Hi. It's Mr. Andersen and welcome to Biology Essentials Video Number 2. This
is examples of Natural Selection. In the first video I talked specifically about what natural
selection is and how it can affect a gene pool. In this one I am going to talk about
real world examples of evolution and natural selection taking place right now. I wanted
to start by showing you this picture of Glacier National Park. What's interesting and a little
sad about Glacier National Park is over the next few years all of the glaciers will actually
melt. And the reason why is that the Earth is getting warmer and as a result of that
it's impacting the glaciers and it will impact the living things in Glacier National Park
as well. So these right here are glacier lilies that come out right after the snow moves away.
And so plants across the world are having to adapt to these changing climates. So that's
an example of real world evolution. I always like to start with kind of an overlay of what
we are going to talk about in this podcast. Natural selection, remember, causes evolution.
What's neat about it, it's different then random events that cause evolution. What's
interesting about natural selection is it actually creates organisms that are better
adapted to their environment. So the first thing I am going to talk about is how changes
to the environment, especially climate changes right now are affecting life on our planet.
Next I want to briefly talk about how mutations can cause changes in phenotypes and those
gene changes can have huge implications when it comes to organisms. Some of those make
big phenotype or physical changes. Some don't make any changes at all. Next I'll talk about
how those phenotypes or those changes can actually affect the fitness of organisms.
And so there was one mutation in the protein that makes blood that actually created sickle
cell anemia. And that was bad but it also saved millions of lives in protecting them
from malaria. And then finally I want to talk about another environmental change and that's
the environmental change that is humans and how we're impacting evolution on the planet
right now. A really scary example of that would be antibiotic resistant bacteria. Bacteria
that were once curable but aren't anymore. And so that's what I am going to talk about.
I wanted to start with poet naturalist Henry David Thoreau. What's interesting about him,
he lived on Walden Pond and if you have read any of his work it's really inspirational.
He's an amazing writer. But what's interesting is we're actually able to use some of his
work to show evolution and natural selection taking place. Because most people know that
he was a writer, but most people don't know he was a naturalist as well. And so he would
study, for example, St. John's wart and blueberries. And he would detail when they would flower
and we can use that data to show how climate is actually affecting plants. And so here's
a quote where he's talking about, in 1853, how the blueberry buds were starting to come
out. And we have a date, and so we can actually look at that. And so let me give you an example
of that. So let's say we've got the blueberry and it is flowering on the seventh of April
back in 1853. So if this is 1853. Now maybe this is the first blueberry, but this bell
shaped curve represents when all the blueberries on Walden Pond were coming out. Now if you
were a blueberry and you were to come out earlier than that, there would probably be
snow. There wouldn't be anything to help you flower or to transfer that pollen. And if
you were to come out later than that then you probably wouldn't survive as well. And so the average
blueberries would probably start to flower around the early part of April. Now what's
happened since then is that the climate has changed. And so if we look now in 2011, it's
going to be much warmer on April 7th then it was in 1853. And so the blueberries that
were able to come out a little bit earlier have done fine. And so if we were to look
at the bell shaped curve of blueberries today, we would find that it is probably shifted
quite a bit and things are flowering earlier just because the climate is getting warmer
and warmer. And if you were a blueberry right now and to flower really really late you'd be behind
the ball. You'd be way behind and so what we've seen is directional selection. In other
words that bell shaped curve has moved. Nice thing about the work of Thoreau is that we
can actually quantify that because we can see what days it's changing today. Next I
want to talk specifically about phenotypes. Remember phenotypes are going to be the physical
characteristics that you have but remember all changes, all novel changes in organisms
comes from changes in their DNA. So when we get changes in the base pairs, or in the bases
inside that DNA, that eventually leads to things like the way we look. So this is a
type of mollusk. It's the Donox variabiliis. And it has a number of different patterns
that come from one species of mollusk. These ones live in the sand and you can see how
genes have added this striation and then it also looks like there's a gene that's adding
these vertical striations as well. And so those phenotypes started as a mutation, or
a change in the DNA, but it ends up changing the physical appearance. And if it wasn't
for all of this variety, all of these different types of shells then natural selection wouldn't
work. In other words, if all organisms look the same then there's nothing for them to
select. Okay, let me talk about an example of this found in humans. This right here is
the most dangerous animal that we have on our planet, the anopheles mosquito. And the
reason it's dangerous is it passes the disease called malaria. And you can see where malaria
is found in subsaharan Africa. It's killed millions and millions of people. Now we would
say thousands of years ago, I can't remember on the specific day, there was a mutation
in one person who lived maybe in Africa. And that mutation caused a red blood cell that
normally looks like this to be made like that. It's a change in one letter of the DNA which
affects the hemoglobin protein inside the blood. And so you get a sickle shaped red
blood cell. Now this is very painful if you're sickle cell anemic. It causes organ failure.
It's a really bad disease to have. What's interesting about it is if you are heterozygous
for that, in other words, if you have two genes for it you're going to have sickle cell
anemia, but if you only have one, you can't get malaria. So you're protected from malaria.
And so here we had one mutation which caused one phenotype change, or one change in the
blood which protected them against malaria. So what we see is natural selection in humans.
In other words this is where sickle cell gene is found, so right here in the darker areas,
greater than 20% of the people have that sickle cell gene and the reason they do here is that
they're protected against malaria. But again, if you lived here, and you have that sickle
cell disease where malaria is not present, that would actually be a negative. And so
you can see how natural selection is at play. But first you had to have that mutation, first
you had to have that change. Last thing is kind of a warning call and humans are starting
to figure out that we can really have huge impacts on the organisms that live on our
planet. And the example here that I am talking about is tuberculosis or TB. Tuberculosis
has killed humans for years and years and years. This would be a good way to diagnose
it. You look at a chest x-ray and you can see that the bacteria are actually feeding
on the lungs. And this would be the bacteria right here. They're a rod shaped bacteria.
Tuberculosis has been around since humans, pretty much way back in the day of the pharaohs,
we had tuberculosis. And so what we did is we discovered that you can kill tuberculosis
using antibiotics. And so if somebody has tuberculosis, we give them antibiotics, it
kills all the bacteria except those that are highly resistant. We then take another dose,
we take another dose and if we quite taking it, what we end up with, if we can't kill
all of the bacteria, is we end up with highly resistant bacteria. And so we've created a
disease, multi drug resistant tuberculosis, and what that is, is a form of tuberculosis
that is resistant to sometimes a dozen different antibiotics that humans have created. And
so that's a human made problem. And so who is doing the selecting? Well, we are. And
that's why it's important when you take antibiotics, that you don't take them unless you really
need them. And when you do take antibiotics, that you take them until the course has run
its . . . all the way through. We are seeing some nasty types of multi drug resistant tuberculosis.
This person is actually being treated in Russia where lots of times they don't get complete
treatment and were just spawning this disease as they get worse and worse. The sad part
about that is all these diseases that we once had a cure to, we don't anymore. And the reason
why is that natural selection and us are actually creating this problem. And so those are some
examples of natural selection and evolution and I hope that's helpful.