Hi. It' Paul Andersen and this
is Life Science Core Idea 1C (LS1C). It's
on Matter and Energy Flow in Organisms. And
by the time students graduate from high school
they should really have a good understanding
of how matter is recycled on our planet and
how energy moves through living material and
eventually becomes heat. And so if you're
teaching this a good place to start is with
plants. And so at the lower elementary grades
you want to start by talking about what a
plant needs to survive. Basically they need
two things. You need to give them light and
you need to give then water. If they don't
have those two things, they're going to die
right away. But what do animals need? We need
plants. And so this mouse is feeding on plants.
And this hawk is feeding on the mouse which
fed on the plants. And so that's a good place
to start. What are some of the requirements
of life. And light and water are a good place
to start. But it's more complex than that.
And so as we move through elementary we want
to add two areas. We want to add material
that we get from the soil, minerals. And minerals
that we get from the air. And so basically
if we look at a plant, what does a plant require
to live? It needs light and water. But it
also needs minerals that it's taking out of
the soil. And so it's talking those in through
its roots and it's also getting minerals from
the air, in the form of carbon dioxide. And
so if they don't have all of those things
they can't survive. But what about animals?
We don't need light to survive, but we do
need water and we need plants. Because those
plants are going to contain minerals that
we require. And then we're also going to get
minerals out of the air in the form of oxygen.
But there are some organisms, like the bacteria
that live in the gut of this cow that don't
require oxygen. And we call those anaerobic
organisms. And so all of this matter we get
from the earth or from plants that get it
from the earth. But we also get energy and
that energy again comes from plants. As you
move into middle school you want to start
talking about how that actually occurs. I
mean how does that matter, how does that energy
get stored in organisms? And the big process
is called photosynthesis. Now you don't want
to get too much into the details of the light
reaction and the Calvin Cycle and electron
transport, but you do want to talk about photosynthesis
and really the overall of what's going on.
And so the nice thing about the work photosynthesis
is that it's broken into two parts. You've
got the photo part and the synthesis part.
And so in the photo part, plant or you know
protists or algae or phytoplankton are all
taking in light and water and they're using
the energy of that light to activate chemicals
inside the plant. They then use that energy
that's stored to convert carbon dioxide into
sugar. And that's the synthesis part. We're
making something out of the carbon dioxide.
So let's go over that again. We start with
the light and the water and in the light reaction
we store that energy and then we use that
energy to take carbon dioxide and convert
it into a sugar. So that's photosynthesis.
What are we using the sugar for? Well in plants
they're using the sugar to build the plant.
And so the sugar that eventually makes the
cellulose that eventually makes the wood in
a tree comes from this process of photosynthesis.
And it's important that you understand that
matter is actually coming in from the carbon
dioxide that the leaves take in. And so most
of the mass of a tree actually comes from
the air. Comes in from carbon dioxide. So
they're taking in the sugar and they're using
that to build but they're also using that
for energy. If we now look at organisms, so
animals, where do we get our energy? Well
we get it from the food. In other words it's
in the sugar that was produced by the plants
that we eat or the animals that ate the plants.
And so the way we release that energy is through
a process called cellular respiration. So
how does that work? We're taking in food and
oxygen and we're using that to store energy
inside our body that we can utilize. What
are the byproducts of that? Water and carbon
dioxide. And what's nice about that is that
those are used again in photosynthesis. Let's
go over that again. We take in food from the
organisms or the plants that we eat. We combine,
using oxygen to store that energy inside us.
And it's way more complex than that. But we
can wait on that. And so there are some organisms
again, anaerobic that can just take in food
and they don't require oxygen to release that
energy. Now that's kind of the energy, where
it's coming from. But we also build the parts
of cells. And so plants are not only using
that sugar to release energy, but they're
building the parts of the cell. And we can
metabolize that sugar and use it to make DNA
and proteins and other things inside the cell.
And so we're getting the matter of life from
that. And so there's definitely a flow, a
flow of energy. And that flow of energy goes
from the sun to you. And so when you move
your hand like that the energy of your moving
hand originally came from the energy in the
sun. And so how does it flow? Well, it flows
into our food through a process of photosynthesis.
That energy is being stored in plants and
it's eventually being stored in our food.
Now along each of these steps we're loosing
energy and we're loosing energy in the form
of heat. But we're taking that free energy
of the sun and we're storing it in free energy
of our food. We then use cellular respiration,
and we use mitochondria to do this and release
this energy. To transfer energy to the muscles
in the form of ATP. And so as you move into
high school, then you can get into more of
the specifics of photosynthesis, cellular
respiration and even talking about ATP and
how that energy is transferred. But the big
picture is this. Energy is going to flow through
life in one direction. The energy from the
sun becomes energy in the plants, energy in
the animals, but eventually it leaves as heat.
And if the sun isn't there, if the sun were
to go out, then the plants die, the animals
die as a result. And so it's a one way direction.
We're still conserving the energy. It's just
that were switching it into a different form,
eventually becoming heat. The matter is different.
That matter on our planet is recycled over
and over and over again. And so what makes
me up, that matter, used to be in the air
or used to be in plants or used to be in my
food. I literally am what I eat. And it's
recycled over and over and over on our planet.
In other words there's a set amount of water
on our planet and it's just recycled over
and over again. And so that's matter. And
that's energy. And I hope that was helpful.
