Download Biol. 4974/5974 Evolution Lecture #1

Darwin’s legacy
Evolution
Biol 4974/5974
Biol. 4974/5974 Evolution
Darwin and the
“Origin”
Learning goals
 Understand how the voyage of the HMS Beagle
influenced Charles Darwin’s career.
 Understand the “literary approach” of On the Origin
of Species. Why did he structure the first four
chapters and content as he did?
 Understand the concepts and inter-relationship of
chapter III, “Struggle for existence”, and chapter IV,
“Natural Selection.”
Understand other key concepts, including:
 The power of selective breeding.
 The existence of individual variation.
 Why rudimentary (vetigial) structures exist.
Learning goals--continued
 Criticisms anticipated by Darwin, e.g., How
complex organs can evolve.
 Why “instinct” (behavior) is inherited.
 The reason for sterility in hybrids.
 The “succession” of species over time.
 The great significance of “descent with
modification” and explanatory power.
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Darwin’s legacy
Evolution
Biol 4974/5974
Outline
 Brief biography of Charles Darwin
 Bibliography for Darwin
 Chapter by chapter overview of
On the Origin of Species
Charles Robert Darwin
Darwin at 40 yrs of age from
a lithograph by T.H. Maguire
Brief biography
 Born February 12, 1809, in Shrewsbury,
England.
 Father was Robert Waring Darwin, a country
physician. Uncle was Erasmus Darwin,
doctor, philosopher, naturalist.
 Darwin’s parents directed him towards
medicine or divinity after his studies at
Cambridge University. So how did this go?
 Young Charles was interested in natural
history and involved in current science.
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 In 1831 at the age of 22, Darwin sailed on
the exploration vessel, the H.M. S. Beagle.
 The ship had a naturalist, Robert
McCormick, who was also ship’s surgeon.
 So what was Darwin’s role? Box 10.2: “His
qualifications as a gentleman, good shot, and
sportsman were quite sufficient.”
 The ship’s 26 year old aristocratic captain,
Robert Fitzroy, required a social equal on
board.
 Darwin somewhat ruthlessly forced
McCormick out of favor. Darwin wrote in one
of his letters: “My friend the Doctor is an
ass, but we jog on very amicably….”
 McCormick ultimately quit as naturalist
and left the Beagle in South America.
 McCormick ended up exploring the
Antarctic with the historical James Ross
expedition 1839-1843.
Navy used for exploration? (great
concept!)
 Much has been suggested about the differences
between Darwin and Fitzroy, particularly with respect
to politics and religion.
 Their correspondence suggests, instead, that they
were both intelligent, interested in exploration, and
good friends.
 Very capable navigator and captain, Fitzroy rose in
rank to vice- admiral. He pioneered weather
forecasting and the use of barometers.
 In later years, Fitzroy appeared to be disturbed about
Darwin’s ideas, attending scientific meetings waving a
bible.
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Darwin’s legacy
Evolution
Biol 4974/5974
Voyage of the Beagle
From 1831 to 1836,
The HMS Beagle surveyed the
coast of South America and
off-lying islands.
Darwin explored:
 Tropical forests in Brazil.
 Fossils on the pampas of
Argentina.
 Indigenous peoples of
Tierra del Fuego and their culture.
 The geology of the Andes.
www.aboutdarwin.com
Figure 10.B2.1: H.M.S. (His Majesty’s Ship) Beagle in the
Strait of Magellan at the southern tip of South America.
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Darwin’s legacy
Evolution
Biol 4974/5974
Galapagos land iguanas
www.rit..edu
Observed and collected the
animal life of the Galapagos
Islands
Darwin’s finches
Grant and Grant (2006)
Science 313:224-226
After the voyage:
 Darwin settled in the village of Down in Kent
outside of London.
 He married his cousin Emma Wedgwood in 1839
and had 9 children.
 He was financially independent and spent the
next 40 years at home, with health problems.
 Studied and bred plants and animals.
 Analyzed and interpreted the volumes of
observations gathered during the voyage of the
Beagle.
 Wrote 18 books between 1839 and 1881.
 Died on April 19, 1882 at the age of 73.
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Darwin’s legacy
Evolution
Biol 4974/5974
Bibliography of Charles Darwin
Chronological order:
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2 journals from the voyage of the Beagle;
one in 3 volumes dealing with zoology
Structure and Distribution of Coral Reefs
Geological Observations on Volcanic Islands
Geological Observations on South America
3 monographs on barnacles
On the origin of species
 On the Various Contrivances by which British and
Foreign Orchids are Fertilized by Insects and on
the Good Effects of Intercrossing
 The Variation of Plants and Animals under
Domestication
 The Descent of Man, and Selection in Relation to
Sex
 The Expression of Emotions in Man and Animals
 Insectivorous Plants
 The Effects of Cross- and Self-pollination in the
Vegetable Kingdom
 The Different Forms of Flowers on Plants of the
Same Species
 The Power of Movement in Plants
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Darwin’s legacy
Evolution
Biol 4974/5974
Some of these later books were based on chapters from
On the Origin of Species
Last book: The Formation of Vegetable Mould,
Through the Action of Worms, with
Observations of their Habits
This book is Darwin’s metaphor for
evolutionary processes:
Slow, gradual change.
Wikipedia.org
On the Origin of Species by Means of
Natural Selection,
or the Preservation of Favoured Races
in the Struggle for Life
by Charles Darwin, M.A., London: John Murray, 1859
Chapter by chapter outline and
discussion of main points
Chapter I: Variation under domestication
•Individual variation exists; it is heritable.
•Domestic races exaggerate variation.
•Examples from pigeon breeding.
•The power of selective breeding.
Chapter II: Variation under Nature
•Individual variation exists as well within and among
Fig. 11-6
natural populations.
•So much so: Problem distinguishing varieties from
species.
•Species with large geographical ranges have more
variation across their range than do species with smaller
ranges.
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Chapter III: Struggle for existence
•Reproductive potential: geometric powers of increase: theme of
Thomas R. Malthus.
•There are limits to population growth—climate, competition,
predation, disease.
Chapter IV: Natural selection
•The mechanism behind adaptation and evolution.
•Individuals with certain variation will be more successful in
surviving or reproduction; leave more offspring.
•“Descent with modification” indicates change from natural
selection; divergence of character.
•It can account for species formation from previously existing
species.
Figure 11.3: The illustration Charles Darwin used in his book, On the Origin
of Species, to represent progressive divergence within individual species.
Chapter V: Laws of Variation
•Effects of “use and disuse.”
What does Darwin mean here?
•Flightlessness on islands, eyes in caves.
•Rudimentary (vestigial) structures and
secondary sexual characters vary.
•Not essential for survival, so not under
selection.
Chapter VI: Difficulties on theory
•Possible criticisms of natural selection.
•Absence of transitional forms in fossil record.
•“Organs of extreme perfection”.
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Chapter VII: Instinct
•Instinct is inherited like other traits.
•There is individual variation in behavior, which can be
sorted by natural selection; look at domestic animals.
•This explains similarities and differences in behavior
among species.
VIII: Hybridism
•Makes a substantial case for inherited differences, based
on degree of sterility in hybrids.
•Sterility is not to prevent hybridization but the
consequence of incompatibility.
•Degree of sterility parallels systematic relationships.
Chapter X: On the geological succession of organic
beings
•Only certain groups have been preserved, representing only
a small proportion of species which have lived.
•Extinction of old forms is the consequence of new forms.
•Dominant forms spread and produce related descendants.
Chapter XIII: Mutual affinities of organic beings-morphology, embryology, rudimentary organs
•Recurring theme—we see relationships among species both
living and extinct.
•By means of descent with modification, all the “great facts in
morphology” become intelligible; explains embryonic
resemblances, anatomical similarities, rudimentary organs.
Chapter XIV: Recapitulation and conclusion
“It is interesting to contemplate an entangled bank, clothed with
any plants of many kinds, with birds singing on the bushes,
with various insects flitting about, and with worms crawling
through the damp earth, and to reflect that these elaborately
constructed forms, so different from each other, and dependent
on each other in so complex a manner, have all been produced
by laws acting around us…..”
Thus, from the war of nature, from famine and death, the most
exalted object which we are capable of conceiving, namely, the
production of the higher animals, directly follows. There is
grandeur in this view of life, with its several powers, having
been originally breathed into a few forms or into one; and that,
whilst this planet has gone cycling on according to the fixed
law of gravity, from so simple a beginning endless forms most
beautiful and most wonderful have been, and are being,
evolved.”
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Study questions
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In what ways were Darwin’s first books more
conventional science books of the time?
Why did Darwin begin On the Origin of Species with a
discussion of “Variation under domestication?”
Why was this followed by “Variation under nature?”
Explain the importance of chapter III and chapter IV.
How do the first four chapters then illustrate his ideas
of natural selection and speciation?
Did Darwin ever actually discuss a complete
mechanism of speciation in chapter IV?
What other major points can you find from the brief
outlines of the other chapters?
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