- [Instructor] In this
video, we are going to focus
even more on the idea of evolution.
We introduce it in other videos,
but here were really
gonna focus on what it is
and what it isn't.
And as I've mentioned before,
it's a super important idea.
If you were to try to understand
life on another planet,
well you would have to
understand how evolution works.
And so evolution as we know it is based
on two underlying principles.
It's based on a principle
that in a population
of a species, that there is variation.
That there's variation in the phenotype,
in the traits that that population has.
Now the other idea that's
related to that variation
is that you have natural selection.
Natural selection, if
someone tries to explain
evolution without variation
and natural selection,
they might not be explaining evolution,
they might be explaining something else.
So this idea, so if I have
a population of circles,
some of the circles are blue circles,
some are yellow circles,
yellow circles, some are pink circles;
and there are, for sure, traits,
there are phenotypes that
might not have any bearing
on an organism's ability
to survive or reproduce.
In that case, that variation
would probably continue.
But there will be some
variations, some phenotypes;
remember, phenotypes is what's expressed
versus genotypes which
are the actual genes,
the actual alleles that an organism has.
But evolution occurs because,
depending where we are in our environment
and the time and space of our environment,
certain phenotypes might be slightly more
advantageous than others.
They might make it slightly more likely
that the organism will
survive and reproduce,
slightly less likely that it will die
or not be able to reproduce.
And so if we said these
circles were living things,
and let's say the environment
that they happen to be in
right now, it's that much more likely
for them to reproduce and survive
if they're warmer colors, if
they are an orange or a pink
verus a blue.
So then in your next generation,
the yellows and the pinks
are more likely to reproduce,
and so they might reproduce
a little bit more.
Let me put some of the pinks in there.
They're going to reproduce
a little bit more.
And the blues might have
a lower probability,
or would have, based on
this situation I described,
of reproducing.
So you'll still have some blues,
but you might have fewer blues.
And then this process could keep going on
for a very, very, very, very long time.
And at some point you might
see only pinks and yellows.
And this is only one
phenotype that we're talking
about being selected for.
There might be another
one, if we're talking about
circles it might be
roundness or whatever else.
So the key thing is is
you need that variation.
And depending on where
in time and space you are
in that environment, that
some of those variations,
some of those phenotypes,
the exhibited traits,
might make you more
successful at reproducing
and passing on that
trait to your offspring.
And I really wanna contrast
this with what some
people think of when
they think of evolution.
Some people think that
evolution is a process
of going from basic to advanced.
And the reason why we
sometimes think this is
we think of many of the
early organisms on Earth
maybe being unicellular organisms.
And now we have these complex
animals like ourselves
that we consider much more
advanced than those things,
we have trillions of cells.
But remember, unicellular
organisms continue
to be very successful even today.
And some of them aren't
all to more advanced
than things that might've existed, say,
500 million years ago, or
even a billion years ago.
And so even though these things might be
the product of evolution, all it says is
that overtime you have this variation,
and then based on which
variations, which phenotypes,
were more suited to their environment,
those are the ones that were
able to pass on their traits.
Another place where this
misconception comes from
is you've seen these
diagrams where you have
these apes where the first apes are
kind of hunched over, and
then they get upright,
or more and more upright.
And eventually you see a walking person,
and we are officially apes as well.
And we tend to think that
we are pretty advanced,
we do things like wear hats and things.
And so we say, oh yeah, it's going from
primitive to advanced,
or from basic to advanced.
But that is not the case.
Remember, even today's world, we aren't
the end of evolution.
Even in our world, there's many animals
in the animal kingdom that
are at all different levels
of complexity or if we wanna think about
intelligence or sophistication.
And there could, for
sure, be a reality where
you could imagine a human
colony goes to another planet,
and it's actually suitable
to be more hunched over.
In which case, the human
beings, the variant,
the variations of humans who
are better at hunching over
might be more successful.
Maybe they need to go into these tunnels
to find some animals to
eat or whatever else,
or to farm.
And then on that planet,
that variation might be
the one that wins out.
Now another misconception that people have
with evolution is, when they hear it,
they kinda think, hey, this might be due
to the effort of an
animal over its lifetime.
Some of the early
explanations that folks gave
before Darwin of why a
giraffe, for example,
has a long neck,
some people believe that, hey,
some of the early giraffes
might've been straining to
get leaves on tall trees,
and that straining somehow
stretched out their necks,
and somehow they might've
been able to pass that on
to their offspring.
This is not the case.
The explanation consisted
with our understanding
of evolution is that you
would've had a population
of giraffe ancestors,
and they would've had variation in their,
in their neck length.
And because of the
environment that they happen
to be in for that population,
the variance that had longer neck lengths
would have been able to have a slightly
higher probability of
reproducing and surviving.
And so overtime, those longer necks
became more predominant in the population.
And at some point, you might say,
well why don't giraffe neck lengths
become indefinitely tall?
Well that's because at some the variations
that had super long
necks, even longer than
the giraffes we had today,
that might've created
some other difficulties
making it harder for them
to survive and reproduce.
Maybe their heats weren't strong enough
and so they died of heart attacks.
Or maybe it was more
difficult to escape predators
for the variations where
the necks were too long.
And so it's really important to recognize
that evolution is a byproduct
of variation that happens in populations
and then natural selection,
due to the environment,
on those variations.
And they act on the phenotype,
they act on the exhibited
traits that are shown.
Evolution is not necessarily a process
going from basic to advanced.
And it's not due to an individual organism
somehow exercising or training
itself to the environment that it's in.
