Transcript The Origin of Life: How? When? Where?

Fig. 22-2
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.
Argument from Design (Paley, 1802)
In crossing a heath, suppose I pitched my foot against a
stone, and were asked how the stone came to be there; I
might possibly answer, that, for any thing I knew to the
contrary, it had lain there for ever: nor would it perhaps be
very easy to show the absurdity of this answer. But
suppose I had found a watch upon the ground, and it
should be inquired how the watch happened to be in that
place; I should hardly think of the answer which I had
before given, that, for any thing I knew, the watch might
have always been there. Yet why should not this answer
serve for the watch as well as for the stone? Why is it not
as admissible in the second case, as in the first? For this
reason, and for no other: that, when we come to inspect
the watch, we perceive (what we could not discover in the
stone) that its several parts are framed and put together for
a purpose, e.g., that they are so formed and adjusted as to
produce motion so regulated as to point out the hour of the
day.
Fig. 22-3
Layers of deposited
sediment
Younger stratum
with more recent
fossils
Older stratum
with older fossils
What Were the Main Accomplishments of
Charles Darwin and Alfred Wallace?
• Descent with Modification and Mutability (vs. Great Chain of Being)
– Darwin studied beetles in the Amazon, mockingbirds on Galapagos Islands,
other fauna and fossils in South America
– Darwin’s Origin of Species convinced most naturalists of evolution; added to
earlier concepts of “transmutation” (Buffon, Lamarck, Chambers, Lyell)
– Mutability of species: giant sloth and armadillo fossils; giant tortoise, marine
iguana of Galapagos Islands suggested that species could be transformed
• Adaptations
– Darwin wrote about adaptations observed during voyage of HMS Beagle,
and multiple functions of adaptations (ex., steamers using wings to row)
– Wallace especially interested in cryptic coloration and mimicry (ex., stick
insects)
• Biogeography
– Both noted similarities of island fauna to fauna of nearby continents
• Natural Selection: proposed jointly as the main mechanism of change
(“survival of the fittest” later coined by Herbert Spencer)
– Both influenced by Thomas Malthus’ “Tragedy of the Commons” thesis
– Darwin influenced by results of selective breeding (artificial selection)
– Reigning paradigm: Inheritance of Acquired Characteristics (Jean
Baptiste Lamarck); Darwin grudgingly accepted as the mechanism of
inheritance; August Weismann (1888) disproved by cutting tails off mice
CHARLES ROBERT DARWIN
1840
1882
Fig. 22-5
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
Figure 22.12
What are the Postulates of
Darwin’s Theory?
• Darwin’s Postulates (theory of natural selection as the
major cause of evolution – each postulate can be
tested; each potentially falsifiable)
1. Individuals within populations are variable
2. Variations among individuals are, at least in part, passed from
parents to offspring (Darwin was not aware of genetic
mechanisms)
3. In every generation, some individuals are more successful at
surviving and reproducing than others
• Most juveniles die before reproducing (note biotic potential)
4. The survival and reproduction of individuals are not random;
instead, they are tied to the variation among individuals. The
individuals with the most favorable variations, those who are better
at surviving and reproducing, are naturally selected
• Fitness: measurement of organism’s ability to survive and reproduce
Fig. 23-13
Original population
Original
Evolved
population population
(a) Directional selection
Phenotypes (fur color)
(b) Disruptive selection
(c) Stabilizing
selection
What Factors Cause Evolution?
• Evolution (population genetics definition):
change in gene frequencies in a population
(changes in gene pool)
• Factors that can change the nature of a gene
pool:
1. Natural selection: a strong force in evolution
2. Migration: especially strong in island populations
3. Mutation: a weak force in evolution, but the ultimate
source of novelty; mutations are generally mildly
deleterious (due to second copy of gene)
4. Non-random mate choice: sexual selection
generally involves female choice (among competing
males)
5. Chance events: environmental changes and catastrophes; “random” evolution called genetic drift
What Evidence Supports the Modern
Theory of Evolution?
1. Direct observations of change through time
– Ex., changes in beak morphologies among Darwin’s
finches (long-term study at Galapagos Islands)
– Ex., change in beak lengths of soapberry bugs after
introduction of golden rain trees in Florida
2. Vestigial traits: functionless or rudimentary
version of functional feature in other, closely
related species or subspecies
– Examples: eye sockets in blind cave fishes; wings in
flightless birds; pelvic and leg bones (and spurs)
in snakes (similar situation with cetaceans);
reduced tailbone (coccyx) and arrector pili
muscles in humans ( goosebumps; lift hair in
other mammals)
100
Patient
No. 1
Patient No. 2
75
50
Patient No. 3
25
0
0
2
4
6
Weeks
8
10
12
Fig. 22-14
What Evidence Supports the Modern
Theory of Evolution?
3. Evidence from the fossil record
– Extinction: in 1812, Cuvier provided strong evidence of
extinction with analysis of fossils (mammoths,
mastodons, and Irish elk)
– Law of Succession: general pattern of correspondence
between fossil and living forms from the same
locale; supported from wide variety of locations
and taxonomic groups (ex. marsupials of
Australia)
– Transitional forms: exhibit various characteristics seen
in ancestral species and other characteristics
seen in more recent descendents (the latter
often including important novel features)
•
Examples: Archaeopteryx; Basilosaurus; transitional tetrapods
0
2
Fig. 22-15
4
4
6
4 Bristolia insolens
8
3 Bristolia bristolensis
10
12
3
2 Bristolia harringtoni
14
16
18 1 Bristolia mohavensis
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)
What Evidence Supports the Modern
Theory of Evolution?
4. Homology: the study of likeness (modern meaning:
similarity due to inheritance of traits from a common
ancestor)
–
Structural and developmental homology
•
•
–
Ex., pattern of limb bones similar in all tetrapods
Ex., vertebrate embryos undergo similar developmental stages
before acquiring group-specific features (first noted by Karl
Ernst von Baer in 1828)
Molecular homology: shared genetic code for nearly all living
organisms; genes for critical enzymes with few
differences among groups; shared genetic flaws in
related species
5. Thousands of lab, field, and in silico studies that document
the importance of natural selection, sexual selection,
mutation, and migration in the evolution of populations
Fig. 22-17
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Fig. 22-18
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
(a) Cactus-eater
(c) Seed-eater
(b) Insect-eater
Fig. 22-6
What are Adaptations?
• Adaptation: a feature used for some function that has
become prevalent or is maintained in a population
because of natural selection for that function
– Multiple functions of single traits: many traits have multiple uses
(ex. functions of fish swim bladder include buoyancy, oxygen
storage, and sound production)
– Trade-offs: single traits may have off-setting benefits and detriments (ex. fish swim bladder provides buoyancy, but is a good
target for dolphin echolocation)
– Key innovations: traits that are associated with large gains in
evolutionary success (ex. skeletal fin rays in bony fishes)
– Preadaptation: a feature already present in a population that
fortuitously serves a new function
• Examples: wings in ancestral insects likely selected for surfaceskimming performance; bird wings likely enabled uphill running,
gliding, and/or thermoregulation before birds obtained flight
What is the function of the
hammerhead’s cephalofoil?
How Does Speciation Occur?
• The Biological Species Concept: species are groups of
actually or potentially interbreeding populations, which
are reproductively isolated from other such groups
(Ernst Mayr, 1942); emphasizes reproductive isolation
(lack of gene flow); later modified to account for
existence of fertile animal hybrids (animal hybrids are
rare, and are typically sterile or exhibit low fitness)
• Mechanisms of Speciation
– Speciation: origin of new species (process vs. event)
– Allopatric Mechanisms (physical isolation triggers
reproductive isolation)
• Via dispersal and colonization (ex., islands, edge of range)
• Via physical split of original range (ex., new mountain range or
isthmus, change in river’s course)
– Sympatric Mechanisms
• Genetic mechanisms: polyploidy (ex., wheat), mutations in
regulator genes
• Behavioral mechanisms: temporal separation, courtship displays
Fig. 24-5
(a) Allopatric speciation
(b) Sympatric speciation
Fig. 24-6
A. harrisi
A. leucurus
Fig. 24-7
Mantellinae
(Madagascar only):
100 species
Rhacophorinae
(India/Southeast
Asia): 310 species
Other Indian/
Southeast Asian
frogs
100
60
80
1
2
40
20
0
3
Millions of years ago (mya)
1
3
2
India
Madagascar
88 mya
65 mya
56 mya
Fig. 24-4
Prezygotic barriers
Habitat Isolation
Temporal Isolation
Individuals
of
different
species
(a)
Postzygotic barriers
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
Mating
attempt
(c)
(d)
(e)
(f)
Reduced Hybrid Viability
Reduced Hybrid Fertility
Hybrid Breakdown
Viable,
fertile
offspring
Fertilization
(g)
(h)
(i)
(j)
(b)
(k)
(l)
Fig. 24-4a
Prezygotic barriers
Habitat Isolation
Temporal Isolation
Individuals
of
different
species
(a)
Mating
attempt
(c)
(d)
(b)
Mechanical Isolation
Behavioral Isolation
(e)
(f)
Fig. 24-4i
Prezygotic barriers
Gametic Isolation
Postzygotic barriers
Reduced Hybrid Viability Reduced Hybrid Fertility
Hybrid Breakdown
Viable,
fertile
offspring
Fertilization
(g)
(h)
(i)
(j)
(k)
(l)
What are Some Patterns of Macroevolution?
• Adaptive Radiation: ancestral species evolves into multiple descendent
species, with each exploiting a different available lifestyle in their
respective environment
– Darwin’s finches on Galapagos Islands
– African cichlids (very diverse family of fishes in African Great Lakes)
• Convergence: independent evolution of superficially similar traits (in
response to similar selection pressures)
– Streamlining in dolphins, penguins, tunas (reduces drag in water)
– Echolocation in bats and dolphins (swarmed, patchy food sources)
• Coevolution: reciprocal changes in two or more species in close
association with each other
– “Arms races” between predators and their prey
– Adaptations for pollination (insects/hummingbirds/bats and flowering plants)
• Gradualism: slow emergence of new species (Darwin emphasized)
• Punctuated Equilibrium: long periods of stasis interrupted by sudden
emergence of new species (Stephen J. Gould and Niles Eldridge,
1972)
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Fig. 22-20
Flying
squirrel
Fig. 40-2
(a) Tuna
(b) Penguin
(c) Seal
Fig. 24-17
(a) Punctuated pattern
Time
(b) Gradual pattern