Download AP Chap 22 Mechanisms of Evolution

Mechanisms of Evolution
AP Biology Chapter 22
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
• Darwin noted that current species are
descendants of ancestral species
• Evolution can be defined by Darwin’s
phrase “descent with modification”
• Species are descendants of ancestral
species that were different from the
present-day species
giant sloths to small sloths
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More narrow definition
Evolution is a change
in the genetic
composition of a
population from
generation to
generation
Did Darwin know this?
• Evolution can be viewed as both a
pattern and a process:
pattern - data accumulated
process - mechanisms in place to
cause change
Prevailing ideas about the
origin of life
• Species were fixed and individually
created
• The earth was only 6000 years old
Fig. 22-2
Climate of the times
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Wallace (evolution, natural selection)
American Revolution
French Revolution
U.S. Civil War
1800
1900
1750
1850
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his hypothesis of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks.
1844 Darwin writes essay on descent with modification.
1858 Wallace sends his hypothesis to Darwin.
1859 The Origin of Species is published.
People and ideas that influenced
Darwin
• The Greek philosopher Aristotle viewed
species as fixed and arranged them on a
scala naturae
• The Old Testament holds that species
were individually designed by God and
therefore perfect
• Carolus Linnaeus interpreted 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
Fig. 22-3
The study of fossils
helped to lay the
groundwork for
Darwin’s ideas
Layers of deposited
sediment
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 advocated catastrophism,
speculating that each boundary between
strata represents a catastrophe
• Geologists James Hutton and Charles
Lyell perceived that changes in Earth’s
surface can result from slow continuous
actions still operating today. Hutton
called his ideas gradualism.
• Lyell’s principle of uniformitarianism
states that the mechanisms of change are
constant over time
• This view strongly influenced Darwin’s
thinking
• 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
• However, he did come up
with a mechanism for
evolution.
Was Lamarck totally wrong?
A study shows that when mice are taught to fear an
odor, both their offspring and the next generation are
born fearing it. The gene for an olfactory receptor
activated by the odor is specifically demethylated in
the germ line and the olfactory circuits for detecting
the odor are enhanced.
About Darwin
• 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 for a 5-year around
the world voyage on the Beagle
Fig. 22-5
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
Fig. 22-6
(a) Cactus-eater
(c) Seed-eater
(b) Insect-eater
He noticed how
finches’
beaks were
adapted for
their diet.
• 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
Let’s get together on this so we
can both be famous!
The Origin of Species
• Darwin developed two main ideas:
– Descent with modification explains life’s unity and
diversity
– Natural selection is a cause of adaptive evolution
• 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
Fig. 22-7
Fig. 22-8
Hyracoidea
(Hyraxes)
Sirenia
(Manatees
and relatives)
Moeritherium
Barytherium
Deinotherium
Mammut
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
Adaptations
• 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
Observation #1: Members of a population
often vary greatly in their traits
What is the ultimate source of
variations in natural populations?
MUTATIONS
• Observation #2: Traits are inherited
from parents to offspring
• Observation #3: All species are
capable of producing more offspring
than the environment can support
• Observation #4: Owing to lack of food or
other resources, many of these offspring
do not survive
My idea
Precisely!
MALTHUS
• Inference #1: 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 (fitness)
• Inference #2: This unequal ability of
individuals to survive and reproduce will
lead to the accumulation of favorable
traits in the population over generations
***Favorable – NOT BEST NECESSARILY
• Darwin was influenced by Thomas
Malthus who noted the potential for
human population to increase faster than
food supplies and other resources
Struggle
for
survival
• 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…Nature selects
individuals to survive. Individuals do not
change to survive.
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
What is the relationship between
evolution and natural selection?
Natural selection is one mechanism
that can result in the process of
evolution.
One more important thing….
• Populations evolve, NOT
INDIVIDUALS!
• Natural selections acts on individuals
but the population as a whole evolves!
Evidences for Evolution
• Direct observations
• The Fossil Record
• Homology
• Biogeography
1. Direct Evidences Today
• Ex- Evidence of Drug-resistant HIV
• Ex – Evidence of Drug-resistant
bacteria such as MRSA
• Ex – Evidence of Pesticide-resistant
insects
• Coloration patterns in guppies due to
predation
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
2. Fossil Evidence
• The fossil record provides evidence
of the extinction of species, the
origin of new groups, and changes
within groups over time
Fig. 22-15
0
2
4
4
6
4 Bristolia insolens
8
3 Bristolia bristolensis
10
12
3
2 Bristolia harringtoni
14
16
18 1 Bristolia mohavensis
3
2
1
Latham Shale dig site, San
Bernardino County, California
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)
3. Homology
• Homology is similarity resulting from
common ancestry
• Can be both anatomical and
molecular
• Anatomical similarities seen in
comparative embryology suggest
common ancestry
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Fig. 22-17
Homologous structures are anatomical
resemblances that represent variations on a
structural theme present in a common ancestor
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
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
Examples of homologies at the molecular level
are genes shared among organisms inherited
from a common ancestor
• Convergent evolution is the evolution of
similar, or analogous, features in
distantly related groups
• Analogous - having the same function
but not necessarily evolutionarily related.
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Flying
squirrel
4. 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
Bird Biogeography
Phylogeny – the evolutionary
history of an organism
Evolutionary trees show
common ancestry and
homologous structures
linking organisms.
Evolutionary Tree
Is natural selection the ONLY
mechanism responsible for
evolution?