(inspirational music)
- Hello, this is Miss Jetta coming at you
from Seattle, Washington.
I hope you are enjoying
learning about natural selection
and I'm excited to dive into chapter two,
lesson 2.1 with you today.
Let's get started.
Here's what you'll need for this lesson,
a pencil or a pen, some
lined or blank paper,
and here are some optional
but encouraged things
you can add on.
A family, a friend, or even a pet
that you can check in with,
a computer logged into Amplify.
Let's warm up.
Pause the video and read
Sherman's story about bird beaks.
Turn and talk to a
friend or a family member
or jot your responses
down on a piece of paper
about the following questions
after you read Sherman's story.
In this environment, which
trait is adaptive for the birds?
Sherman suggests that reproduction
always creates individuals
with adaptive traits.
Does this seem correct?
Why or why not?
The trait that is
adaptive for these birds,
that is the one that helps them survive,
is their strong and tough beaks.
That's because their
strong and tough beaks
allow them to eat the
food that is available
in their environment.
Now in terms of reproduction
always creating individuals
with adaptive traits,
I'm not quite sure if
the birds with weak beaks
all had offspring with strong beaks
so that they would survive.
I feel like we need more evidence
to see if Sherman is correct.
This brings us to our
chapter two question,
which is how do
individuals in a population
get their trait?
Let's take a look at some new evidence
considering this question.
How did the trait for
increased poison level
become more common in the new population?
Pause the video and turn
and talk to a friend
or family member or
jot down your responses
on a piece of paper about
the following question.
What differences do you notice
between these two histograms
on the right hand side?
What I notice is that in
this population 50 years ago,
there was a large number of newts
that included low poison level
and the environment that they were in
did not include snakes.
However in this population today,
I notice that there's
a large number of newts
that have a high poison level
and their environment does include snakes.
What we're gonna do now
is use the simulation
to investigate a claim.
That claim is, reproduction
always creates individuals
with adaptive traits.
We're gonna see if that claim
is supported or refuted.
Now in the natural selection
simulation on Amplify
here's what I'm gonna do.
I'm gonna into my hamburger menu
and go into Reproduction Claims.
This will allow us to gather evidence
about the claim we are investigating.
I'm gonna load that
Reproduction Claims mode
and what I'm going to do,
is I'm going to choose
an ostrilope to follow
and we'll follow that
ostrilope until it mates
and be able to see the
offspring that results
in the process of reproduction.
I'm gonna choose an ostrilope
with non-adaptive traits first.
I'm gonna click on my ostrilope
and I'm going to follow that ostrilope
and then select pause
to pause the simulation after running it.
Okay, so I see that the
ostrilope is about to reproduce
and I can see here
we have one ostrilope
that has a color of three
mating with an ostrilope
also with a color of three.
Let's see what their offspring looks like.
Their offspring also has a color of three.
I'm gonna write that down
on my data table sheet.
All right, so what we saw
is that we had one parent
with a color trait level of three,
another parent with a
color trait level of three,
and then the offspring color was also
a color trait level of three.
Let's do another trial
and see what happens.
Now let's see what happens
when these ostrilopes mate.
This ostrilope has a color level of four.
This ostrilope has a color level of one.
The ostrilope that they
have produced as offspring
is a color level of one.
Let's record that on our data table.
Remember these are ostrilopes
with non-adaptive traits.
Our first pair was an
ostrilope with level three,
an ostrilope with level three
and they had offspring
with a level three as well.
The second pair, one
ostrilope was a level four,
one was a level one,
and then their offspring
was a level one also.
Now let's see what
happens when an ostrilope
with an adaptive trait reproduces.
Notice how the carnithon
just passed by the ostrilope
and another carnithon as well.
Our ostrilope is now looking for a mate
and he's found a mate with
a color level of seven.
We can see here that both ostrilopes
have a color level of seven.
Let's see what their offspring looks like.
What do you think it might be?
So their offspring ostrilope
also had a color level of seven.
Let's do another trial
with another ostrilope
that has an adaptive trait
for this environment.
We're gonna follow this
ostrilope right here
who has a color level of seven.
They're looking for a mate.
The mate that they have chosen
has a color level of five.
And let's see what their
offspring might look like?
What do you think?
Their offspring has a
color level of seven.
Let's document this on our data sheet.
So let's go ahead and record
what we just saw on the sim
on our data table.
For trial one, we had one parent
with a color trait level of seven.
We had the other parent of that pair
with a color trait level of seven.
And their offspring had a
color trait level of seven.
And our second pair for trial two,
we had one parent with a
color trait level of seven,
one with a trait color level of five,
and their offspring had a
trait color level of seven.
So what does this all mean?
If we compare our two data tables,
showing the ostrilopes
with non-adaptive traits
and the ostrilopes with
the adaptive traits,
what we can see here is,
given the environment which had carnithons
and a color level of seven,
in both cases, non-adaptive ostrilopes
reproduced with ostrilopes
that had non-adaptive traits
and adaptive ostrilopes reproduced
with ostrilopes that did
have adaptive traits.
Let's look at the distribution
of this color trait
on the population level.
So here as we can see, in generation one,
that we had a large number of ostrilopes
that had a blue color trait level,
and that would be a color trait level
of like one to five, essentially.
However in that same
population at generation 10,
what we can see here is that
there are less ostrilopes
with blue and green color trait levels
and our trait distribution is
now leaning towards yellow,
so the colors at seven, eight, nine,
seven, eight, and nine.
Now using all this data,
all this evidence that
we just found in the sim,
but looking at our ostrilope populations
and their colors,
let's think about that claim again.
Reproduction always creates individuals
with adaptive traits.
Pause the video, turn and
talk to a family member
or jot a response down on a piece a paper.
Was our claim supported
or refuted by the evidence
that we just gathered in the simulation?
How do you know?
So let's discuss this claim together.
The claim of course was,
reproduction always creates individuals
with adaptive traits.
We can see now with the evidence
and thus the data that
we gathered in the sim,
this claim is in fact refuted,
because non-adaptive traits were passed on
just like the adaptive
traits were passed on.
There was no difference there.
Additionally, in a population the traits
of the offspring are generally similar
to those of their parents.
So if there were blue
ostrilopes in the environment,
then they would be passing on those traits
to their offspring, generally speaking.
And if there were more yellow ostrilopes
in the population,
then those ostrilopes would pass on
their traits of color
to their offspring, generally speaking.
In a population the traits of offspring
are generally similar
to the traits of their parents,
whether those traits are
adaptive or non-adaptive.
Reproduction plays a key role
in how the distribution of the traits
in a population changes over time.
But this involves of course
having the opportunity
to reproduce in the first place.
So let's take a look at how
trait distribution changes
over generations with a
predator and without a predator.
Here we have our trait distribution
diagrams over generations.
This the diagram we just looked at
and this is our population
with carnithons.
In our ostrilope color distribution,
what we can see here in
generation one with carnithons
we had more ostrilopes with a level one
through five color levels,
that would be blue to green.
In generation 10 though,
our distribution shifted
and changed so that more of our ostrilopes
were at a color level of seven to nine.
Now we can see here, there are still some
of the lower color trait levels existing,
but just not as prominent as
those in the seven to nine
color trait levels.
Now without carnithons, let's take a look.
In generation one, just like we saw before
we have more ostrilopes in color levels
from one to six
and less in seven to 10.
However, in generation 10 over here,
what we can see here is that
we don't get that same shift
that we saw in the
population with carnithons.
So we can see here that
our color trait level
maintains at a level of
prominence from one to five,
compared to seven through 10,
versus that shift that we saw
in the environment that had carnithons.
So the next question we have to tackle
is understanding how this genetic shift
is actually possible.
In other words, what is going
on at the molecular scale
in these organism cells
that are allowing for
this shift to take place.
One important vocabulary word
that we need to understand
for this is gene.
Genes are instructions for
making a protein molecule.
Here is a diagram that shows genes.
Genes are located on chromosomes.
There are one, two,
three sets of chromosomes
in our diagram.
And what chromosomes are
are tightly wound bundles of DNA,
kinda like a bundle of yarn all balled up.
There are two copies of each gene,
one on each chromosome of the pair.
And when an organism reproduces sexually,
it gives the offspring one
of each of its chromosomes
and therefore one copy of each gene.
Another way of saying that
is that parents pass on
one copy of each gene
to their offspring.
Another vocabulary word
we need to be aware of
is protein molecule.
A protein molecule is a
type of large molecule
that performs important
functions inside of organisms.
In science of course,
when we can't actually
have our hands on something
that's so microscopic
like chromosomes or
like protein molecules,
we love to create models
as you might be aware of.
So in our diagram here,
these are two different
models of protein molecules.
This first one is called a ribbon diagram
and the second one is called
a space filling model.
Both show the structure of a protein.
These words will help us as we read
a little bit more about what is going on
in terms of genetics in organisms.
The article we are going to read today
that will help us with this understanding
is called "Glowing Jellies."
Imagine splashing in a
calm ocean cove at night.
As you splash, you notice green flashes
in the water, glowing jellies.
These are called crystal jellies.
They can't sting humans,
so you can swim and watch them glow green
as you bump into them.
Where does this trait of
being able to glow come from?
In 1992, some scientists
decided to find out.
They examined the cells of crystal jellies
and discovered the glow
comes from a a protein.
They gave the protein the
name green fluorescent protein
or GFP for short.
To find out how these jellies made GFP,
scientists investigated the jellies genes.
So I'm seeing here that
this glowing property
comes from a protein.
So this makes me think about how proteins
allow for traits,
traits like glowing to be expressed.
Let's move on.
A gene is instructions
for an organism's cells
to make a particular protein.
Scientists were able to find the gene
that gave the jellies' cells
instructions to make the GFP protein.
If a jelly has the GFP gene,
its cells can make green
fluorescent protein.
If its cells make green
fluorescent protein
the jelly can glow.
The gene leads to the protein,
which leads to the trait.
That is a really important point.
I'm going to make sure
that I underline that.
The gene leads to the protein
which leads to the trait.
I also think I might
wanna create a flow chart
to be able to demonstrate
the connection between these three items.
So we have genes
that provide instructions for proteins
that are then able to
be expressed as traits.
Let's move forward with our reading now.
How does a jelly get the gene for glowing?
When a pair of adult jellies reproduce,
each one passes down
genes to the offspring.
Genes are found in chromosomes
and chromosomes come in pairs.
An organism has two
copies of any given gene,
because there's one copy on
each chromosome in the pair.
However, the two copies
of any particular gene
can be the same version
or different versions.
These different versions of
a gene are called alleles.
When jellies reproduce sexually,
each parent passes down one
of each of their chromosomes
with their genes on it to the offspring.
That's an important point,
and we'll pop back over
in a second to our diagram
to demonstrate this as well.
So each parent passes down one
of each of their chromosomes
with their genes on it to the offspring.
Now humans have 46 chromosomes,
which means that 23 of our chromosomes
come from our biological mother
and 23 of our chromosomes come
from our biological father.
If at least one of the adult jellies
has the version of the gene
that is instructions for GFP
then the gene could be
passed down to the offspring.
Offspring with the gene will have cells
that produce GFP, so they will glow also.
Moving back to our diagram
from our definition of gene
as well as on this page,
we can see here there
are different versions
that the genes can be.
These are different versions.
We can see that from the different colors
that are presented in these diagrams.
Those different genes
versions are called alleles.
And we can also see, like
we demonstrated before,
that each set of chromosomes,
in each set of chromosomes,
one of those chromosomes comes
from the biological mother
and one comes from the biological father.
Therefore each chromosome
carries one of those genes,
so one of the genes in this case
comes from the biological mother
and one comes from the biological father.
Let's move forward with some
reflection questions as well.
So let's reflect on what
we've learned today.
First, where do genes that determine
an individual's traits come from?
A, an individual can
be born with any genes
since genes are random.
B, individuals grow genes
specific to their environment.
Or C, parents pass their
genes down to their offspring.
Or D, parents choose which
genes their offspring have
when each individual is born.
Pause the video and
respond to this question
with a, b, c, or d, based on
what we learned in this lesson.
That's right, it's c,
parents pass their genes
down to their offspring.
Here's another question for you.
How do genes determine
and individual's trait?
A, genes directly lead to traits.
B, genes are random and
don't lead to traits.
C, genes give organisms the
ability to change their traits.
Or D, genes are instructions
for making protein molecules
and protein molecules determine traits.
Turn and talk to someone near you
and respond to this
question with a, b, c, or d.
That's right, it's d.
Genes are instructions for
making protein molecules
and protein molecules determine traits.
Let's do one more question
to reflect on our learning for today.
How can an individual be
born with an adaptive trait?
A, the individual can choose to change
the adaptive trait when they want to.
B, the parents had genes
for the adaptive trait
which they passed down to the individual.
C, the individual can choose to have
an adaptive trait at birth.
Or d, the parents can
choose for the offspring
to have genes for the adaptive trait.
Write your response down
or turn to someone near you
and respond to this
question with a, b, c, or d,
based on our lesson today.
That's right, it's b.
Parents had genes for the adaptive trait
which they passed down to the individual.
Great job today and I will
see you for chapter two,
lesson two next.
(upbeat music)
