DO NOW
1.
2.
3.
4.
5.
What is fitness?
If an organism does not have high fitness
what will happen to it? What will happen to
its species?
In natural selection, what decides the best
traits to “keep”
What are changes in genetic info called?
What is a fossil?
EVIDENCE FOR
EVOLUTION
Objectives:
Understand homologous structures
Be able to give an example of a vestigial
structure
Know that molecules can also be vestigial
Vocabulary
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Homologous structures
Analogous structures
Vestigial structure
Homologous Protein
Homologous Genes
Evidence for Evolution
•
By Darwin’s time, scientists had noted that all
vertebrate limbs had the same basic bone
structure.
Common Descent
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Common descent – all organisms on this
planet come from a single common ancestor
This was from Monday’s vocabulary
Comparing Anatomy and
Embryology
– The front limbs of amphibians, reptiles, birds,
and mammals contain the same basic bones.
Homologous
•
Darwin proposed that animals with similar
structures evolved from a common ancestor
with a basic version of that structure.
•
homologous structures - Structures that are
shared by related species and that have been
inherited from a common ancestor
Homologous Structures
Analogous Structures
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Analogous structures – structures that share a
common function, but not structure
Vestigial Structures
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Vestigial Structures – structures that have lost
much or all of their original function
Vestigial structures/ vestigial genes are some
of the strongest evidence for evolution
Brainstorm!
Vestigial Structures
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Dolphins have hip bones that do nothing, heck
they aren’t even attached anymore!
Vestigial Structures
Vestigial Structures
Refresher
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Proteins are made of amino acids
The instructions for making proteins comes
from DNA
The flow of information in a cell (any cell) is
DNA -> RNA -> Protein
Question:
 If
the DNA is changed what happens to the
protein?
Vestigial Genes
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In our Genome (our DNA) we have the genes
that code for things our ancestors had, but we
no longer need.
These genes have been sitting in our DNA for
millions of years
Every once in a while, these genes are
expressed.
Because they have been dormant for so long
they often do not work very well.
Atavisms
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Atavisms also are called "throwbacks" and can
be found in modern horses and their relatives
despite millions of years of evolutionary
separation from their fossil horse ancestors.
Atavisms
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Atavisms are caused because we still have the
DNA from our ancient ancestors.
Chicken With Teeth
Homologous Molecules
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Homologous proteins – proteins that share
extensive structural and chemical properties.
That means that they do the same job and
look similar.
Homologous Genes
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Homologous genes – are genes that perform
the same task
These are NO DIFFERENT that homologous
alleles
Homologous Genes
Embryology
DNA these letters also spell DAN
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Everything we are is just an expression of
DNA
Your eye for example, is at its core nothing
more than thousands of T’s G’s C’s and A’s.
If one of those T’s G’s C’s or A’s is changed
then it is possible that the structure of the eye
will change as well.
Every time your cells go through mitosis
mistakes are made in the DNA
Over time these mistake add up
We can actually tell how closely related to
species are by looking only at these mistakes
Exit Ticket
1.
2.
What is the difference between a
homologous structure and an analogous
structure?
Give an example of a vestigial structure.