(upbeat music)
- We're moving on to
Natural Selection, 1.3,
Exploring Variation and
Distribution in Populations.
I'm gonna introduce you
to our digital model,
the natural selection simulation.
The reason scientists use digital models,
that the sim that we're about to use,
is that it allows them to look at things
that are too big or too small
or, in our case, take a really long time.
We want to look at populations
and how they change.
It takes hundreds, thousands,
and millions of years
for the population to change,
but we can see changes
in a very short amount of time in the sim.
If you're able to log in,
go ahead to 1.3, activity 2,
and launch the natural
selection simulation,
and follow along.
We're gonna explore the sim
and get to see what tools it has.
If your time is exploration at home,
what I want you to consider
is what do the different buttons do,
what do you notice about
what you can change,
and are there any questions.
If you're not able to login, don't worry,
I'll take you through the sim.
This is my cat Akimbo,
he's decided to join us
for the next little part
while we explore the sim.
There are four main things
that you need to know about the sim.
The first two are in the build mode.
There are two different
things that you can build,
you can build abiotic and biotic.
So abiotic factors are all the
non-living parts of the sim.
The temperature, the rainfall,
and the service color.
The second thing to know in the build mode
is that you can change the biotic factors.
We have three organisms
in our environment,
we have thorn palms,
ostrilopes, and carnifons.
We'll look at all of them
closer in a little bit.
The thing to know though is
they have different traits
and we'll look at
differences in those traits.
The third piece to the sim
is the run mode.
This is where you see what happens
based on the environment that you set up.
And the final step is the analyze phase.
This is where you look at your populations
and their different traits,
and you can see how they
changed over time as well.
Now that you've seen the tools of the sim,
let's try it out.
So I click on run, and I can
see our different organisms.
So I've got ostrilopes are the
little bird-like creatures,
carnifons are the big red meat-eaters,
and the thorn palms are the trees.
So these organisms aren't real,
but they're based on real organisms.
The idea being that you have a plant
that does photosynthesis, an
organism that eats plants,
and an organism that eats other animals.
They need energy in order to survive
and they also reproduce.
So we can use these organisms
to look at changes over time.
Now we're gonna try some
missions in the sim.
Again, if you're logged in,
go ahead and pause this video
and try them on your own,
but if you're not logged in, don't worry,
I'll take you through
the missions right now.
Our first three missions are
all about the thorn palms,
so I'm going to turn off the
ostrilopes and the carnifons
so that I can focus on our thorn palms.
So my first mission with the thorn palms
is to have all of them have medium thorns.
So I look at their thorn size,
and I can see all of
them have medium thorns.
So then I look around at them
and I can see these little spikes on them,
and the size thorns that they have.
So the second mission is to have
many different sizes of thorns.
So I look down here
and I see this little
bar that says variation.
If I move it over to low variation,
now I can see that I have a
few different thorn sizes.
If I move it over to medium,
then I have even more
different thorn sizes.
If I move it over to high,
then I can see that I have
all the different thorn sizes.
So I look at this, and now this one
has thorn size 10, so I
can see it's really spiky,
kind of reminds me of my cousin
when he had a mohawk.
This one is thorn size 7,
another thorn size 7,
and so I can see that we
have different sized thorns.
This one is thorn size 4, and I can see
it barely has any spikes on it at all.
Our third mission with the thorn palms
is to have many short thorns,
short thorn palms, a few that are medium,
and none that are tall.
So I'm gonna leave them
with a lot of variety
with the thorn size, and
I'm gonna switch to height.
So right now, they're all the same height.
If I want to have many that are short,
a few that are medium,
and none that are tall,
I'm gonna bump up my variation
a little bit to medium,
but now it's kinda spread out
and most of them are medium.
But I want most of them to be short,
so I'm gonna drag this over,
and then you can see that more of them
are now gonna be short,
a few of them will be medium,
and none will be tall.
So now I look at this one,
and it's a short little thorn palm.
And so I can see these differences
in the height of the thorn palms.
Our next two missions
are with the ostrilopes,
so I'm going to get rid of the thorn palms
and I'm going to bring
our ostrilopes back.
So our first one is to change
the color of the ostrilopes,
so I'm gonna switch to the color,
and I can see right now,
I have no variation in color,
and so they're all color number 5,
so I look at this, and color
number 5 looks like a green.
So I want to have blue, green, and yellow.
So if I move the variation up more,
now we can see this one's yellow,
so this is color number 8. Okay,
so yellow is a higher number.
Green is number 5, so that's
in the middle is green.
See if I can find some other colors.
Here's kind of a blue, so
this is color number 3,
so what I figured out is the low numbers,
these are blues, the
middle numbers are greens,
and the high numbers are yellows.
Then I wanna make it so
that one of my features
of the ostrilope has a lot of variation
and one feature has no variation.
So I'm gonna try armor.
So right now, the armor has no variation.
So I'm gonna make it so it
has a lot of variation, okay,
so then when I look at the ostrilopes
I can see these little
spikes on their back,
and how much armor it has.
I can't really see the spikes on that one,
here we go.
There's some--
There's some big spikes on that one,
so that is the armor nine,
so it's got some big spikes on it,
so I have lots of variation in the armor.
And then neck length, I have no variation,
so all of their necks are the same length.
Our last two missions
are with the carnifons,
so I'm going to remove the ostrilopes
and bring the carnifons back.
I'm gonna zoom out a little bit until I--
Oh, can find some carnifons, there we go.
Okay.
And what I want to look at
is having a lot of fur,
and some with medium fur.
So I already figured this
out with the ostrilopes,
that in order to get that,
I want to move to medium variation,
and this time, instead of moving
the distribution to the
left like I did before,
this time I'm gonna move it to the right.
Once there, I can see the carnifons
now have a bunch of fur on them,
and some of them have a little bit less.
So most of them have a lot of fur,
and some of them have less fur.
And our last challenge with the carnifons
is to have the maximum variation possible,
so I'm gonna go poison resistance,
and I'm going to go with the
maximum variation,
and so they each have
a different amount of
poison level resistance.
So this one's a level nine, which means
that it can withstand a lot of poison.
This one's eight,
so it can also withstand a lot of poison.
See if we can find one,
poison resistance two,
which means that it can't stand up
to much of the ostrilope poison.
Those are all the missions for today,
but in future lessons,
we'll look at the organisms
interacting with each other, and see how
their populations change over time.
As you watch the video, listen for
why we use histograms and
what it shows about variation.
(xylophone music)
- Biologists use graphs called histograms
to show variation and
populations of organisms.
Let's look at a population of ostrilopes
to understand how historgrams
can show variation.
If you look at the ostrilopes,
you can see that although they are all
from the same population,
they are all different from each other.
They have different traits.
For example, the ostrilopes vary in color
from yellow to green to blue,
and they have different amounts of fur
on their bodies.
Their necks range from very short
to very long.
These are examples of variation
in the ostrilope population.
If the population is broken into groups
according to a single feature,
such as the length of their neck,
and they line up according to the trait
of how long their necks are,
we can see how many individuals
have short necks,
and how many have medium, long,
and very long necks.
The lines of organisms
are like bars in a graph.
The taller the bar in the graph,
the more organisms that
have that neck length.
This type of graph is called a histogram.
This is the same histogram represented
in a different way.
It shows the same variation in neck length
within the ostrilope population.
If the ostrilopes are grouped
by a different feature,
the shape of the histogram will change.
Now the ostrilopes are lining up
according to color.
You could count how many
ostrilopes are each color
by looking at every individual ostrilope,
one by one.
But using the histogram is easier.
One quick look shows that
most of the ostrilopes
in this population are blue,
some are yellow, and a
small amount are green.
Histograms help biologists understand
the variation of traits in a population.
They are also useful for comparing
two or more populations,
or for investigating how populations
change over time.
(xylophone music)
- Hopefully that video helped
add to your understanding of
three more important words:
Variation, distribution, and histogram.
Variation is any difference in traits
between individual organisms.
You saw lots of variations
of the ostrilopes,
there were different colors,
they had different neck lengths,
all the things are
differences in their traits.
Distribution is the number of individuals
with each trait in a population.
So when we look at the distribution
of our ostrilope's color, we
can see most of them are blue,
many of them are yellow, and
very few of them are green.
And our final important
word for today, histogram.
So a histogram is a graph that uses bars
to show how characteristics or values
are distributed within a group.
It's much easier to look
at changes and populations
if you can visually represent
what the population looked like before,
and what it looked like afterwards.
We'll use histograms a
lot to show variation
in populations.
Let's practice making some histograms.
For this, you'll need a piece of paper
with a grid on it.
I just used a piece of lined
paper and drew a grid on it,
and 12 small objects that you can sort.
So it can be coins or
Legos or building cubes,
something, anything will work
as long as there is
variation in your materials.
Here, my materials that
I have that I'm gonna use
to practice making historgrams,
you can see I grabbed 12 random coins,
and then I made a grid
on a piece of paper.
Whatever materials you have works great.
We're gonna start by making a histogram
that shows no variation.
So if I want to think about something
that all of my materials have in common,
one of the things they all have
in common is they are metal.
So I would sort into one
column, showing them that all
of them are metal.
It is totally fine if your materials
go off your paper, if your
historgram is not big enough,
especially when we're doing things
where they are all one
thing, it's totally fine.
Then if I want to show low variation,
I might do something like sort by color.
Then I sort them into
columns based on what color they are,
and you see I have super low variation
because they're either silver or copper.
Or if I want to increase my variation,
I might sort them by their value,
and so my pennies are all worth one cent,
my nickels are worth five,
my dimes are worth 10,
and my quarters are worth 25.
And so I can increase the
amount of variation that I show
based on the trait that I select.
Keep using your materials,
try making different histograms
showing different amounts of variation.
We'll use histograms a lot
as we look at what
happens to our populations
and how they change over them.
We'll end today with our first key concept
for natural selection,
make sure you record this.
A population can be described
by the traits present
and by the number of
individuals who have each trait.
Again a population can be described
by the traits present, by
the number of individuals
who have each trait.
We saw this today with our butterflies
and the variety of traits that they had
with their wing color.
You saw this with our ostrilopes,
they had different neck lengths,
different colors, different fur amounts.
Saw this with our thorn
palms and our carnifons,
so any time you're
looking at a population,
you're looking at what traits they have,
and how many have each of those traits.
Thanks for joining me today,
as we started natural selection.
I hope you'll join me next time
when we look at what happens to ostrilopes
when their environment changes.
See you next time!
(upbeat music)
