Transcript Introduction to Evolution

What is Evolution?
 In biology, evolution is the change in the inherited traits
(a.k.a. genes/alleles, genotypes/phenotypes) of species (or
populations of a species) over time.
 Throughout this unit, you will see that three main
processes determine the rate of evolution:
 1) variation within a species (i.e. the fact that no one is an
identical clone to another person)
 2) reproduction: the method of reproduction and the rate at
which a species reproduces will affect how fast it evolves.
 3) selection: whether natural selection or sexual selection, you
will see that those best suited to their particular environment
will pass on their genes more frequently.
Evolution by Natural Selection
 The most famous
explanation of evolution
was made by Charles
Darwin, who stated that
those organisms best
suited to their
environment will be more
successful at passing on
their traits to the next
generation.
 This he called Evolution by
Natural Selection.
Darwin’s Influences
 Charles Darwin did not foresee himself getting into
the field of evolutionary biology.
 He wanted to be a doctor like his father, but he could
not stand the sight of blood and the savagery of
surgery.
 He then wanted to be a minister, but he did not want
to study. He preferred riding and shooting to
studying.
 He eventually became interested in biology through
his fascination with such exciting animals as barnacles,
beetles and pigeons.
Darwin’s Influences
 He changed his path at college and took more biology
courses as he developed a great love of taxonomy (yes,
the classification stuff we did last unit) and studied
intensely under the tutelage of botany professor John
Stevens Henslow.
 Henslow recommended Darwin for work as an unpaid
naturalist on a voyage around the world upon the HMS
Beagle, under captain Robert Fitzroy.
 As you will see, this journey not only changed Darwin’s
life, but also the face of biology forever…
But that is for Next Lecture…
 Now, we will look at some of the people whose prior
work shaped and influenced Darwin’s thinking and
lead him towards his theory of evolution by natural
selection.
Pre-Darwinian Times
 Aristotle (circa 400 BCE)
 He believed in the Scala
Natura (Scale of Nature).
 All living things were
arranged on a scale of
increasing complexity with
humans at the top.
 He felt all species were
perfectly adapted to their
environment and there was
no evolution/change.
Pre-Darwinian Times
 Natural Theology (~1700s)
 This was the church’s plan
to study nature to discover
God’s plan (the secret of
Life).
 It was thought that since
each species was made by
God, by discovering,
classifying and naming all
God’s creatures, man
would get closer to the
divine plan.
Written in the 1700s
Pre-Darwinian Times
 Carolus Linnaeus (1707-
1778)
 He came up with the
binomial nomenclature
system of taxonomy we
use today in which each
species gets a scientific
name based on its genus
and species.
Ornithorhynchus anatinus
Darwinian Times
 Georges Cuvier (1768-
1832)
 He was a paleontologist.
 He found that rocks
deeper in the Earth had
much different fossils
than anything that was
walking around during
his life time.
Darwinian Times
 He did not believe in evolution. He believed in
catastrophism.
 Catastrophism is the belief that each strata of rock contained
different fossils because it was associated with a catastrophic
event (i.e. the flood in Genesis)
 The Earth was a place where catastrophes happened and
different animals emerged afterwards.
Darwinian Times
 James Hutton (1726-1797)
 Introduced gradualism.
 Gradualism states that
geological changes are
slow and gradual and
take long periods of
time.
Darwinian Times
 Charles Lyell (1797-1875)
 Famed geologist whose book,
Principles of Geology, Darwin
took with him on the HMS
Beagle.
 He brought up the idea of
uniformitarianism.
 Uniformitarianism states that
geologic processes have not
changed throughout earth’s
history.
 That means that volcanoes,
sedimentation, etc., that we
observe today have occurred
since the beginning of time.
Why are these dead guys
important???
 There theories kept stretching the time that Earth was
formed further and further back in time, which
conflicted with religious teachings, but made more
sense scientifically.
The Church
 Previous to these men,
Irish Archbishop James
Ussher stated that from
biblical study he had
found out the precise day
the Earth was formed.
 The night before
October 23rd, 4004 B.C.
 Cuvier, Hutton and Lyell
pretty much sank the
Church’s theory.
Darwinian Times
 Jean Baptiste Lamarck (1744-1829)
 He placed fossils in an evolutionary context
and published a theory of evolution in 1809.
 His theory used two common ideas of his time:
 1) Use and disuse - parts of the body used on a
regular basis become larger and stronger; those not
used deteriorate.
 2) Inheritance of these acquired characteristics (I.e.,
the modifications) are passed onto the
offspring.
 Lamarck’s theory was based on observations of
fossils, but gave no mechanism for
evolution. However, he set the stage for Darwin… and
your homework and our next lecture.