect of differential predation on
guppy populations and the evolution of drugresistant HIV
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Predation and Coloration in Guppies : Scientific
Inquiry
• John Endler has studied the effects of
predators on wild guppy populations
• Brightly colored males are more attractive to
females
• However, brightly colored males are more
vulnerable to predation
• Guppy populations in pools with fewer
predators had more brightly colored males
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-13
EXPERIMENT
Predator: Killifish; preys
mainly on juvenile
guppies (which do not
express the color genes)
Experimental
transplant of
guppies
Pools with
killifish,
but no
guppies prior
to transplant
Guppies: Adult males have
brighter colors than those
in “pike-cichlid pools”
Predator: Pike-cichlid; preys mainly on adult guppies
Guppies: Adult males are more drab in color
than those in “killifish pools”
RESULTS
12
Number of
colored spots
12
10
8
6
4
2
0
Source
population
Transplanted
population
10
8
6
4
2
0
Source
population
Transplanted
population
Fig. 22-13a
EXPERIMENT
Predator: Killifish; preys
mainly on juvenile
guppies (which do not
express the color genes)
Guppies: Adult males have
brighter colors than those
in “pike-cichlid pools”
Experimental
transplant of
guppies
Pools with
killifish,
but no
guppies prior
to transplant
Predator: Pike-cichlid; preys mainly on adult guppies
Guppies: Adult males are more drab in color
than those in “killifish pools”
Fig. 22-13b
RESULTS
12
Number of
colored spots
12
10
8
6
4
2
0
Source
Transplanted
population population
10
8
6
4
2
0
Source
Transplanted
population population
• Endler transferred brightly colored guppies
(with few predators) to a pool with many
predators
• As predicted, over time the population became
less brightly colored
• Endler also transferred drab colored guppies
(with many predators) to a pool with few
predators
• As predicted, over time the population became
more brightly colored
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Evolution of Drug-Resistant HIV
• The use of drugs to combat HIV selects for
viruses resistant to these drugs
• HIV uses the enzyme reverse transcriptase to
make a DNA version of its own RNA genome
• The drug 3TC is designed to interfere and
cause errors in the manufacture of DNA from
the virus
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Some individual HIV viruses have a variation
that allows them to produce DNA without errors
• These viruses have a greater reproductive
success and increase in number relative to the
susceptible viruses
• The population of HIV viruses has therefore
developed resistance to 3TC
• The ability of bacteria and viruses to evolve
rapidly poses a challenge to our society
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-14
100
Patient
No. 1
Patient No. 2
75
50
Patient No. 3
25
0
0
2
4
6
Weeks
8
10
12
• 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Fossil Record
• The fossil record provides evidence of the
extinction of species, the origin of new groups,
and changes within groups over time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• The Darwinian view of life predicts that
evolutionary transitions should leave signs in
the fossil record
• Paleontologists have discovered fossils of
many such transitional forms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-16
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)
Homology
• Homology is similarity resulting from common
ancestry
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomical and Molecular Homologies
• Homologous structures are anatomical
resemblances that represent variations on a
structural theme present in a common ancestor
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-17
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
• Comparative embryology reveals anatomical
homologies not visible in adult organisms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-18
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
• 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Homologies and “Tree Thinking”
• The Darwinian concept of an evolutionary
tree of life can explain homologies
• Evolutionary trees are hypotheses about the
relationships among different groups
• Evolutionary trees can be made using different
types of data, for example, anatomical and
DNA sequence data
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-19
Branch point
(common ancestor)
Lungfishes
Amphibians
1
Mammals
2
Tetrapod limbs
Amnion
Lizards
and snakes
3
4
Homologous
characteristic
Crocodiles
Ostriches
6
Feathers
Hawks and
other birds
Birds
5
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Flying
squirrel
Biogeography
• Darwin’s observations of biogeography, the
geographic distribution of species, formed an
important part of his theory of evolution
• Islands have many endemic species that are
often closely related to species on the nearest
mainland or island
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-UN1
Observations
Individuals in a population
vary in their heritable
characteristics.
Organisms produce more
offspring than the
environment can support.
Inferences
Individuals that are well suited
to their environment tend to leave
more offspring than other individuals
and
Over time, favorable traits
accumulate in the population.
Fig. 22-UN2
Fig. 22-UN3
You should now be able to:
1. Describe the contributions to evolutionary
theory made by Linnaeus, Cuvier, Lyell,
Lamarck, Malthus, and Wallace
2. Describe Lamarck’s theories, and explain why
they have been rejected
3. Explain what Darwin meant by “descent with
modification”
4. List and explain Darwin’s four observations
and two inferences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5. Explain why an individual organism cannot
evolve
6. Describe at least four lines of evidence for
evolution by natural selection
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings