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Tonight we are going to talk about Darwin and Darwinís voyages and some of the discoveries
he made while on his voyage. Darwin was a young man in England. He was
not a first born son. First born sons of the aristocracy received all the money and the
title and things like that. He didnít receive that. He had a choice. He could go to school;
he could go into the military or become part of the church. He chose to go to school and
to study. At the end of his schooling when he was about 19 years old after finishing
college, he was kind of at loose ends and didnít know what to do. A friend recommended
he join this ship, the H.M.S. Beagle, and sail around the world and collect specimens
on this trip. What this trip was for was it was a scientific expedition that was supposed
to collect specimens from all over the world wherever they stopped. So his job on this
boat was to go ashore and collect plants and animals and fossils and store them in the
hole of the boat. So he did that for five years. It was a very long trip. Eventually
he ended up at the Galapagos Islands. This is a picture of the Galapagos Islands. You
can see kind of, the red line is where his boat traveled around the Galapagos Islands.
We will talk more about his voyage as we go through this lecture tonight.
Before Darwin left on his voyage, there were several scientists who had developed several
different ideas and had published them, trying to make sense of the world. Basically that
is what they were trying to doótrying to make it make sense, scientifically and religiously
and everything like that. So he had some background information to draw from. One of the first
early scientists, Carl Linnaeus, what he did, he lived I think in France or something, he
went through all the different specimens that had ever been collected and he created the
binomial system of taxonomy to classify them. We still use his taxonomy today. Do you remember
the thing that goes Kingdom, Phylum, Class, Order, Family, Genus, and Species? Linnaeus
is the scientist who did that. He tried to figure out what animals were related to other
ones and fossils. He tried to look at plants, fungus and everything. He tried to put it
all in this system so everybody would know who is related to whom. That was Linnaeus.
A lot of the things he discovered was that a lot of the organisms really are very very
similar. Another scientist, Georges Cuvier, proposed
that basically catastrophes happen and animals go extinct. No one had ever thought about
that before because in the religious texts God created the heavens and the earth and
everything that has ever been alive has always been alive and nothing has gone extinct. All
of a sudden Cuvier is looking at the fossil records and he is saying hey, look at this
stuff, look at all these fossil. This is not alive today. He had dinosaur fossils and he
was saying we donít have something this large. We donít have anything like this alive today.
He was the first one whoever noticed that. Cuvier was a really cool guy. He dissected
everything that is alive today. He went through and dissected all the birds and dogs and everything.
He really knew anatomically what was related to what. He knew looking at the fossils that
there was nothing that had a vertebrae that big or whatever. So he was saying some catastrophes
must have happened to cause organisms to go extinct.
There was another guy; his name was Hutton. He proposed a theory called gradualism. He
is saying the earth is much older than what religious scholars have been saying. Up until
this time they thought the earth was about 2000 to 3000 years old. Hutton was looking
at geographic and geological formations and saying, you know, it would take so long to
form these mountains and for volcanoes to form and for South America and Africa to separate.
The earth is probably very, very old and all of these things are very gradual in their
formation and it is a slow continuous process. Charles Lyell was another scientist and what
he proposed is that the processes that formed all the geologic features we have today, the
mountains, the oceans, the rivers and erosion and all of that, are caused from the same
processes that formed them millions of years ago. Those processes donít change. He is
saying that the earth probably is a lot older than people thought it was. Erosion erodes
but at a fairly continuous rate. It doesnít all of a sudden erode catastrophically, really
fast. Another scientist came along and he is again
looking at fossils and trying to make sense. Lamarck proposed an idea, his idea for evolution,
for how organisms change. He looked at things like a giraffe. In the fossil records for
a giraffe, they have very short necks and they have very long necks today. He proposed
the idea that if an organism needs some characteristic, some trait, it is going to grow it and then
pass it on to its offspring. The issue really for him is more of a timing issue. He is saying
it is going to happen in one generation where in actuality traits like that take thousands
and thousands and thousands of generations. You are not just going to grow a neck overnight.
By the way, the giraffe have 7 vertebrae in their neck, the same number you have in your
neck, but a hummingbird has 12. I think that is a cool little fact. Lamarck also proposed
that if you donít use something, you lose it. He used the idea of the human appendix.
Since we do not use it like other organisms use their appendix, we are in the process
of losing it. Which is a correct idea, but where he is saying it is going to happen overnight
where in actuality it happens over thousands and thousands of generations.
So Darwin went on his tour, went on the boat, the H.M.S Beagle and he sailed from 1831 to
1836. He collected plants and animals along the way and made all kinds of interesting
observations. For example, one of the things that happened, he was collecting specimens
off shore of Chile and during the daytime he had been collecting stuff and he went back
on the boat during the night. Then during the night they had had a very large earthquake.
He went back on the shore the next morning and he saw the changes that had occurred to
the beach where areas of the rock literally had risen for 8 feet or so straight up into
the air. He looks behind back up at the Andes Mountains and he looks back at the beach again
and he realizes that if earthquakes make the earth rise, how many earthquakes would it
have taken to actually build the Andes Mountains? He knew the earth was much much older than
people really thought it was. Another time, I think he was in Argentina and he was collecting
fossils and collecting specimens. They were talking with native people. He asked them
to bring him things to collect. Again he collected fossils and he collected plants and animals
and stuff like that. One of the people brought him a very large fossil of an ancient armadillo
that is no longer alive today. The fossil was probably 4 feet tall and kind of ball
shaped, a very ancient form of an armadillo. Just looking at it he knew it looked like
an armadillo, but there were no armadillos alive today like that. He just looked at that
and he collected it. It kind of impacted in his memory and his ideas that there are animals
that have gone extinct. He hadnít realized that before, though these other people had
written on it. That kind of had an impact on him. Another time while he was sailing
around the Galapagos Islands, the governor of the Galapagos Islands decided to throw
a party in honor of the voyage and of Darwin. He was trying to show off. They were served
a 12 course dinner that night which is a lot of food. It takes hours and hours. The first
course was turtle soup and it was served in the tortoise shell. The governor was bragging
that as they carried the tortoise shell out and was serving people from it, he could even
tell which of the islands that tortoise had been caught from because of the shape of the
shell. Darwin didnít really think about that until he was actually on the voyage home.
He realized on the voyage home that every tortoise on every island had a different shaped
shell. Why would that have happened? What was unique about the islands? What caused
the tortoises to have these different shaped shells? He thought about it and thought about
it and it kind of put a bee in his bonnet. It kind of made him think about what was going
on. When he got home he turned over all of his specimens to various scientists to look
at it. The person doing the ornithology, which means birds, said, ìYou collected all these
birds in the Galapagos, but they were all finches.î Darwin said, ìno they are not.
That is honey sucker, that is a seed eater and that is a blah, blah, blah.î The ornithologist
said, ìNo, they are all finches.î Darwin was kind of flabbergasted and didnít know
what to think about that. He thought and thought and his ideas kind of coalesced and he decided
to write an essay. It is called On the Origin of Species. He wrote it in 1844 but he didnít
publish it until 1858. The reason was it was very controversial. It went against what the
church said. It went against what everybody believed. He didnít know if he wanted to
tell people what he believed. So he wrote this and he kind of just let it set. He didnít
do anything with it. When he was in groups, he would go to scientific meetings and things
like that--he would kind of say certain things. People kind of got the idea that he had some
interesting ideas. In 1858 he got a letter from another scientist called Alfred Wallace
asking him about his opinion on an essay that he was writing. So Darwin read the essay realizing
it was exactly what he had written in 1844. Very quickly Darwin published his. Then he
wrote back to Wallace said, ìGreat idea. Too bad I already had that idea.î So Darwin
gets credit for it. Although in my mind, he was a little bit of a chicken because he didnít
publish what he really thought when he thought about it first. That is kind of the history
behind this long essay. So what did this essay, by the way it is like 100 pages long, what
did this essay actually say?
Some of the ideas that he thought of in there, the blue things here tell you, one was: Organisms
produce way more offspring than can ever possibly survive. While on his voyages he realized,
standing on deck looking out over the oceans, he realized that clams and marine invertebrates
when they reproduce they reproduce hundreds of thousands, if not millions of offspring
at a time. If every single one of those produced millions of offspring, pretty soon the oceans
would be filled with clams there would be no water left. He knew that is not what is
happening. So he thought about it and kind of came to the conclusion that these organisms
are actually providing a food source. These babies are a food source for other organisms.
It is kind of like the food chain. You have got these clams producing babies. The babies
are called zooplankton because they are little tiny single celled swimming animals. They
swim around on the top couple inches of the ocean water. They provide for food for things
like choral and really small fish. Even whales will eat plankton, zooplankton being part
of it. These organisms are eating them. Those are eaten by other organisms and by other
organisms so it is kind of like the beginning of the food chain. To be able to survive,
a species has to at least, at the very minimum, reproduce the same number as the parents.
So if two parents reproduce 3 million babies which clams do, two of them have to survive
to be parents. The other 2,999,998 are going to die, are going to be eaten. That is kind
of what he is talking aboutóthey produce way more offspring than ever could possible
survive.
The other thing he thought about it was something called descent with modifications. That means
when organisms reproduce, their offspring are not clones of the parents. They are a
combination with differences, with modifications (he used the term). Keep in mind, Darwin does
not know anything about DNA or mutation or anything like that. He did know that when
you reproduce, the offspring are not identical. His grandfather was a scientist and had written
several articles about this. What he noticed is that farmers breed. If you have two dogs
and you want to have a dog that is really good at hunting because it has a really good
nose, you are going to reproduce it with another dog with a really good nose and the offspring
are also going to have even better noses. In society, farmers and even aristocracy will
breed their pets, their animals, and even plants to get the highest yield, to get the
characteristics that they want. Those are mutations. Those are differences. Those are
modifications. That is what Darwin thought about.
He also made the observation that out of those many offspring that are produced, many of
them will die. The ones that survive are going to be best suited to the environment. They
have some characteristic that gives them a slight advantage over the others. Whether
it is that they could run faster, they could see predators, they could hideówhatever it
was, they survived to pass on their genes to their offspring. It is called Survival
of the Fittest. That was another of Darwinís ideas.
So letís put it more in terms of today. Natural Selection causes a differential success in
reproduction. That means basically survival of the fittest. Organisms that are more fit
produce more offspring that survive better than organisms that are less fit. Natural
Selection also occurs through an interaction between the environment and the variability
inherent among the individual organisms making up the population. So, Survival of the Fittest.
Some organisms have characteristics that make them more fit and are able to survive.
One of the products of natural selection is the adaptation of organisms to their environment.
The organisms best fit for the environment produce the most offspring. So in the Galapagos,
all of those Galapagos finches that Darwin collected, here are pictures of all of them
and you can see the differences in the beak sizes, beak shape, head shape, coloration
and even in what they ate, they all arose from one type of finch. That finch probably
ended up on the island because of a hurricane or something. It ended up there. It reproduced.
Whatever mutations arose in their offspring, because there werenít any other birds on
the island, they could find some type of food source and some type of niche. If you look
at this, some of them might have had a difference in their beak size. Some were eating big seed;
some were eating little seed; some were eating cactus because that is what was on that particular
island; some were eating insects and different sizes of insects. Some were fruit eaters.
So whatever type of mutation they had, many of them were able to find food and adapt.
From that one species, we now have 10 different species of finches.
So what is natural selection? Natural selection is how the environment favors various individuals
over others. Sometimes the environment becomes very hostile. Letís say in the Galapagos,
some years where there is a lot of rainfall so the seeds are very plump and rich and actually
hard to crack for birds with small beaks. So birds with small beaks are not able to
get food, to crack the seeds. So they might have fewer babies or might even die themselves.
But in some years when they have a La NiÒa year, they have much less rainfall than normal
so the seeds are very small, and hard to crack and slippery. Birds with a big beak might
not be able to manage to get the seed where they need to in their bill to crack it, but
ones with little tiny beaks can.
Letís look at another example. I want to look at bacteria and viruses. Letís say you
have a bacterial infection in your body or a viral infection in your body, but letís
do bacteria. You have one bacterium that starts. Then it clones itself. All the bacteria are
identical clones of that original bacterium. You have millions and millions of them in
your body. Well, you take an antibiotic. The antibiotic creates a hostile environment that
makes it so the bacteria die. If by chance though one of those bacteria had a genetic
mutation which made it a little bit more tolerant of that particular antibiotic, not necessarily
immune to it but a little more tolerant of it, if you donít take your antibiotics for
the full length of time (letís say you only take them for three or four days and then
you feel better and you stop taking it) that one is going to survive. When it survives,
it starts to breed and produce lots of bacteria just like itself who are also tolerant of
the antibiotic. Then you get sick a second time, but with a much worse bacteria because
now the antibiotics are not going to work on it. That is a form of natural selection.
Here is another example of natural selection. You have some farmers who are crop dusting.
They are going to spray their field to kill the bugs. If you look at the bugs they all
have different genes--this one has a particular gene on it which makes it resistant to the
insecticide. Well, the other bugs all died, but that one survived. Because that one survived,
when it reproduces and it is going to reproduce several times, all the babies have that particular
gene that makes them insecticide resistant. Artificial selection is when that type of
thing happens but humans decide which organisms get to survive and which ones donít. For
example, this is a wild type of mustard, a wild mustard thing. From this plant, humans
have altered the plant, selected which seeds to grow, developing all of these different
types of vegetables. All of these are descendants of wild mustard. So you have broccoli, cauliflower,
kale, cabbage, brussel sprouts--they are all little tiny descendants of mustard. We also
decide for example, which dogs to breed. For thousands of years we have looked at dogs
and bred dogs to be very small like Chihuahuas or very big like Great Danes. We have bred
them to have excellent noses and be able to really track. We have bred them to have different
types of fur. We didnít genetically go in and select which genes; we selected which
traits by deciding I have a really good dog that has a good nose and you have a really
good dog that has this characteristic. Letís breed them together and see what kind of puppies
we get. We have done that for thousands and thousands of years. That is artificial selection.
Some of the evidence we currently have for evolution comes from lots of different disciplines,
more so than any other discovery mankind has ever made. There is more evidence for evolution,
flat out. For example, letís read through these real quick:
ï In 1908 Morgan discovered the role of chromosomes ï Gregor Mendel discovered the inheritance
of genetics ï Watson and Crick discovered the structure
of DNA ï In the 1960ís discoveries were made about
allele frequencies and how those change over time
ï Looking at several different types of evidence from DNA analysis, PCR, Electrophoresis, Geology
paleontology, anatomy, physiology and the list goes on and on and onÖ
All of these different disciplines have evidence that shows evolution has occurred and is still
occurring. We are going to look at just a few brief things;
these are common lines of evidence. One is called homologous structures; this is from
anatomy. Homologous structures are parts of the body which are the same parts in different
organisms but have completely different functions. If you look at this picture, a human arm is
used for carrying. A cat arm, these yellow parts are all the same bone structures, that
is used for walking. In a whale, it is used for swimming; it is a flipper. In a bat it
is used for flying. They are all the same bones but with completely different functions.
How did those arise? They arose because we had a common ancestor that also had those
bones.
Vestigial structures are the historical remnants of structures that were once important in
your ancestors but have very little importance to you. For example, in a whale, whales have
pelvis bones and a femur bone. They donít even have a leg, but they still have pelvis
and femurs. They donít stick out from the body. They are not attached to anything. They
are remnants of when whales used to be land creatures and then they went back into the
water. Boa constrictors actually also have legs; they have leg bones. They even have
a claw, males have a claw that sticks out, I think females do too; the claw just barely
sticks out from the skin. It is there but it doesnít seem to have any apparent function,
at least not the function their ancestors had which was for walking. Snakes used to
be lizards; they are not anymore. Those are vestigial structures.
Embryological homologies are homologies which are similarities that embryos have as they
go through the developmental stages. For example, in humans, very early on, when you were just
a little tiny embryo, you used to have pharyngeal slits in your neck. In fish, pharyngeal slits
become the gills. We donít have gills. In you, those pharyngeal slits that you developed,
then close over and it becomes your trachea, the cartilage in your trachea. Those are the
pharyngeal slits. You used to have a tail. You used to have webbed fingers and toes.
All of those are embryological homologies and you have reabsorbed those.
So if you look at the pictures, these are real embryos very early on. You can see what
they are up here. Here on you, here are your pharyngeal slits. This, by the way, would
have been the head and here is the tail. The tail does stick quite far beyond the leg,
which is right here, which is just starting to form. This is going to be the placenta.
All of these organisms had pharyngeal slits. You can hardly see it in that one but it is
right in here. Even fish had the pharyngeal slits; it is hard to see in this particular
picture. Those are embryological homologies.
Another line of evidence is molecular homologies, similarities in your molecules. For example,
all DNA, no matter if you are a fungus, a pine tree or a chicken, all DNA is based on
the same four nucleotides: adenine, cytosine, thymine and guanine. You have the same structure.
The difference is the order of the nucleotides. A¨ll proteins in your body are based on the
same twenty amino acids. Those are molecular homologies, similarities. Why is all of our
DNA based on the same molecules?--because we all arose from bacteria based on the same
molecules. That is molecular. Here is an example looking at similarities
in hemoglobin, looking at yours. A rhesus monkey has, out of a 146 amino acids that
build hemoglobin, they have 8 of them that are different. A mouse has 27 differences.
The further away from a human you get, the more differences. If you look at a sea lamprey,
125, their hemoglobin is very different from your hemoglobin.
Biogeography is another line of evidence. Biogeography talks about the distribution
of species worldwide. Darwin noted that similar animals that lived in the same area were more
alike than animals that lived in different areas. That is a form of biogeography.
Another line is convergent evolution where very different species can end up having very
similar characteristics because they live in similar niches in very different environments.
For example, a sugar glider in Australia is a marsupial, very different from a placental
mammal. They have very immature young, kind of related to a kangaroo type of a thing.
It has very similar characteristics to a flying squirrel in North America which is a rodent,
a placental mammal. This is a form of convergent evolution.
The fossil record also gives lines of evidence for evolution. There are many different links
between species that you can find in the fossil record. For example, back around 2000 or 2002
someplace in that range, a fossil called tiktaalic was discovered in Alaska that is a direct
link between salamanders and fish. This tiktaalic fossil has characteristics of fish. It has
scales on its body and it has gills, those types of characteristics, but it also has
the flattened head of a salamander and it has arms with fingers like a salamanders.
It is a direct link. It is fossil record evidence. Not all animals are preserved as fossils but
a lot of them are and you can find really cool evidence.
Here is another line of evidence. This is an ancient whale. This whale had hip bones,
had a pelvis, had a femur and a tibia and a fibula, a patella and a foot inside a flipper.
If you look at the fossil of various whales, that hip bones and leg bones become smaller
and smaller until you look at that picture I showed you of a modern whale where there
is very little left, very little vestigial left from that.
The reason I am showing you this, this is Harriet. This is a tortoise that Darwin brought
back from his travels in the Galapagos back to England. How she ended up at the Australia
Zoo, I donít know. She was the last remnant of Darwinís Voyages. She died in 2006 at
the age of 176 years old. That is Harriett. One of the issues I would like you to read
about is crop biodiversity issues. You need to go to this website. You have to read the
article. Then I want you to answer these three questions:
ï What is meant by the term ìbiodiversityî? ï Why is biodiversity important in crops?
ï Develop three questions that arose in your mind as you are reading the article.
Those three things. Take a minute. Write down this website. Go there. That is your homework
for tonight. Bye.