Transcript Evolution - Sauer Science

Evolution
Evolution= genetic change of a
population over time
How do we know about evolution?
In 1831, at the tender age of 22,
Charles Darwin set sail on HMS
Beagle. The original purpose of the
voyage was to map out trade routes for
Great Britain, but Darwin arranged to
work as a field naturalist, recording
details and illustrations of interesting
flora and fauna as he sailed (read: job
for slackers). The voyage did not
return to England until 1836.
Voyage of the Beagle
Interesting Galapagos Species
Galapagos Tortoise “Lonesome George”
Blue-Footed Booby!
Marine Iguana
Galapagos Penguin
Darwin began to notice that organisms in isolated locations
(i.e., on islands) often bore resemblance to their mainland
counterparts, but with slight morphological changes.
He began to wonder about the long-held assumption that
species were created in their present forms.
In 1859, Darwin published his
magnificent work, The Origin of
Species.
Two main points of the text were:
1. Descent with Modification (a
fancy/non-controversial way of
saying evolution!) - Darwin
proposed that species were, in
fact, not created in their present
forms, but rather had common
ancestry with other extant
species.
2. Darwin proposed natural
selection as the mechanism for
this descent with modification.
A word on Thomas Huxley
But wait… What took him so long?!
1. Natural theology had ruled the sciences for many
years.
2. He was unsure about the nature of variation which
natural selection acted upon (didn’t know about
Mendel).
“We are profoundly
ignorant of the
causes [of
variations]…”
- Charles Darwin
3. He was young and insecure about the idea (he was
only 27 when he returned from trade voyage).
He was (sort of) forced to show his
cards…
Alfred Russel Wallace
(1823-1913)
A professional collector
stumbled upon the ideas
of Descent with
Modification and Natural
Selection while observing
beetles in Malaysia.
He wrote Darwin a
famous letter in 1858 and
disclosed his ideas.
Darwin’s magnum opus, The Origin of
Species, laid out a clear and simple
description of natural selection that helped
to support their claims.
The two men presented joint letters to the Linnaean Society
in 1859. This means they both got credit, but because
Darwin had been working on this longer, and had more
evidence, he got most of the credit. Think about it—do we
call Wallace the Father of Evolution?
Darwin’s Four Postulates
1. In every population, there is variety.
2. Some of that variety is passed on to
offspring.
Aw, he has your
eyes!
3. There are always more individuals
produced than can survive.
Some will die
because of
disease,
predators, or
resource
availability
4. So, over time, the individuals who are the most
fit for their environment will survive better to
reproduce.
If that fitness is attributed to their genetics, this
will lead to an increased representation of their
alleles in future generations (genetic
change/time)
(not THIS kind of fit!)
Natural Selection
Individuals with traits that
allow them to survive, will
go on to reproduce
offspring with those traits.
Did he do it alone?
Not only did Wallace have similar
ideas, Darwin was influenced by the
work of many scientists before him…
Carolus Linnaeus
AKA Hot Pants
(1707-1778)
- Father of Taxonomy
- Developed binomial
nomenclature
Okay, so this
thing definitely
doesn’t look
like my dog…
Georges Cuvier
(1769-1832)
-Father of Paleontology
-Described hundreds of
fossils evidencing extinct
life forms
True to natural
theology, Cuvier
described these fossils
as a result of
CATASTROPHISM.
And, to be
clear, many
of them were
the result of
major
catastrophes
James Hutton and Charles Lyell
Fathers of Geology
Gradualism
Uniformitarianism
Jean-Baptiste Lamarck
1. “You get what
you need”
(use/disuse)
2. Inheritance of
acquired
characteristics
So, what’s the evidence?
What convinced Darwin and what have we learned since?
Biogeography: Distribution of
species around the earth
Biological diversity results from
descendants of a common
ancestor becoming adapted to
diverse environments.
The process of nuclear division that
reduces the number of chromosomes by
half
Start with somatic cell
End with gamete
Homologous Structures
Homologous structures provide
strong evidence that all fourlimbed vertebrates have
descended, with modifications,
from a common ancestor.
Homologous Structures
Similar structures, but different functions
Vestigial Structures
Structures that were used by
common ancestors, but are
useless today
Vestigial Organs
The organs of many animals are so
reduced in size that they are just
vestiges, or traces, of
homologous organs in other
species.
(leftovers)
Fossils
Fossils prove the existence of
many different organisms through
time that are related to existing
organisms.
Looked at fossils from each of the
different strata and compared their
morphologies.
Fossil Analysis
Comparative Embryology
There are many similarities in the
early stages of development of
vertebrates, which suggests
common ancestry.
Comparative Embryology
Molecular Biology
Molecular Biology
• Protein synthesis is essentially the same in all
organisms.
• Proteins in all organisms are composed of the
same 20 amino acids.
• DNA is very similar between two closely related
organisms
– Compare amino acid sequences of 2 organisms
– The more amino acids organisms share, the more
closely related they are