All language subtitles for 4700xLec01Sec04DivofLife-en

Now, in the interest of full disclosure,

I have to tell you all the things

that this course is not about, because biology

is a vast, vast subject.

In a mere 25 lectures, like we're going to have here,

we can't possibly do what usually

gets done in a lot of introductory biology courses.

So I have to tell you what those are.

And I have to tell you they're really interesting, really

important.

And my only hope is you will be interested enough

to want to follow on and learn more

biology to learn about them.

But because this is usually the traditional fare of an Intro

Bio course, rather than the stuff I just talked about,

I feel obliged to describe this, because it's really

very, very important.

So section two, what's not in this course?

A, the stunning diversity of life.

If you think about it, introductory biology courses

teach you the kingdoms, and the phyla, and the genera,

and the species, and all of that systematics

of the amazing things that are here

on our planet, all the different plants, all

the different animals, all the different bacteria and fungi

and things like that, the extraordinary diversity of life

life.

Life is amazing.

And I'm not going to tell you about that at all.

I'm not going to describe all of this amazing diversity.

It is worth really learning about it.

It's a motivation.

But I'm going to assume that you've

observed around you for a long period of time

how much extraordinary diversity there is.

And rather than the diversity, what I want to do

is focus on the commonality.

When I speak about the secret of life,

I'm talking about what is common to all of life,

what underlies all of life.

And for that, we kind of have to forget about the differences.

In this course, there is no difference between an elephant

and a mouse.

Although outside of this room, you

would be well-advised to pay attention to that difference.

We're not even going to fuss a great deal

about the difference between a sequoia tree and a mouse.

There are significant differences,

but it's really not going to be the thing we care a great deal

about in this course.

Instead, what's really common to us

is at lower and lower levels of organization.

See, you can study life at the level of an entire biosphere,

an entire planet interacting.

At present, we are aware of exactly one biosphere.

The only biosphere we know about is the Earth.

At a lower level, one can really study ecosystems,

sets of interacting organisms of all different sizes,

all different varieties, say forest on the Earth,

like that forest I brought up over there.

You could study an individual organism within an ecosystem,

like a human being, maybe an MIT undergraduate,

for example, walking in the forest.

At a lower level, you could study--

there might be undergraduates walking in the forest, right?

They do sometimes.

That's OK.

You could study an organ, an organ like the eye of that MIT

undergraduate in the forest, looking around

at the amazing things in the forest,

and study the eye as an entire organ.

You might decide to study it at a finer level,

not the whole organ, but individual tissues

within that organ, homogeneous sets of cells.

So you might study tissues, like the retina in that eye.

So we have muscles, and the lens,

and the retina is back there.

So you might study the retina.

You might decide to study individual cells in biology,

like a specific cell type in the retina,

like the rod cell, a particular funny kind of cell that's

involved in being able to receive light and detect light.

And the cell biology of rod cells

could be really interesting.

You can zoom into a higher level and study

organelles within the cell, subcomponents of the cell.

You might study the nucleus of the cell.

You might study the mitochondrion of the cell.

You might decide to study the molecules of life

in the nucleus, the DNA, from the mitochondria, the ATP.

All of those are important valid ways to study biology.

They're all important.

To really understand biology, you've

got to know all of those different levels.

But because we're in fundamental principles,

we're going to ignore the top of that picture.

And we're going to focus down at the bottom.

We're going to look not at the mouse.

We're not even going to be up here at the level of a coffee

bean or a grain of rice.

We're going to mostly be zooming in.

We're going to zoom in.

We might start getting interested over here

at particular cells.

Very little we're even going to say about organs and things

like that.

As we zoom in further, mitochondria.

Here's a bacteria.

As we zoom in further, we get down to viruses.

As we zoom in further, we get down to proteins.

And zooming in further, we get down

to sugars, and water molecules, and carbon atoms.

And we will not go further than that.

We have to leave something for the physicists to do, right?

So we're down here, because the truth

is, once you get down to this level,

all these sorts of things are more and more common to life.

And as we come out of here, all the diversity comes in.

But I would argue, we can't understand the diversity

without understanding the commonality.

Take a few minutes to think about what you've just heard

by answering this question.