ESL Video Quiz: TOEFL Quiz 10: "Living" Structures

Quiz by: Danielle_BIA
Quiz #: 12200
(ESL Category: listening) Listening Comprehension from TED
Listening Comprehension 6042




So historically there has been a huge divide
between what people consider to be non-living
systems on one side, and living systems on the
other side. So we go from, say, this beautiful and
complex crystal as non-life, and this rather
beautiful and complex cat on the other side. Over
the last hundred and fifty years or so, science
has kind of blurred this distinction between non-
living and living systems, and now we consider
that there may be a kind of continuum that exists
between the two. We'll just take one example here:
a virus is a natural system, right? But it's very
simple. It's very simplistic. It doesn't really
satisfy all the requirements, it doesn't have all
the characteristics of living systems and is in
fact a parasite on other living systems in order
to, say, reproduce and evolve.

But what we're going to be talking about here
tonight are experiments done on this sort of non-
living end of this spectrum -- so actually doing
chemical experiments in the laboratory, mixing
together nonliving ingredients to make new
structures, and that these new structures might
have some of the characteristics of living
systems. Really what I'm talking about here is
trying to create a kind of artificial life.

So what are these characteristics that I'm talking
about? These are them. We consider first that life
has a body. Now this is necessary to distinguish
the self from the environment. Life also has a
metabolism. Now this is a process by which life
can convert resources from the environment into
building blocks so it can maintain and build
itself. Life also has a kind of inheritable
information. Now we, as humans, we store our
information as DNA in our genomes and we pass this
information on to our offspring. If we couple the
first two -- the body and the metabolism -- we can
come up with a system that could perhaps move and
replicate, and if we coupled these now to
inheritable information, we can come up with a
system that would be more lifelike, and would
perhaps evolve. And so these are the things we
will try to do in the lab, make some experiments
that have one or more of these characteristics of
life.

So how do we do this? Well, we use a model system
that we term a protocell. You might think of this
as kind of like a primitive cell. It is a simple
chemical model of a living cell, and if you
consider for example a cell in your body may have
on the order of millions of different types of
molecules that need to come together, play
together in a complex network to produce something
that we call alive. In the laboratory what we want
to do is much the same, but with on the order of
tens of different types of molecules -- so a
drastic reduction in complexity, but still trying
to produce something that looks lifelike. And so
what we do is, we start simple and we work our way
up to living systems. Consider for a moment this
quote by Leduc, a hundred years ago, considering a
kind of synthetic biology: "The synthesis of life,
should it ever occur, will not be the sensational
discovery which we usually associate with the
idea." That's his first statement. So if we
actually create life in the laboratories, it's
probably not going to impact our lives at all.

"If we accept the theory of evolution, then the
first dawn of synthesis of life must consist in
the production of forms intermediate between the
inorganic and the organic world, or between the
non-living and living world, forms which possess
only some of the rudimentary attributes of life" -
- so, the ones I just discussed -- "to which other
attributes will be slowly added in the course of
development by the evolutionary actions of the
environment." So we start simple, we make some
structures that may have some of these
characteristics of life, and then we try to
develop that to become more lifelike. This is how
we can start to make a protocell. We use this idea
called self-assembly. What that means is, I can
mix some chemicals together in a test tube in my
lab, and these chemicals will start to self-
associate to form larger and larger structures. So
say on the order of tens of thousands, hundreds of
thousands of molecules will come together to form
a large structure that didn't exist before. And in
this particular example, what I took is some
membrane molecules, mixed those together in the
right environment, and within seconds it forms
these rather complex and beautiful structures
here. These membranes are also quite similar,
morphologically and functionally, to the membranes
in your body, and we can use these, as they say,
to form the body of our protocell.

Likewise, we can work with oil and water systems.
As you know, when you put oil and water together,
they don't mix, but through self-assembly we can
get a nice oil droplet to form, and we can
actually use this as a body for our artificial
organism or for our protocell, as you will see
later. So that's just forming some body stuff,
right? Some architectures. What about the other
aspects of living systems? So we came up with this
protocell model here that I'm showing. We started
with a natural occurring clay called
montmorillonite. This is natural from the
environment, this clay. It forms a surface that
is, say, chemically active. It could run a
metabolism on it. Certain kind of molecules like
to associate with the clay. For example, in this
case, RNA, shown in red -- this is a relative of
DNA, it's an informational molecule -- it can come
along and it starts to associate with the surface
of this clay. This structure, then, can organize
the formation of a membrane boundary around
itself, so it can make a body of liquid molecules
around itself, and that's shown in green here on
this micrograph. So just through self-assembly,
mixing things together in the lab, we can come up
with, say, a metabolic surface with some
informational molecules attached inside of this
membrane body, right?

So we're on a road towards living systems. But if
you saw this protocell, you would not confuse this
with something that was actually alive. It's
actually quite lifeless. Once it forms, it doesn't
really do anything. So, something is missing. Some
things are missing. So some things that are
missing is, for example, if you had a flow of
energy through a system, what we'd want is a
protocell that can harvest some of that energy in
order to maintain itself, much like living systems
do. So we came up with a different protocell
model, and this is actually simpler than the
previous one. In this protocell model, it's just
an oil droplet, but a chemical metabolism inside
that allows this protocell to use energy to do
something, to actually become dynamic, as we'll
see here. You add the droplet to the system. It's
a pool of water, and the protocell starts moving
itself around in the system. Okay? Oil droplet
forms through self-assembly, has a chemical
metabolism inside so it can use energy, and it
uses that energy to move itself around in its
environment.

As we heard earlier, movement is very important in
these kinds of living systems. It is moving
around, exploring its environment, and remodeling
its environment, as you see, by these chemical
waves that are forming by the protocell. So it's
acting, in a sense, like a living system trying to
preserve itself. We take this same moving
protocell here, and we put it in another
experiment, get it moving. Then I'm going to add
some food to the system, and you'll see that in
blue here, right? So I add some food source to the
system. The protocell moves. It encounters the
food. It reconfigures itself and actually then is
able to climb to the highest concentration of food
in that system and stop there. Alright? So not
only do we have this system that has a body, it
has a metabolism, it can use energy, it moves
around. It can sense its local environment and
actually find resources in the environment to
sustain itself.

Now, this doesn't have a brain, it doesn't have a
neural system. This is just a sack of chemicals
that is able to have this interesting and complex
lifelike behavior. If we count the number of
chemicals in that system, actually, including the
water that's in the dish, we have five chemicals
that can do this. So then we put these protocells
together in a single experiment to see what they
would do, and depending on the conditions, we have
some protocells on the left that are moving around
and it likes to touch the other structures in its
environment. On the other hand we have two moving
protocells that like to circle each other, and
they form a kind of a dance, a complex dance with
each other. Right? So not only do individual
protocells have behavior, what we've interpreted
as behavior in this system, but we also have
basically population-level behavior similar to
what organisms have. So now that you're all
experts on protocells, we're going to play a game
with these protocells. We're going to make two
different kinds. Protocell A has a certain kind of
chemistry inside that, when activated, the
protocell starts to vibrate around, just dancing.
So remember, these are primitive things, so
dancing protocells, that's very interesting to us.
(Laughter)

The second protocell has a different chemistry
inside, and when activated, the protocells all
come together and they fuse into one big one.
Right? And we just put these two together in the
same system. So there's population A, there's
population B, and then we activate the system, and
protocell Bs, they're the blue ones, they all come
together. They fuse together to form one big blob,
and the other protocell just dances around. And
this just happens until all of the energy in the
system is basically used up, and then, game over.
So then I repeated this experiment a bunch of
times, and one time something very interesting
happened. So, I added these protocells together to
the system, and protocell A and protocell B fused
together to form a hybrid protocell AB. That
didn't happen before. There it goes. There's a
protocell AB now in this system. Protocell AB
likes to dance around for a bit, while protocell B
does the fusing, okay?

But then something even more interesting happens.
Watch when these two large protocells, the hybrid
ones, fuse together. Now we have a dancing
protocell and a self-replication event. Right.
(Laughter) Just with blobs of chemicals, again. So
the way this works is, you have a simple system of
five chemicals here, a simple system here. When
they hybridize, you then form something that's
different than before, it's more complex than
before, and you get the emergence of another kind
of lifelike behavior which in this case is
replication.

So since we can make some interesting protocells
that we like, interesting colors and interesting
behaviors, and they're very easy to make, and they
have interesting lifelike properties, perhaps
these protocells have something to tell us about
the origin of life on the Earth. Perhaps these
represent an easily accessible step, one of the
first steps by which life got started on the early
Earth. Certainly, there were molecules present on
the early Earth, but they wouldn't have been these
pure compounds that we worked with in the lab and
I showed in these experiments. Rather, they'd be a
real complex mixture of all kinds of stuff,
because uncontrolled chemical reactions produce a
diverse mixture of organic compounds. Think of it
like a primordial ooze, okay? And it's a pool
that's too difficult to fully characterize, even
by modern methods, and the product looks brown,
like this tar here on the left. A pure compound is
shown on the right, for contrast.

So this is similar to what happens when you take
pure sugar crystals in your kitchen, you put them
in a pan, and you apply energy. You turn up the
heat, you start making or breaking chemical bonds
in the sugar, forming a brownish caramel, right?
If you let that go unregulated, you'll continue to
make and break chemical bonds, forming an even
more diverse mixture of molecules that then forms
this kind of black tarry stuff in your pan, right,
that's difficult to wash out. So that's what the
origin of life would have looked like. You needed
to get life out of this junk that is present on
the early Earth, four, 4.5 billion years ago. So
the challenge then is, throw away all your pure
chemicals in the lab, and try to make some
protocells with lifelike properties from this kind
of primordial ooze.

So we're able to then see the self-assembly of
these oil droplet bodies again that we've seen
previously, and the black spots inside of there
represent this kind of black tar -- this diverse,
very complex, organic black tar. And we put them
into one of these experiments, as you've seen
earlier, and then we watch lively movement that
comes out. They look really good, very nice
movement, and also they appear to have some kind
of behavior where they kind of circle around each
other and follow each other, similar to what we've
seen before -- but again, working with just
primordial conditions, no pure chemicals. These
are also, these tar-fueled protocells, are also
able to locate resources in their environment. I'm
going to add some resource from the left, here,
that defuses into the system, and you can see,
they really like that. They become very energetic,
and able to find the resource in the environment,
similar to what we saw before. But again, these
are done in these primordial conditions, really
messy conditions, not sort of sterile laboratory
conditions. These are very dirty little
protocells, as a matter of fact. (Laughter) But
they have lifelike properties, is the point.

So, doing these artificial life experiments helps
us define a potential path between non-living and
living systems. And not only that, but it helps us
broaden our view of what life is and what possible
life there could be out there -- life that could
be very different from life that we find here on
Earth. And that leads me to the next term, which
is "weird life." This is a term by Steve Benner.
This is used in reference to a report in 2007 by
the National Research Council in the United
States, wherein they tried to understand how we
can look for life elsewhere in the universe, okay,
especially if that life is very different from
life on Earth. If we went to another planet and we
thought there might be life there, how could we
even recognize it as life?

Well, they came up with three very general
criteria. First is -- and they're listed here. The
first is, the system has to be in non-equilibrium.
That means the system cannot be dead, in a matter
of fact. Basically what that means is, you have an
input of energy into the system that life can use
and exploit to maintain itself. This is similar to
having the Sun shining on the Earth, driving
photosynthesis, driving the ecosystem. Without the
Sun, there's likely to be no life on this planet.
Secondly, life needs to be in liquid form, so that
means even if we had some interesting structures,
interesting molecules together but they were
frozen solid, then this is not a good place for
life. And thirdly, we need to be able to make and
break chemical bonds. And again this is important
because life transforms resources from the
environment into building blocks so it can
maintain itself.

Now today, I told you about very strange and weird
protocells -- some that contain clay, some that
have primordial ooze in them, some that have
basically oil instead of water inside of them.
Most of these don't contain DNA, but yet they have
lifelike properties. But these protocells satisfy
these general requirements of living systems. So
by making these chemical, artificial life
experiments, we hope not only to understand
something fundamental about the origin of life and
the existence of life on this planet, but also
what possible life there could be out there in the
universe. Thank you. (Applause)

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