中級 4497 分類 收藏
開始影片後,點擊或框選字幕可以立即查詢單字
字庫載入中…
回報字幕錯誤
Hi. It's Mr. Andersen and welcome to biology video essentials 51. This is on
ecosystems and how ecosystems can be impacted by changes in their environment. This right
here is a picture of some contrails that are created. Contrail are created when jets fly
over an area. Pollutants coming from the combustion of the jet fuel will actual have water vapor
adhere to it. And so you get the creation of a man-made cloud. And you can see how many
of these contrails are created. This is a satellite image over Nova Scotia. And these
are all the contrails that are created in a typical day. And so we're actually making
clouds. Now what do those clouds do? Clouds will actually hold heat in. And so in Montana,
when it's going to be a clear night I know that in the winter especially like now, it's
going to get really, really cold at night. Because the clouds aren't going to hold in
that heat. And so how could we ever study how much of an impact are we having on the
weather? Well we'd have to have a time when there are no jets flying. And when would that
happen? Well it's only happened really once. After 9/11 we shut down jet traffic in the
United States for a 3 day period. And so scientists were able to observe that three day period
and compare it to the days proceeding it, days after that. And we were able to find
that we had roughly a 1 degree Celsius change on the weather. Just during that one day period.
And weather remember over a long term is called climate. And so we can impact ecosystems just
by changing the climate. So basically in this podcast I'm going to talk about how ecosystems
can be impacted by changes in their environment. Some of those are human changes. And of course
I'm going to talk about global warming or climate change. We could also have geologic
changes. An example I'll give you is continental drift. And then finally we could have meteorological
changes. Meteorological just simply means weather changes. And so an example I'll talk
about is el Nino. Or warming of the oceans and how that's actually impacting ecosystems
on our planet. So let's start with global warming. This is a famous map. It basically
compares the average temperature from 1950 to 1981. So a 30 year period to the ten year
period that we're just finishing. And basically anything on the map that's red means that
it got warmer. Anything on the map that's blue, which I can find a little bit down here,
means it got cooler. And then the grey areas means we didn't get much data from that. And
so you can see that there's a huge warming over the last decade compared to the 50s to
1980. And so basically there's no credible scientist out there that's saying that there's
not global warming. And there's no credible scientist out there who's saying humans aren't
having an impact on that. And so a couple of examples of feedback loops, because that's
again one of our major themes, this would be in the permafrost. So as permafrost starts
to melt it gives off a methane gas. Methane gas is a really good green house gas. And
so that's going to increase the temperature through the green house effect. Which is going
to warm the permafrost. Which is going to create more methane gas. And so you know we
call that a positive feedback loop. Now some of that heat is going to dissipate from the
arctic. And so this is not really a localized phenomena. But it is going to increase global
warming. That's why were going to see an increase over the next 100 years. One that's more global
would be the increase that we're seeing in water vapor. And so this is from 1980 to 2004.
This is just looking at the amount of water vapor in the atmosphere. And you can see that
we're seeing an increase in the amount of water vapor. What is that H20 going to do
in the atmosphere? Well, it's going to increase the temperature. It's going to increase the
temperature which creates more water vapor which is going to increase the temperature.
And so basically our temperature is being increased by changes that we're having on
our planet. Because it's not just weather, excuse me, it's not just water and methane,
it's going to be carbon dioxide that we're putting into the atmosphere. And other green
house gases that are increasing the temperature. And it'll take awhile for that to actually
take off. And we're starting to experience that right now. How much of an impact is it
going to have on ecosystems? Well it's first of all going to effect ecosystems that are
more susceptible to changes in temperature. And so this is data that I got from the intergovernmental
panel on climate change. So it's basically almost 200 countries take all their data.
They compile it together. And they're looking at how changes in the temperature are going
to effect our planet. Now they're not necessarily looking at ecosystems. But that's a part of
the study that they did. And basically what they predicted is if we see 1/2 of a degree
of Celsius change over the next 100 years, we're going to have damage to the coral reefs
and the arctic ecosystems. Now of course we're going to impact the arctic ecosystems more
than those closer we'll say to the equator, because any warming is going to change that
climate there. And so it's going to impact species that have evolved to live in a cold
area. An example could be like the polar bears. Now coral reefs are damaged in a different
way. Let me click to the next slide. If we see a 1 degree change, all the coral reefs
will become bleached. So basically a coral is made up of two things. You have a coral
which is essentially an animal. And then you have an algae that lives mutualistically with
them. And so basically the coral will extrude that algae so they become bleached. And they
can't use the photosynthetic features of the algae anymore. And so it's a defense mechanism
to changes in the temperature. That's why they will be impacted. But if we see a 1 degree
change they're predicting we'll see 10% of the global ecosystems will be transformed.
And so basically what's going to happen is as we increase temperature, it's going to
get warmer and warmer and warmer. And so it's going to impact these areas near the arctic
more than those areas near the equator as we warm up the temperature. Now it's happening
so quickly that species who normally could evolve to changes like that aren't able to
evolve quickly enough. And so they're going to be impacted by that. So if we get a 2 degree
change over the next 100 years we'll see mass mortality in the coral reefs. 1/6 of all ecosystems
will be transformed. Then this is where it gets a little bit scary. A fourth of all species
will be committed to extinction. It doesn't mean that they necessarily will go extinct,
but they will be headed down a pathway of extinction. And so what is extinction? It
means when all the organisms of a specific species are gone from our planet. The opposite
of that is an extant species is one that's around today. And so just a 2 degree change
could have huge impacts on that. And they predicted a 3 degree change could get a third
of all species on our planet going extinct. And so when you hear numbers about this being
the greatest extinction that we've ever had, this man-made extinction, it's because we
are getting changes in the temperature. And those global changes in the temperature are
going to impact ecosystems and thereby impact species in that area. They also predict that
half of all nature preserves ail be unable to meet their conservation objectives. So
this is Pelican Island, one of the first national refuges that we have in the United States.
And all of these are going to be impacted by changes in temperature. And the reason
why is that species simply can't evolve quickly enough to changes that are 3 degree changes
over 100 year period. And so those are going to be man-made changes. But there have also
been global changes not caused by man over time. One great example of that would be continental
drift. All the continents on our planet, remember, used to be organized into one super continent
called Pangea. Pangea broke apart into two subcontinents. We had, this is Gondwanaland
or Gondwana. And then we had Laurasia in the north. And so basically when they figured
this out, they looked at fossils and where fossils were found. And so we had fossils,
not only did the continents fit together, but those continents had fossils that would
move throughout all of them. So it was a good way to show, scientists show, that the continents
had actually drifted apart. But basically that drifting has caused biogeographical changes,
or changes in the life that are living on those planets. And so we can look at where
species are found. And we can predict how those ecosystems had changed over time. Or
we can at least go back and look through the evidence and figure out what happened over
time. Example could be in the mammals or the marsupial mammals. So basically there are
three types of mammals. You've got the egg-laying mammals. An example would be the platypus.
You have the marsupial mammals. Example would be like the kangaroo. And then you have the
placental mammals. Which is essentially everything that you think of as a mammal. And so if you
think about where are the marsupials found on our planet, well almost all of the marsupials
you can think of are found Australia. So Koala Bear is an example of that. But we also have
marsupials in South America. And we have one marsupial in North America. This is the possum.
And so how did marsupials get where they were? Well basically what happened is we had marsupials
in Gondwana. So we had them in Antarctica. We had them in Australia, and we had some
of them in South America. Scientists don't think we had movement into Africa at all.
So we had marsupials that are all across here. And so basically as those continents drifted,
Antarctica got so cold that the ecosystem changes so much that all the marsupials died
off there. We had the marsupials here in Australia that were adrift. So we didn't have the placental
mammals there. And then we had those in South America. Now South America eventually drifted
into North America. And we had the movement of some of those marsupial mammals into North
America, but mostly we had the movement of all the placental mammals down. So we had
this battle of the mammals. And so basically as continents drift about, they're going to
change their climate. And thereby they're going to change the ecosystems that they have.
Now the last and the third type is how meteorological changes can actually impact ecosystems. And
so this is el Nino. El Nino happens somewhere between every two to seven years. It kind
of centers around 5 years. And basically what'll happen is you'll have a warming of these waters
in the Pacific. So along the coast of South America. So you get a warming in this area.
And then it'll kind of go away. And then we have la Nina. And then we'll have el Nino.
And so we have these changes of the temperatures. And so basically that's going to impact the
ecosystems during those time periods. And so this is a marine iguana. It's really cool
kind of an animal. Basically what it'll do is it'll sit on land and it'll get warmed
up. They live the Galapagos Islands which are going to be right down here. You could
imagine in the middle of el Nino. And so basically what they do is they will feed on algae underwater.
So they swim down under the water. They feed on algae. They come back up to the surface.
They are cold blooded so they have to warm up their bodies so they can digest that food.
Then they go down again. Get algae. Really cool looking creature. Look kind of prehistoric.
But basically what happens to them during el Nino is that most of the land will actually
do well, because we're going to warm up the temperature. We get more precipitation. So
a lot of the plants are going to do well. But the algae that live under water are going
to be impacted by that increase. So what does that do? Well there is less algae. Now the
marine iguanas, when they go down, aren't going to find as much algae. And so they're
going to be impacted by that. Or the ecosystem will be impacted by that. And so scientists
found that you see a 20% decrease in the length of iguanas during an el Nino period. Now why
is that? Well there are two reasons. Number one is that they'll actually shrink their
body in response to el Nino. So their bones will actually get shorter. Which is crazy.
If you think about what if I were to get 20% shorter when it gets just a little bit warmer?
And so there's a stress hormone that's released that actually making their bones short. Which
is pretty cool. But there's also selection going on. In other words if your a big marine
iguana, you're going to have to dive deeper to find algae. You're going to have to come
back on land. It's going to take you longer for your body to warm up. So you can actually
digest the food so you can go back down again. And so now we see selective pressure on the
larger marine iguanas. And so we're going to see a movement towards smaller body size.
And so again, just simple changes in the temperature can have huge impacts on an ecosystem. And
even though we might think we're having small impacts on our climate, humans are having
great impacts on our climate which is going to kind of feedback out of control over the
next hundred years. And we're going to see changes in the environment. But hopefully
we can mediate some of that just through eduction. And so I hope that's helpful. }
    您必須登入才有此功能
提示:點選文章或是影片下面的字幕單字,可以直接快速翻譯喔!

載入中…

生態系統改變 (Ecosystem Change)

4497 分類 收藏
Jan 發佈於 2014 年 1 月 8 日
看更多推薦影片

影片討論

載入中…
  1. 1. 單字查詢

    在字幕上選取單字即可即時查詢單字喔!

  2. 2. 單句重複播放

    可重複聽取一句單句,加強聽力!

  3. 3. 使用快速鍵

    使用影片快速鍵,讓學習更有效率!

  4. 4. 關閉語言字幕

    進階版練習可關閉字幕純聽英文哦!

  5. 5. 內嵌播放器

    可以將英文字幕學習播放器內嵌到部落格等地方喔

  6. 6. 展開播放器

    可隱藏右方全文及字典欄位,觀看影片更舒適!

  1. 英文聽力測驗

    挑戰字幕英文聽力測驗!

  1. 點擊展開筆記本讓你看的更舒服

  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔