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Evolutionary view of life
陳嘉祥, MD, Ph.D.
林口長庚醫院精神科
長庚大學生物醫學系
Evolution accounts for the unity and
diversity of life
“Nothing in biology makes sense
except in the light of evolution”
-Theodosius Dobzhansky
1900-1975
Traditional view
• 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 organismal
adaptations as evidence that the Creator had
designed each species for a specific purpose
Figure 22.2
1809
Lamarck publishes his
hypothesis of evolution.
1798
Malthus publishes
“Essay on the Principle
of Population.”
1812
1858
Cuvier publishes his extensive
studies of vertebrate fossils.
1795
Hutton proposes
his principle of
gradualism.
1830
Lyell publishes
Principles of Geology.
While studying species
in the Malay Archipelago,
Wallace sends Darwin
his hypothesis of natural
selection.
1790
1809
183136
Charles Darwin
is born.
Darwin travels around
the world on HMS
Beagle.
1870
1859
On the Origin of
Species is published.
1844
Darwin writes his
essay on descent
with modification.
The Galápagos Islands
Figure 22.3
Sedimentary rock
layers (strata)
Younger stratum
with more recent
fossils
Older stratum
with older fossils
The Fossil Record
• The fossil record provides evidence of the
extinction of species, the origin of new groups,
and changes within groups over time
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Video: Grand Canyon
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Ideas About Change over Time
• 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
• 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
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Lamarck’s Hypothesis of Evolution
• Lamarck hypothesized that species evolve
through use and disuse of body parts and the
inheritance of acquired characteristics
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Figure 22.5
Darwin in 1840,
after his return
from the
voyage
HMS Beagle in port
Great
Britain
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
PACIFIC
OCEAN
Pinta
Genovesa
Santiago
Fernandina
Isabela
0
20
40
Kilometers
Daphne
Islands
Pinzó n
Santa Santa
Cruz
Fe
Florenza
Equator
SOUTH
AMERICA
Equator
Chile
PACIFIC
OCEAN
San
Cristobal
Españ ola
Andes Mtns.
Marchena
Brazil
Malay Archipelago
PACIFIC
OCEAN
AUSTRALIA
Cape of
Argentina Good Hope
Cape Horn
Tasmania
New
Zealand
The Voyage of the Beagle
• During his travels on the Beagle, Darwin
collected specimens of South American plants
and animals
• He observed that fossils resembled living
species from the same region, and living species
resembled other species from nearby regions
• He experienced an earthquake in Chile and
observed the uplift of rocks
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Figure 22.5c
The
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Genovesa
Marchena
Santiago
Fernandina
Isabela
0
20
40
Kilometers
Equator
Daphne
Islands
Pinzó n
Santa Santa
Cruz
Fe
Florenza
San
Cristobal
Españ ola
Video: Galápagos Islands Overview
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Video: Blue-footed Boobies Courtship Ritual
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Video: Albatross Courtship Ritual
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Video: Galápagos Sea Lion
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Video: Soaring Hawk
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Video: Galápagos Tortoises
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Video: Galápagos Marine Iguana
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Darwin’s Focus on Adaptation
• In reassessing his observations, Darwin
perceived adaptation to the environment and
the origin of new species as closely related
processes
• In 1844, Darwin wrote an essay on natural
selection as the mechanism of descent with
modification, but did not introduce his theory
publicly
• Natural selection is a process in which
individuals with favorable inherited traits are
more likely to survive and reproduce
The origin of Species
• 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
Alfred Russel Wallace
•
•
•
•
•
1823-1913
Co-discovery of natural selection
Pioneering work on biogeography
Wallace Line
Wallace effect
Biogeography
Frontispiece to Alfred Russel Wallace's book The
Geographical Distribution of Animals
Wallace line
Wallace effect
• Natural selection can contribute to the
reproductive isolation of incipient species by
evolving barriers against hybridization.
• When two varieties of a species had diverged
beyond a certain point, each adapted to
different conditions, hybrid offspring would
be less well adapted than either parent form.
At that point natural selection will tend to
eliminate the hybrids.
The Origin of Species
• Darwin explained three broad observations:
– The unity of life
– The diversity of life
– The match between organisms and their
environment
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• Observation #1: Members of a population often
vary in their inherited traits
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Figure 22.10
Figure 22.6
(b) Insect-eater
(a) Cactus-eater
(c) Seed-eater
Figure 22.5c
The
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Genovesa
Marchena
Santiago
Fernandina
Isabela
0
20
40
Kilometers
Equator
Daphne
Islands
Pinzó n
Santa Santa
Cruz
Fe
Florenza
San
Cristobal
Españ ola
The Beak of the Finch: A Story of
Evolution in Our Time
• Johnathan Weiner, Pulitzer Prize for General
Non-Fiction in 1995
• Peter and Rosemary Grant
• 1973-
2005 Balzan Prize for Population Biology
• "Peter and Rosemary Grant are distinguished for their
remarkable long-term studies demonstrating
evolution in action in Galápagos finches. They have
demonstrated how very rapid changes in body and
beak size in response to changes in the food supply
are driven by natural selection. They have also
elucidated the mechanisms by which new species
arise and how genetic diversity is maintained in
natural populations. The work of the Grants has had a
seminal influence in the fields of population biology,
evolution and ecology."
Descent with Modification
• Darwin never used the word evolution in
the first edition of The Origin of Species
• The phrase descent with modification
summarized Darwin’s perception of the
unity of life
• The phrase refers to the view that all
organisms are related through descent from
an ancestor that lived in the remote past
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Herbert Spencer
• 1820-1903, Philosopher, biologist,
anthropologist, sociologist, classical liberal
political theorist, polymath
• Evolution
• Survival of the fittest
• (Striving for the best)
• Social Darwinism
• 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
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• Observation #2: All species can produce more
offspring than the environment can support,
and many of these offspring fail to survive and
reproduce
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Figure 22.11
Spore
cloud
• Inference #2: This unequal ability of
individuals to survive and reproduce will
lead to the accumulation of favorable traits
in the population over generations
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Thomas Robert Malthus
An Essay on the Principle of
Population
1766-1834
1. That the increase of population is
necessarily limited by the means of
subsistence,
2. That population does invariably
increase when the means of
subsistence increase, and,
3. That the superior power of
population is repressed, and the actual
population kept equal to the means of
subsistence, by misery and vice.
• Darwin was influenced by Thomas Malthus,
who noted the potential for human
population to increase faster than food
supplies and other resources
• If some heritable traits are advantageous,
these will accumulate in a population over
time, and this will increase the frequency of
individuals with these traits
• This process explains the match between
organisms and their environment
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Evolution by natural selection
• It is a process inferred from three facts about
populations
– more offspring are produced than can possibly
survive
– traits vary among individuals, leading to different
rates of survival and reproduction
– trait differences are heritable
• This process creates and preserves traits that are
seemingly fitted for the functional roles they
perform
Fitness
• A potential for an individual to survive and
reproduce (a function of its reproductive success
or the number of the reproducing offspring it
produces) under certain selection conditions.
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
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Inheritance and variation
Gregor Mendel
1822-1884
August Weismann
Hugo de Vries
1834-1914
1848-1935
Germ cell
Mutation
Debate of two schools (1900-1915)
• Saltationism (large mutations or jumps), favored
by early Mendelians who viewed hard inheritance
as incompatible with natural selection.
• Biometric school: led by Karl Pearson and Walter
Weldon, argued vigorously against it, saying that
empirical evidence indicated that variation was
continuous in most organisms, not discrete as
Mendelism predicted.
Modern evolutionary synthesis
• is a 20th-century union of ideas from several
biological specialties which provides a widely
accepted account of evolution
• produced between 1936 and 1947, reflects the
consensus about how evolution proceeds
• The previous development of population genetics,
between 1918 and 1932, was a stimulus.
• The synthesis is still, to a large extent, the current
paradigm in evolutionary biology
Population genetics-1
• R.A. Fisher:
– the continuous variation measured by the
biometricians could be the result of the action of many
discrete genetic loci
– how Mendelian genetics was, contrary to the thinking
of many early geneticists, completely consistent with
the idea of evolution driven by natural selection
Population genetics-2
• J.B.S. Haldane,
– applied mathematical analysis to real world examples
of natural selection such as the evolution of industrial
melanism in peppered moths
– established that natural selection could work in the
real world at a faster rate than even Fisher had
assumed
Population genetics-3
• Sewall Wright,
– introduced the concept of an adaptive landscape in
which phenomena such as cross breeding and genetic
drift in small populations could push them away from
adaptive peaks, which would in turn allow natural
selection to push them towards new adaptive peaks
Summary of modern evolutionary
synthesis-1
• All evolutionary phenomena can be explained in a
way consistent with known genetic mechanisms
and the observational evidence of naturalists.
• Evolution is gradual: small genetic changes
regulated by natural selection accumulate over
long periods. Discontinuities amongst species (or
other taxa) are explained as originating gradually
through geographical separation and extinction.
Summary of modern evolutionary
synthesis-2
• Natural selection is by far the main mechanism of
change. The object of selection is the phenotype
in its surrounding environment.
• Thinking in terms of populations, rather than
individuals, is primary: the genetic diversity
existing in natural populations is a key factor in
evolution.
Summary of modern evolutionary
synthesis-3
• In palaeontology, the ability to explain historical
observations by extrapolation from
microevolution to macroevolution is proposed.
Historical contingency means explanations at
different levels may exist. Gradualism does not
mean constant rate of change.
Refinement of modern evolutionary
synthesis
• The synthesis as it exists now has extended the
scope of the Darwinian idea of natural selection to
include subsequent scientific discoveries and
concepts unknown to Darwin, such as DNA and
genetics.
Gene-centered view of evolution
• The Selfish Gene: Richard Dawkins
• Since heritable information is passed from
generation to generation by genetic material,
natural selection and evolution are best
considered from the perspective of genes.
• Genes whose phenotypic effects successfully
promote their own propagation will be favorably
selected in detriment to their competitors.
基因與個体間的関係
DNA
在生殖的過程中
完成複製.
Organism
身體是DNA的載具，它
所有的作為都是在保
存並散播DNA。
Punctuated equilibrium
• 1972: Stephen Jay Gould and Niles Eldredge
• selective pressures were heightened, punctuating
long periods of morphological stability, as welladapted organisms coped successfully in their
respective environments.
Punctuated equilibrium
Stasis vs Cladogenesis
Evolution by artificial selection
Cabbage
Selection for
apical (tip) bud
Brussels
sprouts Selection for
axillary (side)
buds
Broccoli
Selection
for flowers
and stems
Selection
for stems
Selection
for leaves
Kale
Wild mustard
Kohlrabi
競爭：生命中無可逃避的宿命！
食物
交配
陽光和水
生物為什會有利他的行為？
合作的好處：互利互惠！
Wolves hunt in packs and then share their prey.
無私的個人與自私的基因
Parent birds feed their chick
無私的行為源自於自私的基因！
Altruistic donor individual
Selfish “helping” gene
W.D. Hamilton (1936-2000)
Kin selection
Hamilton’s Rule (1964)
Relatedness to partner
r.B > C
Benefit to partner
Personal cost
This rule predicts when a gene for altruism should be selected.
Prediction: cooperation at high relatedness, conflict at low relatedness.
The peacock’s tail
Extravagant male ornaments
The peacock’s tail greatly impairs his mobility…how could such a trait evolve?
Why a theory of sexual
selection?
Darwin needed a theory to explain the many
extravagant traits that seem to reduce survival
e.g. the peacock’s tail
Theory of Sexual Selection
Darwin (1871, p256):
“We are, however, here
concerned only with that kind of
selection, which I have called
sexual selection. This depends
on the advantage which certain
individuals have over other
individuals of the same sex and
species, in exclusive relation to
reproduction.”
Intersexual
Selection
Fisher’s runaway model
Survival Selection
Sexual Selection
Total male fitness
(survival + mating)
Fitness
Female choice
adaptive for survival
Fitness due to survival
Tail length