Hi. It's Paul Andersen and this Life Science Core Idea 2B (LS2B). It's basically
on matter and energy and how they're transferred in an ecosystem. And so we want students to
really understand how ecosystems function. How matter moves in and out of life. And so
how do we get there? Well in the elementary level, at the lower elementary grades we want
to make sure that we know the difference between what an organism is and what the environment
is. And a picture like this is a great place to start. You could have them list all of
the organisms they can see and then what are all the parts of the environment. We don't
have to use the words biotic and abiotic. So what are some of the living things that
you see here? Well the elk for sure. We see pine trees. We see grass. But don't neglect
there's going to be trout here in the stream. There's going to be insects everywhere. There's
going to be bacteria everywhere. And so those are going to be the organisms. And then what
is the environment? Well the environment is going to be the atmosphere. It's going to
be the water. It's going to be the chemicals that are found in the soil. It's going to
be the soil itself. Those are going to be the environment. And matter is required by
organisms. And so they're going to get that from their environment. As we move forward
in elementary school we really want to talk about how matter is recycled. How it's used
over and over again. And the standards put forward this idea of composting as a good
place to start. And it's great. And if we think about how plant material on a farm for
example is made. How do these crop grow? Well they're getting matter from the soil and they're
also getting matter from the atmosphere. So they're getting matter from the air. So what's
the matter from the air that the plants are taking in? They're taking in carbon dioxide.
What is the matter from the soil? Nitrogen. They're taking in water. Taking in nutrients
they require and so this matter will combine to make life or living matter. And it's conserved.
The amount of matter that we have before and after is going to be exactly the same. In
composting what are we doing? Well now that material is died and we need to return the
matter to the environment. And bacteria are really good and breaking down that waste and
then removing it from the living material and moving back into the environment. And
so what happens? A lot of that matter goes back into the atmosphere and a lot of it becomes
part of the soil itself. So nitrogen that's going to be found in that really rich composted
material is going to be matter that we can then return back to plant material in the
whole process goes over and over again. And so the amount of matter that we have on our
planet, tell them, is the same. It's just moving in to life and out of life. And the
same could be said for animals. That when we eat plants, that matter becomes part of
us. And through our waste, or when we die and as we break down, it's going to be returned
back to the environment. And so as we move into the middle school we want to start talking
about how the energy is actually flowing. And food webs are a great place to start with
that. And what they're really showing, what are the arrows showing is they're showing
where energy and matter goes. And so right here this bird is feeding on seeds on a tree,
but if it's eaten by a coyote, we're going to get movement of matter in this direction.
And what you can see is that everything is going to come from the producers. It's going
to come from the plants but if we want to return that matter so it can be used again,
by the plants we have to have decomposers that can do that. The problem with the food
web is it doesn't show your one thing. It doesn't really show you the environment and
where matter is coming from. And so a good thing to look at would be a matter cycle.
So we're looking at where the cycle actually flows. And so this picture right here, where
is the matter found? Where is it going? And then how is it being returned back into the
environment? And so basically it all begins with the environment. So what's some type
of matter that we would find in the environment? Carbon dioxide would be something that's found
that you can't see in this picture. But it's going to become part of the producers or part
of the plants. And so that carbon dioxide is being used by plants through photosynthesis
to create sugar. To actually create the plant. Where could the matter go next? Well it could
be eaten by an insect. And so now it moves the matter from a producer to a consumer.
And maybe that insect in turn is eaten by another consumer like this frog that is waiting
here for a tasty meal. Now the matter flows into the frog. But when the frog dies, or
it leaves waste behind. That matter can be decomposed and can be returned to the environment
again. Now this is usually where matter goes from the environment to the producers, consumers,
decomposers. But know that it doesn't have to go in that direction. Obviously we're taking
in material from the environment. So for example oxygen is something that I'm breathing in
from the environment. And plants don't have to be eaten by consumers for them to be decomposed
and moved back into the environment. But it does show where matter is flowing. And the
neat thing about matter is that it stays the same on our planet. The amount of matter that
we have is the same. It just moves through life, is utilized by life and then it returns
back to the environment, different then energy. And so these two processes that allow us to
do this are photosynthesis and cellular respiration. So what is photosynthesis allow plants to
do? Take material in their environment and actually make plants out of it. And so in
photosynthesis we're taking in water. We're taking in carbon dioxide and then we're using
the power of the sun to actually make material. To make sugars. Those sugars are going to
be combined with oxygen in animals and we're going to break that down into water and carbon
dioxide through cellular respiration so we can get energy out of it. And so one big thing
you should note is that we're going to loose matter and we're going to loose energy along
the way. And so we're going to have way more producers generally in an ecosystem then we
are going to be consumers. And so as you're at the high school level it's really important
that you start talking about ecological pyramids. And this idea that at the low level of the
food web or the low level of a feeding pyramid, we're going to have way more matter, energy
and individuals. And so let's start there. This would be a number pyramid in a temperate
grassland. And so basically in 0.01 hectares, which is not very much area, these are the
number of individuals in this study that they found at the level of producers, first consumers,
second consumers and third consumers. And what you can see is there's a nice pyramid
in the number of individuals that we have. And so what are these 1.5 million individuals.
It's going to be grass that's found within that temperate grassland. What's feeding on
them? Well insects are going to be one of the big things that are feeding on that. What's
feeding on those insects? Other insects, but also things like mice. And then what is this
one consumer here? Well if you've been in a temperate grassland one thing that you're
going to see a lot of are going to be hawks. But not that many, and the reason why is that
we're losing energy in matter along the way. And so if we look at the actual biomass or
the matter in an ecosystem, so this is a coral reef ecosystem on the Marshal Islands. In
this study what they looked at was the grams per meter squared, we found that we're going
to have way more grams on a square meter, at the producer level. And so this is mostly
in a coral reef going to be that algae, then the consumers that feed on top of that and
then the consumers that feed on top of the consumers. So a lot of these are going to
be fish at that level. And if we were to look at energy we'd find the same thing. And so
this is at Silver Springs State Park in Florida, and what they're studying here is that energy
within an ecosystem, this is in kilocals per meter squared per year. And so basically the
producers are going to have way more energy. Where do they get that energy from? The sun.
What do they do with the energy? They converted it into the energy of their food and then
that energy is given off to the consumers who are then are given off to consumers and
consumers again. And there's this general rule called the ten percent rule. And this
kind of follows that. That you're basically only moving ten percent of the energy to the
next level. And so basically that's ecological pyramids. It's based on this idea that photosynthesis
is taking matter in the environment and making it usable matter. And then cellular respiration
is used by consumers to release energy. And I hope that was helpful.