Transcript Honors Biology - WordPress.com

Honors Biology
Module 9 Part 2
Evolution: Part Scientific Theory,
Part Unconfirmed Hyposthesis
Class Challenge
Quiz
Define the following:
1. Microevolution
2. Macroevolution
3. Transitional fossils
Microevolution: The theory that natural
selection can, over time, take an organism
and transform it into a more specialized
species of that organism. It is simply the
variation of a type of organism within its
genetic code.
Macroevolution: The hypothesis that a
given life form has an unlimited ability to
change. It assumes that some process
must exist to add information to the
creature’s genetic code and that
processes similar to those at work in
microevolution (that natural selection can,
over time, take an organism and transform
it into a more specialized species of that
organism) can, over eons of time,
transform an organism into a completely
different kind of organism.
Transitional Fossils
These are fossils that represent a link (or
transition) between one species and
another.
They are also known as intermediate links or
transitional forms.
Cambrian Rock
(Figure 9.2)
The geological column is used to classify the rock
layers and gives the impression that the
“simplest” multicellular life lived in the lower
levels (Cambrian Rock – 570-500 million years)
and then through the years as organisms
evolved the higher forms of organisms would be
found in the subsequent layers of rock.
(Ordovician rock: 500-435 million years),
(Silurian rock 400 – 435 million years), and
(Devonian rock 360 – 410 million years)
As a result, the diverse life that we see in
the oceans did not fully evolve until about
400 million years ago.
Remember, all of these number for how
many millions of years ago these things
happened are based on a lot of
assumptions and how macroevolutionists
interpret the geological column.
In the early 1900’s Charles Walcott (a
paleontologist) discovered a lot of fossils
in a layer of Cambrian rock called the
“Burgess Shale.”
However these fossils were not what Walcott
expected.
Only the “simplest” of the multicellular life was
suppose to have existed in the times
represented by Cambrian rock.
However Walcott found thousands of fossils of
very complex life and when the collection was
complete, he had found representative fossils
from every major animal phylum that exists in
our classification scheme.
What does that mean?
That the bottom of the geological column as
presented is wrong. Walcott found fossils
of the “simple” animals that were
supposed to be in the Cambrian rock, but
he also found thousands of examples of
animals that were too complex to have
evolved in the short time represented by
Cambrian Rock. These fossils should
have formed much later and found in the
Silurian and Devonian rock.
Walcott had discovered something
Revolutionary!
But, unfortunately he only wrote a few
modest articles in Smithsonian
Miscellaneous Collection and then
reburied the fossils in his laboratory
drawers.
It would be 80 years before the fossils were
“rediscovered” and their importance
understood.
What is their importance?
The geological column pictures the animals in the
“simple” phyla evolving into animals of the more
complex phyla over a period of about 170 million
years (Cambrian rock to the middle of Devonian
rock)
The fossils discovered by Walcott (more than
60,000) and those discovered later by others tell
us that all of the major animal phyla can be
found in Cambrian rock.
These fossils lead to a serious
problem for Macroevolution…
All macroevolutionists agree that it takes a
long time to evolve.
No one presently understands how such a
huge amount of evolution could have
taken place in the relatively “short” time
supposedly represented by Cambrian
rock.
Even if the currently-assumed ages for Cambrian
rock are correct, it took “only” 70 million years for
evolution to go from the simplest animal phyla to
the most complex animal phyla.
At present, no one understands how this could
have happened in the context of macroevolution.
This “problem” is so well known in paleontology,
it is called the “Cambrian explosion.” This
explosion refers to the fact that there seems to
have been an “explosion” of life in Cambrian
times.
An additional problem for
macroevolutionists…..
Not only is this a “short” time period for
organisms to evolve, but there were no
intermediate links in the fossil record.
Structural Homology
Is the study of similar structures in different
species.
In figure 9.6, Darwin considered structural
homology to be evidence for
macroevolution.
Notice that although these arm bones come from very
different species, they have an amazing amount in
common.
1. They are all jointed about halfway down.
2. They all have a single, upper arm bone, the humerus
(shaded green)
3. They have two lower arm bones, the radius, (shaded
purple)
4. They have the ulna, (shaded blue)
5. They all end in a palm consisting of carpals (shaded
red);
6. Metacarpals (shaded yellow)
7. All have phalanges, except the bird.
Darwin hypothesized that these incredible
similarities among such vastly different
species were excellent evidence that they
all had a common ancestor.
This general forearm structure, then over
eons of time and guided by natural
selection, simply adapted to the needs of
each individual species as it arose.
Common Ancestry vs.
Structural Homology
If structural homology was the result of common
ancestry, it should show up in the genetic codes
of organisms that possess similar structures.
If the forearms of the bat, bird, man, and porpoise
look so similar because they all inherited their
forearms from a common ancestor, then the
parts of their DNA that contain the information
regarding the forearms should be similar.
Homologous Structures
The evolutionary basis of homology is perhaps
even more severely damaged by the discovery
that apparently homologous structures are
specified by quiet different genes in different
species…With the demise of any sort of
straightforward explanation for homology one of
the major pillars of evolution theory has become
so weakened that its value as evidence for
evolution is greatly diminished.
(Michael Denton, Evolution: A Theory in Crisis
[Bethesda, MD: Adler and Adler, 1985], 149 and
151)
Molecular Biology
There are certain proteins that are common to
many species.
Most animals have the protein hemoglobin. This
protein transports oxygen through the
bloodstream to the cells.
Most organisms have the protein cytochrome C
which takes part in cellular metabolism.
These proteins are not identical from species
to species. In other words, the
cytochrome C that you find in a bacterium
is a bit different from the cytochrome C
that you find in a human.
Remember Amino Acids Chains in Module 5?
Table 9.1
The sequences are very similar with only difference
in the second amino acid (see horse and
kangaroo.)
These proteins are made in the cells according to
the instructions of the DNA.
Looking at the amino acid sequences in a protein
that is common among many species, you are
actually looking at the differences between
specific parts of those organisms’ genetic code:
the part that determines the makeup of that
protein.
If macroevolution is true…..
Then the portion of the genetic code should reflect
how “closely related” the two species are. If two
species are closely related, the DNA sequences
that code for a common protein should be very
similar.
If they are only distantly related, however, the DNA
sequences that code for the same protein
should have more significant differences
between them.
The portion of the amino acid seqquence for
cytochrome C shown in the table is 11
amino acids long. Of those amino acids,
there is only one difference between the
horse and the kangaroo.
Percent difference = 1/11 x 100= 9.1%
Comparing the amino acid sequences in
cytochrome C for yeast and the horse,
however, there are four differences.
Percent difference = 4/11 x 100 = 36.4%
These two comparisons tell us….
The portion of the horse’s genetic code that
determines the makeup of this part of
cytochrome C protein is much closer to the
kangaroo’s than to the yeast’s .
A macroevolutionary point of view, this would tell
us that the horse is more closely related to the
kangaroo than to the yeast and the kanagroo is
more closely related to the horse than the yeast.
This makes more sense because the yeast is
considered by macroevolutionists to be more a
“simple” life form whereas the horse and
kanagroo are rather complex.
So it makes sense that a horse is more closely
related to a kangaroo than a yeast. Even though
comparing this portion of cytochrome C in the
horse, kangaroo and yeast makes sense in
terms of macroevolution, if you continue to make
comparisons you will find that there are serious
problems for macroevolution.
Table 9.2
Consider the Bacterium Rhodospirilum rubrum. When its
cytochrome C amino acid sequence is compared to
vastly different organisms, nothing makes sense in terms
of the macroevolutionary hypothesis.
Look at the yeast (a single-celled fungus) is probably the
next “simple” compared to the bacterium. The data for
each organism in the table is essentially as closely
related to the bacterium as any other organism on the
table. The bacterium is more closely related to the most
complex organisms, not the simple ones.
Regardless of the protein studied, the amino
acid sequences seem to indicate that each
individual type of organism is just as
different from one type of organism as it is
from another.
Note tables 9.3 and 9.4
Since Darwin’s time….
Changes have occurred to his theory.
1. Neo-Darwinism (also known as Gradualists) has
emerged to help explain the genetics portion of
microevolution. So in order for macroevolution to
occur, a species would have to add information to
its genetic code. Neo-Darwinism say that it could
happen by mutation. Darwin thought that
macroevolution could occur by normal changes
that happen during the reproductive process. So
over time, mutations would be the only way to
deal with the genetic code.
Mutation
Is a mistake that alters the genetic code. A mutation
is often bad for the organism, but that does not
have to be the case every time a mutation occurs.
This explains a means by which an organism can
add information into its genetic code, and it also
allows neo-Darwinists to explain away at least
some of the discrepancy between macroevolution
and the fossil record. The problem is that there is
absolutely NO fossil record (transitional fossils) of
these mutations.
Punctuated Equilibrium
Also known as Punctuationists. Evolution happens in quick
punctuations followed by long times in which no
evolution occurs.
Mutations still add genetic information o the fossil record,
but they add it in steps that occur over very short time
intervals. In between these very short time intervals, no
macroevolution occurs. The idea here is that a group of
organisms might be suddenly exposed to high levels of
toxic chemicals or radiation. This would speed up the
mutation rates. Most of the offspring would die, but a
few would survive. As these organisms reproduced, then
the fittest offspring would survive. Once the radiation
was gone, these offspring would continue in there
altered forms.
• Origins - Mount St. Helens - Explosive
Evidence for Creation with Dr. Steve
Austin
• http://youtu.be/flrhqjN5BHo
Homework
1.
2.
3.
4.
Finish Module 9 OYO questions
Finish Module 9 Study Guide questions
Take Module 9 test
Begin reading Module 10 Ecology
pages 298-309.
5. Quiz
6. Class Challenge