Calculating velocity using energy

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:01.700
- [Instructor] So we have a spring here

00:00:01.700 --> 00:00:04.550
that has a spring constant
of four Newtons per meter.

00:00:04.550 --> 00:00:06.830
What we then do is take a 10-gram mass

00:00:06.830 --> 00:00:08.200
and we put it on top of the spring

00:00:08.200 --> 00:00:11.750
and we push down to compress
the spring by 10 centimeters.

00:00:11.750 --> 00:00:13.290
We then let go.

00:00:13.290 --> 00:00:15.930
And what I'm curious about
is what is going to be

00:00:15.930 --> 00:00:19.460
the magnitude of the
velocity of our ball here,

00:00:19.460 --> 00:00:21.170
of our 10-gram mass,

00:00:21.170 --> 00:00:25.170
right as the spring is no
longer compressed or stretched,

00:00:25.170 --> 00:00:27.970
or essentially when the
ball is being launched?

00:00:27.970 --> 00:00:29.840
Pause this video and see
if you can figure that out.

00:00:29.840 --> 00:00:32.860
And I'll give you a hint, the
energy in this first state,

00:00:32.860 --> 00:00:35.880
the total energy has got to
be equal to the total energy

00:00:35.880 --> 00:00:36.840
of this second state.

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We can't create or destroy energy.

00:00:40.210 --> 00:00:43.470
All right, now let's work
through this together.

00:00:43.470 --> 00:00:47.550
So let's call this first
scenario state one.

00:00:47.550 --> 00:00:50.500
So in state one, what is the
total energy going to be?

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Well, it's going to be the sum

00:00:51.790 --> 00:00:53.750
of the gravitational potential energy,

00:00:53.750 --> 00:00:57.570
so that's mg times the
height in state one,

00:00:57.570 --> 00:00:59.870
plus our elastic potential energy,

00:00:59.870 --> 00:01:02.110
that's 1/2 times the spring constant times

00:01:02.110 --> 00:01:05.640
how much we've compressed that
spring in state one squared,

00:01:05.640 --> 00:01:07.100
plus our kinetic energy,

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so that's 1/2 times our
mass times the magnitude

00:01:10.850 --> 00:01:13.640
of our velocity in state one squared.

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And that has got to be equal to,

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as we just talked about, the
total energy in state two.

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Well, what's that going to be?

00:01:21.810 --> 00:01:24.140
Well, that's your
gravitational potential energy

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in state two plus your elastic
potential energy in state two

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plus your kinetic energy in state two.

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Now let's think about which
of these variables we know

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and which ones we need to solve for.

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So, first of all, mass,
your spring constant,

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the strength of your gravitational field,

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well, we know what these are going to be.

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These are going to be our
mass is equal to 10 grams.

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The strength of the gravitational field,

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also the acceleration due to gravity near

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the surface of the earth, is
9.8 meters per second squared.

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Our spring constant is
four Newtons per meter,

00:02:10.760 --> 00:02:13.100
and I like to remind
myself what a Newton is,

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a Newton is kilogram
meter per second squared.

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So this is also equal

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to four kilogram meter per second squared,

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and then we also have a meter over there.

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And actually, these
meters will cancel out.

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And that's useful
because it's reminding us

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that we want everything to
be in kilograms and meters.

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And with that in mind, actually,

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let me rewrite our mass right
over here as 0.01 kilograms.

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And then let's think about
what's going on specifically

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in each of those states.

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So what is going to be our
h one, our initial height?

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Well, I didn't give it to you,

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but what really matters is the difference

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between h one and h two.

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So we could just define
h one right over here

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to be equal to zero.

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So let me write that down.

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H one is equal to zero.

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And if we say that, then
what is h two going to be?

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H two would then be
equal to 10 centimeters,

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but remember, we want everything
in kilograms and meters,

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so 10 centimeters is the
same thing is 0.1 meters.

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What is our spring compression

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in scenario one going to be?

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Well, that is going to be 10 centimeters.

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But once again, we wanna
write that in terms of meters.

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So I'll write that as 0.1 meters.

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And then what is our spring compression

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in scenario two going to be?

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Well, we're completely
uncompressed and unstretched,

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so that is going to be zero meters.

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And then what is going to be our velocity,

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or at least the magnitude of
our velocity in state one?

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Well, we're stationary, so
it's zero meters per second.

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And what is going to be the magnitude

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of our velocity in state two?

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Well, that's exactly
what we wanna solve for.

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That is our launch velocity.

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So let's see if we can simplify this

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and then solve for v two.

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So we know that h one is equal to zero.

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So that simplifies that right
over there, that term is zero.

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We know that v one is zero.

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So that simplifies that term there.

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We know that delta x in
scenario two is equal to zero.

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So that simplifies that
term right over there.

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And so we can now rewrite all of this,

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and I'll switch to one color
just to speed things up

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a little bit, as 1/2 k
times delta x one squared

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is equal to mgh sub two
plus 1/2 mv sub two squared.

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And now let's just try to
solve for this character.

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So let's subtract mgh
sub two from both sides.

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So we're going to have 1/2 k
times delta x sub one squared

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minus mgh sub two is equal
to 1/2 mv sub two squared.

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Now let's see, if we multiply
both sides by two over m,

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then that will get rid
of this 1/2 m over here.

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So let me multiply that.

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I'm kind of doing two
steps at the same time.

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One way to think about it
is I'm multiplying times

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the reciprocal of the
coefficient on the v squared.

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So right over here, it's m over two,

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so the reciprocal is two over m.

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I'm gonna have to make sure
that I'm gonna multiply it times

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that whole side.

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And so what do we now have?

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This is going to be equal to, let's see,

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it's going to be k delta
x sub one squared over m

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minus two gh sub two

00:05:53.120 --> 00:05:55.610
is going to be equal to v sub two squared.

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And then to solve for our launch velocity,

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we just take the principal route,

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the square root of both sides.

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So I could say v sub two,

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which is equal to our launch velocity,

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is equal to the square
root of our spring constant

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times delta x sub one squared
over our mass minus two times

00:06:15.640 --> 00:06:19.870
the gravitational field times h two.

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And so we just have to
plug in the numbers now.

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This is going to be equal to,

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and I'll switch colors
just to ease the monotony.

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I'm gonna use a new color right over here.

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This is going to be equal
to the square root of,

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and I wanna make sure
all the units work out.

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So I'm actually gonna write this version

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of my spring constant, so I
can work with all the units.

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So it's gonna be four
kilograms per second squared.

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And now delta x one we know is 0.1 meters.

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So if we square it,

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it's going to be times
0.01 meters squared.

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And then all of that is
going to be over our mass,

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which we know is 0.01
kilograms, 0.01 kilograms,

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and then minus two times 9.8
meters per second squared

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times height in the second scenario,

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which we already know is 0.1
meters, so times 0.1 meters.

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Let me extend this
radical right over here.

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And let's look at the units first

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to just to make sure we're
getting the right units.

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So this kilogram is going to
cancel with this kilogram.

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And then we have, over here,

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we're going to have
something that's in terms

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of meters squared per second squared,

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and then over here,

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we're gonna have something in terms

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of meters squared per second squared.

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So that makes sense.

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We're gonna have a difference

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of two meters squared per second squared.

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And then when you take
the principal route,

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you're going to get meters per second,

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which is the unit for the
magnitude of velocity.

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So now we just have to
get our calculator out

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and calculate this.

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So the .01s will cancel out.

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So this part right over
here is going to be four.

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And then from that,

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I am going to subtract
two times 9.8 times .1,

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close the parentheses.

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That's going to be equal to that.

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And then I needed to take the square root

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of all of that business, and
I get this right over here.

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So this is approximately
1.43 meters per second,

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1.43 meters per second.

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And we're done.


Natural selection and adaptation

WEBVTT
Kind: captions
Language: en

00:00:00.840 --> 00:00:02.540
- [Dr. Samuel] Hi
everybody, Dr. Samuel here,

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your friendly neighborhood entomologist.

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And I was hoping that we
could take a few minutes

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to talk about adaptation.

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What comes to mind when
you think about adaptation?

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You might think of cryptic morphology

00:00:13.720 --> 00:00:15.960
that helps organisms hide from predators,

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scaly armor or spines to
protect organisms in a scuffle,

00:00:20.060 --> 00:00:23.020
or increased melanin
pigmentation in the skin

00:00:23.020 --> 00:00:25.632
to shield an organism
from the damaging impacts

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of harsh sunlight in really sunny areas.

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And if this is the sort of
thing that you thought of,

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you're right, these are all adaptations.

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But what people often
miss about adaptations

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is that they all help
organisms survive and reproduce

00:00:41.187 --> 00:00:44.240
in a particular environment.

00:00:44.240 --> 00:00:49.086
The word adaptation can refer to a trait

00:00:49.086 --> 00:00:54.086
that makes an organism more
suited to its environment.

00:00:55.560 --> 00:00:57.430
But it can also mean

00:00:57.430 --> 00:01:01.030
the process by which a population

00:01:01.030 --> 00:01:04.340
becomes dominated by organisms

00:01:04.340 --> 00:01:08.180
that are suited to their environment.

00:01:08.180 --> 00:01:11.890
The point is that adaptation
happens in a population

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as its organisms accumulate adaptations.

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And this all happens through the process

00:01:18.660 --> 00:01:20.250
of natural selection,

00:01:20.250 --> 00:01:22.010
which you may have heard about.

00:01:22.010 --> 00:01:24.670
With natural selection, we see organisms

00:01:24.670 --> 00:01:26.910
with beneficial heritable traits,

00:01:26.910 --> 00:01:30.120
increasing their share of the
gene pool in the population

00:01:30.120 --> 00:01:33.870
because they're more likely
to mate and produce offspring.

00:01:33.870 --> 00:01:38.870
This means these well-adapted
organisms have higher fitness,

00:01:39.320 --> 00:01:44.110
a measure of an organism's ability

00:01:44.110 --> 00:01:48.420
to survive and reproduce

00:01:48.420 --> 00:01:51.540
in its specific environment.

00:01:51.540 --> 00:01:56.130
These traits or adaptations
make the organisms better suited

00:01:56.130 --> 00:01:58.200
to survive and reproduce

00:01:58.200 --> 00:01:59.400
because they're better suited

00:01:59.400 --> 00:02:02.740
to the specific environmental
context that they live in.

00:02:02.740 --> 00:02:05.110
That is our green caterpillars blend in,

00:02:05.110 --> 00:02:07.090
and thus, survive better
on the green leaves,

00:02:07.090 --> 00:02:09.440
and the orange caterpillars
on the orange leaves.

00:02:09.440 --> 00:02:11.360
As you can see, natural selection

00:02:11.360 --> 00:02:14.190
is intimately intertwined
with the environment

00:02:14.190 --> 00:02:15.690
in which it takes place.

00:02:15.690 --> 00:02:19.980
And this is why natural
selection can lead to adaptation.

00:02:19.980 --> 00:02:22.960
Even the concept of adaptation is diverse.

00:02:22.960 --> 00:02:25.292
Adaptations can be anatomical,

00:02:25.292 --> 00:02:30.292
changes to physical
structures, or physiological,

00:02:30.520 --> 00:02:34.710
changes in the function
of these structures,

00:02:34.710 --> 00:02:39.710
or adaptations can be changes to behavior.

00:02:39.740 --> 00:02:43.161
We see this with honeybees
adapted to life in Africa,

00:02:43.161 --> 00:02:45.750
sometimes called by the suboptimal names,

00:02:45.750 --> 00:02:49.870
Africanized honeybees or killer bees.

00:02:49.870 --> 00:02:54.090
They're the same species
as and look identical too.

00:02:54.090 --> 00:02:57.650
Populations of honeybees
adapted to North America,

00:02:57.650 --> 00:03:01.090
but their behaviors diverge dramatically.

00:03:01.090 --> 00:03:02.780
Because the African populations

00:03:02.780 --> 00:03:05.980
are adapted to life in a
hot, tropical environment,

00:03:05.980 --> 00:03:09.180
sometimes, they construct nests
right out in the open air,

00:03:09.180 --> 00:03:12.300
nests in open air.

00:03:12.300 --> 00:03:14.810
This is extremely rare for populations

00:03:14.810 --> 00:03:17.160
adapted to the temperate
climate of North America,

00:03:17.160 --> 00:03:19.560
where the temperature
range is far too broad

00:03:19.560 --> 00:03:22.960
between winter and
summer for open air nests

00:03:22.960 --> 00:03:24.173
to be successful.

00:03:25.050 --> 00:03:27.730
So, North American honeybee populations

00:03:27.730 --> 00:03:30.660
much prefer to live inside
of protected structures

00:03:30.660 --> 00:03:33.170
like inside of the trunks of hollow trees

00:03:33.170 --> 00:03:35.790
or the boxes that beekeepers provide,

00:03:35.790 --> 00:03:40.150
nests in protected structures.

00:03:40.150 --> 00:03:41.860
And in Africa,

00:03:41.860 --> 00:03:45.040
there are also more
large, fearsome predators

00:03:45.040 --> 00:03:47.730
interested in getting into the bees' nest.

00:03:47.730 --> 00:03:51.580
So, the frequency of traits
related to hyper defensiveness

00:03:51.580 --> 00:03:53.310
is much more common

00:03:53.310 --> 00:03:56.000
than in populations
adapted to North America,

00:03:56.000 --> 00:03:59.220
where there are fewer
aggressive predators,

00:03:59.220 --> 00:04:02.467
heightened defensiveness, low

00:04:04.630 --> 00:04:08.563
to moderate defensiveness.

00:04:10.040 --> 00:04:13.040
The success of honeybees
adapted to life in Africa

00:04:13.040 --> 00:04:14.470
left a lot of people worried

00:04:14.470 --> 00:04:17.270
that they would be similarly
successful in North America

00:04:17.270 --> 00:04:19.220
and replace the honeybees there.

00:04:19.220 --> 00:04:21.640
But those concerns ignored the connection

00:04:21.640 --> 00:04:24.740
between adaptation and the environment.

00:04:24.740 --> 00:04:27.650
Traits that helped those
bees survive in Africa

00:04:27.650 --> 00:04:29.540
and even helped them
in similar environments

00:04:29.540 --> 00:04:31.230
found in many regions of tropical,

00:04:31.230 --> 00:04:33.030
South and Central America,

00:04:33.030 --> 00:04:35.830
well, those same exact traits

00:04:35.830 --> 00:04:39.140
were liabilities in much of North America.

00:04:39.140 --> 00:04:41.890
Okay, so, this is all fascinating,

00:04:41.890 --> 00:04:43.640
but you may be wondering,

00:04:43.640 --> 00:04:47.060
if natural selection is
passing out adaptations,

00:04:47.060 --> 00:04:50.620
why doesn't it choose better stuff?

00:04:50.620 --> 00:04:55.620
Fish tend to get eaten
by birds and bears a lot.

00:04:56.080 --> 00:05:00.420
And that's gone on for
literally millions of years.

00:05:00.420 --> 00:05:02.220
So, why I haven't fish populations

00:05:02.220 --> 00:05:06.630
developed something like
laser eyes or teleportation?

00:05:06.630 --> 00:05:10.440
Instead, when a population
of fish does evolve defense,

00:05:10.440 --> 00:05:13.150
it's typically something like a few bones,

00:05:13.150 --> 00:05:16.350
that it already has,
getting longer and sharper

00:05:16.350 --> 00:05:18.320
and protruding out of their fins,

00:05:18.320 --> 00:05:21.488
like in the case of the
three-spined stickleback fish.

00:05:21.488 --> 00:05:24.300
These spines protect the stickleback

00:05:24.300 --> 00:05:26.730
from birds and other predators,

00:05:26.730 --> 00:05:28.950
but only if the spines are long enough

00:05:28.950 --> 00:05:31.390
to make it difficult for
that specific predator

00:05:31.390 --> 00:05:32.530
to swallow them.

00:05:32.530 --> 00:05:35.350
Birds with wider throats
are still able to eat

00:05:35.350 --> 00:05:39.640
even fully grown fish with
fully elongated spines.

00:05:39.640 --> 00:05:43.660
Laser eyes really do seem like
they would be more effective.

00:05:43.660 --> 00:05:46.030
It's almost like natural selection

00:05:46.030 --> 00:05:48.541
is just tinkering with
whatever it has lying around

00:05:48.541 --> 00:05:51.680
instead of going out
and buying something new

00:05:51.680 --> 00:05:54.180
and perfectly suited to the task.

00:05:54.180 --> 00:05:56.840
And that is exactly what's happening.

00:05:56.840 --> 00:06:00.380
Populations don't adapt by
accessing a bottomless well

00:06:00.380 --> 00:06:03.150
of awesome problem-solving options.

00:06:03.150 --> 00:06:06.360
Quite the contrary, with
natural selection as the driver,

00:06:06.360 --> 00:06:08.970
adaptations can be pretty limited.

00:06:08.970 --> 00:06:11.130
You might already be
tracking with the idea

00:06:11.130 --> 00:06:13.040
that if an increase in fitness

00:06:13.040 --> 00:06:15.180
is what natural selection is after,

00:06:15.180 --> 00:06:17.800
you don't need an adaptation
that allows you to incinerate

00:06:17.800 --> 00:06:18.890
all of your enemies.

00:06:18.890 --> 00:06:22.400
You just need one good enough
to solve whatever problem

00:06:22.400 --> 00:06:24.410
is keeping others in your population

00:06:24.410 --> 00:06:26.410
from surviving in mating.

00:06:26.410 --> 00:06:29.300
If that's a kingfisher
bird eating the other fish,

00:06:29.300 --> 00:06:31.760
the resolution might be just a spine

00:06:31.760 --> 00:06:34.040
that's only a half a centimeter longer

00:06:34.040 --> 00:06:35.420
than the other fishes.

00:06:35.420 --> 00:06:37.940
That's the reason why we see adaptations

00:06:37.940 --> 00:06:40.350
that look like natural
selection just grabbed

00:06:40.350 --> 00:06:43.690
whatever happened to be
lying around and modified it

00:06:43.690 --> 00:06:46.150
because it kinda did.

00:06:46.150 --> 00:06:48.470
A turtle's remarkably protective shell

00:06:48.470 --> 00:06:50.230
may look fancy and novel,

00:06:50.230 --> 00:06:53.070
but it's literally the
turtle's overgrown ribs

00:06:53.070 --> 00:06:54.850
fused with its spine.

00:06:54.850 --> 00:06:57.030
A narwhal's face spear,

00:06:57.030 --> 00:06:59.035
that there is just a tooth

00:06:59.035 --> 00:07:02.640
that grew all the way out of its face.

00:07:02.640 --> 00:07:04.860
Natural selection only has the options

00:07:04.860 --> 00:07:06.940
currently in the genes of a population

00:07:06.940 --> 00:07:08.080
with the occasional addition

00:07:08.080 --> 00:07:10.110
of new genetic sequences through mutation

00:07:10.110 --> 00:07:12.000
to work with when a problem arises.

00:07:12.000 --> 00:07:14.070
And you might be thinking, "Oh great!

00:07:14.070 --> 00:07:15.910
Mutations, those will help!

00:07:15.910 --> 00:07:18.720
That's how my favorite
superhero got her powers."

00:07:18.720 --> 00:07:21.240
Well, unlike what we see in movies,

00:07:21.240 --> 00:07:23.970
most mutations either have no real effect

00:07:23.970 --> 00:07:26.110
or result in problematic gene expression

00:07:26.110 --> 00:07:28.060
or nonfunctional proteins

00:07:28.060 --> 00:07:32.090
which is pretty bad
news for living things.

00:07:32.090 --> 00:07:35.510
So, adaptations are not
likely to be super weapons

00:07:35.510 --> 00:07:38.150
that ensure survival in all circumstances.

00:07:38.150 --> 00:07:39.609
Instead, they're useful traits

00:07:39.609 --> 00:07:42.270
that help increase an organism's fitness

00:07:42.270 --> 00:07:45.020
as the environmental
conditions apply pressure.

00:07:45.020 --> 00:07:47.810
So, adaptation is a remarkable system,

00:07:47.810 --> 00:07:50.790
but one with some pretty
pronounced limitations.

00:07:50.790 --> 00:07:54.140
Natural selection has to work
with what an organism has.

00:07:54.140 --> 00:07:56.950
But consider for a moment
what it has given us

00:07:56.950 --> 00:07:59.130
despite those limitations.

00:07:59.130 --> 00:08:00.790
Pistol shrimp have the ability

00:08:00.790 --> 00:08:03.230
to slam their claws shut so quickly

00:08:03.230 --> 00:08:06.090
that the water around them
collapses in on itself.

00:08:06.090 --> 00:08:10.490
It implodes knocking
nearby fish unconscious.

00:08:10.490 --> 00:08:12.520
Some honeybees can bundle together

00:08:12.520 --> 00:08:15.370
and vibrate their flight
muscles so rapidly

00:08:15.370 --> 00:08:18.190
that they can create a
biological convection oven

00:08:18.190 --> 00:08:20.400
which can cook predators to death.

00:08:20.400 --> 00:08:22.600
And there are parasitic wasps

00:08:22.600 --> 00:08:26.060
that have evolved to live
inside of parasitic wasps

00:08:26.060 --> 00:08:28.630
that live inside of parasitic wasps

00:08:28.630 --> 00:08:31.130
that live inside of caterpillars,

00:08:31.130 --> 00:08:34.720
like tiny, strange, little
Russian nesting dolls.

00:08:34.720 --> 00:08:37.880
And don't even get me
started on the hornets

00:08:37.880 --> 00:08:39.940
that have yellow patches on their abdomen

00:08:39.940 --> 00:08:41.770
that absorb solar energy

00:08:41.770 --> 00:08:44.450
to supplement the energy
provided by their diet.

00:08:44.450 --> 00:08:47.132
They have solar panels!

00:08:47.132 --> 00:08:51.293
I'd say natural selection has
done pretty well for itself.


Acid Rain

WEBVTT
Kind: captions
Language: en

00:00:00.190 --> 00:00:02.590
- [Narrator] Acid rain
sounds like something

00:00:02.590 --> 00:00:04.570
straight out of a sci-fi film,

00:00:04.570 --> 00:00:07.260
like strange raindrops that fall in a city

00:00:07.260 --> 00:00:09.250
and corrode everything.

00:00:09.250 --> 00:00:10.860
The truth is not far off,

00:00:10.860 --> 00:00:12.760
but the good news is that we know a lot

00:00:12.760 --> 00:00:14.510
about what causes acid rain

00:00:14.510 --> 00:00:16.990
and how to address its
impact on the environment,

00:00:16.990 --> 00:00:19.250
our bodies and the built world.

00:00:19.250 --> 00:00:21.130
Interestingly, normal rain

00:00:21.130 --> 00:00:24.030
is actually slightly acidic as well.

00:00:24.030 --> 00:00:26.000
If you think back to the pH scale,

00:00:26.000 --> 00:00:29.840
you'll remember that it
goes from zero to 14,

00:00:29.840 --> 00:00:31.600
acidic to basic,

00:00:31.600 --> 00:00:35.260
and that seven, right in
the middle, is neutral.

00:00:35.260 --> 00:00:40.260
Normal rain is around 5 or 5
1/2, so it's slightly acidic,

00:00:42.380 --> 00:00:45.160
but acid rain is even more acidic

00:00:45.160 --> 00:00:47.993
and typically around a pH of four.

00:00:49.070 --> 00:00:51.530
Now this might not sound
like a big difference,

00:00:51.530 --> 00:00:54.280
but remember that this
is a logarithmic scale.

00:00:54.280 --> 00:00:56.810
So each increment, like from four to five,

00:00:56.810 --> 00:00:59.120
is actually a tenfold difference.

00:00:59.120 --> 00:01:01.860
So if we're comparing
normal rain, at about 5 1/2,

00:01:01.860 --> 00:01:04.760
and acid rain at four,
that's a pretty big deal.

00:01:04.760 --> 00:01:07.830
So now the questions are,
how does acid rain form?

00:01:07.830 --> 00:01:08.930
Why does it matter?

00:01:08.930 --> 00:01:13.110
And what effects can acid
rain have on our communities?

00:01:13.110 --> 00:01:15.740
So the short answer to
how it forms is pollution.

00:01:15.740 --> 00:01:17.900
So let me try to bring
that to life for you

00:01:17.900 --> 00:01:21.030
with my imaginary hand-drawn drawn city.

00:01:21.030 --> 00:01:22.350
Now remember that most of the fuels

00:01:22.350 --> 00:01:25.080
we burn to make energy
are from fossil fuels,

00:01:25.080 --> 00:01:26.730
so that animal and plant matter

00:01:26.730 --> 00:01:29.630
that has been in the ground
for millions of years.

00:01:29.630 --> 00:01:31.420
And when we burn these fuels,

00:01:31.420 --> 00:01:34.110
they tend to have remaining
traces of sulfur in them,

00:01:34.110 --> 00:01:35.450
especially coal.

00:01:35.450 --> 00:01:38.530
And both coal and oil burn
at such high temperatures

00:01:38.530 --> 00:01:41.470
that they can cause nitrogen
and oxygen in the air

00:01:41.470 --> 00:01:43.830
to form different compounds.

00:01:43.830 --> 00:01:46.190
So imagine we have here an oil refinery

00:01:46.190 --> 00:01:48.890
and a coal burning
plant, and a lot of cars.

00:01:48.890 --> 00:01:52.320
A common byproduct of coal
burning plants or smelters

00:01:52.320 --> 00:01:56.690
and other industrial facilities
is sulfur dioxide, SO2.

00:01:56.690 --> 00:02:00.290
At the same time, high temperatures
from combustion engines

00:02:00.290 --> 00:02:02.950
and oil refineries provide enough energy

00:02:02.950 --> 00:02:07.150
to break apart nitrogen and
oxygen molecules in the air.

00:02:07.150 --> 00:02:09.160
These molecules can then recombine

00:02:09.160 --> 00:02:14.160
to form different nitrogen
oxides, like nitric oxide, NO,

00:02:14.475 --> 00:02:17.220
and nitrogen dioxide, NO2.

00:02:17.220 --> 00:02:20.580
Together, these are referred
to as nitrogen oxides,

00:02:20.580 --> 00:02:23.900
which you can abbreviate by NOx.

00:02:23.900 --> 00:02:26.240
So the same can be said
about sulfur dioxide.

00:02:26.240 --> 00:02:31.240
That falls into the category
of sulfur oxide, SOx, or SOX.

00:02:31.940 --> 00:02:34.450
So a fun way to remember the precursors

00:02:34.450 --> 00:02:37.670
to acid rain are SOX and NOX.

00:02:37.670 --> 00:02:40.870
Now these precursors belonging
to the SOX and NOX family

00:02:40.870 --> 00:02:42.850
are hanging out up in the air.

00:02:42.850 --> 00:02:45.530
When they interact with
UV radiation from the sun

00:02:45.530 --> 00:02:48.430
and water molecules that
are also in the air,

00:02:48.430 --> 00:02:52.270
they form different
vapors, these acid vapors,

00:02:52.270 --> 00:02:55.680
sulfuric acid vapor, H2SO4,

00:02:55.680 --> 00:02:58.453
and nitric acid vapor, HNO3.

00:02:59.545 --> 00:03:01.370
And these acids are no joke.

00:03:01.370 --> 00:03:05.560
Sulfuric acid is highly
corrosive. It can burn your skin.

00:03:05.560 --> 00:03:08.690
The vapors can irritate
your respiratory tract.

00:03:08.690 --> 00:03:10.219
And nitric acid is known to be used

00:03:10.219 --> 00:03:13.130
in explosives and rocket launches.

00:03:13.130 --> 00:03:14.490
And these are the acids

00:03:14.490 --> 00:03:17.190
that make up the phenomenon of acid rain.

00:03:17.190 --> 00:03:20.860
Over time, these smoke stacks
have actually gotten taller.

00:03:20.860 --> 00:03:23.030
One example in the early 1970s,

00:03:23.030 --> 00:03:25.820
when the EPA wanted to reduce emissions

00:03:25.820 --> 00:03:29.450
from these coal burning
facilities and oil refineries

00:03:29.450 --> 00:03:32.930
to control the air quality
around those communities.

00:03:32.930 --> 00:03:37.080
What these facilities did was
build larger smoke stacks,

00:03:37.080 --> 00:03:38.530
or taller smoke stacks,

00:03:38.530 --> 00:03:42.150
so that those pollutants
would disperse and spread out

00:03:42.150 --> 00:03:45.870
over a larger area and not
fall over the local community

00:03:45.870 --> 00:03:48.370
as much or as fast.

00:03:48.370 --> 00:03:51.360
Instead, what ended up happening
is that these pollutants

00:03:51.360 --> 00:03:53.100
were carried by the wind

00:03:53.100 --> 00:03:56.550
to communities and natural
environments downwind

00:03:56.550 --> 00:03:58.960
of where they were being created,

00:03:58.960 --> 00:04:03.170
up to 1,000 kilometers, or over 600 miles.

00:04:03.170 --> 00:04:06.370
And when these acid
vapors cause acid rain,

00:04:06.370 --> 00:04:08.420
it's not always rain like we think of

00:04:08.420 --> 00:04:10.730
with water falling from the sky.

00:04:10.730 --> 00:04:12.900
Acid rain is just a general term

00:04:12.900 --> 00:04:15.950
and it really includes all
forms of precipitation,

00:04:15.950 --> 00:04:19.370
like snow, fog, cloud vapor,

00:04:19.370 --> 00:04:22.230
and dry deposition, like dust particles.

00:04:22.230 --> 00:04:25.453
And also it can have different
combinations of these forms.

00:04:26.560 --> 00:04:29.940
And now the other big question
is why does it matter, right?

00:04:29.940 --> 00:04:31.180
How are we affected?

00:04:31.180 --> 00:04:34.160
And also does that acid burn your skin,

00:04:34.160 --> 00:04:37.570
a very logical thing
(laughs) to want to know.

00:04:37.570 --> 00:04:40.990
So for cities, first of
all, acid rain is bad news

00:04:40.990 --> 00:04:43.600
because it can damage
buildings and statues,

00:04:43.600 --> 00:04:45.960
particularly those that
are made of limestone,

00:04:45.960 --> 00:04:47.930
marble, and some metals.

00:04:47.930 --> 00:04:51.640
Here in this photo is a gargoyle
from the Munich Town Hall,

00:04:51.640 --> 00:04:54.470
which is almost unrecognizable

00:04:54.470 --> 00:04:58.500
because of all the damage
it sustained from acid rain.

00:04:58.500 --> 00:05:01.330
There's also been a lot
of studies over the years,

00:05:01.330 --> 00:05:03.410
looking at the US Capitol

00:05:03.410 --> 00:05:06.410
and a lot of the surfaces
there that are made of marble

00:05:06.410 --> 00:05:08.620
and how they can strengthen them

00:05:08.620 --> 00:05:13.090
to protect them from acid
rain before it's too late.

00:05:13.090 --> 00:05:16.400
Now, if we go a little
deeper, acid rain can leach

00:05:16.400 --> 00:05:19.160
or pull out heavy metals, like aluminum,

00:05:19.160 --> 00:05:21.060
from the soil or rocks,

00:05:21.060 --> 00:05:23.380
which can then be washed out to lakes,

00:05:23.380 --> 00:05:26.500
and as you can imagine, can
lead to a lot of bad things

00:05:26.500 --> 00:05:28.910
like contaminating drinking water

00:05:28.910 --> 00:05:31.770
and harming aquatic ecosystems.

00:05:31.770 --> 00:05:34.950
Many fish can't survive at a lower pH.

00:05:34.950 --> 00:05:39.150
Acid rain also has impacts on
other natural environments,

00:05:39.150 --> 00:05:42.520
especially because of how far it reaches.

00:05:42.520 --> 00:05:46.090
Acid rain can damage and
weaken forests and trees

00:05:46.090 --> 00:05:48.560
by stripping nutrients from the soil

00:05:48.560 --> 00:05:51.830
and even damaging the waxy outer coat,

00:05:51.830 --> 00:05:56.430
leaving them much more vulnerable
to losing more nutrients.

00:05:56.430 --> 00:05:59.510
Now, when it comes to
humans, these acid vapors

00:05:59.510 --> 00:06:02.820
and the different
precipitation that they create

00:06:02.820 --> 00:06:06.340
are very harmful to
our respiratory system,

00:06:06.340 --> 00:06:09.023
and especially those that have asthma.

00:06:10.260 --> 00:06:12.260
And of course, I have
to answer the question,

00:06:12.260 --> 00:06:14.560
does acid rain burn your skin?

00:06:14.560 --> 00:06:18.010
The answer is no, it's
just not acidic enough.

00:06:18.010 --> 00:06:21.100
Remember acid rain is around a pH of four

00:06:21.100 --> 00:06:23.070
and for something to burn your skin,

00:06:23.070 --> 00:06:27.023
it has to be much more acidic,
usually around a pH of one.

00:06:28.950 --> 00:06:32.410
There is some good news
when it comes to acid rain.

00:06:32.410 --> 00:06:36.230
In 1990, the EPA created
the Acid Rain Program

00:06:36.230 --> 00:06:38.800
to help power plants reduce emissions.

00:06:38.800 --> 00:06:43.800
In 2019, when they looked at
the levels compared to 1990,

00:06:44.090 --> 00:06:46.650
they saw pretty great reductions,

00:06:46.650 --> 00:06:50.270
a 94% reduction in sulfur dioxide

00:06:50.270 --> 00:06:54.520
and an 86% reduction in nitric oxides.

00:06:54.520 --> 00:06:57.360
Now this is in the United
States, but around the world,

00:06:57.360 --> 00:06:59.510
acid rain is still a problem,

00:06:59.510 --> 00:07:02.520
particularly nitrates getting into the air

00:07:02.520 --> 00:07:07.510
from sources like fertilizer
and livestock feed.

00:07:07.510 --> 00:07:11.720
And even though we've had
great reductions since 1990,

00:07:11.720 --> 00:07:13.890
there is still some work to be done.

00:07:13.890 --> 00:07:16.080
And one of the ways that we can improve

00:07:16.080 --> 00:07:20.130
is by switching over to
cleaner burning fuels,

00:07:20.130 --> 00:07:22.990
or we can use renewable energy sources

00:07:22.990 --> 00:07:26.500
like solar power, wind
power, and hydro-power

00:07:26.500 --> 00:07:30.690
that ultimately reduce our
dependence on coal and oil.

00:07:30.690 --> 00:07:33.330
So now I hope you learned a
little bit about acid rain,

00:07:33.330 --> 00:07:35.830
how it's made, the impacts it can have,

00:07:35.830 --> 00:07:38.040
and I hope you don't lose any sleep

00:07:38.040 --> 00:07:39.773
over it burning your skin.


Evolution of group behavior

WEBVTT
Kind: captions
Language: en

00:00:00.390 --> 00:00:02.740
- [Instructor] In our
journey, studying evolution

00:00:02.740 --> 00:00:05.590
and natural selection, we often index on

00:00:05.590 --> 00:00:07.000
individual organisms.

00:00:07.000 --> 00:00:10.430
If we look at a species or
population of a certain species,

00:00:10.430 --> 00:00:13.470
we've talked about how
there could be variation

00:00:13.470 --> 00:00:15.500
in that population, which I will depict

00:00:15.500 --> 00:00:19.280
by these colors and
these shapes over here.

00:00:19.280 --> 00:00:22.410
And sometimes the variation
really doesn't confer

00:00:22.410 --> 00:00:25.710
any advantage or disadvantage
for reproduction,

00:00:25.710 --> 00:00:27.540
but sometimes it might.

00:00:27.540 --> 00:00:29.267
And if a certain variation

00:00:29.267 --> 00:00:31.220
maybe because the environment changed

00:00:31.220 --> 00:00:33.700
or maybe this population finds themselves

00:00:33.700 --> 00:00:36.097
in a new ecosystem confers an advantage,

00:00:36.097 --> 00:00:40.320
well, that variant will be
more likely to multiply.

00:00:40.320 --> 00:00:43.210
And the genes which produce that phenotype

00:00:43.210 --> 00:00:45.520
are more likely to become
a larger and larger

00:00:45.520 --> 00:00:47.080
part of the gene pool.

00:00:47.080 --> 00:00:48.900
Similarly, if there's some disadvantage,

00:00:48.900 --> 00:00:51.990
maybe because the environment
has changed some way,

00:00:51.990 --> 00:00:54.920
well, that might select
out certain variants

00:00:54.920 --> 00:00:57.530
and the underlying genetics that cause it.

00:00:57.530 --> 00:00:59.090
But this is when we're
thinking about traits

00:00:59.090 --> 00:01:02.420
that primarily affect an
individual's chances of survival

00:01:02.420 --> 00:01:03.670
and reproduction.

00:01:03.670 --> 00:01:05.100
But what we're going to do in this video

00:01:05.100 --> 00:01:07.390
as this title implies, is focus on...

00:01:07.390 --> 00:01:09.810
it's not just about individual traits.

00:01:09.810 --> 00:01:12.628
There is also evolution of group behavior,

00:01:12.628 --> 00:01:15.660
and we see that right over
here in a school of fish.

00:01:15.660 --> 00:01:19.300
Why does it make sense
for these fish to ball up

00:01:19.300 --> 00:01:21.140
into this huge school?

00:01:21.140 --> 00:01:22.760
It might seem like it makes it very easy

00:01:22.760 --> 00:01:26.300
for a predator to just go
right into the middle of that

00:01:26.300 --> 00:01:28.930
and open its mouth and
get as much as it wants,

00:01:28.930 --> 00:01:31.440
an all you can eat buffet, so to speak.

00:01:31.440 --> 00:01:34.110
Well, it turns out that
this type of behavior

00:01:34.110 --> 00:01:36.200
does confer a benefit.

00:01:36.200 --> 00:01:39.210
The benefit is yes, this
shark that I just drew

00:01:39.210 --> 00:01:41.820
might be able to get a mouth full of fish,

00:01:41.820 --> 00:01:43.290
but the great majority of the fish

00:01:43.290 --> 00:01:44.730
are going to be protected.

00:01:44.730 --> 00:01:47.190
And by being in a big ball like this,

00:01:47.190 --> 00:01:48.740
instead of just having your own eyes,

00:01:48.740 --> 00:01:49.870
looking for a predator,

00:01:49.870 --> 00:01:52.420
as soon as any one of
these tens of thousands,

00:01:52.420 --> 00:01:55.180
or maybe hundreds of thousands
of fish spot a predator,

00:01:55.180 --> 00:01:56.920
well, the whole school will know it.

00:01:56.920 --> 00:01:59.470
So they're able to share information.

00:01:59.470 --> 00:02:02.850
Also, even though some
fish might get eaten up,

00:02:02.850 --> 00:02:06.240
the probability that any one
will be eaten by this shark

00:02:06.240 --> 00:02:07.810
is actually lower versus

00:02:07.810 --> 00:02:09.510
if there was just one of these fish,

00:02:09.510 --> 00:02:11.060
just swimming by itself,

00:02:11.060 --> 00:02:13.640
that one is much more
likely to be picked off.

00:02:13.640 --> 00:02:15.570
And we see this type of behavior in

00:02:15.570 --> 00:02:17.560
many, many, many types of animals.

00:02:17.560 --> 00:02:19.876
This right over here is
a herd of wildebeest.

00:02:19.876 --> 00:02:22.491
And once again, if you have
an individual wildebeest,

00:02:22.491 --> 00:02:24.750
it would be easy to be surrounded by say,

00:02:24.750 --> 00:02:28.175
hyenas, by predators, that
could be caught by surprise.

00:02:28.175 --> 00:02:31.860
The younger of the wildebeest
would be easy to pick off

00:02:31.860 --> 00:02:33.320
if they were by themselves.

00:02:33.320 --> 00:02:34.430
But if they're in a herd,

00:02:34.430 --> 00:02:36.120
maybe they can be in
the middle of the herd.

00:02:36.120 --> 00:02:39.880
Here's an example of adult
elephants protecting their young

00:02:39.880 --> 00:02:41.680
when they see a threat approaching.

00:02:41.680 --> 00:02:44.040
And notice, more than just the parents

00:02:44.040 --> 00:02:45.480
are protecting the young.

00:02:45.480 --> 00:02:47.870
These elephants are probably
related to each other.

00:02:47.870 --> 00:02:51.130
And so even though one elephant
might sacrifice themselves,

00:02:51.130 --> 00:02:52.890
maybe from some type of a threat,

00:02:52.890 --> 00:02:54.530
if they're able to protect the young,

00:02:54.530 --> 00:02:56.440
even though it might not be their child,

00:02:56.440 --> 00:02:58.660
it might be their nephew,
it might be their cousin,

00:02:58.660 --> 00:03:02.400
their shared genetics are
more likely to be passed on.

00:03:02.400 --> 00:03:04.670
You've sometimes heard
people say things like

00:03:04.670 --> 00:03:07.730
I'd be willing to die for two
brothers or eight cousins.

00:03:07.730 --> 00:03:09.180
And that would actually make sense

00:03:09.180 --> 00:03:11.100
from a genetic point of view,

00:03:11.100 --> 00:03:13.130
but it's not just about protection,

00:03:13.130 --> 00:03:15.190
where we see the evolution
of group behavior.

00:03:15.190 --> 00:03:17.746
We could also see it
in terms of predation.

00:03:17.746 --> 00:03:20.123
So this right over here
as a pack of wolves

00:03:20.123 --> 00:03:23.400
that are attacking this
bison here, and first of all,

00:03:23.400 --> 00:03:25.990
you can see how much more
vulnerable this bison is

00:03:25.990 --> 00:03:28.640
when it's alone than if
it were part of a herd.

00:03:28.640 --> 00:03:29.580
If it was part of a herd,

00:03:29.580 --> 00:03:31.350
it would be much harder to surround it.

00:03:31.350 --> 00:03:33.770
You'd have a ton of these
other bison all around

00:03:33.770 --> 00:03:36.380
that could run and
chase individual wolves.

00:03:36.380 --> 00:03:38.510
But when this bison is
surrounded like this,

00:03:38.510 --> 00:03:40.760
when it's outnumbered,
it is more vulnerable.

00:03:40.760 --> 00:03:41.890
And these wolves, which are

00:03:41.890 --> 00:03:44.570
much, much smaller
individually than this bison

00:03:44.570 --> 00:03:47.190
have a decent chance of taking it down.

00:03:47.190 --> 00:03:49.240
So once again, this group
behavior of these wolves

00:03:49.240 --> 00:03:51.486
to not hunt by themselves,
but to hunt together,

00:03:51.486 --> 00:03:54.420
to surround animals, to
coordinate with each other,

00:03:54.420 --> 00:03:56.650
that allows them to prey on animals

00:03:56.650 --> 00:03:59.160
much, much larger than themselves.

00:03:59.160 --> 00:04:01.240
So I encourage you to
think about this idea

00:04:01.240 --> 00:04:03.110
because it's happening all around us,

00:04:03.110 --> 00:04:05.257
including in human beings.

00:04:05.257 --> 00:04:07.530
We are social animals.

00:04:07.530 --> 00:04:10.250
This is occurring through
out the animal kingdom.

00:04:10.250 --> 00:04:12.400
And it's a really
fascinating thing to observe

00:04:12.400 --> 00:04:13.293
all around you.


Ocean acidification

WEBVTT
Kind: captions
Language: en

00:00:00.400 --> 00:00:01.233
- [Instructor] In this video,

00:00:01.233 --> 00:00:05.670
we're going to talk a little
bit about ocean acidification.

00:00:05.670 --> 00:00:06.970
And as we'll see,

00:00:06.970 --> 00:00:11.270
it's all related to increased
carbon dioxide concentrations

00:00:11.270 --> 00:00:12.520
in the atmosphere.

00:00:12.520 --> 00:00:15.180
And we have talked about
this in other videos,

00:00:15.180 --> 00:00:18.280
but we can see if we look at
carbon dioxide concentrations

00:00:18.280 --> 00:00:21.390
over the last 800,000 years,

00:00:21.390 --> 00:00:24.450
which is well before modern
human beings existed,

00:00:24.450 --> 00:00:28.030
it has oscillated between
roughly 200 parts per million

00:00:28.030 --> 00:00:29.790
and 300 parts per million.

00:00:29.790 --> 00:00:32.280
But then if we look at modern times,

00:00:32.280 --> 00:00:35.150
the spike has gone well beyond that range.

00:00:35.150 --> 00:00:38.450
And this axis right over here,
it's covering so much time.

00:00:38.450 --> 00:00:41.870
It might not be obvious when
or why the spike has happened.

00:00:41.870 --> 00:00:43.570
So let's zoom in a little bit

00:00:43.570 --> 00:00:46.393
on the last several hundred years or so.

00:00:48.620 --> 00:00:49.970
And when you do that,

00:00:49.970 --> 00:00:52.240
this graph is showing us two things.

00:00:52.240 --> 00:00:55.100
In blue, we're seeing the actual emissions

00:00:55.100 --> 00:00:56.570
of carbon dioxide.

00:00:56.570 --> 00:00:58.330
And if we go pre-industrial revolution,

00:00:58.330 --> 00:01:00.750
or the early stages of
the industrial revolution,

00:01:00.750 --> 00:01:03.710
our emissions of carbon
dioxide were very low

00:01:03.710 --> 00:01:04.660
and fairly flat,

00:01:04.660 --> 00:01:07.490
and we have seen that they
have gone up dramatically,

00:01:07.490 --> 00:01:10.290
especially over the last 100 or so years.

00:01:10.290 --> 00:01:12.150
And that carbon dioxide

00:01:12.150 --> 00:01:14.490
doesn't just immediately
leave the atmosphere.

00:01:14.490 --> 00:01:16.520
It stays in the atmosphere for a while.

00:01:16.520 --> 00:01:18.130
So as we increase our emissions,

00:01:18.130 --> 00:01:21.890
the cumulative concentration
of carbon dioxide has gone up

00:01:21.890 --> 00:01:23.840
to those levels that we just saw.

00:01:23.840 --> 00:01:26.400
Before the industrial
revolution, or the early stages,

00:01:26.400 --> 00:01:27.850
we were within that range

00:01:27.850 --> 00:01:30.210
that we saw over the last 800,000 years,

00:01:30.210 --> 00:01:32.210
but then it cumulatively has increased

00:01:32.210 --> 00:01:35.770
so to get us to this place
that is far out of that range.

00:01:35.770 --> 00:01:38.800
And to appreciate what
it's doing to our oceans,

00:01:38.800 --> 00:01:41.680
we just have to recognize that
the carbon dioxide in the air

00:01:41.680 --> 00:01:44.330
is in interaction with the ocean,

00:01:44.330 --> 00:01:46.340
actually with water everywhere.

00:01:46.340 --> 00:01:50.700
So if I were to have some H2O, or water,

00:01:50.700 --> 00:01:53.770
in reaction with carbon dioxide,

00:01:53.770 --> 00:01:56.660
that is going to react, or
it could be in equilibrium,

00:01:56.660 --> 00:02:00.473
to form what is known as
carbonic acid, which is H2CO3.

00:02:02.210 --> 00:02:03.710
If you wanna know how
the bonds are structured,

00:02:03.710 --> 00:02:07.160
it looks like this,

00:02:07.160 --> 00:02:11.560
where each of the oxygens
are attached to a hydrogen.

00:02:11.560 --> 00:02:13.870
And the reason why this
is called carbonic acid,

00:02:13.870 --> 00:02:17.380
is because it can easily
release a hydrogen ion.

00:02:17.380 --> 00:02:21.180
So this can be in
equilibrium with bicarbonate,

00:02:21.180 --> 00:02:24.910
which is HCO3 minus.

00:02:24.910 --> 00:02:28.650
So it's really just our carbonic
acid minus a hydrogen ion,

00:02:28.650 --> 00:02:31.700
plus a hydrogen ion.

00:02:31.700 --> 00:02:34.070
So as you have more
carbon dioxide in the air

00:02:34.070 --> 00:02:36.520
that reacts with water in the ocean,

00:02:36.520 --> 00:02:39.000
well, then you're going
to have more carbonic acid

00:02:39.000 --> 00:02:42.670
and you're going to have
more of your hydrogen ions.

00:02:42.670 --> 00:02:44.730
The reaction is going to go this way

00:02:44.730 --> 00:02:47.180
as you have more of this stuff,

00:02:47.180 --> 00:02:50.220
and especially more of the carbon dioxide.

00:02:50.220 --> 00:02:52.870
And we have observed that
in the oceans themselves.

00:02:52.870 --> 00:02:55.870
We have seen that ocean pH,

00:02:55.870 --> 00:02:58.020
if we go to the early
industrial revolution,

00:02:58.020 --> 00:03:02.250
it was around 8.2 and it has gone to 8.1.

00:03:02.250 --> 00:03:04.170
And you might recognize
that the lower the pH,

00:03:04.170 --> 00:03:06.857
the more acidic it is, but
you also might be saying,

00:03:06.857 --> 00:03:09.460
"Hey, that doesn't look
like that much of a change,"

00:03:09.460 --> 00:03:11.710
but it actually turns
out that pH is measured

00:03:11.710 --> 00:03:13.520
on a logarithmic scale,

00:03:13.520 --> 00:03:15.860
so we're actually talking
about powers of 10.

00:03:15.860 --> 00:03:18.680
So this change, if you really
wanna get into the math,

00:03:18.680 --> 00:03:22.200
pH is the negative log of the
hydrogen ion concentration,

00:03:22.200 --> 00:03:24.470
and so the hydrogen ion concentration

00:03:24.470 --> 00:03:26.680
here relative to there,
if we wanted to compare,

00:03:26.680 --> 00:03:28.260
if we wanted see how much it grew,

00:03:28.260 --> 00:03:32.570
you would say 10 to the
negative 8.1 over 10

00:03:32.570 --> 00:03:34.710
to the negative 8.2.

00:03:34.710 --> 00:03:36.210
And if you look at this analysis,

00:03:36.210 --> 00:03:39.530
you'll see that this
is approximately 1.26,

00:03:39.530 --> 00:03:40.700
or another way of thinking about it,

00:03:40.700 --> 00:03:42.560
over the course of the
industrial revolution,

00:03:42.560 --> 00:03:45.220
because of the trends we
have seen in this graph

00:03:45.220 --> 00:03:49.640
that our oceans are about 26% more acidic.

00:03:49.640 --> 00:03:52.450
And to appreciate why this is a big deal,

00:03:52.450 --> 00:03:56.250
I will remind you that
things like coral reefs

00:03:56.250 --> 00:03:58.600
or shells in sea animals,

00:03:58.600 --> 00:04:02.210
these are formed with calcium carbonate.

00:04:02.210 --> 00:04:04.050
In calcium carbonate,

00:04:04.050 --> 00:04:09.050
you have a positively charged
calcium ion forming ionic bond

00:04:09.690 --> 00:04:14.690
with a carbonate ion, and
carbonate looks like this,

00:04:15.870 --> 00:04:18.810
which looks a awful lot of
what we see right over here

00:04:18.810 --> 00:04:21.630
in the carbonic acid, or the bicarbonate.

00:04:21.630 --> 00:04:23.840
And so if all of a sudden
you have a lot more

00:04:23.840 --> 00:04:27.190
of these hydrogen ions in
the water and dissolved,

00:04:27.190 --> 00:04:28.810
everything's more acidic now,

00:04:28.810 --> 00:04:31.110
it might disrupt this
process of formation.

00:04:31.110 --> 00:04:32.880
Some of this carbonate might go

00:04:32.880 --> 00:04:34.750
and nab some of these hydrogen ions,

00:04:34.750 --> 00:04:37.610
less likely to form an
ionic bond with the calcium.

00:04:37.610 --> 00:04:39.640
It also doesn't just
directly affect things

00:04:39.640 --> 00:04:42.000
like calcium carbonate,
which is everywhere,

00:04:42.000 --> 00:04:43.940
it's actually the main
constituent of pearls.

00:04:43.940 --> 00:04:45.480
It's the structure of so many,

00:04:45.480 --> 00:04:48.550
especially rigid structures
in life, including sea life,

00:04:48.550 --> 00:04:49.970
it's actually also antacid.

00:04:49.970 --> 00:04:52.020
TUMS is mainly calcium carbonate,

00:04:52.020 --> 00:04:53.520
but this acidity in general

00:04:53.520 --> 00:04:56.040
is going to throw all
sorts of organisms off

00:04:56.040 --> 00:04:57.620
of their homeostasis.

00:04:57.620 --> 00:05:01.120
Organisms are highly, highly
sensitive to changes in pH,

00:05:01.120 --> 00:05:02.600
to changes in acidity.

00:05:02.600 --> 00:05:04.530
But the big picture takeaway,

00:05:04.530 --> 00:05:06.900
a lot of talk is about global warming

00:05:06.900 --> 00:05:09.730
and carbon dioxide
concentrations in the air,

00:05:09.730 --> 00:05:12.300
but it's also not only warming the ocean

00:05:12.300 --> 00:05:14.120
because of the greenhouse effect,

00:05:14.120 --> 00:05:16.990
but it's also making
the oceans more acidic,

00:05:16.990 --> 00:05:19.650
which is having some
obvious consequences now,

00:05:19.650 --> 00:05:21.910
and probably some follow on consequences

00:05:21.910 --> 00:05:24.513
that we are just beginning to understand.


Science, technology, and the environment

WEBVTT
Kind: captions
Language: en

00:00:00.290 --> 00:00:02.620
- [Narrator] So I really
like to snack and one

00:00:02.620 --> 00:00:04.200
of my most favorite snacks

00:00:04.200 --> 00:00:06.760
of all time happens to be bananas.

00:00:06.760 --> 00:00:08.930
I mean, you can have them in a smoothie,

00:00:08.930 --> 00:00:13.390
with some peanut butter, on
some toast, in any way, really.

00:00:13.390 --> 00:00:15.050
And usually like most people,

00:00:15.050 --> 00:00:17.740
I just throw away the peels
after I'm done eating,

00:00:17.740 --> 00:00:19.680
but did you know that banana peels

00:00:19.680 --> 00:00:22.810
and leaves can be used to
make all kinds of things now?

00:00:22.810 --> 00:00:25.580
In fact, since over 100 billion bananas

00:00:25.580 --> 00:00:28.030
are consumed annually around the world,

00:00:28.030 --> 00:00:30.050
scientists have developed technologies

00:00:30.050 --> 00:00:32.100
that convert banana peels and leaves

00:00:32.100 --> 00:00:35.860
into useful materials that
are also bio-degradable.

00:00:35.860 --> 00:00:39.010
For example, bananas can
be used to make shoe soles,

00:00:39.010 --> 00:00:40.980
which is truly mind blowing.

00:00:40.980 --> 00:00:44.400
So a designer named Sarah
Harbarth used banana peel waste

00:00:44.400 --> 00:00:49.180
to create a durable material
called Kouri, K-U-O-R-I,

00:00:49.180 --> 00:00:52.510
which is used for everything
from glasses, to belts,

00:00:52.510 --> 00:00:56.020
and even phone cases and shoe soles.

00:00:56.020 --> 00:00:58.680
Banana leaves are also
used for making things

00:00:58.680 --> 00:01:01.840
like disposable tableware or containers.

00:01:01.840 --> 00:01:05.890
So in 2010, a young inventor
named Tenith Adithyaa saw

00:01:05.890 --> 00:01:07.800
how banana leaves were going to waste

00:01:07.800 --> 00:01:11.100
and developed a technology that
would preserve banana leaves

00:01:11.100 --> 00:01:13.040
for up to three years.

00:01:13.040 --> 00:01:14.500
And these could also be used

00:01:14.500 --> 00:01:17.130
to create biodegradable containers.

00:01:17.130 --> 00:01:19.200
So you're probably
wondering why I'm rambling

00:01:19.200 --> 00:01:20.880
so much about bananas

00:01:20.880 --> 00:01:23.020
and as much as I love them as a snack,

00:01:23.020 --> 00:01:25.560
I personally think that
it's even more awesome

00:01:25.560 --> 00:01:27.040
that scientists and engineers

00:01:27.040 --> 00:01:31.010
are creating useful, biodegradable
materials out of them.

00:01:31.010 --> 00:01:33.480
Technologies like Sarah and Tenith's

00:01:33.480 --> 00:01:36.450
that help reduce plastic
waste are super great

00:01:36.450 --> 00:01:38.730
for our planet and its biodiversity

00:01:38.730 --> 00:01:41.270
because they prevent
more plastic microfibers

00:01:41.270 --> 00:01:43.070
from polluting our environment.

00:01:43.070 --> 00:01:44.730
And that's the great news.

00:01:44.730 --> 00:01:46.510
With science and engineering,

00:01:46.510 --> 00:01:48.930
we humans can create technologies

00:01:48.930 --> 00:01:51.430
that prevent ecosystem degradation,

00:01:51.430 --> 00:01:55.700
reduce pollution and
improve sustainability.

00:01:55.700 --> 00:01:57.230
So let's take a look at a couple

00:01:57.230 --> 00:01:59.200
of other really cool examples.

00:01:59.200 --> 00:02:02.590
Since I live in the sunny all
year long state of Arizona,

00:02:02.590 --> 00:02:05.370
it's not uncommon to
see residents making use

00:02:05.370 --> 00:02:07.520
of solar panels here.

00:02:07.520 --> 00:02:10.840
So this kind of technology
was created to allow photons,

00:02:10.840 --> 00:02:14.810
or light particles, to
generate a flow of electricity.

00:02:14.810 --> 00:02:17.440
And since it harnesses
energy from the sun,

00:02:17.440 --> 00:02:21.400
this kind of electricity doesn't
require using fossil fuels.

00:02:21.400 --> 00:02:23.840
So this means that solar panels help limit

00:02:23.840 --> 00:02:26.690
greenhouse gas emissions, which contribute

00:02:26.690 --> 00:02:28.740
to global warming and pose a threat

00:02:28.740 --> 00:02:32.360
to the biodiversity
present on earth right now.

00:02:32.360 --> 00:02:35.880
And even cooler for people
who want a more sleek option

00:02:35.880 --> 00:02:38.480
to use for their homes,
we now have this thing

00:02:38.480 --> 00:02:40.760
called solar roof tiles.

00:02:40.760 --> 00:02:43.910
So these are roof tiles
that generate solar energy

00:02:43.910 --> 00:02:45.520
and isn't that so cool?

00:02:45.520 --> 00:02:48.970
Well technologies like this
will only continue improving,

00:02:48.970 --> 00:02:51.140
which will help us combat climate change

00:02:51.140 --> 00:02:53.810
and preserve biodiversity.

00:02:53.810 --> 00:02:56.140
Now, if we drive westwards from Arizona

00:02:56.140 --> 00:02:58.550
to California, the chances are you'll spot

00:02:58.550 --> 00:03:01.550
these huge white
windmills lining the Hills

00:03:01.550 --> 00:03:04.830
and windmills are another
source of clean energy.

00:03:04.830 --> 00:03:07.030
They are designed to harness wind

00:03:07.030 --> 00:03:08.970
and convert it to electricity.

00:03:08.970 --> 00:03:12.640
So windmills function in a
similar way to solar panels.

00:03:12.640 --> 00:03:14.570
thanks to the people who designed them,

00:03:14.570 --> 00:03:17.630
we have another alternative
to fossil fuels,

00:03:17.630 --> 00:03:19.813
which is super great for our planet.

00:03:20.750 --> 00:03:23.070
And I could go on and on about all

00:03:23.070 --> 00:03:25.670
of the amazing new technology
that's being created

00:03:25.670 --> 00:03:27.200
to protect the environment.

00:03:27.200 --> 00:03:29.810
Even now people are developing things

00:03:29.810 --> 00:03:34.810
like eco-friendly vehicles,
buildings, household devices,

00:03:35.080 --> 00:03:36.840
even waste management systems.

00:03:36.840 --> 00:03:38.750
And as you can probably tell from all

00:03:38.750 --> 00:03:40.410
of these unique technologies,

00:03:40.410 --> 00:03:42.710
scientists and engineers
have already found

00:03:42.710 --> 00:03:44.880
many different solutions to try

00:03:44.880 --> 00:03:47.310
and address environmental issues.

00:03:47.310 --> 00:03:48.947
But we also have to ask,

00:03:48.947 --> 00:03:52.470
"Are there any drawbacks to all
of these new contributions?"

00:03:52.470 --> 00:03:55.520
Well, there are some cons
that we have to consider.

00:03:55.520 --> 00:03:58.070
For instance, since these
environmental friendly

00:03:58.070 --> 00:04:01.650
technologies, or green
technologies are still

00:04:01.650 --> 00:04:04.100
relatively new ideas, we have to do a lot

00:04:04.100 --> 00:04:05.880
of research on them to make sure that

00:04:05.880 --> 00:04:08.730
the technology can make
a significant impact

00:04:08.730 --> 00:04:11.070
and succeed, and that we minimize

00:04:11.070 --> 00:04:14.950
the environmental impacts that
these technologies can have.

00:04:14.950 --> 00:04:18.740
So for example, solar panels
can take up a lot of space

00:04:18.740 --> 00:04:20.900
and impact sensitive habitats.

00:04:20.900 --> 00:04:24.870
So we need to research ways
to mitigate these effects.

00:04:24.870 --> 00:04:26.910
So this requires large amounts of money

00:04:26.910 --> 00:04:28.440
to be spent on researching

00:04:28.440 --> 00:04:30.310
and developing these technologies,

00:04:30.310 --> 00:04:32.770
which means that companies
may be less willing to switch

00:04:32.770 --> 00:04:35.400
and pay so much for green alternatives.

00:04:35.400 --> 00:04:38.110
And the high implementation
costs also means

00:04:38.110 --> 00:04:40.290
that at first consumers like you

00:04:40.290 --> 00:04:42.630
and me will probably
have to pay higher prices

00:04:42.630 --> 00:04:44.200
for these technologies compared

00:04:44.200 --> 00:04:45.960
to traditional products.

00:04:45.960 --> 00:04:48.570
Going back to our
discussion on solar panels,

00:04:48.570 --> 00:04:50.220
the drawback to installing panels

00:04:50.220 --> 00:04:52.900
at home is usually a higher price.

00:04:52.900 --> 00:04:55.760
So even though solar panels
would save homeowners money

00:04:55.760 --> 00:04:58.380
in the long run on electricity,

00:04:58.380 --> 00:05:00.130
some consumers might not be willing

00:05:00.130 --> 00:05:03.320
or able to pay for the
higher initial price.

00:05:03.320 --> 00:05:05.640
And last but not least,
some people who work

00:05:05.640 --> 00:05:07.740
in conventional industries may go out

00:05:07.740 --> 00:05:09.840
of business or lose their jobs.

00:05:09.840 --> 00:05:12.140
So in order for the world to go greener,

00:05:12.140 --> 00:05:14.530
we have to figure out ways
to protect these workers

00:05:14.530 --> 00:05:16.550
and businesses as well.

00:05:16.550 --> 00:05:18.870
So clearly there are many
challenges that we have

00:05:18.870 --> 00:05:21.270
to address if we want
to implement technology

00:05:21.270 --> 00:05:23.100
that's better for the environment,

00:05:23.100 --> 00:05:26.120
but there's plenty of pros
to, seeing how scientists

00:05:26.120 --> 00:05:29.500
and engineers can do so
much for the environment.

00:05:29.500 --> 00:05:31.340
With science and
engineering we can come up

00:05:31.340 --> 00:05:35.680
with methods to save
energy, reduce pollution,

00:05:35.680 --> 00:05:38.740
conserve our planet's precious resources,

00:05:38.740 --> 00:05:40.370
even feed more people

00:05:40.370 --> 00:05:42.170
and also create new business

00:05:42.170 --> 00:05:44.720
opportunities and jobs for people.

00:05:44.720 --> 00:05:45.800
And that's the great thing.

00:05:45.800 --> 00:05:48.170
Scientists and engineers and thinkers

00:05:48.170 --> 00:05:50.270
around the world can use our existing pool

00:05:50.270 --> 00:05:54.430
of knowledge to address some
of the biggest issues of today.

00:05:54.430 --> 00:05:56.900
So to wrap up this video, today we learned

00:05:56.900 --> 00:05:59.380
that scientists and
engineers can find solutions

00:05:59.380 --> 00:06:01.790
to preserve the environment and make way

00:06:01.790 --> 00:06:03.600
for a better future.

00:06:03.600 --> 00:06:05.540
So the next time you have a banana,

00:06:05.540 --> 00:06:08.700
or any fruit for that
matter, spot solar panels

00:06:08.700 --> 00:06:10.520
or a drive by some windmills,

00:06:10.520 --> 00:06:12.200
I hope you can reflect on the fact

00:06:12.200 --> 00:06:15.610
that these green
innovations start as ideas.

00:06:15.610 --> 00:06:18.200
So if you ever have an
idea for a technology

00:06:18.200 --> 00:06:20.210
that you think can help our environment,

00:06:20.210 --> 00:06:21.530
you should write it down.

00:06:21.530 --> 00:06:23.763
It just might be useful one day.


Solid waste disposal

WEBVTT
Kind: captions
Language: en

00:00:00.760 --> 00:00:03.180
- [Narrator] Time for a little trash talk,

00:00:03.180 --> 00:00:06.640
the United States produces
more solid waste each year,

00:00:06.640 --> 00:00:11.160
than any other nation and as
we make more and more trash,

00:00:11.160 --> 00:00:13.580
we're running out of places to put it,

00:00:13.580 --> 00:00:16.380
there are two main types of solid waste,

00:00:16.380 --> 00:00:20.830
industrial solid waste
and municipal solid waste.

00:00:20.830 --> 00:00:23.540
Industrial solid waste
comes from industries,

00:00:23.540 --> 00:00:27.980
like factories, mines and farms,

00:00:27.980 --> 00:00:31.140
municipal waste on the
other hand comes from homes

00:00:31.140 --> 00:00:33.350
and workplaces like offices,

00:00:33.350 --> 00:00:35.880
it's basically the stuff
you'd put in your trash can

00:00:35.880 --> 00:00:40.770
or dumpster like paper, plastic
bags, cardboard, food waste,

00:00:40.770 --> 00:00:43.910
cans, bottles and yard waste.

00:00:43.910 --> 00:00:46.740
Suppose you're on a
picnic with your friends,

00:00:46.740 --> 00:00:49.300
being an AP Environmental
Science student and all,

00:00:49.300 --> 00:00:52.030
you brought reusable utensils,

00:00:52.030 --> 00:00:55.650
you see an old empty potato
chip bag on the ground,

00:00:55.650 --> 00:00:58.140
you're able to identify
it as a fine specimen

00:00:58.140 --> 00:01:00.280
of municipal solid waste,

00:01:00.280 --> 00:01:03.180
you decide to pick it up
and put it in the trash

00:01:03.180 --> 00:01:06.270
but now that it's in the
trash where will it go?

00:01:06.270 --> 00:01:09.210
Most likely it'll end up in a landfill,

00:01:09.210 --> 00:01:10.350
just like more than half

00:01:10.350 --> 00:01:12.980
of the United States
municipal solid waste,

00:01:12.980 --> 00:01:17.100
to store so much waste
landfills have to be really big,

00:01:17.100 --> 00:01:19.950
one kind of landfill is an open dump,

00:01:19.950 --> 00:01:23.740
which is a large field
or pit filled with trash

00:01:23.740 --> 00:01:26.350
and let's think about
the pros of an open dump

00:01:26.350 --> 00:01:28.620
for one thing they're really big,

00:01:28.620 --> 00:01:32.240
so, they allow a lot of people
to get rid of a lot of waste,

00:01:32.240 --> 00:01:34.210
this is why they're often
used near big cities

00:01:34.210 --> 00:01:36.160
with large populations,

00:01:36.160 --> 00:01:38.970
they're also pretty
inexpensive to maintain

00:01:38.970 --> 00:01:41.330
and they do a great job at keeping waste,

00:01:41.330 --> 00:01:44.190
away from people's homes and workplaces

00:01:44.190 --> 00:01:46.850
but if we take a closer
look at open dumps,

00:01:46.850 --> 00:01:49.980
we can see that there are
some potential problems too,

00:01:49.980 --> 00:01:52.870
first off open dumps can be smelly,

00:01:52.870 --> 00:01:54.440
which could be unpleasant for the people,

00:01:54.440 --> 00:01:55.920
who live around them

00:01:55.920 --> 00:01:59.840
because open dumps are
uncovered and uncompacted,

00:01:59.840 --> 00:02:02.340
the wildlife and the weather
could spread the waste,

00:02:02.340 --> 00:02:04.310
into the surrounding environment.

00:02:04.310 --> 00:02:07.820
The trash in open dumps
can emit dangerous gases

00:02:07.820 --> 00:02:09.853
and even catch on fire,

00:02:11.220 --> 00:02:14.160
so, we can add gases and
fires to our list of cons

00:02:14.160 --> 00:02:17.350
because these could be
dangerous to wildlife.

00:02:17.350 --> 00:02:20.480
Another problem happens when it rains,

00:02:20.480 --> 00:02:24.400
the water seeps into the
landfill and as it goes through,

00:02:24.400 --> 00:02:27.360
it gets contaminated with toxic materials,

00:02:27.360 --> 00:02:29.470
like heavy metals from electronics

00:02:29.470 --> 00:02:32.740
or waste from discarded
prescription drugs,

00:02:32.740 --> 00:02:35.420
this contaminated water
that comes out of landfill

00:02:35.420 --> 00:02:39.130
is called leachate and
when you think about it,

00:02:39.130 --> 00:02:42.830
the word leachate makes sense
because the root word leach,

00:02:42.830 --> 00:02:44.350
means that this water absorbs

00:02:44.350 --> 00:02:47.860
and carries some of the
dissolved waste material with it

00:02:47.860 --> 00:02:49.630
and leachate can be dangerous

00:02:49.630 --> 00:02:51.560
because it can seep into the soil

00:02:51.560 --> 00:02:52.810
and contaminate groundwater,

00:02:52.810 --> 00:02:54.750
that people rely on for drinking,

00:02:54.750 --> 00:02:58.310
so, this can make the water
supply toxic to humans.

00:02:58.310 --> 00:03:00.190
Another problem with open dumps

00:03:00.190 --> 00:03:02.330
is that they require a lot of land,

00:03:02.330 --> 00:03:04.483
which means they cause
habitat destruction.

00:03:07.640 --> 00:03:10.490
Another kind of landfill
is a sanitary landfill

00:03:11.530 --> 00:03:12.550
and you may be thinking,

00:03:12.550 --> 00:03:16.440
how can a landfill, a
pit of trash be sanitary?

00:03:16.440 --> 00:03:17.880
Well, sanitary landfills,

00:03:17.880 --> 00:03:21.100
have something that open
dumps don't a liner,

00:03:21.100 --> 00:03:25.560
which is a layer of clay or
plastic that keeps the trash in

00:03:25.560 --> 00:03:28.890
and every day when trash
is put in the landfill,

00:03:28.890 --> 00:03:31.240
it's covered by a layer
of construction debris

00:03:31.240 --> 00:03:34.920
or low quality soil and then
it's compacted into a cell

00:03:35.880 --> 00:03:37.253
and the process repeats.

00:03:38.290 --> 00:03:40.910
With all of it's tightly
sealed and compacted cells,

00:03:40.910 --> 00:03:43.570
it's very hard for water
to get into the landfill,

00:03:43.570 --> 00:03:46.070
so, sanitary landfills keep
the environment inside,

00:03:46.070 --> 00:03:48.750
really dry but over time,

00:03:48.750 --> 00:03:51.260
rainwater will eventually
infiltrate the layers

00:03:51.260 --> 00:03:52.720
and form leachate,

00:03:52.720 --> 00:03:55.970
the tightly sealed cells
prevent water from leaving too,

00:03:55.970 --> 00:03:58.960
so, leachate can build
up inside the landfill,

00:03:58.960 --> 00:04:01.740
some sanitary landfills are
built with double liners

00:04:01.740 --> 00:04:05.720
and pipes so that leachate
can be stored and treated.

00:04:05.720 --> 00:04:08.130
If you went inside a sanitary landfill,

00:04:08.130 --> 00:04:10.100
you wouldn't be able to breathe

00:04:10.100 --> 00:04:12.370
and not because it would be super smelly,

00:04:12.370 --> 00:04:15.190
this is because the cells
are sealed up so tightly,

00:04:15.190 --> 00:04:17.960
that it's hard for oxygen
to get in and circulate,

00:04:17.960 --> 00:04:21.440
the environment inside
is mostly anaerobic,

00:04:21.440 --> 00:04:23.830
which means that there is little oxygen,

00:04:23.830 --> 00:04:26.900
you see the prefix an means not or without

00:04:26.900 --> 00:04:30.810
and the word aerobic means
involving or requiring oxygen,

00:04:30.810 --> 00:04:34.023
so, the word anaerobic describes
a place without oxygen.

00:04:34.960 --> 00:04:38.370
So, aerobic decomposition
which is a process of decay,

00:04:38.370 --> 00:04:41.040
that takes place in aerobic environments

00:04:41.040 --> 00:04:44.660
and involves microorganisms
that need oxygen to survive,

00:04:44.660 --> 00:04:48.990
can't occur instead
anaerobic decomposition,

00:04:48.990 --> 00:04:50.770
which is decay by microorganisms,

00:04:50.770 --> 00:04:54.070
that don't need oxygen takes place,

00:04:54.070 --> 00:04:57.220
this process produces
methane, a greenhouse gas,

00:04:57.220 --> 00:04:59.440
that contributes to global warming,

00:04:59.440 --> 00:05:02.960
it could take several decades
or even hundreds of years

00:05:02.960 --> 00:05:04.370
for the tightly compacted waste

00:05:04.370 --> 00:05:06.580
in a sanitary landfill to decompose,

00:05:06.580 --> 00:05:08.610
so, this type of landfill can contribute,

00:05:08.610 --> 00:05:10.673
to global warming for a long time.

00:05:11.710 --> 00:05:15.580
So, what are the pros and
cons of sanitary landfills?

00:05:15.580 --> 00:05:19.950
Compared with open dumps sanitary
landfills are less smelly

00:05:19.950 --> 00:05:22.510
and less likely to catch on fire

00:05:22.510 --> 00:05:25.370
and because sanitary landfills
keep the waste inside,

00:05:25.370 --> 00:05:28.630
covered and compacted we
don't have the same problem

00:05:28.630 --> 00:05:31.640
of the wildlife and the
weather moving around the waste

00:05:31.640 --> 00:05:34.490
but no landfill is perfectly sealed,

00:05:34.490 --> 00:05:37.580
so, leachate can still seep out,

00:05:37.580 --> 00:05:42.010
adding and compacting layers
of trash causes dust and noise,

00:05:42.010 --> 00:05:44.420
also remember that the
anaerobic decomposition

00:05:44.420 --> 00:05:48.140
in sanitary landfills produces
methane, a greenhouse gas

00:05:48.140 --> 00:05:50.900
but some sanitary landfills
capture the methane,

00:05:50.900 --> 00:05:52.330
emitted by the decomposition,

00:05:52.330 --> 00:05:54.840
so, that it can be burned
to generate electricity,

00:05:54.840 --> 00:05:56.980
this can capture 60% to 90%

00:05:56.980 --> 00:05:59.030
of the methane produced by the landfill,

00:05:59.030 --> 00:06:01.150
so, that methane capture could be a pro

00:06:01.150 --> 00:06:03.960
because it generates electricity.

00:06:03.960 --> 00:06:07.780
Sanitary landfills are really expensive,

00:06:07.780 --> 00:06:09.210
so, they are a lot more common

00:06:09.210 --> 00:06:11.810
in more economically developed countries

00:06:11.810 --> 00:06:16.210
and like open dumps they
require a lot of land.

00:06:16.210 --> 00:06:18.270
One way to reduce the amount of material,

00:06:18.270 --> 00:06:19.830
that needs to be landfilled

00:06:19.830 --> 00:06:22.170
is by burning it in an incinerator,

00:06:22.170 --> 00:06:24.170
this reduction in the volume of the waste

00:06:24.170 --> 00:06:27.410
is really helpful in areas
with limited land space,

00:06:27.410 --> 00:06:29.530
so, reducing the volume of trash

00:06:29.530 --> 00:06:31.660
is one of incineration's pros,

00:06:31.660 --> 00:06:34.700
modern high-tech waste
to energy incinerators,

00:06:34.700 --> 00:06:37.690
have another pro they
can produce electricity

00:06:37.690 --> 00:06:39.800
and sell it to consumers,

00:06:39.800 --> 00:06:41.770
some of the cons of burning trash,

00:06:41.770 --> 00:06:46.020
are that it emits CO2,
ash waste, hazardous gases

00:06:46.020 --> 00:06:47.970
and other air pollutants.

00:06:47.970 --> 00:06:50.730
Incinerators could be built to
help reduce these emissions,

00:06:50.730 --> 00:06:52.980
by using a series of filters,

00:06:52.980 --> 00:06:56.880
to remove mercury and dioxins
from the exhaust gases.

00:06:56.880 --> 00:06:59.330
Another way to lessen the
danger of burning trash

00:06:59.330 --> 00:07:01.540
is by sorting out the hazardous materials,

00:07:01.540 --> 00:07:04.890
before the incineration
but these safety features,

00:07:04.890 --> 00:07:06.550
like the filters and the sorting,

00:07:06.550 --> 00:07:09.273
make waste incineration
much more expensive.

00:07:10.340 --> 00:07:12.800
Despite all these ways
of getting rid of waste,

00:07:12.800 --> 00:07:15.600
we're still having trouble
finding places to put it,

00:07:15.600 --> 00:07:17.570
the landfill near my home filled up,

00:07:17.570 --> 00:07:19.890
so, my county transfers its waste,

00:07:19.890 --> 00:07:22.490
to a sanitary landfill
in a neighboring state

00:07:22.490 --> 00:07:25.280
and this transportation burns fossil fuels

00:07:25.280 --> 00:07:27.173
and produces greenhouse gases.

00:07:28.450 --> 00:07:30.170
But what can we do with the landfills,

00:07:30.170 --> 00:07:31.780
that are already filled up?

00:07:31.780 --> 00:07:34.780
Some old landfills are
mined for valuable metals

00:07:34.780 --> 00:07:36.720
and recyclable materials,

00:07:36.720 --> 00:07:39.580
my home state of Virginia,
turned an old closed landfill

00:07:39.580 --> 00:07:41.840
in Virginia Beach into a public park,

00:07:41.840 --> 00:07:44.460
called Mount Trashmore park,

00:07:44.460 --> 00:07:48.350
it's actually one of the most
popular parks in the area,

00:07:48.350 --> 00:07:51.100
so if you ever feel like
picnicking on a landfill,

00:07:51.100 --> 00:07:52.550
that might be the one to try.


Extinction

WEBVTT
Kind: captions
Language: en

00:00:01.035 --> 00:00:03.200
- [Instructor] When we think
of the term extinction,

00:00:03.200 --> 00:00:05.950
we tend to think of
events like what happened,

00:00:05.950 --> 00:00:09.020
what we believe happened
63 million years ago

00:00:09.020 --> 00:00:11.430
when a large meteor hit the earth

00:00:11.430 --> 00:00:14.260
and killed most of the dinosaurs.

00:00:14.260 --> 00:00:15.580
And I say most of them,

00:00:15.580 --> 00:00:17.510
because a lot of animals
that we know today

00:00:17.510 --> 00:00:19.550
especially birds, birds like chickens,

00:00:19.550 --> 00:00:20.990
we believe are actually descended

00:00:20.990 --> 00:00:24.050
from some of the dinosaurs that survived.

00:00:24.050 --> 00:00:26.300
And other species not just dinosaurs

00:00:26.300 --> 00:00:27.490
would have gone extinct,

00:00:27.490 --> 00:00:30.140
but clearly some other
species did survive.

00:00:30.140 --> 00:00:31.740
Our ancestors might've been

00:00:31.740 --> 00:00:34.650
some type of burrowing
squirrel rodent like thing

00:00:34.650 --> 00:00:36.190
that maybe was under the ground

00:00:36.190 --> 00:00:38.990
and was able to survive
the immediate shocks

00:00:38.990 --> 00:00:40.680
and then somehow find food

00:00:40.680 --> 00:00:43.020
even when the earth was covered by dust

00:00:43.020 --> 00:00:44.960
and there wasn't a lot of
photosynthesis going on,

00:00:44.960 --> 00:00:47.770
but they were able to survive somehow.

00:00:47.770 --> 00:00:49.870
What we're gonna do in this
video though is think about

00:00:49.870 --> 00:00:52.200
more subtle notion of extinction.

00:00:52.200 --> 00:00:53.580
It's not always caused

00:00:53.580 --> 00:00:56.530
by these massive changes
in the environment.

00:00:56.530 --> 00:00:58.040
But one thread,

00:00:58.040 --> 00:01:00.960
one theme that we will be
talking about in extinction

00:01:00.960 --> 00:01:04.430
is that the environment is to
some degree always changing.

00:01:04.430 --> 00:01:07.580
And when there is
variation in a population,

00:01:07.580 --> 00:01:09.600
so I'm gonna draw some variation as I do

00:01:09.600 --> 00:01:12.170
with the different colored circles.

00:01:12.170 --> 00:01:14.820
If the environment changes gradually

00:01:14.820 --> 00:01:16.820
or in certain slow ways,

00:01:16.820 --> 00:01:20.750
there will oftentimes be variants,
members of the population

00:01:20.750 --> 00:01:23.350
that will be more likely
to succeed than others.

00:01:23.350 --> 00:01:26.050
And so those variants
that are more suitable

00:01:26.050 --> 00:01:28.000
for those changes in the environment,

00:01:28.000 --> 00:01:30.810
well, they will reproduce
more, they will survive more.

00:01:30.810 --> 00:01:32.330
They will become the dominant variant

00:01:32.330 --> 00:01:36.330
and over time they can
even become a new species.

00:01:36.330 --> 00:01:39.420
And so over time you have
species won't go extinct,

00:01:39.420 --> 00:01:41.620
but they would be adapting
or maybe even evolving

00:01:41.620 --> 00:01:45.510
into other species that are
more suited to the environment.

00:01:45.510 --> 00:01:47.850
But our meteorite dinosaur example

00:01:47.850 --> 00:01:50.790
shows us that change is
not always a gradual.

00:01:50.790 --> 00:01:54.140
And clearly in a situation
where the sky is burning

00:01:54.140 --> 00:01:56.010
as you have in the dinosaur example,

00:01:56.010 --> 00:01:58.110
very few organisms we're
gonna be able to adapt

00:01:58.110 --> 00:02:00.420
to those types of circumstances.

00:02:00.420 --> 00:02:02.120
But you can also have fast change

00:02:02.120 --> 00:02:05.790
that might not seem so
fast to us as human beings.

00:02:05.790 --> 00:02:08.420
For example, this chart right over here

00:02:08.420 --> 00:02:11.110
shows extinctions since 1500.

00:02:11.110 --> 00:02:12.290
And I encourage you to pause this video

00:02:12.290 --> 00:02:14.680
and make sure you're processing
what is going on here,

00:02:14.680 --> 00:02:16.570
because that's a skill in and of itself,

00:02:16.570 --> 00:02:18.000
but it's really interesting.

00:02:18.000 --> 00:02:19.980
This tells us the cumulative percentage

00:02:19.980 --> 00:02:24.600
of species driven extinct
over the last 500 years or so.

00:02:24.600 --> 00:02:25.450
And so you can see

00:02:25.450 --> 00:02:28.520
relative to the species
that were there in 1500,

00:02:28.520 --> 00:02:31.610
if we follow let's say
the line for amphibians,

00:02:31.610 --> 00:02:35.440
amphibians it looks like
someplace between 2% and 2 1/2%

00:02:35.440 --> 00:02:38.350
of all species of amphibians
have gone extinct.

00:02:38.350 --> 00:02:41.670
This is not saying 2% to 2 1/2%
of the amphibians have died.

00:02:41.670 --> 00:02:44.130
This is saying the species of amphibians,

00:02:44.130 --> 00:02:45.720
they don't exist anymore.

00:02:45.720 --> 00:02:48.490
That variant of amphibian genotypes

00:02:48.490 --> 00:02:51.310
don't exist in our world anymore.

00:02:51.310 --> 00:02:52.970
And it's pretty bad for amphibians

00:02:52.970 --> 00:02:54.370
but we can see it's pretty bad

00:02:54.370 --> 00:02:56.670
for other types of animals as well.

00:02:56.670 --> 00:02:57.503
And you might say,

00:02:57.503 --> 00:03:00.500
well, this isn't so bad, 2% to 2 1/2%.

00:03:00.500 --> 00:03:01.430
But once again,

00:03:01.430 --> 00:03:04.640
these are entire species
that we will never see again

00:03:04.640 --> 00:03:06.300
and what's also troubling

00:03:06.300 --> 00:03:09.430
is how these curves are
just rocketing upwards.

00:03:09.430 --> 00:03:10.590
And some of you all might be thinking,

00:03:10.590 --> 00:03:13.240
isn't there always some
baseline level of extinction?

00:03:13.240 --> 00:03:15.690
Maybe this isn't so much
worse than that baseline.

00:03:15.690 --> 00:03:18.170
And what's interesting
about this graphic here is

00:03:18.170 --> 00:03:19.890
it shows us the baseline.

00:03:19.890 --> 00:03:21.400
This little gray square they're saying

00:03:21.400 --> 00:03:23.690
that's the cumulative
percentage of species

00:03:23.690 --> 00:03:28.340
based on background rate
of 0.1 to 2 extinctions

00:03:28.340 --> 00:03:31.210
per million species per year.

00:03:31.210 --> 00:03:33.900
And so you see the baseline
in this little gray

00:03:33.900 --> 00:03:35.030
right down here.

00:03:35.030 --> 00:03:37.960
If we didn't have unusual
amounts of extinction,

00:03:37.960 --> 00:03:41.090
we would just be charting
roughly close to this line.

00:03:41.090 --> 00:03:44.430
But you can see since 1500,
we have gone well above it

00:03:44.430 --> 00:03:46.440
and we know why this is happening.

00:03:46.440 --> 00:03:49.650
Their environments are
changing very, very quickly.

00:03:49.650 --> 00:03:51.530
And who is the main culprit here

00:03:51.530 --> 00:03:54.500
of changing the environment
very, very quickly?

00:03:54.500 --> 00:03:57.980
Well, what group's population
has really expanded

00:03:57.980 --> 00:04:00.140
over the last 500 years?

00:04:00.140 --> 00:04:03.580
And you would of course say human beings.

00:04:03.580 --> 00:04:05.790
And human beings, it's
not just where they live

00:04:05.790 --> 00:04:07.180
and they're taking habitats away,

00:04:07.180 --> 00:04:10.130
you can imagine this
environment is very different

00:04:10.130 --> 00:04:12.900
than the environment of
what modern day Los Angeles

00:04:12.900 --> 00:04:15.700
would have been say 500 years ago.

00:04:15.700 --> 00:04:17.720
And it's not just where we live,

00:04:17.720 --> 00:04:20.370
it's also the food we
need and we do need food.

00:04:20.370 --> 00:04:22.750
But that takes up ecosystems environments

00:04:22.750 --> 00:04:24.790
where other animals might have lived

00:04:24.790 --> 00:04:25.960
and it could be a dramatic change

00:04:25.960 --> 00:04:28.390
where they can't live anymore.

00:04:28.390 --> 00:04:30.920
And so human land and
agricultural land use

00:04:30.920 --> 00:04:33.330
is a major source of extinctions.

00:04:33.330 --> 00:04:34.630
But on top of that,

00:04:34.630 --> 00:04:37.930
we go into the sea and we
sometimes will over fish.

00:04:37.930 --> 00:04:40.520
That can be a source of extinction.

00:04:40.520 --> 00:04:42.020
Lack of diversity.

00:04:42.020 --> 00:04:45.060
As more and more species
learn to live with humans

00:04:45.060 --> 00:04:47.123
and maybe our lack of diversity,

00:04:47.960 --> 00:04:49.530
we only have a few types of crops,

00:04:49.530 --> 00:04:51.500
a few types of cattle that we grow.

00:04:51.500 --> 00:04:53.480
There might be certain species
that live well with them

00:04:53.480 --> 00:04:55.320
that are able to live off of them,

00:04:55.320 --> 00:04:56.870
but they might not have as much variation

00:04:56.870 --> 00:04:59.390
because the ecosystem is so not diverse

00:04:59.390 --> 00:05:00.810
and so there's some change,

00:05:00.810 --> 00:05:04.660
the species won't have the
variation necessarily to survive.

00:05:04.660 --> 00:05:07.320
On top of that, you throw
in things like pollution,

00:05:07.320 --> 00:05:09.710
global warming, invasive species,

00:05:09.710 --> 00:05:12.320
and you can see why
these curves are going up

00:05:12.320 --> 00:05:14.660
in a very, very, very troubling way.

00:05:14.660 --> 00:05:15.493
And I will add,

00:05:15.493 --> 00:05:17.640
this isn't just for us
to care about animals,

00:05:17.640 --> 00:05:18.980
although that is a good motivation

00:05:18.980 --> 00:05:20.190
for us to care about the species,

00:05:20.190 --> 00:05:21.970
because once a species has gone,

00:05:21.970 --> 00:05:23.840
you're never going to get it back again.

00:05:23.840 --> 00:05:25.290
But in general,

00:05:25.290 --> 00:05:28.050
the less diversity that
earth as a whole has,

00:05:28.050 --> 00:05:30.130
it means that our ecosystems
are going to become

00:05:30.130 --> 00:05:32.663
less and less robust to change.


Species and the environment

WEBVTT
Kind: captions
Language: en

00:00:00.170 --> 00:00:01.960
- [Instructor] So we
tend to view evolution

00:00:01.960 --> 00:00:05.530
and natural selection and
the formation of new species,

00:00:05.530 --> 00:00:07.550
which is often called speciation,

00:00:07.550 --> 00:00:10.260
as a slow process that could take

00:00:10.260 --> 00:00:12.300
tens or hundreds of thousands of years,

00:00:12.300 --> 00:00:14.350
or, in many cases, millions of years.

00:00:14.350 --> 00:00:17.110
And that's why it's always
interesting to see examples

00:00:17.110 --> 00:00:18.840
of when it might actually be happening

00:00:18.840 --> 00:00:21.360
more on a human timeframe.

00:00:21.360 --> 00:00:22.880
So this right over here is a picture

00:00:22.880 --> 00:00:26.480
of a male Central European blackcap.

00:00:26.480 --> 00:00:30.100
So historically Central European blackcaps

00:00:30.100 --> 00:00:33.270
would spend their
summers in Central Europe

00:00:33.270 --> 00:00:34.103
right over here,

00:00:34.103 --> 00:00:36.510
in what we would now consider Germany.

00:00:36.510 --> 00:00:39.550
So let me write summer right over here.

00:00:39.550 --> 00:00:42.150
And then, when it gets
colder in Central Europe,

00:00:42.150 --> 00:00:46.460
they would migrate and spend
their winters in Spain.

00:00:46.460 --> 00:00:49.090
So this is where they
would spend their winters.

00:00:49.090 --> 00:00:52.340
Now, whenever we talk about
migratory patterns like this,

00:00:52.340 --> 00:00:53.880
it's always interesting to note

00:00:53.880 --> 00:00:56.004
that it's not that all
of the birds always go

00:00:56.004 --> 00:00:58.780
on the exact same migration path.

00:00:58.780 --> 00:01:00.480
As we've talked about in many videos,

00:01:00.480 --> 00:01:03.150
you tend to have
variation in a population.

00:01:03.150 --> 00:01:06.120
There are birds that because
of genetic differences,

00:01:06.120 --> 00:01:07.610
they might go in other directions.

00:01:07.610 --> 00:01:10.360
They might go that way,
they might go that way,

00:01:10.360 --> 00:01:11.830
they might go that way.

00:01:11.830 --> 00:01:14.670
But those variants probably
weren't successful.

00:01:14.670 --> 00:01:16.570
Some of them might end
up in the North Sea.

00:01:16.570 --> 00:01:18.750
Some of them might end
up freezing to death.

00:01:18.750 --> 00:01:21.540
Some of them might not be
able to have sources of food

00:01:21.540 --> 00:01:24.870
while the dominant variant
that wintered in Spain

00:01:24.870 --> 00:01:25.720
was successful.

00:01:25.720 --> 00:01:26.960
It was warmer there.

00:01:26.960 --> 00:01:28.810
They had access to food.

00:01:28.810 --> 00:01:31.200
Now, this is where it gets interesting.

00:01:31.200 --> 00:01:36.150
In the 1960s and 1970s, it
became more and more popular

00:01:36.150 --> 00:01:39.930
to put backyard bird feeders in England.

00:01:39.930 --> 00:01:43.710
And so some of those
Central European blackcaps

00:01:43.710 --> 00:01:46.020
just happened to go in that direction.

00:01:46.020 --> 00:01:48.160
They might've always been
happening to go there,

00:01:48.160 --> 00:01:50.690
some small percentage of the population,

00:01:50.690 --> 00:01:52.260
but those didn't do so well.

00:01:52.260 --> 00:01:55.480
But now all of a sudden you
had these backyard bird feeders

00:01:55.480 --> 00:01:57.710
in England, and so these birds were able

00:01:57.710 --> 00:01:59.120
to be quite successful.

00:01:59.120 --> 00:02:00.750
They were able to get food.

00:02:00.750 --> 00:02:02.270
They were able to thrive.

00:02:02.270 --> 00:02:05.920
And so over time, this became
a larger and larger proportion

00:02:05.920 --> 00:02:09.130
that was able to successfully
go in that direction

00:02:09.130 --> 00:02:12.720
and then migrate back in the
summer and then reproduce.

00:02:12.720 --> 00:02:15.890
Now, not only did that gene
not get selected against,

00:02:15.890 --> 00:02:17.590
and now the birds that had the genes

00:02:17.590 --> 00:02:19.508
to go in that direction were thriving,

00:02:19.508 --> 00:02:21.443
but they also started
mating with each other

00:02:21.443 --> 00:02:23.070
more and more frequently

00:02:23.070 --> 00:02:25.910
because they would all get
back to Germany earlier.

00:02:25.910 --> 00:02:27.360
Because when the winter ended,

00:02:27.360 --> 00:02:30.450
they had a shorter distance
to travel on the way back

00:02:30.450 --> 00:02:31.794
than the ones that went to Spain.

00:02:31.794 --> 00:02:34.820
And so as they started
reproducing with each other

00:02:34.820 --> 00:02:36.560
more, and more, and more,

00:02:36.560 --> 00:02:40.420
we started to see differences
beyond migration direction

00:02:40.420 --> 00:02:43.930
in these two groups of
Central European blackcaps.

00:02:43.930 --> 00:02:46.700
The ones that traveled northwest

00:02:46.700 --> 00:02:48.860
started to see rounder wings

00:02:49.910 --> 00:02:53.160
versus pointier wings for the ones

00:02:53.160 --> 00:02:55.170
that were historically going to Spain.

00:02:55.170 --> 00:02:58.320
Well, pointier wings are better
for traveling long distances

00:02:58.320 --> 00:03:00.210
and rounder wings are more maneuverable,

00:03:00.210 --> 00:03:02.400
and if you don't have to
travel as long of a distance

00:03:02.400 --> 00:03:03.930
that is more desirable.

00:03:03.930 --> 00:03:05.590
Now, it's not like these birds knew

00:03:05.590 --> 00:03:07.180
that they needed rounder wings.

00:03:07.180 --> 00:03:09.450
But once again, even in
the pool that was going

00:03:09.450 --> 00:03:11.830
to the northwest, you
would have had variation,

00:03:11.830 --> 00:03:14.480
some pointy wings, some round wings.

00:03:14.480 --> 00:03:16.760
But the round wings might've
been more successful

00:03:16.760 --> 00:03:20.290
so that became a more
pronounced trait in that group.

00:03:20.290 --> 00:03:22.740
While, similarly, the
ones that went to Spain,

00:03:22.740 --> 00:03:24.500
some of them might've had rounder wings,

00:03:24.500 --> 00:03:26.630
but they might not have been as successful

00:03:26.630 --> 00:03:28.370
to get all the way to Spain and back

00:03:28.370 --> 00:03:32.760
so the pointier wings, that
phenotype, seemed to thrive.

00:03:32.760 --> 00:03:35.850
So this is an example how
an environmental change,

00:03:35.850 --> 00:03:37.830
and here the environmental
change is people deciding

00:03:37.830 --> 00:03:40.180
to put bird feeders in
their backyards in England

00:03:40.180 --> 00:03:42.300
in the 1960s and 1970s,

00:03:42.300 --> 00:03:44.610
has actually over just
the course of roughly

00:03:44.610 --> 00:03:47.980
30 or 40 generations
began what some biologists

00:03:47.980 --> 00:03:50.130
view as a speciation event.

00:03:50.130 --> 00:03:52.640
The ones that go northwest
can still interbreed

00:03:52.640 --> 00:03:54.830
with the ones that go to the southwest.

00:03:54.830 --> 00:03:56.717
But over time, if the
two groups keep breeding

00:03:56.717 --> 00:03:59.890
amongst themselves because of
the timing of their migration,

00:03:59.890 --> 00:04:01.940
they might not be able
to interbreed anymore

00:04:01.940 --> 00:04:04.880
and then you would have
two different species.

00:04:04.880 --> 00:04:06.600
So this is just one example.

00:04:06.600 --> 00:04:08.312
There are many other examples
about how the physical

00:04:08.312 --> 00:04:11.970
environment can contribute to
the expansion of some species,

00:04:11.970 --> 00:04:15.010
the emergence of new distinct species,

00:04:15.010 --> 00:04:16.700
or, in certain situations,

00:04:16.700 --> 00:04:18.130
cause a decline in the species

00:04:18.130 --> 00:04:19.609
and, in the extreme. an extinction,

00:04:19.609 --> 00:04:21.913
which we'll talk about in another video.