Impact of changes to trophic pyramids

WEBVTT
Kind: captions
Language: en

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- [Instructor] What we see here is known

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as a trophic pyramid,
and the word trophic,

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in a biology context, is
referring to food relationships.

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So one way to think about this,

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it tells us who is eating whom,
and who is producing energy,

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and then who is able to
leverage that energy.

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So the base of a trophic pyramid,

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you have your primary
producers, primary producers.

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These are often known as autotrophs,

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because they're able to
take energy from the sun,

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so sun's energy, and nutrients
that are available to them,

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and store some of that energy as biomass.

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And biomass is just a fancy
word for the actual substance

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of the organism that is
inherently storing energy.

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When someone tells you that that piece

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of food has a certain number of calories,

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that's because there's
energy stored in it.

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Calories are a unit of energy.

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And so, let's just say, if you
were to take a square meter,

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if you were to average on
a per square meter basis,

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these primary producers
in this environment,

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let's say they're able to
store 20,000 kilocalories

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per square meter per year.

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What's interesting
about a trophic pyramid,

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it helps describe, well, okay,

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that energy's stored as
biomass, what happens then?

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Well, then you could go to the next level,

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and you could view these as your primary

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or first-level consumers.

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So first-level, well, I
could call them level one

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or primary consumers,
these are the organisms

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that would eat the primary producers.

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But not all of that energy gets restored

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as biomass in these organisms.

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In fact, there is a lot of loss.

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On average, when we look at ecosystems,

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it tends to be only about 10% makes it

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from one level of our
trophic pyramid to the next.

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So at this level, on a per,
on average, per square meter,

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instead of 20,000
kilocalories being stored

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as biomass per year, you'd
only have 10% of that.

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So it might only be 2,000.

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2,000 kilocalories per
square meter per year.

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So notice, you have that drop-off.

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And then you could go to
the next level after that,

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you could view these as
the secondary consumers.

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These are the folks who might
eat the primary consumers,

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the first-level consumers.

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You get another 10%
drop-off, so you would,

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or I should say, a 90% drop-off,
only 10% gets transferred.

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So about 200, 200 kilocalories
per square meter per year.

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And it keeps happening, the
folks who eat those folks,

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well then, you've dropped off
at this level right over here.

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You could call these the
third-level consumers,

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or sometimes viewed as tertiary consumers.

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This would be about 20 kilocalories

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per square meter per year.

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And this doesn't mean that
every square meter will have

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exactly 20 kilocalories of biomass of,

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let's say in this example, snake.

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It just means that if you
were to look at the biomass

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of snakes, and you were to average them

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across this ecosystem, the surface area,

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then you might average
about 20 kilocalories

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per square meter per year.

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And then you get to the
top of this pyramid.

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And this, you could view as
your level four consumer.

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You could view this as,

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since they're at the top of the pyramid,

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this is sometimes known
as the apex predator.

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But every stage here, you only are able

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to transfer 10% of the biomass.

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So here, you have two kilocalories

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per square meter per year.

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And what's useful about
this, it helps us understand

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what an ecosystem can support.

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It can support a lot of biomass
of our primary producers,

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but it can support very little biomass

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of our apex predators, and that's why,

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if you were to go into the forest,

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you would see very few apex predators.

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If you were to look at the apex predators

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and you were to think about their biomass

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in terms of kilocalories, and
spread it over their region

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where they have to find
food, it would be much lower

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than the average biomass
per square meter of,

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say, the grass and the trees.

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Now, an interesting thing is, well,

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where is a lot of that
energy getting lost to?

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Well, in a lot of cases, these
organisms are moving around.

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They have to do things,
they have processes

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in their own body, and those
things all generate heat.

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So even plants, even plants generate heat.

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So all of these characters
are, there's some energy

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that's being released as heat.

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Also, when these players die,

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they are decomposed by other organisms.

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So all this biomass, it's
either just going to die,

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or it's going to get eaten,
but even when it gets eaten,

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all of the energy doesn't get transferred.

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Some of it stays in the
undigested material,

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which we refer to as poop, and so,

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those dead bodies, that
dead biomass, or this poop

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that still contains energy,
is going to be fed on

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by what we call decomposers, decomposers.

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And they really break
things down into nutrients,

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which then can be consumed
by the primary producers

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as they utilize the sun's energy

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and keep the cycle going after that.

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Now, one interesting
thing to think about is,

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what if there are
changes to the ecosystem?

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What if, for example, a
nearby volcano erupts?

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And that volcano, let me draw that,

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it's a fun thing to draw,

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that volcano erupts and
ash goes into the sky,

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and all year it's just really gray.

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What do you think would happen?

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Well, the sun's energy that's
able to hit the surface

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of the earth in this area
would go down by a good bit.

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And so, if that went down by a good bit,

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then the primary producers
might not be able

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to store 20,000 kilocalories
per square meter per year.

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It might go down to 2,000 kilocalories

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per square meter per
year, and in which case,

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you'd drop to a zero off of all of these.

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So instead of 20,000,
it might go to 2,000.

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Instead of 2,000, this would be 200.

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Instead of 200, this would be 20.

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Instead of 20, this would be two.

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Instead of two, this would 0.2.

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And so, something like
the loss of light energy,

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even though this apex predator doesn't

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directly photosynthesize, a
lot fewer of them are going

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to be able to be supported
in that ecosystem

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if you have a lot less
energy stored at biomass,

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at the primary production
level, because there's just less

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of sun's energy to be able
to be stored as biomass.

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There could be other things
that happen in the ecosystem.

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Let's say that some
pesticides get introduced,

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and some of these level one
consumers start dying out.

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Well then, you might have less
of the transfer of biomass

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from the primary producer level

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to the primary consumer
level, which, once again,

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might affect these other
levels of the trophic pyramid.

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So this is an interesting
thing to think about.

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Ecosystems are these really complex,

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intertwined things, and one impact

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at one area could have
far-reaching consequences

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throughout the entire ecosystem.

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It's also interesting to think

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of ecosystems as energy transfer.

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Energy's coming from the
sun, and it's being cycled

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through this ecosystem,
through this pyramid.

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Some of it gets stored as
biomass and gets transferred

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to other forms of biomass, but
a lot of it gets lost as heat

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as these organisms' cells go
through different processes.

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The organisms are running around,

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living their life, doing whatever.


Cellular evidence of common ancestry

WEBVTT
Kind: captions
Language: en

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- [Instructor] Perhaps
the most mind-blowing idea

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in all of biology is the concept

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that all living things we know of,

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based on current evidence that we have,

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all originated from a common ancestor.

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So it doesn't matter
whether we're talking about

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a simple bacterial cell, which actually,

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in reality, isn't so simple after all,

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a tree made up of trillions
and trillions of cells,

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a hairy primate made up of
trillions and trillion cells,

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or seemingly well-dressed
agriculture kittens,

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which are also made of trillions
and trillions of cells,

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that they all share a common ancestor.

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You might have seen things
like these evolutionary trees.

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This is an example right over here.

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This is saying the same thing.

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That everything that we
see in the world today,

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all living things, regardless
of what domain they're in,

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and we would be a subset of
animals, right over here.

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There's so many animal species.

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That they all share a common ancestor

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several billions of years ago.

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But you should be skeptical.

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We are scientists here.

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How do we believe this, what
is the evidence for that?

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And one piece of evidence is

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by looking at the cellular level,

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and look at commonalities
amongst different groups,

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and realize that it would
be unlikely for them

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to develop independently of each other.

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For example, all lifeforms
that we know of have DNA.

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They all have RNA.

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And it isn't just how the
encode information, it's also

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processes, biochemical processes,
that occur in the cells.

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They all have some form of glycolysis.

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But this seems, and these
aren't the only things

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that we've observed are
common to all lifeforms,

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they're all based on
cells as the basic units,

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which are bound by a membrane.

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And so, in theory, these things, I guess,

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could have developed
independently of each other,

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without having a common ancestor,

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but having a common ancestor
is the best explanation

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of why we see these different processes.

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Some of these are quite complex for these

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different structures
throughout life as we know it.

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And so you're saying all
right, I can maybe buy that,

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that there's this common
ancestor right over here,

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but how do we constuct this tree?

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How do we know when things branched off?

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Because some of these
branches off of these trees,

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once again, these would have occurred

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hundreds of millions or
billions of years ago,

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and none of us were around
to observe that happening.

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And once again, that goes
to more structural evidence.

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So, for example, amongst what
we now classify as eukaryotes,

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so everything in this brown color,

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this branch of the tree right over here,

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we see that all of them have
membrane-bound organelles.

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Membrane-bound organelles.

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These are things like a
nucleus, or mitochondria

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that we study in many other videos.

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They all have linear chromosomes.

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So, in other groups in this tree of life,

00:03:01.680 --> 00:03:03.290
in this evolutionary tree,

00:03:03.290 --> 00:03:05.020
you might have circular chromosomes.

00:03:05.020 --> 00:03:07.710
But common to all eukaryotes
are the linear chromosomes.

00:03:07.710 --> 00:03:12.390
And they all have chromosomes
that contain introns.

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Introns are sequences of DNA
that don't code for genes

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that will then code into proteins.

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And we're still exploring
what the point of introns are.

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But the reason why all of these have been

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classified together is that
they have these similarities.

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And so we believe that they

00:03:28.420 --> 00:03:30.760
would've formed their own branch.

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And based on how similar
things are, that's where

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we theorize when things
might have branched off.

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And now that we have more sophisticated

00:03:38.610 --> 00:03:40.960
tools of sequencing DNA and RNA,

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we can look at how different
those sequences are

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to construct more and more
precise trees like this.


Artificial selection and domestication

WEBVTT
Kind: captions
Language: en

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- [Instructor] Most of us
are familiar with dogs,

00:00:02.740 --> 00:00:05.430
often times known as man's best friend.

00:00:05.430 --> 00:00:07.330
And what's fascinating about them is that

00:00:07.330 --> 00:00:09.760
they are one species, even
though different types

00:00:09.760 --> 00:00:12.660
of dogs, different breeds could
look very, very different.

00:00:12.660 --> 00:00:14.550
And the fact that they're
one species says that

00:00:14.550 --> 00:00:16.180
if you have a male and a female dog,

00:00:16.180 --> 00:00:18.930
any two, that in theory
they could reproduce

00:00:18.930 --> 00:00:21.290
and produce viable offspring.

00:00:21.290 --> 00:00:23.950
Although in, for example,
the case of this character

00:00:23.950 --> 00:00:27.120
and this character, the mechanics
could get quite difficult.

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But an interesting question
is, is where do dogs come from

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and why do we have these seemingly

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specialized breeds amongst dogs?

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You might have things like
a Rottweiler that's better

00:00:37.180 --> 00:00:40.320
for protection, you might
have things like terriers

00:00:40.320 --> 00:00:44.390
that have been specialized
to maybe go after rodents.

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You have things like border
collies that are good at

00:00:46.830 --> 00:00:49.250
herding other types of animals.

00:00:49.250 --> 00:00:50.790
The simple answer is,

00:00:50.790 --> 00:00:53.940
through artificial
selection and domestication.

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Remember, in any population of a species

00:00:56.390 --> 00:00:58.200
there's variation in that species.

00:00:58.200 --> 00:01:00.630
And when we talked
about natural selection,

00:01:00.630 --> 00:01:03.220
that's where the environment might select

00:01:03.220 --> 00:01:04.660
for certain of those variants.

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Certain of those variants might
make it a little bit easier

00:01:06.560 --> 00:01:09.660
to survive or reproduce, and
then those would predominate

00:01:09.660 --> 00:01:12.890
and that's how evolution happens.

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Artificial selection and
domestication is where

00:01:15.440 --> 00:01:18.080
humans take matters into their own hands.

00:01:18.080 --> 00:01:20.770
And instead of waiting
for nature to do things,

00:01:20.770 --> 00:01:22.810
they are the selection factor.

00:01:22.810 --> 00:01:26.570
They pick which of the
species get to reproduce

00:01:26.570 --> 00:01:27.910
and which ones don't.

00:01:27.910 --> 00:01:30.930
And when you have that type
of artificial selection,

00:01:30.930 --> 00:01:34.040
the change can happen much, much faster.

00:01:34.040 --> 00:01:37.160
Breeding is essentially
artificial selection.

00:01:37.160 --> 00:01:40.410
So dogs like this, and
all the dogs we know of

00:01:40.410 --> 00:01:42.750
had ancestors that looked like this,

00:01:42.750 --> 00:01:45.230
that looked like a wolf, that were a wolf.

00:01:45.230 --> 00:01:47.690
And what we theorize is
that the early stages

00:01:47.690 --> 00:01:51.920
of some wolf eventually evolving into dogs

00:01:51.920 --> 00:01:54.850
might have been more
traditional natural selection

00:01:54.850 --> 00:01:56.990
where tens of thousands of years ago

00:01:56.990 --> 00:01:59.880
our hunter gatherer ancestors
as they hunted and gathering

00:01:59.880 --> 00:02:02.510
they might have left
over food here or there,

00:02:02.510 --> 00:02:05.880
and some of the wolves that
just happened to be the variants

00:02:05.880 --> 00:02:07.720
that were a little bit more
comfortable getting close

00:02:07.720 --> 00:02:10.520
to humans might have
benefited from being able

00:02:10.520 --> 00:02:12.130
to get some of that left over food,

00:02:12.130 --> 00:02:14.450
being able to get some of the remains

00:02:14.450 --> 00:02:16.510
that the human beings left behind.

00:02:16.510 --> 00:02:20.020
But then over time, human
beings probably realized

00:02:20.020 --> 00:02:23.110
that hey, these wolves
are useful to have around.

00:02:23.110 --> 00:02:25.600
Maybe they provide some
form of protection,

00:02:25.600 --> 00:02:28.650
maybe over time they
started breeding the wolves

00:02:28.650 --> 00:02:30.430
so the wolves that were
especially friendly,

00:02:30.430 --> 00:02:32.480
the wolves that were especially
good at a certain task,

00:02:32.480 --> 00:02:36.250
say protection, or going
after some type of an animal

00:02:36.250 --> 00:02:38.790
or retrieving things, they allowed those

00:02:38.790 --> 00:02:40.760
to reproduce together and over time,

00:02:40.760 --> 00:02:42.530
over tens of thousands of years,

00:02:42.530 --> 00:02:45.080
we went from wolves to dogs.

00:02:45.080 --> 00:02:46.580
And even once we had dogs,

00:02:46.580 --> 00:02:48.740
the breeding got even more specialized.

00:02:48.740 --> 00:02:51.020
As I mentioned, things
like border collies,

00:02:51.020 --> 00:02:55.550
this was many years, many
generations of breeding

00:02:55.550 --> 00:02:58.270
where sheep herders
might have selected dogs

00:02:58.270 --> 00:02:59.970
that were good at herding sheep.

00:02:59.970 --> 00:03:02.480
That terriers came from
dogs that were good

00:03:02.480 --> 00:03:05.040
at going after rodents,
things like rottweilers

00:03:05.040 --> 00:03:07.200
or dogs breeding the dogs
that were especially good

00:03:07.200 --> 00:03:10.260
at providing protection or defense.

00:03:10.260 --> 00:03:12.760
And it isn't just dogs that are products

00:03:12.760 --> 00:03:15.940
of artificial selection and domestication.

00:03:15.940 --> 00:03:17.928
Pretty much any animal that you might see

00:03:17.928 --> 00:03:20.350
on say a farm would be the product

00:03:20.350 --> 00:03:23.190
of artificial selection and domestication.

00:03:23.190 --> 00:03:26.010
A wild pig looks like this, while the ones

00:03:26.010 --> 00:03:27.400
that you would see on
a farm look like that.

00:03:27.400 --> 00:03:29.790
And once again, they would
have selected for things like

00:03:29.790 --> 00:03:32.320
docility, things where
they're less aggressive

00:03:32.320 --> 00:03:34.830
and they're easier to take care of.

00:03:34.830 --> 00:03:36.860
And artificial selection and domestication

00:03:36.860 --> 00:03:39.110
does not apply just to animals.

00:03:39.110 --> 00:03:41.890
Pretty much anything you might
see in the produce section

00:03:41.890 --> 00:03:44.500
of your supermarket is the product

00:03:44.500 --> 00:03:46.930
of artificial selection and domestication.

00:03:46.930 --> 00:03:50.210
There might be wild
variants of these different

00:03:50.210 --> 00:03:52.020
vegetables or these different fruits,

00:03:52.020 --> 00:03:54.190
but over roughly 10 or 15,000 years

00:03:54.190 --> 00:03:57.310
of human agriculture,
every generation of crop

00:03:57.310 --> 00:03:59.150
they would have selected for the crops

00:03:59.150 --> 00:04:01.550
that are more robust, that tasted better,

00:04:01.550 --> 00:04:03.770
that were able to grow
in different climates

00:04:03.770 --> 00:04:07.250
and by allowing those
variants to reproduce,

00:04:07.250 --> 00:04:09.530
we eventually ended up
with the domesticated crops

00:04:09.530 --> 00:04:10.443
we see today.


Perfect competition

WEBVTT
Kind: captions
Language: en

00:00:01.280 --> 00:00:03.090
- [Instructor] In our study
of the different types

00:00:03.090 --> 00:00:05.690
of markets, we are now going
to dive a little bit deeper

00:00:05.690 --> 00:00:09.300
and understand perfect competition.

00:00:09.300 --> 00:00:11.930
Now this notion of something
being perfectly competitive,

00:00:11.930 --> 00:00:14.040
you might have a general
idea of what it means.

00:00:14.040 --> 00:00:16.090
You might feel like it's very competitive,

00:00:16.090 --> 00:00:18.750
that there's a lot of
people there maybe competing

00:00:18.750 --> 00:00:20.850
for your business, or maybe
there's a lotta buyers,

00:00:20.850 --> 00:00:22.550
and there are a lotta sellers.

00:00:22.550 --> 00:00:25.140
And that is generally
true, but we're trying

00:00:25.140 --> 00:00:27.780
to be economists here, so
we wanna be very precise

00:00:27.780 --> 00:00:29.210
with our language.

00:00:29.210 --> 00:00:31.930
So when economists talk
about perfect competition,

00:00:31.930 --> 00:00:36.690
they're talking about this
somewhat very abstract state

00:00:36.690 --> 00:00:39.840
where you have many buyers and sellers,

00:00:39.840 --> 00:00:43.343
many sellers and buyers.

00:00:44.480 --> 00:00:46.370
Now that doesn't seem too abstract so far.

00:00:46.370 --> 00:00:48.210
We can imagine a lot of markets

00:00:48.210 --> 00:00:51.370
that have many sellers and buyers.

00:00:51.370 --> 00:00:53.570
Now another thing that
defines perfect competition

00:00:53.570 --> 00:00:55.960
from an economics point of
view is that they're selling

00:00:55.960 --> 00:01:00.150
identical, identical products or services,

00:01:00.150 --> 00:01:04.390
products, products or services.

00:01:04.390 --> 00:01:06.630
Now this one seems a little bit harder

00:01:06.630 --> 00:01:08.830
because even when you can imagine

00:01:08.830 --> 00:01:11.220
a fairly competitive
market, does everyone sell

00:01:11.220 --> 00:01:13.470
exactly the same thing?

00:01:13.470 --> 00:01:17.200
Well you imagine certain
markets, maybe the market

00:01:17.200 --> 00:01:22.200
for water or maybe the market
for some type of energy

00:01:22.810 --> 00:01:25.440
or maybe the market for produce,

00:01:25.440 --> 00:01:29.030
gets pretty close to identical
products or services.

00:01:29.030 --> 00:01:32.330
So so far it doesn't seem
like that abstract of a thing.

00:01:32.330 --> 00:01:35.410
Now another aspect of perfect competition

00:01:35.410 --> 00:01:38.390
is that every agent, so
that would be the buyers,

00:01:38.390 --> 00:01:40.390
the sellers, the producers, the consumers,

00:01:40.390 --> 00:01:44.643
they have perfect information,
perfect information.

00:01:45.560 --> 00:01:48.290
Now what does perfect information mean?

00:01:48.290 --> 00:01:51.150
It means that every
participant in the market,

00:01:51.150 --> 00:01:54.580
the buyers and the sellers,
they all know exactly

00:01:54.580 --> 00:01:56.330
what is happening in the market.

00:01:56.330 --> 00:01:59.980
So what goods or services
are selling for what price

00:01:59.980 --> 00:02:03.130
and who is selling to whom.

00:02:03.130 --> 00:02:05.510
So once again, this gets
a little bit more abstract

00:02:05.510 --> 00:02:07.780
because to get truly perfect information,

00:02:07.780 --> 00:02:10.220
you can't, not everyone in
a market will always know

00:02:10.220 --> 00:02:11.430
everything that's going on.

00:02:11.430 --> 00:02:14.150
So once again, this is a
little bit of an abstract idea

00:02:14.150 --> 00:02:15.930
that economists have introduced

00:02:15.930 --> 00:02:17.990
to be a little bit more precise.

00:02:17.990 --> 00:02:19.910
And the last aspect we're
going to talk about,

00:02:19.910 --> 00:02:22.740
and this is also something
that is a bit idealized

00:02:22.740 --> 00:02:25.130
that doesn't truly
exist in the real world,

00:02:25.130 --> 00:02:27.480
things close to this
exist in the real world,

00:02:27.480 --> 00:02:32.480
is that there is no barriers,
barriers to entry or exit.

00:02:36.360 --> 00:02:38.340
Now we already mentioned some markets,

00:02:38.340 --> 00:02:40.530
say the market for agriculture.

00:02:40.530 --> 00:02:43.690
That doesn't quite have no
barriers to entry or exit.

00:02:43.690 --> 00:02:45.410
You would somehow have to
get land, you would have

00:02:45.410 --> 00:02:47.430
to get seeds, you would
have to get fertilizer,

00:02:47.430 --> 00:02:50.240
you would have to hire
people to put the seeds in

00:02:50.240 --> 00:02:51.630
and to harvest the crops.

00:02:51.630 --> 00:02:55.010
And so almost any industry,
any market you imagine,

00:02:55.010 --> 00:02:58.890
will have some barriers, but
this is an idealized notion

00:02:58.890 --> 00:03:00.690
that economists like to think about,

00:03:00.690 --> 00:03:03.110
and of course in the real world
things might approach this

00:03:03.110 --> 00:03:06.630
or be closer to perfect
competition than say other markets.

00:03:06.630 --> 00:03:09.810
But when you're in this
situation, let's analyze

00:03:09.810 --> 00:03:11.970
what will be happening.

00:03:11.970 --> 00:03:15.460
So we can look at the market
as a whole for whatever

00:03:15.460 --> 00:03:17.310
this product and service is.

00:03:17.310 --> 00:03:21.920
So let me draw price versus quantity here

00:03:21.920 --> 00:03:24.380
for the market as a whole.

00:03:24.380 --> 00:03:28.760
So this is price, and this is quantity.

00:03:28.760 --> 00:03:33.250
And this is the market right over here.

00:03:33.250 --> 00:03:35.470
And so, we've seen this multiple times

00:03:35.470 --> 00:03:37.350
in our economics journey.

00:03:37.350 --> 00:03:39.860
That you have an
upward-sloping supply curve,

00:03:39.860 --> 00:03:42.160
and once again this is
for the entire market.

00:03:42.160 --> 00:03:44.080
Let me do this is in a different color.

00:03:44.080 --> 00:03:48.910
So you have an upward-sloping
supply curve like that.

00:03:48.910 --> 00:03:50.670
And you would have a downward-sloping

00:03:50.670 --> 00:03:54.490
demand curve like that.

00:03:54.490 --> 00:03:57.460
And we know what the
equilibrium price and quantity

00:03:57.460 --> 00:03:59.350
would be for the market.

00:03:59.350 --> 00:04:03.960
So this right over here
would be the equilibrium,

00:04:03.960 --> 00:04:06.420
equilibrium quantity for the market,

00:04:06.420 --> 00:04:10.668
and this right over here
would be the equilibrium price

00:04:10.668 --> 00:04:12.740
for the market.

00:04:12.740 --> 00:04:16.940
Now how would this affect
the decisions for the firm

00:04:16.940 --> 00:04:18.750
in perfect competition?

00:04:18.750 --> 00:04:22.240
Well let's draw, let's
draw a similar analysis,

00:04:22.240 --> 00:04:24.640
but now at the firm level.

00:04:24.640 --> 00:04:29.640
So on this axis, you could
view this for the firm,

00:04:30.590 --> 00:04:33.170
and so this is going to be
the firm right over here,

00:04:33.170 --> 00:04:35.300
one of the participants in
the perfect competition,

00:04:35.300 --> 00:04:37.490
one of the producers, one of the sellers.

00:04:37.490 --> 00:04:39.590
So on this axis, you
could view this as price.

00:04:39.590 --> 00:04:44.220
You could also view this
as marginal revenue.

00:04:44.220 --> 00:04:47.610
And you could also view
this as marginal cost

00:04:47.610 --> 00:04:50.750
because we're going to plot
the different curves here.

00:04:50.750 --> 00:04:53.800
And then on the horizontal axis,

00:04:53.800 --> 00:04:56.709
we're going to have quantity
again, but this is once again

00:04:56.709 --> 00:05:00.320
the quantity that the firm produces.

00:05:00.320 --> 00:05:03.745
Now, first of all, we could
think about the marginal cost

00:05:03.745 --> 00:05:07.600
for the firm, and we've
seen this multiple times.

00:05:07.600 --> 00:05:09.430
That the marginal cost for the firm,

00:05:09.430 --> 00:05:11.950
it might look something like this.

00:05:11.950 --> 00:05:16.570
It over time might trend
upwards something like this

00:05:16.570 --> 00:05:19.372
where at some point every
incremental unit is costing

00:05:19.372 --> 00:05:20.800
more and more to produce.

00:05:20.800 --> 00:05:22.380
Maybe it's harder to get the resources,

00:05:22.380 --> 00:05:24.990
harder to get the labor,
whatever you wanna say.

00:05:24.990 --> 00:05:26.460
So that's the marginal cost curve,

00:05:26.460 --> 00:05:29.220
fairly typical for a firm.

00:05:29.220 --> 00:05:33.080
And then we could think about
their average total cost.

00:05:33.080 --> 00:05:36.210
And so the average total
cost curve might look

00:05:36.210 --> 00:05:38.110
something like this.

00:05:38.110 --> 00:05:39.903
So draw something like this.

00:05:41.730 --> 00:05:46.260
So our average total cost,
we've seen this multiple times.

00:05:46.260 --> 00:05:50.610
Now what is going to be the
marginal revenue for this firm

00:05:50.610 --> 00:05:53.093
that is operating in perfect competition?

00:05:54.040 --> 00:05:56.560
Well when it's operating
in perfect competition,

00:05:56.560 --> 00:05:58.520
it just has to be a price taker.

00:05:58.520 --> 00:06:01.360
So every unit it sells
is just going to get

00:06:01.360 --> 00:06:04.590
the market price for that unit.

00:06:04.590 --> 00:06:08.796
So in perfect competition,
the firm, every participant

00:06:08.796 --> 00:06:11.640
that is really identical in a lotta ways,

00:06:11.640 --> 00:06:13.390
they're just gonna take that price.

00:06:13.390 --> 00:06:15.950
Think about it, they won't
be able to charge any more

00:06:15.950 --> 00:06:18.250
for their product or service
than the market price

00:06:18.250 --> 00:06:20.260
because their product
or service is identical

00:06:20.260 --> 00:06:22.160
to everyone else's, and everyone knows it

00:06:22.160 --> 00:06:24.260
because of perfect information,
and they would have

00:06:24.260 --> 00:06:26.510
no motivation to charge less either.

00:06:26.510 --> 00:06:27.640
They're just passive.

00:06:27.640 --> 00:06:30.190
You could view it that way
when it comes to price.

00:06:30.190 --> 00:06:34.430
So if we just take this
market price across

00:06:34.430 --> 00:06:35.683
just like that.

00:06:36.580 --> 00:06:40.410
This right over here, this
price, is going to define

00:06:40.410 --> 00:06:43.180
the marginal revenue curve for that firm.

00:06:43.180 --> 00:06:47.070
So let me make this a bold
curve right over here.

00:06:47.070 --> 00:06:50.950
This is going to be the
marginal revenue for the firm.

00:06:50.950 --> 00:06:53.610
For every unit it sells on the margin,

00:06:53.610 --> 00:06:56.190
that's how much more
revenue it's going to get.

00:06:56.190 --> 00:06:58.780
Now you could also view
this as the demand curve

00:06:58.780 --> 00:07:00.840
for the firm's product.

00:07:00.840 --> 00:07:03.870
You could also view this
as the average revenue

00:07:03.870 --> 00:07:05.310
for the firm's product.

00:07:05.310 --> 00:07:08.690
And let me make this clear,
this is for the firm,

00:07:08.690 --> 00:07:12.520
demand for the firm, which
is equal to the price

00:07:12.520 --> 00:07:15.030
that the firm actually gets.

00:07:15.030 --> 00:07:17.900
So the big takeaway here
is in perfect competition,

00:07:17.900 --> 00:07:19.820
which is this somewhat idealized state

00:07:19.820 --> 00:07:21.720
that doesn't quite
exist in the real world,

00:07:21.720 --> 00:07:23.780
certain markets can approach it,

00:07:23.780 --> 00:07:27.150
the firms are passive price takers.

00:07:27.150 --> 00:07:29.970
They have no say on what
the price is going to be,

00:07:29.970 --> 00:07:32.411
and so it would be rational
for them to just produce

00:07:32.411 --> 00:07:34.686
where their marginal cost intersects

00:07:34.686 --> 00:07:36.620
with their marginal revenue.

00:07:36.620 --> 00:07:39.100
Because anything more
than that, then for every

00:07:39.100 --> 00:07:42.160
incremental unit, they're
going to be spending more money

00:07:42.160 --> 00:07:44.900
than they get in terms of revenue.

00:07:44.900 --> 00:07:47.130
And this passivity goes
a little bit against

00:07:47.130 --> 00:07:50.240
some of our everyday notions
of fierce competition.

00:07:50.240 --> 00:07:51.750
When we think about fierce competition,

00:07:51.750 --> 00:07:54.040
we often think about many players trying

00:07:54.040 --> 00:07:57.330
to constantly undercut each
other, and in future videos,

00:07:57.330 --> 00:07:59.520
we'll talk about scenarios
where that might happen.

00:07:59.520 --> 00:08:02.690
And you might think about
whether or not you would want

00:08:02.690 --> 00:08:05.760
certain markets to have
perfect competition.

00:08:05.760 --> 00:08:08.390
Because no barriers to
entry means that frankly

00:08:08.390 --> 00:08:10.450
anybody could get into that industry.

00:08:10.450 --> 00:08:13.150
So for example, you might
not want perfect competition

00:08:13.150 --> 00:08:16.640
when it comes to someone
being say your doctor

00:08:16.640 --> 00:08:18.010
because you want barriers to entry.

00:08:18.010 --> 00:08:19.520
You want some level of training.

00:08:19.520 --> 00:08:22.130
You want some level of
experience before someone

00:08:22.130 --> 00:08:24.453
gets into that service.


Khan Stories: Mr. Kile's class

WEBVTT
Kind: captions
Language: en

00:00:00.400 --> 00:00:03.658
- My mom was a teacher, my
grandfather was a teacher.

00:00:03.658 --> 00:00:06.863
(light string music)

00:00:06.863 --> 00:00:09.250
And then we'll be ready to
move on to actually finding

00:00:09.250 --> 00:00:12.123
missing angels using our
Khan Academy program.

00:00:15.560 --> 00:00:17.500
Myself growing up, '80s, '90s kid,

00:00:17.500 --> 00:00:19.120
I was like super into video games,

00:00:19.120 --> 00:00:21.054
and I really wanted to
make my own video games.

00:00:21.054 --> 00:00:23.110
(upbeat video game voice)

00:00:23.110 --> 00:00:25.350
So I got into the computer
programming classes

00:00:25.350 --> 00:00:26.441
and it was really cool.

00:00:26.441 --> 00:00:30.406
So just based on the
diagram you just figure out.

00:00:30.406 --> 00:00:32.260
- Everybody kept saying wow,
you explain things really well,

00:00:32.260 --> 00:00:34.580
so I ended up changing my
minor wanted to pursue teaching

00:00:34.580 --> 00:00:35.413
full-time.

00:00:35.413 --> 00:00:36.740
Ever since then I haven't looked back.

00:00:36.740 --> 00:00:38.780
Perfect, nice job guys.

00:00:38.780 --> 00:00:42.447
(lively instrumental music)


What Reagan policies are still debated today?

WEBVTT
Kind: captions
Language: en

00:00:00.330 --> 00:00:01.163
- [Instructor] How has the debate

00:00:01.163 --> 00:00:03.910
over Reagan's policies evolved into today?

00:00:03.910 --> 00:00:07.100
- When Reagan was making the case for,

00:00:07.100 --> 00:00:09.070
basically, they called
it the Reagan revolution,

00:00:09.070 --> 00:00:11.430
because it was a real departure

00:00:11.430 --> 00:00:14.060
from the way the federal
government had been

00:00:14.060 --> 00:00:15.640
existing in American life.

00:00:15.640 --> 00:00:18.280
The debate had mostly
been between Democrats

00:00:18.280 --> 00:00:21.400
and Republicans over to how
best manage the government.

00:00:21.400 --> 00:00:23.490
Ronald Reagan came in and said no.

00:00:23.490 --> 00:00:26.700
Just get government out
of the conversation.

00:00:26.700 --> 00:00:30.820
That has continued to
bounce along in politics,

00:00:30.820 --> 00:00:33.930
there was the most major
fight on those lines

00:00:33.930 --> 00:00:37.440
with Newt Gingrich and
president Bill Clinton.

00:00:37.440 --> 00:00:40.030
Since then, there have been pockets of it,

00:00:40.030 --> 00:00:42.970
but the appetite for deficit reduction,

00:00:42.970 --> 00:00:46.150
for shrinking government
in order to make sure

00:00:46.150 --> 00:00:48.100
that the bills are paid by government,

00:00:48.100 --> 00:00:50.960
has kind of gone out
of favor in Washington.

00:00:50.960 --> 00:00:53.580
It was a very big deal during the '90s and

00:00:53.580 --> 00:00:56.690
during the first 10 years of this century,

00:00:56.690 --> 00:00:59.990
but it has not really been as much a part

00:00:59.990 --> 00:01:03.760
of the conversation in
politics as it once was.

00:01:03.760 --> 00:01:07.030
It once dominated the way
people talked about government.

00:01:07.030 --> 00:01:09.300
Now there are other things that are taking

00:01:09.300 --> 00:01:10.613
the conversation away.


How have Reagan's policies affected the government?

WEBVTT
Kind: captions
Language: en

00:00:00.390 --> 00:00:02.660
- [Man] How have President
Reagan's policies affected

00:00:02.660 --> 00:00:04.780
the government since he left office?

00:00:04.780 --> 00:00:08.590
- What Ronald Reagan did was
set up a titanic debate really

00:00:08.590 --> 00:00:12.130
between those who believed
in the new deal view

00:00:12.130 --> 00:00:15.550
of government which was that
it was there to help those

00:00:15.550 --> 00:00:20.550
who could not help themselves
and manage an enormous economy

00:00:22.040 --> 00:00:25.330
and the enormous life of
the world's only superpower

00:00:25.330 --> 00:00:28.130
or at least one of the two
superpowers and what that,

00:00:28.130 --> 00:00:30.420
on the new deal style, that
was what government should do.

00:00:30.420 --> 00:00:33.300
On the Reagan side, he said
get government out of the way

00:00:33.300 --> 00:00:37.820
and let American free enterprise
and individual initiative

00:00:37.820 --> 00:00:40.050
create greatness in America again

00:00:40.050 --> 00:00:43.640
and so that was just setting
up that idealogic conversation

00:00:43.640 --> 00:00:46.900
now continued all the way
through New Gingrich's revolution

00:00:46.900 --> 00:00:49.960
in 1994 and his clashes with Bill Clinton.

00:00:49.960 --> 00:00:52.930
They were over the same kinds
of things that Ronald Reagan

00:00:52.930 --> 00:00:57.080
had brought into the debate
when he was elected in 1980.

00:00:57.080 --> 00:01:00.880
Now the challenge was that
Reagan's defense spending

00:01:00.880 --> 00:01:03.870
and his tax cuts ballooned the deficit

00:01:03.870 --> 00:01:05.080
and what that ended up,

00:01:05.080 --> 00:01:07.230
what ended up happening is that the thing

00:01:07.230 --> 00:01:09.610
he had come to Washington to try to solve,

00:01:09.610 --> 00:01:13.400
which was the budget deficit
had actually gotten bigger,

00:01:13.400 --> 00:01:16.970
and so Reagan, who came to
town as a tax cutter ended up

00:01:16.970 --> 00:01:19.180
ultimately having to raise taxes

00:01:19.180 --> 00:01:22.240
to solve some of those problems
of having a large deficit

00:01:22.240 --> 00:01:23.440
and why is that bad?

00:01:23.440 --> 00:01:26.440
Because deficits lead to
inflation and inflation

00:01:26.440 --> 00:01:29.490
is what was strangling America
when Reagan came into office.

00:01:29.490 --> 00:01:32.280
Inflation was very high
and unemployment was high

00:01:32.280 --> 00:01:35.601
and so, his solution to
it while it kicked off

00:01:35.601 --> 00:01:39.160
a strong economic recovery also
ballooned the deficit which

00:01:39.160 --> 00:01:42.453
is a problem that is still
one they wrestle with today.


How did Reagan's policies affect the economy?

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:02.010
- [Instructor] How did
Ronald Reagan's policies

00:00:02.010 --> 00:00:04.270
affect the government and economy?

00:00:04.270 --> 00:00:07.050
- What Ronald Reagan believed
is that good programs,

00:00:07.050 --> 00:00:08.860
he had been a New Deal democrat,

00:00:08.860 --> 00:00:10.280
he believed that what had happened was

00:00:10.280 --> 00:00:12.590
good programs that had
tried to help people

00:00:12.590 --> 00:00:16.590
who needed the help, the
poor, the infirm, the elderly,

00:00:16.590 --> 00:00:19.720
those programs had ballooned,
and what had happened was

00:00:19.720 --> 00:00:21.700
they were no longer prioritizing help

00:00:21.700 --> 00:00:23.770
to those who needed
it, but they had become

00:00:23.770 --> 00:00:27.700
a kind of system where those
who made the loudest noise

00:00:27.700 --> 00:00:30.750
got the most government,
got the most money

00:00:30.750 --> 00:00:32.700
and got the attention from the government,

00:00:32.700 --> 00:00:36.160
and that that in fact stopped
helping people in need

00:00:36.160 --> 00:00:38.650
and ended up hurting
people, ended up sort of

00:00:38.650 --> 00:00:42.190
entrapping them in government dependence.

00:00:42.190 --> 00:00:45.981
And so what he said was he was
going to do two big things.

00:00:45.981 --> 00:00:47.810
Or three big things actually.

00:00:47.810 --> 00:00:50.610
He was going to cut taxes,
and what that was going to do

00:00:50.610 --> 00:00:53.000
was shrink the amount of available money

00:00:53.950 --> 00:00:56.700
towards government, which
he was then going to also do

00:00:56.700 --> 00:00:59.860
by cutting spending, and he
was going to cut regulation.

00:00:59.860 --> 00:01:02.260
So it was essentially
paring down government,

00:01:02.260 --> 00:01:03.907
which he thought was inefficient towards

00:01:03.907 --> 00:01:06.580
giving resources to those who need it,

00:01:06.580 --> 00:01:09.920
he wanted a lot of that power
to go back to the states,

00:01:09.920 --> 00:01:12.530
and he also believed
in an economic program

00:01:12.530 --> 00:01:15.280
that both cut money from domestic spending

00:01:15.280 --> 00:01:17.440
but also cut taxes, which he believed

00:01:17.440 --> 00:01:20.720
would actually generate more revenue

00:01:20.720 --> 00:01:23.040
because of something called
supply-side economics,

00:01:23.040 --> 00:01:25.300
and so his both economic theory

00:01:25.300 --> 00:01:27.520
and his theory about shrinking government

00:01:27.520 --> 00:01:30.130
were kind of matched
up in his first budget

00:01:30.130 --> 00:01:32.063
and in his first major tax cut.


Why was Reagan's presidency so significant?

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:03.620
- [Narrator] Why Ronald Reagan's
presidency so significant?

00:00:03.620 --> 00:00:06.210
- Ronald Reagan plays an important role in

00:00:06.210 --> 00:00:10.110
the modern presidency for
two big things that he did.

00:00:10.110 --> 00:00:14.950
One on the domestic front,
he broke considerably with

00:00:14.950 --> 00:00:17.240
the kind of way of doing
things in Washington.

00:00:17.240 --> 00:00:21.320
He basically in response to the New Deal,

00:00:21.320 --> 00:00:22.650
Franklin Delano Roosevelt,

00:00:22.650 --> 00:00:25.284
and the Great Society from Lyndon Johnson,

00:00:25.284 --> 00:00:28.160
President Reagan came in and said

00:00:28.160 --> 00:00:31.670
no longer is government your
friend in American life.

00:00:31.670 --> 00:00:33.860
The government is actually the problem.

00:00:33.860 --> 00:00:36.571
This is the message of
his inaugural address.

00:00:36.571 --> 00:00:40.780
And he broke with the idea
that the federal government

00:00:40.780 --> 00:00:42.980
through the application of its resources,

00:00:42.980 --> 00:00:44.690
could help American life,

00:00:44.690 --> 00:00:47.570
which was a very stark ideological break

00:00:47.570 --> 00:00:50.080
with the way the American
government had been going

00:00:50.080 --> 00:00:51.610
since the mid 40s.

00:00:51.610 --> 00:00:56.220
And then on foreign policy,
his increased defense spending

00:00:56.220 --> 00:01:00.520
and his very strong position
against the Soviet Union

00:01:00.520 --> 00:01:03.610
coupled with a willingness
to actually negotiate

00:01:03.610 --> 00:01:05.750
with the Soviet Union,
which got him a lot of grief

00:01:05.750 --> 00:01:07.740
from conservatives in his party,

00:01:07.740 --> 00:01:11.830
that both hard line and
ability to negotiate

00:01:11.830 --> 00:01:14.423
helped usher in the end of the Cold War.


Why is the Speaker second in succession?

WEBVTT
Kind: captions
Language: en

00:00:00.320 --> 00:00:02.380
- [Narrator] Why is the
Speaker second in succession

00:00:02.380 --> 00:00:04.690
to the President after the Vice President?

00:00:04.690 --> 00:00:06.290
- The idea of succession actually

00:00:06.290 --> 00:00:09.930
it was a little muddied
and it wasn't until

00:00:09.930 --> 00:00:11.802
the 25th amendment that actually

00:00:11.802 --> 00:00:14.540
the relationship between the President

00:00:14.540 --> 00:00:17.890
and the Vice President
was actually formalized.

00:00:17.890 --> 00:00:20.110
When William Henry Harrison died

00:00:20.110 --> 00:00:22.480
and John Tyler came in,

00:00:22.480 --> 00:00:23.870
his Vice President as President

00:00:23.870 --> 00:00:25.410
there was a big debate about whether

00:00:25.410 --> 00:00:27.720
he was actually really the President.

00:00:27.720 --> 00:00:32.720
So, even though the line of
succession is written down

00:00:33.510 --> 00:00:35.470
there's a lot of debate about whether

00:00:35.470 --> 00:00:37.140
what enforces it and what doesn't.

00:00:37.140 --> 00:00:39.110
The Speaker of the House
though has prominence

00:00:39.110 --> 00:00:41.050
in that line of succession because

00:00:41.050 --> 00:00:43.730
the Speaker of the House
is closest to the people

00:00:43.730 --> 00:00:46.624
and the formation of
the federal government.

00:00:46.624 --> 00:00:49.440
Article one defines the powers of Congress

00:00:49.440 --> 00:00:51.630
because the framers wanted Congress

00:00:51.630 --> 00:00:53.230
really to be the powerful branch,

00:00:53.230 --> 00:00:54.180
close to the people.

00:00:54.180 --> 00:00:55.920
They were worried about a monarchy.

00:00:55.920 --> 00:00:57.960
So they didn't want the President to have

00:00:57.960 --> 00:01:01.730
excessive power and the
Speaker of the House represents

00:01:01.730 --> 00:01:05.550
all of the, is elected
by all of the members

00:01:05.550 --> 00:01:08.640
and so has a closer
relationship to the people

00:01:08.640 --> 00:01:09.990
and that's what gives them power

00:01:09.990 --> 00:01:12.060
in the question of succession.

00:01:12.060 --> 00:01:13.460
What's interesting though is that there's

00:01:13.460 --> 00:01:14.890
only been one Speaker of the House

00:01:14.890 --> 00:01:16.460
who's then gone on to be President,

00:01:16.460 --> 00:01:17.950
James K. Polk.

00:01:17.950 --> 00:01:21.440
So while they are high up
in the order of succession

00:01:21.440 --> 00:01:22.910
behind the Vice President,

00:01:22.910 --> 00:01:25.180
that doesn't necessarily make the job

00:01:25.180 --> 00:01:29.040
a stepping stone to actual
power of the presidency

00:01:29.040 --> 00:01:30.573
through the electoral process.


What kind of levers does the Speaker have?

WEBVTT
Kind: captions
Language: en

00:00:00.330 --> 00:00:02.310
- [Interviewer] What kind of
levers does the Speaker have

00:00:02.310 --> 00:00:05.090
in relation to the other
House representatives?

00:00:05.090 --> 00:00:07.270
- The Speaker has all kinds of levers,

00:00:07.270 --> 00:00:10.090
both formal and informal.

00:00:10.090 --> 00:00:11.760
In fact, a lot of them are informal.

00:00:11.760 --> 00:00:14.255
So, the Speaker can, Speaker
names a lot of people

00:00:14.255 --> 00:00:18.070
to the committees,
particularly to the, quote,

00:00:18.070 --> 00:00:19.590
the Rules Committee in the House.

00:00:19.590 --> 00:00:20.830
And what does the Rules Committee do?

00:00:20.830 --> 00:00:23.300
The Rules Committee sets
the rules for what's debated

00:00:23.300 --> 00:00:24.980
and what comes onto the floor.

00:00:24.980 --> 00:00:27.620
And so, through controlling
the Rules Committee,

00:00:27.620 --> 00:00:30.550
you can control what kinds
of amendments come up,

00:00:30.550 --> 00:00:34.070
how much debate there
is for unpopular ideas,

00:00:34.070 --> 00:00:37.740
and you can help get legislation through

00:00:37.740 --> 00:00:40.520
by managing the rules
under which it's debated.

00:00:40.520 --> 00:00:43.110
There's a famous instance
in which Dennis Hastert,

00:00:43.110 --> 00:00:45.880
who was Speaker of the
House under George W. Bush,

00:00:45.880 --> 00:00:48.620
held open a vote on Medicare Part D.

00:00:48.620 --> 00:00:51.820
This was adding prescription
drugs to the Medicare Plan.

00:00:51.820 --> 00:00:53.850
And what holding open
a vote means is you set

00:00:53.850 --> 00:00:56.220
a certain time for the
number of votes that come in.

00:00:56.220 --> 00:00:58.120
And at the end of that
time, you count the votes,

00:00:58.120 --> 00:00:59.410
are they in, does it pass.

00:00:59.410 --> 00:01:00.920
Well, it wasn't passing.

00:01:00.920 --> 00:01:04.760
And so, Hastert let the vote
stay open while he went around

00:01:04.760 --> 00:01:08.580
and strong-armed individual
members of the Republican side,

00:01:08.580 --> 00:01:11.050
he was a Republican
Speaker, strong-armed them,

00:01:11.050 --> 00:01:12.550
said, "You really gotta vote for this,"

00:01:12.550 --> 00:01:14.120
and finally got enough votes,

00:01:14.120 --> 00:01:16.170
and just when it went over the threshold,

00:01:16.170 --> 00:01:17.190
boom, he closed the window,

00:01:17.190 --> 00:01:19.660
said, "The vote's over," and it passed.

00:01:19.660 --> 00:01:21.580
And what did he do to
get those extra votes?

00:01:21.580 --> 00:01:24.290
Well, you can give people
plum committee assignments,

00:01:24.290 --> 00:01:26.570
you can help their
legislation get to the floor

00:01:26.570 --> 00:01:29.000
that maybe wasn't getting
there fast enough.

00:01:29.000 --> 00:01:31.710
And the other powers you have
is you can go raise money

00:01:31.710 --> 00:01:35.140
for them or get the people
you know on the political side

00:01:35.140 --> 00:01:37.870
to make their run for reelection easier.

00:01:37.870 --> 00:01:40.480
So, there are lot of gifts
you can give to your members

00:01:40.480 --> 00:01:42.630
or things you can withhold from them

00:01:42.630 --> 00:01:44.130
to make them do what you want.


How has the position of Speaker changed over time?

WEBVTT
Kind: captions
Language: en

00:00:00.340 --> 00:00:01.370
- [Narrator] How has the position

00:00:01.370 --> 00:00:04.350
of Speaker of the House changed over time?

00:00:04.350 --> 00:00:05.550
- The position of Speaker of the House

00:00:05.550 --> 00:00:07.150
has changed a lot over time

00:00:07.150 --> 00:00:09.610
and it has had powerful early advocates,

00:00:09.610 --> 00:00:11.980
Henry Clay, an early Speaker of the House

00:00:11.980 --> 00:00:14.870
who had three different
terms as Speaker of the House

00:00:14.870 --> 00:00:17.600
used the position to shepherd all kinds of

00:00:17.600 --> 00:00:21.240
legislation to improve America.

00:00:21.240 --> 00:00:24.620
He also played a crucial
role in John Quincy Adam's

00:00:24.620 --> 00:00:27.370
becoming President because
the election was thrown

00:00:27.370 --> 00:00:28.203
into the House.

00:00:28.203 --> 00:00:29.740
He was quite powerful.

00:00:29.740 --> 00:00:33.680
Then the job kind of got less powerful.

00:00:33.680 --> 00:00:35.310
There were periods during the Civil War

00:00:35.310 --> 00:00:37.060
where there wasn't a Speaker of the House

00:00:37.060 --> 00:00:40.020
for long periods because
there was so much contention

00:00:40.020 --> 00:00:42.926
in the Congress they couldn't
pick a Speaker of the House.

00:00:42.926 --> 00:00:45.730
The modern Speaker of the House has become

00:00:45.730 --> 00:00:50.400
increasingly powerful really growing with

00:00:50.400 --> 00:00:52.350
the growth of the federal government

00:00:52.350 --> 00:00:54.670
around let's say the second World War.

00:00:54.670 --> 00:00:57.220
Various different Speakers
gaining more power

00:00:57.220 --> 00:00:59.130
and in the recent incarnation

00:00:59.130 --> 00:01:01.565
the Speaker is particularly powerful

00:01:01.565 --> 00:01:03.220
in two different ways.

00:01:03.220 --> 00:01:05.480
One is shepherding a
President's legislation

00:01:05.480 --> 00:01:07.870
if the Speaker is from the same party

00:01:07.870 --> 00:01:09.900
and the other is in opposition.

00:01:09.900 --> 00:01:12.670
They become essentially the opposition

00:01:12.670 --> 00:01:16.380
speaking against a President
of an opposite party.

00:01:16.380 --> 00:01:18.700
So people like that would be Nancy Pelosi

00:01:18.700 --> 00:01:19.960
now with President Trump

00:01:19.960 --> 00:01:23.040
or John Boehner with President Obama

00:01:23.040 --> 00:01:25.700
or Tip O'Neill with President Reagan.

00:01:25.700 --> 00:01:29.610
So they are the key person in doing combat

00:01:29.610 --> 00:01:30.840
with whoever's in the White House

00:01:30.840 --> 00:01:32.590
if they're from the opposite party.


Who is the Speaker of the House?

WEBVTT
Kind: captions
Language: en

00:00:00.200 --> 00:00:01.320
- [Narrator] Who is the
Speaker of the House

00:00:01.320 --> 00:00:02.370
and what do they do?

00:00:02.370 --> 00:00:04.030
- The office of the Speaker of the House

00:00:04.030 --> 00:00:06.560
is actually outlined in the Constitution.

00:00:06.560 --> 00:00:08.030
That's one of the things that makes

00:00:08.030 --> 00:00:09.760
the Speaker of the House unique.

00:00:09.760 --> 00:00:11.550
The Speaker of the House
does not have to be

00:00:11.550 --> 00:00:13.790
a member of the House
although there has never been

00:00:13.790 --> 00:00:15.890
a Speaker who has not been
a member of the House.

00:00:15.890 --> 00:00:18.380
And traditionally the Speaker of the House

00:00:18.380 --> 00:00:21.900
is the member picked
by the majority party.

00:00:21.900 --> 00:00:23.470
Doesn't have to be from the majority party

00:00:23.470 --> 00:00:25.270
but that's always the way it's worked out

00:00:25.270 --> 00:00:27.950
and essentially everybody
in the House gets together

00:00:27.950 --> 00:00:31.403
and whoever gets the most
votes of the people voting.

00:00:31.403 --> 00:00:32.780
It's just the people voting,

00:00:32.780 --> 00:00:34.240
not necessarily the entire House.

00:00:34.240 --> 00:00:36.430
Whoever gets the most votes becomes

00:00:36.430 --> 00:00:37.680
the Speaker of the House.


Khan Stories: Christian

WEBVTT
Kind: captions
Language: en

00:00:00.157 --> 00:00:03.574
(gentle uplifting music)

00:00:07.503 --> 00:00:09.670
- They're growing perfect.

00:00:14.223 --> 00:00:17.140
(computer chiming)

00:00:19.580 --> 00:00:23.620
Math was always my difficulty in school

00:00:23.620 --> 00:00:25.060
until I started using Khan Academy.

00:00:25.060 --> 00:00:28.540
I got better math scores
and state testing scores.

00:00:28.540 --> 00:00:31.783
They just help me be more
confident about myself.

00:00:35.290 --> 00:00:39.470
My dream is to work for
NASA, and go to space,

00:00:39.470 --> 00:00:44.470
and see how it looks, like
the stars, and explore space.

00:00:52.570 --> 00:00:55.690
Helps me achieve and makes
me feel more successful

00:00:55.690 --> 00:00:58.710
and more confident that
I can succeed that goal.


Four factors of production

WEBVTT
Kind: captions
Language: en

00:00:00.530 --> 00:00:02.600
- [Instructor] An idea
that will keep coming up

00:00:02.600 --> 00:00:06.330
as you study economics is
the idea of the four factors

00:00:06.330 --> 00:00:09.120
of production, which are
usually listed as land,

00:00:09.120 --> 00:00:12.530
labor, capital, and entrepreneurship.

00:00:12.530 --> 00:00:16.280
And the idea here is if you
want to produce anything,

00:00:16.280 --> 00:00:18.950
so let's just say this circle
is the production process,

00:00:18.950 --> 00:00:22.290
and this arrow is the
output, you need inputs.

00:00:22.290 --> 00:00:25.870
Now, you might have
many, many, many inputs.

00:00:25.870 --> 00:00:28.450
You might need supplies,
you might need a factory,

00:00:28.450 --> 00:00:30.500
you might need people
to work in the factory,

00:00:30.500 --> 00:00:32.720
you need all of these different things.

00:00:32.720 --> 00:00:35.170
But the idea of the four
factors of production

00:00:35.170 --> 00:00:37.820
is that these things can all be classified

00:00:37.820 --> 00:00:40.470
in one of these four
groups, as either land,

00:00:40.470 --> 00:00:43.960
labor, capital, or entrepreneurship.

00:00:43.960 --> 00:00:46.910
Now, these words have
meaning in everyday language.

00:00:46.910 --> 00:00:48.850
And so, some of it might jump out at you.

00:00:48.850 --> 00:00:50.710
Of course, if you need to build factory

00:00:50.710 --> 00:00:54.820
or if you need to farm,
you need land to do so.

00:00:54.820 --> 00:00:56.920
And you can see that in this example here,

00:00:56.920 --> 00:00:58.090
where we see a farm.

00:00:58.090 --> 00:01:01.390
Clearly, the need a lotta land
in order to have the farm.

00:01:01.390 --> 00:01:03.470
Even in a garment
factory, this is a picture

00:01:03.470 --> 00:01:07.300
of a garment factory from
maybe a hundred years ago,

00:01:07.300 --> 00:01:10.170
even there, they needed land
on which to build the factory.

00:01:10.170 --> 00:01:13.250
So, this floor is sitting on land.

00:01:13.250 --> 00:01:15.730
And land doesn't just have to strictly

00:01:15.730 --> 00:01:18.180
mean land in an economics context.

00:01:18.180 --> 00:01:21.950
It can mean natural resources in general.

00:01:21.950 --> 00:01:26.520
This could be things like
water or air or energy.

00:01:26.520 --> 00:01:28.700
So, in some contexts, instead of land,

00:01:28.700 --> 00:01:30.910
some people might say natural resources

00:01:30.910 --> 00:01:33.650
for this first factor of production.

00:01:33.650 --> 00:01:35.770
Now, another important
factor of production,

00:01:35.770 --> 00:01:39.870
and arguably they're all
important, is the idea of labor.

00:01:39.870 --> 00:01:44.870
To produce many or most things,
someone has to work on it.

00:01:44.970 --> 00:01:47.160
So, someone had to plant these seeds,

00:01:47.160 --> 00:01:49.430
and they will have to harvest these crops.

00:01:49.430 --> 00:01:50.940
The labor is very clear here.

00:01:50.940 --> 00:01:53.601
You see people putting in work

00:01:53.601 --> 00:01:58.600
in order to produce the
product right over there.

00:01:58.600 --> 00:02:00.890
Now, capital is an interesting one.

00:02:00.890 --> 00:02:03.080
It means one thing in everyday language,

00:02:03.080 --> 00:02:05.280
and it means something
slightly more specific

00:02:05.280 --> 00:02:08.900
when we talk about it
in an economics context.

00:02:08.900 --> 00:02:11.830
In an economic context, capital is

00:02:11.830 --> 00:02:14.940
something produced to
produce other things.

00:02:14.940 --> 00:02:18.290
So, examples of capital would be tools

00:02:18.290 --> 00:02:20.740
that you use to produce other things.

00:02:20.740 --> 00:02:24.380
It could be a building that you need

00:02:24.380 --> 00:02:26.720
in order to produce other things.

00:02:26.720 --> 00:02:29.640
It could be the machinery in a factory.

00:02:29.640 --> 00:02:33.660
So, in these two pictures,
there's many examples of capital.

00:02:33.660 --> 00:02:36.900
You could view this table and the tools

00:02:36.900 --> 00:02:39.870
that these folks are
using, that is capital.

00:02:39.870 --> 00:02:42.610
You could use, you could view
the whole building itself

00:02:42.610 --> 00:02:45.730
and all of the light fixtures
and all of that as capital.

00:02:45.730 --> 00:02:48.010
So, all of this stuff is capital.

00:02:48.010 --> 00:02:50.310
The hangers that they're
putting the coats on

00:02:50.310 --> 00:02:52.520
after they produce it, that is capital.

00:02:52.520 --> 00:02:56.670
In this farm example, the
capital would be the buildings.

00:02:56.670 --> 00:02:59.690
These were constructed so that they could

00:02:59.690 --> 00:03:02.980
produce the food from the farm.

00:03:02.980 --> 00:03:06.070
This little, it looks like
some type of machinery there,

00:03:06.070 --> 00:03:07.570
that is capital for the farm.

00:03:07.570 --> 00:03:11.510
It's being used to produce
the output of the farm.

00:03:11.510 --> 00:03:14.200
Now, the place that that's
different than everyday language,

00:03:14.200 --> 00:03:16.870
in everyday language, when
people talk about capital,

00:03:16.870 --> 00:03:19.170
they'll often include financial capital,

00:03:19.170 --> 00:03:21.250
financial assets that could be used

00:03:21.250 --> 00:03:23.810
to get benefit in the
future, things like money.

00:03:23.810 --> 00:03:25.910
But in an economic context,

00:03:25.910 --> 00:03:28.930
we are not considering financial assets,

00:03:28.930 --> 00:03:31.670
we're only thinking about
things that were produced

00:03:31.670 --> 00:03:34.490
in order to produce other things.

00:03:34.490 --> 00:03:38.330
The fourth factor of
production is entrepreneurship.

00:03:38.330 --> 00:03:40.650
Entrepreneurship, in our everyday language

00:03:40.650 --> 00:03:42.320
means putting things together

00:03:42.320 --> 00:03:44.350
so you're trying to create other things.

00:03:44.350 --> 00:03:45.730
When someone's an entrepreneur,

00:03:45.730 --> 00:03:48.510
you might imagine someone who's
trying to start a business.

00:03:48.510 --> 00:03:52.010
In an economic context,
it has a related idea.

00:03:52.010 --> 00:03:54.330
Entrepreneurship is putting together

00:03:54.330 --> 00:03:56.120
all of the other factors of production

00:03:56.120 --> 00:03:58.430
so that you can actually produce things.

00:03:58.430 --> 00:04:00.260
You can't just randomly build buildings

00:04:00.260 --> 00:04:01.470
and randomly plant seeds.

00:04:01.470 --> 00:04:03.410
Someone has to think about
how do you put these things

00:04:03.410 --> 00:04:06.560
together so that you can produce
things in a reasonable way?

00:04:06.560 --> 00:04:09.380
And obviously, you wanna
produce as much as possible

00:04:09.380 --> 00:04:11.310
given the other factors that you

00:04:11.310 --> 00:04:13.920
are putting into the production.

00:04:13.920 --> 00:04:16.940
A related idea, and it sometimes
is used interchangeably

00:04:16.940 --> 00:04:19.880
in an economics course, is technology.

00:04:19.880 --> 00:04:22.070
So, sometimes, you'll see the
four factors of production

00:04:22.070 --> 00:04:24.130
as land, labor, capital,
and entrepreneurship;

00:04:24.130 --> 00:04:25.530
and sometimes, you'll see it listed

00:04:25.530 --> 00:04:28.730
as land, labor, capital, and technology.

00:04:28.730 --> 00:04:30.320
But when you see this, when you see

00:04:30.320 --> 00:04:33.000
technology as a factor of production,

00:04:33.000 --> 00:04:36.140
don't think about it as
technology in everyday language,

00:04:36.140 --> 00:04:38.780
where you think of
computer chips or software.

00:04:38.780 --> 00:04:40.680
When people are talking about technology

00:04:40.680 --> 00:04:42.500
as a factor of production,

00:04:42.500 --> 00:04:44.670
they are really talking
about entrepreneurship.

00:04:44.670 --> 00:04:47.610
They're talking about the
know-how of putting together

00:04:47.610 --> 00:04:49.360
the other factors of production

00:04:49.360 --> 00:04:52.330
in order to produce that output.

00:04:52.330 --> 00:04:55.240
Finally, I wanna leave on one idea,

00:04:55.240 --> 00:04:58.710
the idea of the two types
of things that could be

00:04:58.710 --> 00:05:02.450
produced from all of these
factors of production.

00:05:02.450 --> 00:05:05.290
Broadly speaking, we
could produce something

00:05:05.290 --> 00:05:07.840
that could be used to produce more things,

00:05:07.840 --> 00:05:08.970
and we already talk about it.

00:05:08.970 --> 00:05:13.970
We could be, in that situation,
be producing capital goods.

00:05:14.130 --> 00:05:17.520
So, that could be that we
are constructing a factory

00:05:17.520 --> 00:05:20.120
that itself maybe produces
tools for other people

00:05:20.120 --> 00:05:22.800
to use in some other production process.

00:05:22.800 --> 00:05:25.290
The other option we have is to produce

00:05:25.290 --> 00:05:27.580
what are known as consumption goods.

00:05:27.580 --> 00:05:28.790
Consumption

00:05:29.960 --> 00:05:31.010
goods.

00:05:31.010 --> 00:05:34.360
Consumption goods are
goods that are just used.

00:05:34.360 --> 00:05:37.360
It might make people happy,
they might find pleasure in it,

00:05:37.360 --> 00:05:40.290
but it's not being used
to produce other things.

00:05:40.290 --> 00:05:43.710
And because our production
resources are scarce,

00:05:43.710 --> 00:05:46.420
there's a trade-off when
a society or a factory

00:05:46.420 --> 00:05:49.270
or whoever decides how
much capital to produce

00:05:49.270 --> 00:05:51.560
versus how much consumption goods.

00:05:51.560 --> 00:05:53.200
You need some consumption goods;

00:05:53.200 --> 00:05:55.570
otherwise, frankly, we
wouldn't have clothing on.

00:05:55.570 --> 00:05:57.700
We wouldn't be eating nice meals.

00:05:57.700 --> 00:06:00.870
We wouldn't be able to enjoy our lives.

00:06:00.870 --> 00:06:02.860
But at the same time,
you also need capital.

00:06:02.860 --> 00:06:04.876
If we did only consumption
goods, at some point,

00:06:04.876 --> 00:06:07.050
we wouldn't have all the things we need

00:06:07.050 --> 00:06:09.090
to produce the consumption goods.

00:06:09.090 --> 00:06:11.150
So, it's a very interesting trade-off

00:06:11.150 --> 00:06:13.903
that we'll explore more in future videos.


Slope and intercepts from tables

WEBVTT
Kind: captions
Language: en

00:00:00.500 --> 00:00:02.690
- [Instructor] We're told
Kaya rode her bicycle

00:00:02.690 --> 00:00:06.300
toward a tree at a constant speed.

00:00:06.300 --> 00:00:08.700
The table below shows the relationship

00:00:08.700 --> 00:00:11.050
between her distance to the tree

00:00:11.050 --> 00:00:15.020
and how many times her front tire rotated.

00:00:15.020 --> 00:00:17.720
So once her tire rotated four times,

00:00:17.720 --> 00:00:20.780
she was 22 1/2 meters from the tree.

00:00:20.780 --> 00:00:22.800
Then once she's rotated eight times,

00:00:22.800 --> 00:00:25.080
she's 12 1/2 meters from the tree.

00:00:25.080 --> 00:00:26.450
When it rotated 12 times,

00:00:26.450 --> 00:00:29.300
then she's only 2 1/2 meters to the tree.

00:00:29.300 --> 00:00:30.980
So she's getting closer and closer

00:00:30.980 --> 00:00:34.130
the more rotations that her tire has had.

00:00:34.130 --> 00:00:37.100
So then they ask us some questions here.

00:00:37.100 --> 00:00:40.060
So they ask us how far away
was the tree to begin with?

00:00:40.060 --> 00:00:43.070
How far does Kaya travel
with each rotation?

00:00:43.070 --> 00:00:46.960
How many rotations did it
take to get to the tree?

00:00:46.960 --> 00:00:48.830
So like always, pause this video,

00:00:48.830 --> 00:00:50.210
and see if you can answer these questions

00:00:50.210 --> 00:00:52.223
on your own before we do it together.

00:00:53.410 --> 00:00:55.440
So let's start with the first question.

00:00:55.440 --> 00:01:00.210
How far away was the tree to begin with?

00:01:00.210 --> 00:01:02.550
So the way that I would think about it is,

00:01:02.550 --> 00:01:06.200
after four rotations, we're
22 1/2 meters from the tree.

00:01:06.200 --> 00:01:09.800
We see that if we increase
by another four rotations,

00:01:09.800 --> 00:01:12.390
so let's say plus four rotations,

00:01:12.390 --> 00:01:16.150
we see that we have gotten
10 meters closer to the tree,

00:01:16.150 --> 00:01:19.690
or our distance to the tree
has gone down by 10 meters.

00:01:19.690 --> 00:01:22.440
So I'll write negative 10 meters here.

00:01:22.440 --> 00:01:25.310
If we want to figure out how
far the tree was to begin with,

00:01:25.310 --> 00:01:28.670
we have to go back to zero rotations.

00:01:28.670 --> 00:01:32.150
So if we're going back by four,

00:01:32.150 --> 00:01:34.310
so we're subtracting
four from the rotations.

00:01:34.310 --> 00:01:36.340
And if we're going at a constant rate,

00:01:36.340 --> 00:01:39.230
well, then we would add 10 meters.

00:01:39.230 --> 00:01:41.040
So we would add 10 meters.

00:01:41.040 --> 00:01:44.300
If we add four rotations,
we get 10 meters closer.

00:01:44.300 --> 00:01:46.090
If we take away four rotations,

00:01:46.090 --> 00:01:48.130
to get us back to zero rotations,

00:01:48.130 --> 00:01:50.120
then we will go 10 meters further.

00:01:50.120 --> 00:01:53.650
So that would be at 32.5 meters.

00:01:53.650 --> 00:01:57.800
So 32.5 meters is how far the tree was

00:01:57.800 --> 00:02:01.660
to begin with when Kaya
had zero rotations.

00:02:01.660 --> 00:02:04.640
The next question is
how far does Kaya travel

00:02:04.640 --> 00:02:07.210
with each rotation?

00:02:07.210 --> 00:02:10.510
All right, well, we already
saw that with four rotations,

00:02:10.510 --> 00:02:13.470
she's traveling 10 meters,

00:02:13.470 --> 00:02:16.600
so we could say 10 meters

00:02:18.110 --> 00:02:20.713
in four rotations.

00:02:22.070 --> 00:02:24.870
So if we divide both of these
by four, what would we get?

00:02:24.870 --> 00:02:29.870
Well, that's the same thing as
2 1/2 meters in one rotation.

00:02:31.860 --> 00:02:35.800
So this is 2.5 meters.

00:02:35.800 --> 00:02:37.280
And last but not least,

00:02:37.280 --> 00:02:41.630
how many rotations did it
take to get to the tree?

00:02:41.630 --> 00:02:43.820
Well, we know that after 12 rotations,

00:02:43.820 --> 00:02:47.540
she's only 2 1/2 meters
away from the tree.

00:02:47.540 --> 00:02:50.500
We also know that in every one rotation,

00:02:50.500 --> 00:02:53.090
she gets 2 1/2 meters closer.

00:02:53.090 --> 00:02:55.080
So she only needs one more rotation

00:02:55.080 --> 00:02:57.330
to cover this next 2 1/2 meters.

00:02:57.330 --> 00:02:58.700
So,

00:02:58.700 --> 00:03:01.140
if we go plus one rotations,

00:03:01.140 --> 00:03:03.450
we're going to go down 2 1/2 meters.

00:03:03.450 --> 00:03:05.970
We're going to go 2 1/2
meters closer to the tree,

00:03:05.970 --> 00:03:08.000
and we will be at the tree.

00:03:08.000 --> 00:03:09.590
So how many rotations did it take

00:03:09.590 --> 00:03:11.500
to get to the tree in total?

00:03:11.500 --> 00:03:13.450
13 rotations.

00:03:13.450 --> 00:03:15.550
Now one thing that's
interesting is to think about

00:03:15.550 --> 00:03:19.020
what we just did in a graphical context

00:03:19.020 --> 00:03:20.600
that you might have seen before.

00:03:20.600 --> 00:03:25.110
And if we were to put on the
horizontal axis rotations

00:03:25.980 --> 00:03:28.440
and if we were to put on the vertical axis

00:03:28.440 --> 00:03:30.010
distance to the tree,

00:03:30.010 --> 00:03:31.670
distance

00:03:31.670 --> 00:03:33.570
to tree,

00:03:33.570 --> 00:03:35.330
I'll just call the
vertical axis the y-axis

00:03:35.330 --> 00:03:37.780
and the horizontal axis the x-axis,

00:03:37.780 --> 00:03:42.680
well, we could see here
that we have zero, four,

00:03:42.680 --> 00:03:45.600
eight, 12,

00:03:45.600 --> 00:03:47.680
I could go to 16.

00:03:47.680 --> 00:03:50.480
And then we saw that at zero rotations,

00:03:50.480 --> 00:03:54.520
we are 32.5 meters from the tree,

00:03:54.520 --> 00:03:56.400
so 32.5.

00:03:56.400 --> 00:03:58.150
This is all going to be in meters.

00:03:58.150 --> 00:04:00.950
So this first question was
really another way of asking

00:04:00.950 --> 00:04:04.140
what is our y-intercept?

00:04:04.140 --> 00:04:05.650
And this next question,

00:04:05.650 --> 00:04:08.420
how far does Kaya travel
with each rotation,

00:04:08.420 --> 00:04:13.030
well, we saw that when you
increase your rotations by four,

00:04:13.030 --> 00:04:15.850
your distance to the tree
goes down by 10 meters.

00:04:15.850 --> 00:04:19.340
So when this is plus four, we went down,

00:04:19.340 --> 00:04:21.800
we went down 10 meters.

00:04:21.800 --> 00:04:23.480
So it's negative 10 meters.

00:04:23.480 --> 00:04:25.980
So really what we were thinking
about right here, this is,

00:04:25.980 --> 00:04:28.410
you could think about the
magnitude of the slope.

00:04:28.410 --> 00:04:30.150
The slope of this line,

00:04:30.150 --> 00:04:33.880
the slope of this line that
would describe her distance

00:04:33.880 --> 00:04:36.830
to the tree as based on
the number of rotations,

00:04:36.830 --> 00:04:40.200
the slope is going to be
our change in our distance,

00:04:40.200 --> 00:04:41.940
which is negative 10,

00:04:41.940 --> 00:04:44.830
four, our change in rotations, over four.

00:04:44.830 --> 00:04:46.290
So the slope of this line

00:04:46.290 --> 00:04:49.870
is negative 2.5 meters per rotation.

00:04:49.870 --> 00:04:51.350
But when they say how far does Kaya travel

00:04:51.350 --> 00:04:54.050
with each rotation, she's
getting 2 1/2 meters closer.

00:04:55.002 --> 00:04:57.600
Her distance from the tree
goes down by 2 1/2 meters.

00:04:57.600 --> 00:04:58.770
And this last question,

00:04:58.770 --> 00:05:01.300
how many rotations did it
take to get to the tree,

00:05:01.300 --> 00:05:03.920
well, at what point is our y value,

00:05:03.920 --> 00:05:05.210
our distance to the tree, zero?

00:05:05.210 --> 00:05:07.920
And we saw that it is at 13 rotations.

00:05:07.920 --> 00:05:09.710
So this is another way of thinking about

00:05:09.710 --> 00:05:11.400
what was the x-intercept?

00:05:11.400 --> 00:05:13.300
So the line,

00:05:13.300 --> 00:05:15.590
it's a line because we
know that she's traveling

00:05:15.590 --> 00:05:18.110
at a constant rate, looks
something like that.

00:05:18.110 --> 00:05:20.490
So they really were
asking us the y-intercept,

00:05:20.490 --> 00:05:22.483
the slope, and the x-intercept.


Slope and y intercept from equation

WEBVTT
Kind: captions
Language: en

00:00:00.210 --> 00:00:01.300
- [Instructor] What I'd
like to do in this video

00:00:01.300 --> 00:00:02.690
is a few more examples

00:00:02.690 --> 00:00:07.510
recognizing the slope and
y-intercept given an equation.

00:00:07.510 --> 00:00:09.730
So, let's start with something

00:00:09.730 --> 00:00:11.060
that we might already recognize.

00:00:11.060 --> 00:00:11.970
Let's say we have something

00:00:11.970 --> 00:00:16.330
of the form y is equal to five x

00:00:16.330 --> 00:00:17.780
plus three.

00:00:17.780 --> 00:00:22.550
What is the slope and the
y-intercept in this example here?

00:00:22.550 --> 00:00:24.180
Well, we've already talked about

00:00:24.180 --> 00:00:26.410
that we can have something
in slope intercept form

00:00:26.410 --> 00:00:29.280
where it has a form y
is equal to the slope,

00:00:29.280 --> 00:00:30.800
which people use the letter m for,

00:00:30.800 --> 00:00:33.840
the slope times x plus the y-intercept,

00:00:33.840 --> 00:00:35.930
which people use the letter b for.

00:00:35.930 --> 00:00:37.240
So, if we just look at this,

00:00:37.240 --> 00:00:40.510
m is going to be the coefficient
on x right over there.

00:00:40.510 --> 00:00:43.230
So, m is equal to five.

00:00:43.230 --> 00:00:46.070
That is the slope.

00:00:46.070 --> 00:00:49.420
And b is just going to be this
constant term, plus three.

00:00:49.420 --> 00:00:51.660
So, b is equal to three.

00:00:51.660 --> 00:00:54.820
So, this is your y-intercept.

00:00:54.820 --> 00:00:56.030
So, that's pretty straightforward

00:00:56.030 --> 00:00:59.470
but let's see a few slightly
more involved examples.

00:00:59.470 --> 00:01:04.000
Let's say if we had
form y is equal to five

00:01:04.000 --> 00:01:05.810
plus three x,

00:01:05.810 --> 00:01:09.683
what is the slope and the
y-intercept in this situation?

00:01:11.230 --> 00:01:12.870
Well, it might have
taken you a second or two

00:01:12.870 --> 00:01:15.120
to realize how this earlier equation

00:01:15.120 --> 00:01:16.970
is different than the one I just wrote.

00:01:16.970 --> 00:01:19.770
Here, it's not five x, it's just five,

00:01:19.770 --> 00:01:21.860
and this isn't three, it's three x.

00:01:21.860 --> 00:01:22.790
So, if you wanna write it

00:01:22.790 --> 00:01:25.040
in the same form as we have up there,

00:01:25.040 --> 00:01:27.430
you can just swap the
five and the three x.

00:01:27.430 --> 00:01:29.660
It doesn't matter which one comes first,

00:01:29.660 --> 00:01:30.970
you're just adding the two,

00:01:30.970 --> 00:01:34.570
so you can rewrite it as y is
equal to three x plus five.

00:01:34.570 --> 00:01:36.580
And then it becomes a little bit clear

00:01:36.580 --> 00:01:40.870
that our slope is three, the
coefficient on the x term,

00:01:40.870 --> 00:01:43.730
and our y-intercept is five,

00:01:43.730 --> 00:01:45.230
y-intercept.

00:01:45.230 --> 00:01:46.750
Let's do another example.

00:01:46.750 --> 00:01:50.530
Let's say that we have the equation y

00:01:50.530 --> 00:01:53.600
is equal to 12 minus x.

00:01:53.600 --> 00:01:56.170
Pause this video and see if
you can determine the slope

00:01:56.170 --> 00:01:57.763
and the y-intercept.

00:01:59.170 --> 00:02:02.240
All right, so, something
similar is going on here

00:02:02.240 --> 00:02:03.630
that we had over here.

00:02:03.630 --> 00:02:05.620
The standard form, slope intercept form,

00:02:05.620 --> 00:02:09.770
we're used to seeing the x
term before the constant term,

00:02:09.770 --> 00:02:11.320
so we might wanna do that over here.

00:02:11.320 --> 00:02:12.320
So, we could rewrite this

00:02:12.320 --> 00:02:16.680
as y is equal to negative x plus 12,

00:02:16.680 --> 00:02:19.980
negative x plus 12.

00:02:19.980 --> 00:02:22.570
And so, from this, you
might immediately recognize,

00:02:22.570 --> 00:02:23.780
okay, my constant term,

00:02:23.780 --> 00:02:25.510
when it's in this form, that's my b,

00:02:25.510 --> 00:02:27.690
that is my y-intercept.

00:02:27.690 --> 00:02:31.270
So, that's my y-intercept
right over there.

00:02:31.270 --> 00:02:32.890
But what's my slope?

00:02:32.890 --> 00:02:36.150
Well, the slope is the
coefficient on the x term

00:02:36.150 --> 00:02:38.780
but all you see is a negative
here, what's the coefficient?

00:02:38.780 --> 00:02:40.160
Well, you can view negative x

00:02:40.160 --> 00:02:42.710
as the same thing as negative one x.

00:02:42.710 --> 00:02:47.710
So, your slope here is
going to be negative one.

00:02:48.390 --> 00:02:50.030
Let's do another example.

00:02:50.030 --> 00:02:55.030
Let's say that we had the
equation y is equal to five x.

00:02:55.460 --> 00:02:58.550
What's the slope and y-intercept there?

00:02:58.550 --> 00:02:59.383
At first, you might say,

00:02:59.383 --> 00:03:01.860
hey, this looks nothing
like what we have up here.

00:03:01.860 --> 00:03:03.110
I only have one term

00:03:03.110 --> 00:03:04.920
on the right-hand side
of the equality sign.

00:03:04.920 --> 00:03:06.780
Here, I have two.

00:03:06.780 --> 00:03:10.340
But you could just view
this as five x plus zero,

00:03:10.340 --> 00:03:12.110
and then it might jump out at you

00:03:12.110 --> 00:03:15.480
that our y-intercept is zero

00:03:15.480 --> 00:03:17.860
and our slope is a
coefficient on the x term.

00:03:17.860 --> 00:03:20.260
It is equal to five.

00:03:20.260 --> 00:03:22.890
Let's do one more example.

00:03:22.890 --> 00:03:26.170
Let's say we had y is
equal to negative seven,

00:03:26.170 --> 00:03:28.583
what's the slope and y-intercept there?

00:03:29.660 --> 00:03:30.600
Well, once again, you might say,

00:03:30.600 --> 00:03:33.300
hey, this doesn't look
like what we had up here,

00:03:33.300 --> 00:03:35.960
how do we figure out the
slope or the y-intercept?

00:03:35.960 --> 00:03:37.700
Well, we could do a similar idea.

00:03:37.700 --> 00:03:39.360
We could say, hey, this is the same thing

00:03:39.360 --> 00:03:44.360
as y is equal to zero times x minus seven.

00:03:44.720 --> 00:03:47.510
And so now, it looks just
like what we have over here

00:03:47.510 --> 00:03:48.820
and you might recognize

00:03:48.820 --> 00:03:52.180
that our y-intercept is negative seven,

00:03:52.180 --> 00:03:54.320
y-intercept is equal to negative seven.

00:03:54.320 --> 00:03:56.890
And our slope is a
coefficient on the x term,

00:03:56.890 --> 00:03:59.850
it is equal to zero.

00:03:59.850 --> 00:04:01.190
And that makes sense.

00:04:01.190 --> 00:04:04.710
For a given change in x, you
would expect zero change in y

00:04:04.710 --> 00:04:09.053
'cause y is always negative
seven in this situation.


Linear equation word problems

WEBVTT
Kind: captions
Language: en

00:00:00.280 --> 00:00:02.430
- [Instructor] When Quinn
returned from vacation,

00:00:02.430 --> 00:00:05.000
he turned the heat back on in his home.

00:00:05.000 --> 00:00:08.370
He set the temperature
as high as it could go.

00:00:08.370 --> 00:00:10.870
Q represents the
temperature in Quinn's home

00:00:10.870 --> 00:00:13.380
in degrees Celsius after t minutes.

00:00:13.380 --> 00:00:16.930
This Q is equal to 15 plus 0.4t.

00:00:16.930 --> 00:00:21.040
What was the temperature when
Quinn returned from vacation?

00:00:21.040 --> 00:00:21.890
So pause this video

00:00:21.890 --> 00:00:24.520
and see if you can work
this out on your own.

00:00:24.520 --> 00:00:26.560
All right, so they wanna
know the temperature

00:00:26.560 --> 00:00:27.560
and you might get a little confused,

00:00:27.560 --> 00:00:28.880
hey maybe t is for temperature.

00:00:28.880 --> 00:00:31.230
No, t is time in minutes.

00:00:31.230 --> 00:00:33.680
Temperature is Q.

00:00:33.680 --> 00:00:35.730
Q represents the temperature.

00:00:35.730 --> 00:00:36.890
So they really wanna know is,

00:00:36.890 --> 00:00:40.670
what was Q when Quinn
returned from vacation?

00:00:40.670 --> 00:00:42.970
Well, right when Quinn
returned from vacation,

00:00:42.970 --> 00:00:45.010
that is when t is equal to zero.

00:00:45.010 --> 00:00:46.530
So this is equivalent to saying,

00:00:46.530 --> 00:00:51.020
what is Q, our temperature,
when zero minutes have elapsed?

00:00:51.020 --> 00:00:52.790
Well, if you go back to
this original equation,

00:00:52.790 --> 00:00:55.460
we see that Q is equal to 15

00:00:55.460 --> 00:00:59.580
plus 0.4 times the amount
of elapsed time in minutes.

00:00:59.580 --> 00:01:01.490
So that's times zero.

00:01:01.490 --> 00:01:04.980
So that's just going to
be 15 degrees Celsius.

00:01:04.980 --> 00:01:07.470
If you're familiar with
slope intercept form,

00:01:07.470 --> 00:01:09.550
you could think of it as our temperature

00:01:09.550 --> 00:01:14.550
is equal to 0.4 times
the elapsed time plus 15.

00:01:14.700 --> 00:01:18.300
So t equals zero, you're
left with just this term

00:01:18.300 --> 00:01:21.830
which in many cases we
view as our y-intercept.

00:01:21.830 --> 00:01:24.980
What is going on right when
we're just getting started?

00:01:24.980 --> 00:01:28.000
Right when our horizontal
variable is equal to zero.

00:01:28.000 --> 00:01:29.050
And our horizontal variable

00:01:29.050 --> 00:01:32.023
in this situation is elapsed time.

00:01:33.010 --> 00:01:36.690
How much do the temperature
increase every minute?

00:01:36.690 --> 00:01:39.060
There's a couple of ways
you can think about this.

00:01:39.060 --> 00:01:41.700
One if you recognize, this
is slope intercept form.

00:01:41.700 --> 00:01:44.800
You could see that 0.4 is the slope.

00:01:44.800 --> 00:01:48.760
So that says for every one minute

00:01:48.760 --> 00:01:49.830
change in time,

00:01:49.830 --> 00:01:51.940
you're going to have an
increase in temperature

00:01:51.940 --> 00:01:54.520
by 0.4 degrees Celsius.

00:01:54.520 --> 00:01:56.320
So you could do it that way.

00:01:56.320 --> 00:01:58.260
You could try out some values.

00:01:58.260 --> 00:02:01.170
You could say, all
right, let me think about

00:02:01.170 --> 00:02:02.880
what Q is going to be based on t.

00:02:02.880 --> 00:02:06.020
So time, t equals zero
right when you got home.

00:02:06.020 --> 00:02:06.853
We're to figure out

00:02:06.853 --> 00:02:09.490
that the temperature
is 15 degrees Celsius.

00:02:09.490 --> 00:02:11.670
At t equals one, what happens?

00:02:11.670 --> 00:02:15.500
It's going to be 15 plus 0.4 times one.

00:02:15.500 --> 00:02:17.420
That's just gonna be 15.4.

00:02:17.420 --> 00:02:20.780
Notice, when we increased our time by one,

00:02:20.780 --> 00:02:24.160
our temperature increased
by 0.4 degrees Celsius

00:02:24.160 --> 00:02:25.240
by the slope.

00:02:25.240 --> 00:02:28.250
And what happened again
if we increased time

00:02:28.250 --> 00:02:30.380
by another minute, if
we go from one to two,

00:02:30.380 --> 00:02:32.630
we would get two, 15.8.

00:02:32.630 --> 00:02:36.240
We would increase
temperature by another 0.4.

00:02:36.240 --> 00:02:38.430
How much will the temperature increase

00:02:38.430 --> 00:02:41.800
if Quinn leaves the
heat on for 20 minutes?

00:02:41.800 --> 00:02:44.370
Pause the video and see
if you can solve that.

00:02:44.370 --> 00:02:46.410
All right, now we have to be careful here.

00:02:46.410 --> 00:02:47.280
They're not asking us

00:02:47.280 --> 00:02:49.470
what is the temperature after 20 minutes.

00:02:49.470 --> 00:02:52.110
They're saying, how much
will the temperature increase

00:02:52.110 --> 00:02:54.420
if he leaves the heat on for 20 minutes?

00:02:54.420 --> 00:02:56.820
If we just wanna know
what is the temperature

00:02:56.820 --> 00:02:58.270
after 20 minutes, we would just say,

00:02:58.270 --> 00:03:00.880
okay, what is Q when t is equal to 20?

00:03:00.880 --> 00:03:05.180
So it'd be 15 plus 0.4 times 20.

00:03:05.180 --> 00:03:07.880
0.4 times 20 is eight.

00:03:07.880 --> 00:03:10.560
Eight plus 15 is 23.

00:03:10.560 --> 00:03:13.850
So it's 23 degrees
Celsius after 20 minutes.

00:03:13.850 --> 00:03:14.910
But that's not what they're asking us.

00:03:14.910 --> 00:03:18.060
They're asking, how much will
the temperature increase?

00:03:18.060 --> 00:03:19.460
Well, where did we start from?

00:03:19.460 --> 00:03:21.690
We started from 15 degrees Celsius

00:03:21.690 --> 00:03:25.260
and now after 20 minutes we
have gone to 23 degrees Celsius.

00:03:25.260 --> 00:03:28.300
So we have increased by
eight degrees Celsius.

00:03:28.300 --> 00:03:29.170
Or, another way to think about it,

00:03:29.170 --> 00:03:31.420
we have increased by this
amount right over here.

00:03:31.420 --> 00:03:34.150
We started at 15 and after 20 minutes,

00:03:34.150 --> 00:03:36.690
we have increased by 0.4 times 20

00:03:36.690 --> 00:03:39.380
which is eight degrees Celsius.

00:03:39.380 --> 00:03:40.213
We're done!


Constructing linear equation from context

WEBVTT
Kind: captions
Language: en

00:00:00.850 --> 00:00:02.850
- [Instructor] Tara was
hiking up a mountain.

00:00:02.850 --> 00:00:06.180
She started her hike at an
elevation of 1,200 meters

00:00:06.180 --> 00:00:08.370
and ascended at a constant rate.

00:00:08.370 --> 00:00:13.370
After four hours, she reached
an elevation of 1,700 meters.

00:00:13.940 --> 00:00:18.340
Let y represent Tara's elevation
in meters after x hours.

00:00:18.340 --> 00:00:19.990
And they ask us, and this is from

00:00:19.990 --> 00:00:21.490
an exercise on Khan Academy, it says,

00:00:21.490 --> 00:00:23.660
complete the equation for the relationship

00:00:23.660 --> 00:00:25.690
between the elevation
and the number of hours.

00:00:25.690 --> 00:00:27.850
And if you're on Khan
Academy, you would type it in,

00:00:27.850 --> 00:00:29.200
but we can do it by hand.

00:00:29.200 --> 00:00:32.190
So pause this video and
work it out on some paper

00:00:32.190 --> 00:00:34.750
and let's see if we get to the same place.

00:00:34.750 --> 00:00:37.050
All right, now let's do this together.

00:00:37.050 --> 00:00:38.260
So first of all, they tell us

00:00:38.260 --> 00:00:41.220
that she's ascending at a constant rate.

00:00:41.220 --> 00:00:42.927
So that's a pretty good indication

00:00:42.927 --> 00:00:46.040
that we could describe her elevation

00:00:46.040 --> 00:00:48.510
based on the number of hours she travels

00:00:48.510 --> 00:00:50.150
with a linear equation.

00:00:50.150 --> 00:00:52.770
And we could even figure
out that constant rate.

00:00:52.770 --> 00:00:55.420
It says that she goes from 1,200 meters

00:00:55.420 --> 00:00:58.710
to 1,700 meters in four hours.

00:00:58.710 --> 00:01:01.420
So we could say her rate

00:01:01.420 --> 00:01:03.680
is going to be her change in elevation

00:01:03.680 --> 00:01:04.880
over a change in time.

00:01:04.880 --> 00:01:08.450
So her change in elevation is 1,700 meters

00:01:08.450 --> 00:01:13.450
minus 1,200 meters and she
does this over four hours.

00:01:13.510 --> 00:01:17.580
Over, her change in time is four hours.

00:01:17.580 --> 00:01:19.713
So her constant rate
in the numerator here,

00:01:19.713 --> 00:01:23.660
1,700 minus 1,200 is 500 meters.

00:01:23.660 --> 00:01:26.423
She's able to go up 500
meters in four hours.

00:01:28.758 --> 00:01:30.010
If we divide 500 by four,

00:01:30.010 --> 00:01:35.010
this is 125 meters per hour.

00:01:36.100 --> 00:01:38.170
And so we could use this now

00:01:38.170 --> 00:01:41.360
to think about what our equation would be.

00:01:41.360 --> 00:01:44.220
Our elevation y would be equal to,

00:01:44.220 --> 00:01:45.720
well, where is she starting?

00:01:45.720 --> 00:01:47.890
Well, it's starting at 1,200 meters.

00:01:47.890 --> 00:01:50.270
So she's starting at 1,200 meters.

00:01:50.270 --> 00:01:54.050
And then to that, we're going to add

00:01:54.050 --> 00:01:58.360
how much she climbs based on
how many hours she's traveled.

00:01:58.360 --> 00:01:59.920
So it's going to be this rate,

00:01:59.920 --> 00:02:03.030
125 meters per hour times

00:02:03.030 --> 00:02:06.100
the number of hours she has been hiking.

00:02:06.100 --> 00:02:09.460
So the number of hours is x times x.

00:02:09.460 --> 00:02:11.420
So this right over here is an equation

00:02:11.420 --> 00:02:12.957
for the relationship between the elevation

00:02:12.957 --> 00:02:14.560
and the number of hours.

00:02:14.560 --> 00:02:16.110
Another way you could
have thought about it,

00:02:16.110 --> 00:02:16.943
you could have said, okay,

00:02:16.943 --> 00:02:18.980
this is going to be a linear equation

00:02:18.980 --> 00:02:21.060
because she's ascending
at a constant rate.

00:02:21.060 --> 00:02:23.010
You could say the slope intercept form

00:02:23.010 --> 00:02:28.010
for a linear equation is
y is equal to mx plus b,

00:02:28.080 --> 00:02:30.400
where b is your y-intercept.

00:02:30.400 --> 00:02:32.710
What is the value of y
when x is equal to zero?

00:02:32.710 --> 00:02:33.560
And you'd say, all right,

00:02:33.560 --> 00:02:34.470
when x is equal to zero,

00:02:34.470 --> 00:02:36.173
she's at an elevation of 1,200.

00:02:37.020 --> 00:02:38.960
And then m is our slope.

00:02:38.960 --> 00:02:42.600
So that's the rate at which
our elevation is increasing.

00:02:42.600 --> 00:02:44.380
And that's what we
calculated right over here.

00:02:44.380 --> 00:02:47.750
Our slope is 125 meters per hour.

00:02:47.750 --> 00:02:49.190
So notice, these are equivalent.

00:02:49.190 --> 00:02:51.760
I just have, these two terms are swapped.

00:02:51.760 --> 00:02:55.080
So we could either write
y is equal to 1,200

00:02:55.080 --> 00:02:59.470
plus 125x or you could write
it the other way around.

00:02:59.470 --> 00:03:04.030
You could write 125x plus 1,200.

00:03:04.030 --> 00:03:05.513
They are equivalent.


Khan Stories: Anjali

WEBVTT
Kind: captions
Language: en

00:00:00.252 --> 00:00:02.835
(wind blowing)

00:00:04.632 --> 00:00:07.299
(horns honking)

00:00:10.177 --> 00:00:13.260
(upbeat piano music)

00:00:18.446 --> 00:00:23.446
- Rachal!

00:02:35.481 --> 00:02:39.626
- [Anjali] Where this mind is (mumbles)

00:02:39.626 --> 00:02:41.228
Where knowledge is sweet,

00:02:41.228 --> 00:02:43.640
where the wall has not been broken up

00:02:43.640 --> 00:02:47.060
into fragments by (mumbles)

00:02:47.918 --> 00:02:50.617
And to die and have no freedom, my Lord,

00:02:50.617 --> 00:02:52.133
let my country (mumbles).


Khan Stories: Sal's high school math teacher

WEBVTT
Kind: captions
Language: en

00:00:00.319 --> 00:00:03.166
I met Sal when he was a 10th grader at

00:00:03.166 --> 00:00:04.707
Grace King High School.

00:00:04.707 --> 00:00:07.290
He was in my Algebra Two class.

00:00:09.095 --> 00:00:10.819
That was a kid who challenged me,

00:00:10.819 --> 00:00:12.322
he was a natural leader

00:00:12.322 --> 00:00:16.852
as far as getting other
kids involved and active.

00:00:16.852 --> 00:00:19.519
- Oh man, you teaching AP Calculus now?

00:00:19.519 --> 00:00:20.360
- That's right, I am.

00:00:20.360 --> 00:00:23.132
- Really, awesome! Oh man, I
would've brought you on stage!

00:00:23.132 --> 00:00:23.965
- No!

00:00:23.965 --> 00:00:26.014
- No seriously, I didn't
know you were here!

00:00:26.014 --> 00:00:28.405
This guy, he wrote my
recommendations for college,

00:00:28.405 --> 00:00:30.942
like honestly like none
of this would've happened.

00:00:30.942 --> 00:00:31.900
- No.

00:00:31.900 --> 00:00:33.775
- I don't know what to
do, I feel like crying.

00:00:33.775 --> 00:00:35.783
- No, I'm crying.

00:00:35.783 --> 00:00:38.824
This guy really hasn't changed one bit.

00:00:38.824 --> 00:00:41.871
It's still the same Salman Khan
that I saw in high school.

00:00:41.871 --> 00:00:45.705
Down to earth, easy going, accessible,

00:00:45.705 --> 00:00:48.362
nothing pretentious about him, okay.

00:00:48.362 --> 00:00:50.805
And that's one of the
things that really makes

00:00:50.805 --> 00:00:52.911
Khan Academy what it is.

00:00:52.911 --> 00:00:54.426
It's like you know,

00:00:54.426 --> 00:00:57.012
the whole thing is like the
gift that keeps on giving.

00:00:57.012 --> 00:01:00.262
Which I think what education is about.