Hi. It's Mr. Andersen and welcome to Biology Essentials video number 22. This
is on the effect homeostatic disruptions. In other words how changes in the environment
can have huge implications when it comes to cells, molecules, populations and even ecosystems.
And so I wanted to start by showing you a picture of an invasive species. And this invasive
species is something we don't usually think of as invasive. It's the earthworm. What does
that mean? Earthworms in general were not found in North America. And the reason why
is that during the last ice age as glaciers retreated from North America, it scoured the
earth. And as it did that it pulled the soil off. And so it got rid of all of the earthworms
that we have in North America. Now there were some in California and some in the southeast,
but there were generally no earthworms. And so they're really invasive. They don't belong
here. But as the pilgrims came and more recent time as we started bringing soil and
animals and things over, the earthworm established itself. And we're actually helping that problem.
Every time we go fishing and we let some of the earthworms go, we're actually ravaging
some of the forest. And so an example could be in Minnesota. Minnesota's not designed
to have earthworms. And so the problem with having earthworms is that they'll devour the
material on the surface of the leaves, the things that are dying. And normally the
trees and the plants in the forest of northern Minnesota are not evolved to have worms. And
so it's actually making the understory in a lot of the forest very unhealthy. And so
it's a change to the environment. In this case it's a human change. But changes can
effect homeostasis. And so essentially homeostasis is that stable internal environment. Disruptions
then are going to be changes in the environment itself. Now those can affect things at the
level of just cells, individual cells or even individual molecules. An example I'll talk
about is just dehydration in humans. And then they can also have implications when it comes
to larger levels, like the ecosystem. And I'll give you an example of an invasive species
that really shows you the power of changes to the environment. And so let's start with
dehydration. Dehydration, we don't tend to think about it because we always have a steady
supply of water, in general. But dehydration can lead to huge implications very very quickly.
There are actually three types of dehydration. Hypertonic dehydration is when you're just
going to lose water. What does that do to your blood? It's going to cause your blood
to shrivel up. Hypotonic is going to be when we lose solutes. That's rare but it's going
to cause our red blood cells to lyse. Most of the dehydration that we get is when we
lose both water and solutes. And it doesn't take long for us to die as a result of that.
Why is it doing that? Well, we live on land and as a result we have to bring our osmolarity
with us. And we have to maintain that. And water is super crucial to life. And if we
don't have water our circulatory system quickly is going to breakdown. We're eventually going
to die. And so this is a child that is dealing with dehydration after the big earthquake
in Haiti. And some armed service person is helping to give them a little bit of water
at a time. And hopefully bring them back to life. But it doesn't take long to die from
dehydration. And so normally in a human about 75% of our water actually, or our body is
made up of water. So water is polar. It allows it to dissolve material. And so it's
really is the elixir of life. And so most of our body is made up of that. But if we
don't get enough water in our diet, so let's say it drops from 75% to 73%, so we have water
loss, these are some of the consequences of that. We're going to have thirst, discomfort,
loss of appetite, dry skin, constipation. And that's just in a drop of 2%. Now what
is that water loss effecting? It's effecting our blood. It's effecting the tissues in our
body. And so our body tries to accommodate for that. But if you don't have an influx
of water, it's going to be serious really really quickly. And so if that water loss
goes to 5%, then you're going to experience headaches, increased heart rate, as an example
or as a consequence of changes to the circulatory system. Your body is going to crank up its
respiration rate to try to accommodate for that. Nausea. Tingling in the limbs. Just
with the loss of 5%. At 10% you'll get muscle spasms, skin will shrivel up. Your vision
is going to dim and that's because we're going to get an increase in the blood concentration
or the blood pressure. Stop urinating and then you eventually undergo delirium. And
then at 15% you're going to die. As a result of that. And so this is a change in the environment.
In other words we're not getting enough water in. As a result of that the cells are not
going to function correctly. And as a result of the cells not functioning correctly you
will die quickly as a result of that. And so that's an example of an environmental disruption.
Now these organisms here all look pretty cool. Common Myna, the Cane Toad, the Carp, Short-tailed
Weasel. All of these look pretty neat but they are notorious. They're on the list of
a hundred of the worst invasive species on our planet. Now some of those are going to
be fungi. Some are going to be plants. But these are some animals that are wreaking havoc
on our planet. And that's because they're adding to a new ecosystem. In other words
they're being introduced in an area where they normally aren't. And as a result to that,
they normally don't have predators. And things can get out of control really, really quickly.
And so this is a disruption at the level of an ecosystem. One of the probably worst stories
of an invasive species would be on the island of Guam. Guam, after World War II, was a big
part of World War II, but it's now a protected democracy, I think that's how it fits with
us, to place it in the U.S. This is Indonesia. Guam's going to be right up here. And so it's
going to be in the middle of the Pacific Ocean. It's a beautiful island. Had beautiful birds
on it. And it's an island paradise. But unfortunately after World War II, somebody stowed away on
a boat. And this is the brown tree snake. Brown tree snake, it wasn't found on Guam
before then. And once it established itself it just went out of control. There are no
natural predators for that tree snake. And so it quickly could climb up in the trees,
eat the eggs of the birds, eat the birds. And so their populations have plummeted. I think
something like twelve bird species have gone extinct just as a result of the introduction
of this tree snake. The tree snake as a result has bred out of control. I think I read at
one point there are about 100 brown tree snakes per every hectare on Guam. And so it's a huge
number. They're having a hard time getting rid of them. Their causing power outages.
They'll climb up onto the transformers and short them out. And so it's a nasty change
to an island. It's invasive species. As we lose those bird species it's going to be a
change in the inspect species. And so it's thrown the whole homeostasis of an island
kind of out of whack. And so they're trying to trap them. They're trying to use, I think,
acetaminophen to poison them. But what they're not trying to do, is they kind of toyed with
the idea of introducing a natural predator of the brown snake but they're worried that
could lead to other problems. And so islands are super susceptible to invasive species.
But again it's just a change in the environment which is throwing off the homeostasis of either
a cell or a population or even in this case an ecosystem. And so I hope that's helpful.