Download Evolution - Department of Geology UPRM

Evolution
Chapter 5
• Natural selection is daily and hourly
scrutinizing throughout the world of every
variation, even the slightest; rejecting all
that which is bad, preserving and adding up
all that is good; silently and insensibly
working… We see nothing of these slow
changes in progress until the hand of time
has marked the long lapse of ages.
Charles Darwin, On the Origin of Species, 1859
• How exceedingly stupid of me not to have
though of that!
Thomas Henry Huxley, 1859, after reading On the
Origin of Species
The Evolution of Evolution
• On the Origin of species started a scientific
revolution that transformed natural history
into modern biology and for ever changed
our view of ourselves.
• By 1859 was already difficult to interpret
life, fossils, and geology as evidence of the
book of Genesis.
Darwin’s book did not spring out
of a vacuum.
• The idea that one species might be
transformed into another is an old one that
continually crops up in western thought.
• The Greek philosophers of thee fifth century
B.C. promoted the idea that “everything
changes”.
• The dominance of thee Church in the
western civilization put an end to that kind
of free thought for over a millennium.
• During the 1700s it became increasingly
difficult to take Genesis literally.
• Difficult to believe that every animal fit
Noah’s Ark, and then migrated from Mt.
Ararat to their present homes.
• By mid-1700’s, the work of taxonomists
like Linnaeus had already recognized over
6000 species of animals.
• This because exploration in places like
Africa, South America, Australia, southeast
Asia (marsupials and placental).
Fossil Record
• The discovery of faunal succession in the
early 1800s made impossible to treat all
fossils as if they had been victims of a
single flood, or even a series of floods.
• The complexity of the fossil record showed
that life had undergone many changes over
time.
• Hutton, Lyell and other geologist made it
clear that Earth was immensely old and
constantly changing not created only 6000
years ago.
• By 1840s, geologist had all but abandoned
the Bible as having anything to do with the
with the fossil record.
• A sequence of fossils was establish by
creationist geologist more than 40 years
before Darwin published his book.
• In the 1700s the idea of evolution became
more and more popular.
• 1749, George-Louis Leclerc, Count of
Buffon (1707-1788). Historie naturalle- a
34-volume work on evolution and suggested
that Earth was 75,000 years old.
• Lamarck, botanist, was assigned the work in
the museum of invertebrate zoology which
he completely reorganized lying the
foundation of modern invertebrates.
• Lamarck coined the term “Biology” to
combine zoology and botany. His
experience allow him to learn and see the
diversity of life and published “Philospphie
Zoologique” ion 1809.
• He saw the interconnections and variability
of life and realized that species were not
fixed.
• He arrange animals in the “scale of
creation”.
• The “ladder of creation” placed corals,
worms, and other invertebrates at the bottom
and “lower” vertebrates in the middles,
mammals higher, and humans in the top of the
ladder.
• Various ranks of cherubim, seraphim, angels,
and archangels were on the higher rungs,
culminating with God.
• Lamarck believed in life being spontaneously
generated out of mud and moving up the
ladder to the top.Those evolving for a long
time were mammals or even humans.
• Typical of that time Lamarck work was
philosophical and speculative with little or
no hard evidence or experimental data.
• Lamarck also established “inheritance of
acquired characters”- a blacksmith will
pass its on his large muscles to his children,
or a giraffe that stretched its neck would
pass its longer neck on to its descendants
until giraffes reached their current neck.
The Evolution of Darwin
• Charles Darwin (1809-1882)
• He was born the same year that Lamarck
published his evolutionary theory. His
grandfather was the king’s physician and
had published a poem that promoted
evolution.
• Darwin’s father was also a physician and
planned his son to follow in the same family
calling.
Darwin
• Darwin did not have the stomach for the
profession. Instead he developed a passion
for natural history and was very influenced
by the zoologist Robert Grant, who taught
in Edinburgh but was a follower of the
French evolutionists.
• Darwin dropped out of medical school, and
was send to Cambridge to study theology so
he would not disgrace the family.
• In Cambridge he became more involved
with natural history and was trained by the
botanist, John Stevens Henslow and the
geologist Adam Sedgwick.
• He took part of the world oceanographic
voyage on the H.M.S. Beagle. He became
the ship’s naturalist.
• The voyage took five years to go around the
world.
• Darwin collected animals and fossils.
• In Galapagos darwin observed that each
island had its own unique species of
tortoises, and the finches had been modified
to take over many of the roles taken by
other birds on the mainland.
• While in the ship Darwin read the three
volumes of Lyell’s “Principles of Geology”.
• By 1842 Darwin had a rough sketch of his
evolutionary theory, but he sealed and put
away with instruction for her wife to
publish it after he died.
Alfred Russel Wallace (1823-1913)
• Wallace developed his own concept of
natural selection. He got his ideas while
traveling in Indonesia to collect animals in
an expedition. He wrote a letter to Darwin
with his finding.
• Darwin not wanting to rob Wallace of due
credit but also not wanting to lose credit for
his own appealed to the geologist Charles
Lyell and the botanist Joseph Hooker.
• They decided to that both Darwin’s 1842
and Wallace 1858 work be read at the 1858
meeting of the Linnean society so that they
will get equal credit.
• However, they were considered not
important. That years report of the society
mentioned that no important discoveries
were done.
• Darwin summarized his ideas in a 155,000word book: On the Origin of Species by
Means of Natural Selection.
• It sold out all 1250 copies on the day it was
published and went through six editions
while Darwin was alive.
On the Origin of Species by
Means of Natural Selection
• Darwin’s argumentation was very simple
yet very clever.
• First, he drew an analogy to the artificial
selection practiced by the breeders of
domesticated animals.
• If wild dogs could be modify into beasts as
different as house dogs, then species were
much more flexible than naturalist admitted.
• Then he draw arguments from Malthus
(humans are reproducing at higher rates
than resources) animals are capable of
exponential growth of populations, yet in
nature most animals populations remain
constant so:more young are born than can
survive.
• Next he described how natural populations
are also highly variable, and pointed to the
experiments on domesticated animals that
showed how these variations were heritable.
• His major conclusion:
Organism that inherit favorable variations
for their immediate environment will tend
to survive more often than others.
Darwin called this idea Natural selection.
In Africa indivuduals with heterozygous (Aa) have a greater resistance to
malaria than normal individuals. AA are selected against by Malaria,
And (aa) individuals die
from sickel-cell anemia.
Heterozygotes
advantage.
Aa - Aa mating results
in 1/4 (aa) offsprings
combination and die.
Heterozygote
advantsage.
Neutralism-some changes are adaptively neutral. 64
possible combination of genetic code, only 20
aminoacids plus a few stop codes. If 1-U and 2-C is
aminoacid-serine no matter who 3 is.