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So my name is Penny Chisholm and I
am a professor in the Department of

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Civil and Environmental Engineering
with a joint appointment in biology

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and I'm a microbial ecologist.
I'm an ecologist by training and I

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work on microbes in the oceans,
photosynthetic plants in the oceans.

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They're called phytoplankton.
That's the research

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that my lab does.
Whenever I'm using examples in here,

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a lot of times I'll be using
examples of microbes and of plants

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in the oceans.
I know most people know a lot more

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about trees than they know about
things that photosynthesize in the

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oceans.  And I'll convince you that
you should be as bonded to

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phytoplankton as you are to trees in
terms of recognizing your dependency

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on them.  So that's just a little
bit about my background.

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Now, let me find out a little bit
about you.  Is there anyone in here

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who has taken the ecology class 7.
3 or 1.018 that I used to teach but

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haven't taught for the last two
years?  No.  Well,

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that's good because there's some
redundancy.  And are there any

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Terrascope students or alums in here?
OK.  Just curious.

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So let me tell you just briefly
about my hopes for our interactions

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in this class,
and I stress the term interaction.

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I don't want to stand up here
talking at you.

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I really hope that you will ask
questions and interact with me.

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It makes it much more interesting
for us up here if people are asking

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questions and challenging.
I expect you to challenge what I

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say.
The field of ecology is very broad.

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It uses knowledge from physics,
from chemistry,

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from geology, all these diverse
fields, and biology of course.

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And so some of the things I'm going
to talk about,

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I know there are students here who
know more about it than I do because

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I think you all are majoring in very
diverse majors at MIT.

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So I expect that if I'm saying
something wrong that you challenge

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me because we're all in this
together.  The goal is to learn,

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not necessarily to be right all the
time.  OK.  So what I'm going to do

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today is really to give you a broad
overview of the field of ecology.

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And the things that I'll talk about
are things that we're going to go

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into in depth in the next series of
whatever lectures I have,

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ten or eleven.
So most of this you don't need to

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take any detailed notes on or
whatever.  This is just to forecast

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what's to come.
At the end I'll tell you what the

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important points are.
So what is ecology?  It's a very

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broad field and it's basically the
study of the interaction between

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organisms and their environment.
Or the study of what regulated the
mediates the transformation of
energy and mass on earth.
So in this class I'm going to be
talking about all levels of

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distribution and abundance of
organisms.  And what we're going to
do is talk about the subdivisions of
ecology and look at the

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characteristics of ecological
systems, define some general
characteristics and then we'll begin
to talk about ways that life

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organization of living systems from
the biochemical level,

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the gene level to the entire
biosphere, no small challenge.

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So the discipline of ecology, I'm
going to move this down a little bit,

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is only about a hundred years old.
It's a relatively new discipline

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but it's a strict natural science.
Ecology is not environmentalism.

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Ecology is not recycling.
Ecology is a branch of the

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biological sciences.
And it uses the Scientific Method

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which I know you're
all familiar with.

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But let's just review how ecologists

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learn about how systems work.
And it starts with observation.

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Sometimes called descriptive.
You go out and you describe what

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you see in nature.
So description.  And from that you

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form a hypothesis about the things
that are structuring that system.

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And then you actually do
experiments.  And this is something

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that a lot of people don't realize.
We can do experiments with

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ecological systems,
be they microsystems,

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or some of the things we'll talk
about in this class are experiments

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with whole ecosystems.
For example, they'll clear-cut an

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entire forest watershed and compare
then the behavior of the elements

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cycling in that watershed with a
control watershed where you don't

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clear-cut the trees.
So it's a basic experiment,

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just like you would do in test tubes.
And there are numerous other

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examples about manipulating whole
ecosystems, fertilizing

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whole lakes.
Obviously, it's more difficult

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because you have to get permission
to do these kinds of things and have

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hundreds of replicates of these
experiments, but it is a way of

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understanding the systems.
And then from the experimental

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results you test the hypothesis and
then you develop models of how the

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system works.  And then you revise
your description based

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on the models.
And then you keep going through that

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cycle.  Ecology.
At many universities you can get a

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PhD in ecology.
They have whole departments of

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ecology.  We at MIT don't.
We have very few people even who

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are ecologists,
but it is a field and you can go

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onto get a PhD.  OK.
So what are the subdisciplines of

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ecology?  And it has to do with the
hierarchical organization of living

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systems.  Let me go onto my first
slide here.  And I have

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a pointer.  Oh, well.
I have to stand back.

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So when we think of living systems
you can start with the atom.

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And together they come together and
make up molecules,

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come together and make up the cell.
And then the cells come together

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and make up tissues and organs,
and then eventually you have an

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organism.  Although,
you can have unicellular organisms.

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Here's an organism.
And then a group of organisms

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belonging to the same species is
called a population in ecology.

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And there's a whole field called
population ecology.

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We'll have a few lectures on that
where you study what regulates the

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growth and the life cycles of a
particular species of organism.

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And then a collection of
populations is called a community.

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And there's a whole field called
community ecology.

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And then a collection of
communities.

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This is a coral reef.
Can you guys see these slides in

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the back or is there too much light?
Is it OK?  OK.  Good.  So this

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would be a coral reef ecosystem.
And then all of the ecosystems

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collectively on earth constitute the
biosphere.  So ecologists study

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these systems at different levels of
organization depending on what

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questions they're interested in.
But of course this is a gross

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oversimplification of what we know
about living systems.

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For example, an organism.
I mean is an organism really an

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organism?  Think of yourself,
for example.  Are you only one

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species?

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You're a human,
yes.  But there are parts of you

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that aren't human, right?
What's in your gut?

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E. coli.  There are more bacteria
in your gut than there are human

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cells in your body.
And without those bacteria you'd be

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in [trouble?].
Also your skin is an ecosystem.

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It's teaming with mites and little
creatures that if you looked under

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the microscope you'd be appalled.
All of your pours have tiny little

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ecosystems in them.
And most of these are doing their

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job.  You're their habitat.
And they're helping you be a living

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being.  So you yourself are an
ecosystem.  So it's really difficult

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to talk about these in a very clean
way.  I mean you cannot really study

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an organism all by itself because
each organism is in itself an

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ecosystem or a community.
Maybe not an ecosystem but a

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community of organisms.
But this is the way we have come to

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divide up the living world at
different levels of organization.

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And we will talk about all of these
in this class.

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So ecology really has two broad
branches.  And that's how my series

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of lectures are divided up.
One is called biogeochemistry.

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And in this branch is the study of

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how organisms mediate the
transformation of energy and matter

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in the biosphere.
And this is essentially talking

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about the metabolism of ecosystems.
In some ways we will talk about,

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you've been learning all about the
biochemistry of cells and how cells

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work and how they process energy,
etc.  The sum of all of that

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biochemistry in cells results in
these biogeochemical cycles,

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the interactions between these
organisms and their environment.

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When we talk about the metabolism of

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the biosphere you almost can think
of yourself as being inside of a

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cell looking at the biochemistry of
the whole cell from the inside.

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It's all a matter of scaling.  And
we'll see that.

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You've learned about photosynthesis
and respiration, right?

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Have they?
Yes.  Well, you'll see that those

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processes that you've learned about
that are subcellular collectively

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also have a metabolism for the
biosphere.  OK.

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The second, and this will be my
second set of lectures,

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is population and community ecology.

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And here we talk about organisms.
Not just the biochemistry, their

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collective biochemistry,
but this is the study of the

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processes that regulate the
distribution and abundance

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of organisms.
What determines the rates of

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population growth of a particular
population?  What determines the

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distribution of different species
over the landscape in a particular

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habitat?  This part of ecology we
often talk about as being the

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function of ecosystems, and
this the structure.

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And the really important thing to
remember is that these two are very

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much obviously dependent on one
another.  If you change the

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structure of an ecosystem,
if you cut down all the trees you

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will change the function of the
ecosystem, there will be no

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photosynthesis.
OK?  So this is a really important

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point that these two are related.
And we'll talk about that a lot in

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more detail when we
go forward here.

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If we can turn the lights off I'll
show you one of my favorite,

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favorite, favorite slides, if it
works.  Ah, yes.

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This is to give you a feeling for
the earth as a living organism,

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in a sense.  This is the biosphere.
This is obviously a NASA image

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showing the green is the plants on
earth and this is the dessert.

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The green in the ocean is the
phytoplankton.

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And so where there's lots of green
there's more phytoplankton.

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Where there's red there's even more.
And now we're zooming into the

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Equatorial Pacific.
Here's a big bloom of phytoplankton.

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And this is about three seasons in
the life of the earth.  OK?

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But it shows you how dynamic the
surface film of the earth is that we

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consider the biosphere.
And all of this life and all of its

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cycling and dynamics influences the
composition of our atmosphere and of

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our oceans, all of the nonliving
components of the earth.

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And really at the biosphere level
what ecology is,

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is understanding the interaction
between the living processes and the

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nonliving processes in the earth and
how they coevolved to shape

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this living planet.
If you were somebody out on mars and

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you saw that, if you could see that
from mars, but you probably could if

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you were living on mars because
you'd be a different species and you

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could do all kinds of things,
but you would really get a feeling

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for this planet is alive,
just seeing those dynamics.

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And it is.  And we don't know if
we're the only ones but it's

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certainly worth understanding how
the whole thing works.

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So that's the goal which is rather
intimidating but very exciting.

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OK.  And very important concept in
ecology is a concept of

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emergent properties.

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And the idea is that at each level
of organization that we talked about

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here, well, if I cannot go back,
I cannot go back.  Oh, there we go.

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At each level of organization of
the system that we talk about there

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has properties that only exist at
that level or organization.

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So if you want to understand
population ecology or community

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ecology you cannot study cellular
ecology and just scale up.

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Now, this runs up against a lot of
MIT reductionist philosophy,

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right?  I mean what we're all about
here is taking things apart down to

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their component parts and
understanding them and then building

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our knowledge from there.
But this whole field of complexity

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theory that has emerged with a force,
say in the last ten years,

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is showing us that that's too
oversimplified and that systems,

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at different levels of organizations,
have their own properties.

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So if you want to understand how the
earth works you've got to understand

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the earth.  You cannot just
understand how all the atoms are

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working.  They're coming together to
make the organisms.

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And this is fundamentally because
of feedbacks in the system.

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So let me give you an example.
OK.

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The brain, and this isn't ecology
but it's an example you can relate

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to, has ten to the twelfth cells
with ten to the fourteenth

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connections.  And the emergent
property is your behavior,

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right?  Those cells are connected in
a certain way which results in the

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way that you think and feel,
your emotions, your behavior, etc.

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And in brain research we now have
learned that the way these cells are

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connected is influenced by the
learning environment for young

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children.  How the brain is
stimulated influences how these are

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connected.  So there's a feedback
between the environment experienced

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by a child and how these
connections are made.

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Similarly in ecology systems and
throughout evolution there's a

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feedback.  You have a bunch of cells
doing a certain kind of metabolism

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which changes the atmosphere of the
planet.  And then that atmosphere

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selects for certain types of cells
that weren't there before.

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So there's a constant feedback
between the emergent property

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feeding back on the system level
below and changing it.

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And that's really the
characteristics of a complex system.

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And we'll talk about, in a minute,
some major examples of that.

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One that I always like to think
about and throw out is that if you

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knew everything,
did any of you had an ant colony

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when you were a kid?
Ah, you're deprived.

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Oh, yes.  OK.  You get the sand and
the two pieces of glass and you put

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some ants in and they make all these
tunnels and everything.

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So if you knew everything about
ants and ant behavior and sand and

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the mechanics of sand could you ever
predict the pattern of those tunnels

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that they're going to build?
Actually, most of the classes I

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talk to say yeah.
If I knew all that I could predict

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00:21:04,000 --> 00:21:08,000
it.  But think about it.
OK.  Because I don't think you

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could.  And this whole field of
complexity theory is really

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exploding now.
In fact, Northwestern University,

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I just noticed on the Web, has just
formed an entire school of

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complexity that has people from all
different fields under one roof,

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social sciences all the way to
physics under one room studying

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this phenomenon.
And ecology is complexity at its

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best.  OK.  So one other thing,
before we move on, is that I said

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ecology is not environmentalism,
but it's a fundamental science.  But

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the knowledge that is gained from
the study of ecological systems and

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the principles of ecology,
that knowledge is used in a field

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that is growing now called
applied ecology.

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And that's where you use ecological
knowledge to influence human

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activities on earth.
And, for example, you'd use

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ecological knowledge to understand
how much of the earth's forests can

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we cut down before the system won't
sustain us, that you won't have

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enough photosynthesis to maintain
the oxygen levels in the atmosphere

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or draw down enough CO2 so that we
don't all boil up.

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We'll talk about that.
If you want to protect a particular

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species, how large of an area do you
have to set aside as a reserve?

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In order to know that you have to
do fundamental studies of the

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ecology of that species.
Basically, how far can we,

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as humans, push these systems from
their ìnatural stateî until they

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won't function for us anymore?
Because we rely on natural systems

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for food, fiber and clean water and
the composition of our air.

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But another point here, I just said
how far from the natural state can

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we push them, another big important
point, as we talk about ecological

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systems, is there is no original
state of nature.  There

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is no baseline.
Nature is ever-changing.

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Nature is evolving.  And we'll talk
about how much the earth has evolved

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since the formation of the earth.
So it's important to keep in mind

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that what humans are doing now,
as we try to have conservation

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programs and worry about global
warming and the extinction of

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species, is that we're trying to
keep the earth the way we think we

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want it right now.
I mean the way we think it was

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00:24:04,000 --> 00:24:09,000
before the Industrial Revolution,
before the massive flux of energy

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into the system has allowed us to
completely change the biosphere.

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And that's a really important thing
because the earth ìhas a mindî of

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its own.  And we know that,
it doesn't have a mind, it has a

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behavior of its own.
And we know that there were massive

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climate changes in the past and
there will be massive climate

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changes in the future.
And asteroid might hit us.

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00:24:37,000 --> 00:24:41,000
And who knows all of these things?
It's going to change.  So our

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challenge is understanding the
degree to which we want to try to

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control that natural change and try
to not impose rapid change in the

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rates of things that are already
going on.  So it's a very tricky

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problem, and you guys are the ones
that are going to inherit

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00:24:59,000 --> 00:25:05,000
it big time.
You're going to be in charge of this

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00:25:05,000 --> 00:25:13,000
biosphere and you're going to have
to figure out how to manage it,

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because, like it or not, we are
influencing it to such a degree that

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we have to manage it.
OK.  So another important concept

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00:25:27,000 --> 00:25:35,000
is that, and I've already alluded to
this, the organism environment

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interaction is two-way.

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00:25:42,000 --> 00:25:46,000
I mean we're all used to thinking
about the ìsurvival of the fittestî,

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00:25:46,000 --> 00:25:50,000
right?  That you have this
environment out there and you have

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organisms, and the organism that's
more fit, has most adapted to that

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00:25:54,000 --> 00:25:58,000
environment will survive and
reproduce and that's how

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00:25:58,000 --> 00:26:02,000
evolution works.
Well, it's more than that.

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00:26:02,000 --> 00:26:07,000
The important thing is that not
only do organisms adapt to the

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environment but they actually change
the environment.

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They co-evolve with the environment.
And so life in the non-living

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00:26:16,000 --> 00:26:21,000
components of the earth are
interacting very intimately and life

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00:26:21,000 --> 00:26:26,000
has fundamentally shaped the nature
of the non-living part

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of our planet.
So an example of this that I draw

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00:26:33,000 --> 00:26:41,000
from your textbook,
just a very simple example,

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00:26:41,000 --> 00:26:50,000
has to do with the influence of
microbes on the succession of plants

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00:26:50,000 --> 00:26:59,000
in a northern ecosystem.
Succession is --

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00:26:59,000 --> 00:27:03,000
If you start with blank soil and you
just let it sit,

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00:27:03,000 --> 00:27:07,000
how will communities of organisms
come in and colonize?

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00:27:07,000 --> 00:27:11,000
You'll start out with very small
plants and then larger plants and

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00:27:11,000 --> 00:27:15,000
then bushes and then trees over time.
So sometimes ecologists study this

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00:27:15,000 --> 00:27:19,000
by clear-cutting an area and then
following it over time.

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00:27:19,000 --> 00:27:23,000
That takes years and years and
years, much longer than the average

301
00:27:23,000 --> 00:27:27,000
scientist's lifespan.
So another way to do this is

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00:27:27,000 --> 00:27:32,000
substitute space for time.
And that's what they've done here.

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00:27:32,000 --> 00:27:38,000
This is a glacier that is receding
in this direction.

304
00:27:38,000 --> 00:27:43,000
And so where it initially retreated
soil was exposed and succession

305
00:27:43,000 --> 00:27:49,000
started.  And then it retreats more.
So this area is growing while this

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00:27:49,000 --> 00:27:54,000
one is just getting exposed.
So eventually, along this gradient,

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00:27:54,000 --> 00:28:00,000
you have the youngest community up
here and the oldest community

308
00:28:00,000 --> 00:28:06,000
down here.
And so they were able to look at the

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00:28:06,000 --> 00:28:12,000
effect of that succession of
different species on the composition

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00:28:12,000 --> 00:28:18,000
of the soil.  And there's an
important successional stage here.

311
00:28:18,000 --> 00:28:25,000
So here's the nitrogen content in
the soil as a function of simulated

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00:28:25,000 --> 00:28:31,000
time here and showing that it
increases steadily as succession

313
00:28:31,000 --> 00:28:38,000
goes on up to a peak and
then levels off.

314
00:28:38,000 --> 00:29:05,000
And that increase is largely due to
the invasion of plants that can fix

315
00:29:05,000 --> 00:29:32,000
nitrogen.  Alder trees are a
specific species of trees that have

316
00:29:32,000 --> 00:29:59,000
in their roots symbiotic
nitrogen-fixing bacteria.

317
00:29:59,000 --> 00:29:54,000
Have you talked about this at all,
nitrogen-fixation?  This is what

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00:29:54,000 --> 00:29:50,000
Professor Walker actually works on
his research in his laboratory.

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00:29:50,000 --> 00:29:46,000
He's a world expert on the
mechanism of this.

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00:29:46,000 --> 00:29:41,000
But these nitrogen-fixing microbes
are the only forms of life really

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00:29:41,000 --> 00:29:37,000
that can take nitrogen gas from the
atmosphere, N2,

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00:29:37,000 --> 00:29:33,000
and using this nitrogenase enzyme
convert it to pneumonia which is

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00:29:33,000 --> 00:29:29,000
what they need to make
proteins, etc.
and only through these microbes can
we get that into the soil so that

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00:29:29,000 --> 00:29:33,000
So there's this huge reservoir of
nitrogen gas in the atmosphere,

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00:29:38,000 --> 00:29:43,000
other organisms can use it.
So here's a process at the

326
00:29:43,000 --> 00:29:48,000
molecular level where the
biochemistry that you're learning in

327
00:29:48,000 --> 00:29:52,000
the rest of this class scaled up
actually completely influences the

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00:29:52,000 --> 00:29:57,000
species that inhabit this ecosystem
by increasing the nitrogen

329
00:29:57,000 --> 00:30:02,000
in the soil.
And just to show you how important

330
00:30:02,000 --> 00:30:06,000
these microbes are globally,
this is the global nitrogen cycle.

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00:30:06,000 --> 00:30:11,000
And don't worry about the details
because we're going to talk about

332
00:30:11,000 --> 00:30:15,000
this in future lectures in big
detail.  So this is just to make the

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00:30:15,000 --> 00:30:20,000
simple point that here's this
biological nitrogen fixation on a

334
00:30:20,000 --> 00:30:24,000
global scale.  We have to start
talking about big units here,

335
00:30:24,000 --> 00:30:29,000
OK?  This is gigatons of nitrogen.
So I've converted it.

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00:30:29,000 --> 00:30:34,000
A gigaton of nitrogen is equal in
weight to a billion Volkswagens.

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00:30:34,000 --> 00:30:40,000
So you have to think on an annual
scale 140 billion Volkswagens worth

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00:30:40,000 --> 00:30:46,000
of nitrogen is dragged out of the
atmosphere and put into living

339
00:30:46,000 --> 00:30:52,000
organisms by the biochemical
processes that you're learning about

340
00:30:52,000 --> 00:30:58,000
at the subcellular level.
So massive quantities of stuff is

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00:30:58,000 --> 00:31:04,000
flying around here that you cannot
appreciate until you see it.

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00:31:04,000 --> 00:31:09,000
Now, if there was no life on earth,
that nitrogen cycle wouldn't be a

343
00:31:09,000 --> 00:31:15,000
cycle.  None of these processes
would work without the microbes.

344
00:31:15,000 --> 00:31:20,000
And we're going to talk about them
in much more detail later.

345
00:31:20,000 --> 00:31:26,000
OK.  The other really important
cycle on earth is the carbon cycle.

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00:31:26,000 --> 00:31:32,000
And so I've put this up here to
very simply --

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00:31:32,000 --> 00:31:36,000
Now, you've talked about these
reactions in the biochemical sense

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00:31:36,000 --> 00:31:41,000
in great detail.
This is what I call my

349
00:31:41,000 --> 00:31:45,000
impressionistic biochemistry,
all right?  The net reaction of

350
00:31:45,000 --> 00:31:50,000
photosynthesis is to take CO2 gas
from the atmosphere using water,

351
00:31:50,000 --> 00:31:54,000
using solar energy and convert it to
organic carbon.

352
00:31:54,000 --> 00:31:59,000
Think of this as glucose.
Multiply that by six and you've got

353
00:31:59,000 --> 00:32:04,000
glucose organic carbon and
oxygen is evolved.

354
00:32:04,000 --> 00:32:08,000
So this is what we call the ìmass
from gas reactionî on a global scale.

355
00:32:08,000 --> 00:32:13,000
This is the foundation of all life
on earth.  Without it there would be

356
00:32:13,000 --> 00:32:17,000
no life.  Life was created from this
gigatons of CO2 in the atmosphere

357
00:32:17,000 --> 00:32:22,000
and the solar energy.
And then the reverse,

358
00:32:22,000 --> 00:32:26,000
of course, is all of the animals and
bacteria, all of the things that

359
00:32:26,000 --> 00:32:31,000
cannot photosynthesis use this
organic carbon and use oxygen and

360
00:32:31,000 --> 00:32:35,000
burn it in respiration,
that you've learned about,

361
00:32:35,000 --> 00:32:40,000
to make chemical energy [as heat?
and cycling the gas back.

362
00:32:40,000 --> 00:32:45,000
Now, in order for this to run,
I love that part.  That took me

363
00:32:45,000 --> 00:32:51,000
about ten minutes to figure out.
This is that all the other elements

364
00:32:51,000 --> 00:32:57,000
on earth need to cycle through.
And it's microbes that do this

365
00:32:57,000 --> 00:33:02,000
cycling.
And we're going to talk about that

366
00:33:02,000 --> 00:33:08,000
in the next lecture.
Because the system would run down

367
00:33:08,000 --> 00:33:13,000
if the elements on earth weren't
cycled by microbes through various

368
00:33:13,000 --> 00:33:19,000
redox states.  So this is just a
more detailed scaled down version of

369
00:33:19,000 --> 00:33:24,000
what you've already learned in class,
photosynthesis,

370
00:33:24,000 --> 00:33:30,000
the Z scheme, making glucose from
the Calvin Cycle.

371
00:33:30,000 --> 00:33:34,000
And then that glucose goes into the
mitochondrion.

372
00:33:34,000 --> 00:33:39,000
And you have respiration and CO2
evolved.  So this is the micro scale

373
00:33:39,000 --> 00:33:43,000
version of what I just showed you
and this is the macro scale version

374
00:33:43,000 --> 00:33:48,000
of what I just showed you.
This is the global carbon cycle.

375
00:33:48,000 --> 00:33:53,000
And you have a hundred gigatons of
carbon coming into the system

376
00:33:53,000 --> 00:33:58,000
through photosynthesis and going out
through respiration.

377
00:33:58,000 --> 00:34:03,000
So that's the collective
photosynthesis and respiration

378
00:34:03,000 --> 00:34:09,000
metabolism of the earth.
What I'm trying to have you get a

379
00:34:09,000 --> 00:34:14,000
feeling for here is that this whole
phenomenon of scaling,

380
00:34:14,000 --> 00:34:20,000
that these processes occur at
multiple scales from the subcellular

381
00:34:20,000 --> 00:34:25,000
to the biosphere level.
And this is the flat earth version

382
00:34:25,000 --> 00:34:31,000
of the globe.  In the northern
hemisphere you can see winter.

383
00:34:31,000 --> 00:34:36,000
There's winter,
no green.  There's summer,

384
00:34:36,000 --> 00:34:41,000
everything green.  Winter, no green.
Summer, everything green.  And now

385
00:34:41,000 --> 00:34:46,000
wait until you see this.
This is cool.  Because that pulsing

386
00:34:46,000 --> 00:34:51,000
you can actually see.
This is the CO2 concentration in

387
00:34:51,000 --> 00:34:56,000
the atmosphere over a period of
three years or so showing that when

388
00:34:56,000 --> 00:35:01,000
respiration is greater than
photosynthesis in the northern

389
00:35:01,000 --> 00:35:06,000
hemisphere in the winter,
CO2 in the atmosphere goes up.

390
00:35:06,000 --> 00:35:12,000
When photosynthesis greater
respiration, CO2 goes down.

391
00:35:12,000 --> 00:35:18,000
So you can see the signature of the
earth breathing in the CO2

392
00:35:18,000 --> 00:35:24,000
concentration in the atmosphere.
Also you can see that this is

393
00:35:24,000 --> 00:35:30,000
increasing.  And does anybody
know why that is?

394
00:35:30,000 --> 00:35:35,000
Hello.  Did somebody say something?
Global warming, yeah.  Greenhouse

395
00:35:35,000 --> 00:35:40,000
effect, yeah.  But what's causing
that?  There you go,

396
00:35:40,000 --> 00:35:45,000
fossil fuel.  Burning fossil fuel is
causing an increasing trend in the

397
00:35:45,000 --> 00:35:50,000
CO2 concentration which is causing
the greenhouse effect which is

398
00:35:50,000 --> 00:35:55,000
causing global warming.
And we'll talk about that.

399
00:35:55,000 --> 00:36:00,000
This is an emergent property of the
system, the CO2 concentration.

400
00:36:00,000 --> 00:36:05,000
Now, in the last slide I showed you
these arrows were the same width.

401
00:36:05,000 --> 00:36:10,000
But life on earth was not always
that way.  Respiration didn't always

402
00:36:10,000 --> 00:36:16,000
balance photosynthesis.
And this gets to my point about

403
00:36:16,000 --> 00:36:21,000
there's no original state of nature.
In the early earth photosynthesis

404
00:36:21,000 --> 00:36:27,000
way outpaced the consumption of
organic matter.  So what

405
00:36:27,000 --> 00:36:33,000
would that result in?
If this arrow is much more rapid

406
00:36:33,000 --> 00:36:39,000
than this arrow?
Oxygen in the atmosphere increased,

407
00:36:39,000 --> 00:36:45,000
exactly.  Now, if oxygen in the
atmosphere increases,

408
00:36:45,000 --> 00:36:51,000
what happens?  What else happens in
order for that to happen?

409
00:36:51,000 --> 00:36:57,000
This increased, too, right?
And, in fact, that is the

410
00:36:57,000 --> 00:37:02,000
deposition of fossil fuel.
This is billions of years.

411
00:37:02,000 --> 00:37:06,000
Now we're going back to the
formation of the earth 4.

412
00:37:06,000 --> 00:37:11,000
billion years ago, origin of life.
Then we have the beginning of

413
00:37:11,000 --> 00:37:15,000
oxygenic photosynthesis here.
And it's the phytoplankton in the

414
00:37:15,000 --> 00:37:20,000
oceans that started this.
And so oxygen started to accumulate

415
00:37:20,000 --> 00:37:25,000
in the oceans but not in the
atmosphere at first.

416
00:37:25,000 --> 00:37:29,000
So you have all this photosynthesis
in the oceans which were a very

417
00:37:29,000 --> 00:37:34,000
reduced environment.
So the minute the oxygen was evolved

418
00:37:34,000 --> 00:37:38,000
in photosynthesis it reacted with
iron, all these reduced compounds,

419
00:37:38,000 --> 00:37:42,000
particularly iron, and made iron
oxides.  So it never made it to the

420
00:37:42,000 --> 00:37:46,000
atmosphere at first.
So you had the deposition of these

421
00:37:46,000 --> 00:37:50,000
banded iron formations in the
ancient marine environment.

422
00:37:50,000 --> 00:37:54,000
Then eventually all of that got
oxidized and it escaped into the

423
00:37:54,000 --> 00:37:58,000
atmosphere and you started to have a
buildup of oxygen in

424
00:37:58,000 --> 00:38:02,000
the atmosphere.
And at the same time that was

425
00:38:02,000 --> 00:38:07,000
building up there was burial of this
organic carbon because it wasn't be

426
00:38:07,000 --> 00:38:12,000
respired by the heterotrophic
organisms.  And that's the fossil

427
00:38:12,000 --> 00:38:17,000
fuel that was built up over all of
these billions of years.

428
00:38:17,000 --> 00:38:22,000
Well, not billions.  Yeah,
billions of years.  That we have now

429
00:38:22,000 --> 00:38:27,000
burned over a period of a hundred
years releasing all that CO2

430
00:38:27,000 --> 00:38:32,000
into the atmosphere.
So we're burning ancient

431
00:38:32,000 --> 00:38:36,000
photosynthate over a tiny little
period in the earth's history and

432
00:38:36,000 --> 00:38:41,000
throwing it into the atmosphere.
And the earth is saying I don't

433
00:38:41,000 --> 00:38:46,000
know how to handle this.
So there's a big question of what

434
00:38:46,000 --> 00:38:50,000
the earth's system is going to do
with all of that CO2 that we're

435
00:38:50,000 --> 00:38:55,000
putting up there.
And this is all going to happen in

436
00:38:55,000 --> 00:39:01,000
like the next 50 years.
And, as I always say in this class,

437
00:39:01,000 --> 00:39:07,000
I'll be dead but you won't when it
really hits the fan unless we do

438
00:39:07,000 --> 00:39:13,000
something.  So here are the banded
iron formations.

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00:39:13,000 --> 00:39:20,000
We can see the legacy of that
history of the earth in today's rock

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00:39:20,000 --> 00:39:26,000
formations, banded iron formations
of marine origin and terrestrial

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00:39:26,000 --> 00:39:32,000
origin here.  And we can see in the
earth's composition of the earth's

442
00:39:32,000 --> 00:39:39,000
atmosphere the signature of the
evolution of life.

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00:39:39,000 --> 00:39:45,000
The composition of the earth's
atmosphere is highly improbable.

444
00:39:45,000 --> 00:39:51,000
Thermodynamically improbable if you
didn't have the influence of

445
00:39:51,000 --> 00:39:57,000
converting this solar energy into
living biomass.

446
00:39:57,000 --> 00:40:04,000
And so the CO2 concentration is
much lower than these planets.

447
00:40:04,000 --> 00:40:09,000
And the nitrogen concentration
higher and the temperature a nice

448
00:40:09,000 --> 00:40:15,000
balmy 16 degrees.
OK.  So this is just to remind you

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00:40:15,000 --> 00:40:20,000
that these processes operate at all
scales.  Biosphere.

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00:40:20,000 --> 00:40:26,000
This is a little ecosphere I'm
going to bring next time showing you

451
00:40:26,000 --> 00:40:32,000
a sealed ecosystem in which all of
these properties go on.

452
00:40:32,000 --> 00:40:36,000
And finally.  So I've been talking
about levels of organization from

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00:40:36,000 --> 00:40:41,000
the molecular level up to the
biosphere level.

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00:40:41,000 --> 00:40:45,000
And there's an exciting new thing
happening in my field that is so

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00:40:45,000 --> 00:40:50,000
exciting I have to tell you about it.
And I'll probably be telling you

456
00:40:50,000 --> 00:40:55,000
about it more and more as I go along
here.  And that is a whole new field

457
00:40:55,000 --> 00:40:59,000
is emerging called molecular ecology
where we're viewing the biosphere as

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00:40:59,000 --> 00:41:04,000
a network of genes.
It's not that you either study

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00:41:04,000 --> 00:41:09,000
cellular molecular biology or
biochemistry or you study the

460
00:41:09,000 --> 00:41:13,000
biosphere but you try to think of
the biosphere as a network of genes.

461
00:41:13,000 --> 00:41:18,000
And in oceanography we're actually
able to start to do this because the

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00:41:18,000 --> 00:41:23,000
oceans are dominated by
microorganisms,

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00:41:23,000 --> 00:41:27,000
although in this picture I don't
have that properly represented,

464
00:41:27,000 --> 00:41:32,000
but we're starting to think about a
sea of organisms as being simply a

465
00:41:32,000 --> 00:41:37,000
network of genes.
Most of the genetic information in

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00:41:37,000 --> 00:41:43,000
the oceans is in microorganisms.
And I like to think of the oceans

467
00:41:43,000 --> 00:41:49,000
as dissolved information essentially.
When you look out and you see that

468
00:41:49,000 --> 00:41:54,000
blue water, there is so much DNA in
there and so many genes doing so

469
00:41:54,000 --> 00:42:00,000
many different things it's just
phenomenal.  And there are a billion

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00:42:00,000 --> 00:42:05,000
microbes per liter in sea water.
99.9% have never been cultivated.

471
00:42:05,000 --> 00:42:10,000
We know nothing about them.  There
is as much information in that liter

472
00:42:10,000 --> 00:42:14,000
as in the entire human genome,
and most of it is of unknown

473
00:42:14,000 --> 00:42:19,000
function in this biosphere.
And so just within the last year,

474
00:42:19,000 --> 00:42:24,000
this is Craig Venter who was one of
the people who sequences the human

475
00:42:24,000 --> 00:42:28,000
genome.  And now that that's over
with, he needs a new challenge.

476
00:42:28,000 --> 00:42:33,000
So he's taking on the ocean genome
meaning sequencing all of

477
00:42:33,000 --> 00:42:38,000
the DNA in the oceans.
And he's taken his yacht,

478
00:42:38,000 --> 00:42:43,000
because he's rich now, which is his
research vessel.

479
00:42:43,000 --> 00:42:47,000
And they're going around the oceans
collecting samples,

480
00:42:47,000 --> 00:42:52,000
filtering them onto filters and
collecting all the microbes.

481
00:42:52,000 --> 00:42:57,000
And then you take it and you grind
it up, you extract the DNA

482
00:42:57,000 --> 00:43:02,000
and you sequence it.
And you just get a bunch of little

483
00:43:02,000 --> 00:43:07,000
pieces that you identify as genes.
You don't know what organisms they

484
00:43:07,000 --> 00:43:12,000
belong to, but you've got genes.
And this is his cruise trek which

485
00:43:12,000 --> 00:43:18,000
you notice doesn't have many
northern climbs here,

486
00:43:18,000 --> 00:43:23,000
although they did do something up in
Halifax.  And it kind of resembles

487
00:43:23,000 --> 00:43:28,000
the Challenger Expedition back in
the 1800s which was one of the first

488
00:43:28,000 --> 00:43:33,000
major oceanographic expeditions.
So they published a paper in Science

489
00:43:33,000 --> 00:43:37,000
last year.  Just off Bermuda they
found 1.2 million new genes that had

490
00:43:37,000 --> 00:43:42,000
never been in the database.
They had to create a new database

491
00:43:42,000 --> 00:43:46,000
in order to even put these genes in
it and 1800 new species.

492
00:43:46,000 --> 00:43:51,000
And he is estimating the genetic
inventory of the planet,

493
00:43:51,000 --> 00:43:55,000
most of which are in these microbes,
to be 20 to 30 billion genes.  And

494
00:43:55,000 --> 00:44:00,000
then we're going to have to figure
out what they're all doing.

495
00:44:00,000 --> 00:44:04,000
OK.  So just the take-home message.
I'm going to try to do this at the

496
00:44:04,000 --> 00:44:08,000
end of each lecture so that you know
what I think is important.

497
00:44:08,000 --> 00:44:13,000
So we've talked about life at
different scales.

498
00:44:13,000 --> 00:44:17,000
Ecology is the study of life at all
these different scales.

499
00:44:17,000 --> 00:44:22,000
Emergent properties is a really
important concept to understand.

500
00:44:22,000 --> 00:44:26,000
There's nothing more important than
understanding this organism

501
00:44:26,000 --> 00:44:31,000
environment is a two-way street.
There's really no such thing as a

502
00:44:31,000 --> 00:44:36,000
free living organism either.
They are all dependant on one

503
00:44:36,000 --> 00:44:41,000
another.  Even if you have a culture
of say E. coli which you've supplied

504
00:44:41,000 --> 00:44:46,000
glucose to so it can grow,
where do you think that glucose came

505
00:44:46,000 --> 00:44:51,000
from?  It's the photosynthetic
product of some plant somewhere.

506
00:44:51,000 --> 00:44:56,000
So organisms are not really
free-living.  They are all dependent

507
00:44:56,000 --> 00:45:01,000
on one another.
Life has shaped the earth's features,

508
00:45:01,000 --> 00:45:05,000
its atmosphere.
The biosphere that I've shown you

509
00:45:05,000 --> 00:45:10,000
and the geosphere,
which is what we refer to the

510
00:45:10,000 --> 00:45:14,000
nonliving part of the earth,
have coevolved over evolutionary

511
00:45:14,000 --> 00:45:19,000
time.  And the genetic inventory of
this is completely unknown.

512
00:45:19,000 --> 00:45:23,000
And, of course, microbes rule the
planet, don't forget that.

513
00:45:23,000 --> 00:45:26,000
See you next time.