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hey everyone you got here just in time
for a story it's a great one too and
it's about something that really
happened this is the story of the
peppered moth a long time ago most
peppered moths had white or gray wings
with little dots on them that's why
people called them peppered because the
dots kind of looked like pepper instead
of sleeping at night like we do these
moths are awake at night and sleep
during the day while they're sleeping
they like to hang out on trees in some
parts of the world they spent lots of
time resting on a type of tree called a
birch tree which normally has
light-colored bark with dark spots on it
something called lichen grew on the tree
bark which made it look even lighter
that way with the moss light-colored
wings they could blend in with the tree
while they were resting and it would be
harder for other animals like birds to
find and eat them when animals blend in
like that is called camouflage but even
though almost all peppered moths had
light-colored wings there were a few
with dark-colored wings with light spots
on them there weren't very many moths
with dark wings because it was really
easy for birds to spot them against the
light birch trees but then something
happened to make the light trees become
dark about 200 years ago people started
building factories places where all
sorts of things are made this was an
exciting time because lots of stuff was
being made and fast - everything from
clothes to huge metal boats but there
was a big problem the factories burned
something called coal for energy to
power their machines they burned so much
coal that the smoke made the air all
dirty which made those birds trees dirty
- it was like sprinkling little tiny
bits of coal all over them and remember
the lichen that grew on the trees the
dirt in the air made the like and died
so they weren't there to brighten up the
tree bark the dirty trees became darker
which was a big problem for peppered
moths it used to be that the light
colored ones would blend in with the
trees but now they didn't and they
really stuck out it was super easy for
birds to find them and
them and soon there weren't as many
peppered moths as there used to be but
those few moths with darker wings were
totally fine now that the trees were
darker it was easier for them to hide
suddenly more darker wing moths were
able to live long enough to have moth
babies which also had darker wings and
then those moths grew up and had more
moths babies so gradually over many
years the moss with darker wings became
way more common than the moths with
lighter wings
scientists call this process natural
selection this is when some living
things have a trait that helps them
survive like the moths darker wings
their end up being more babies that also
have that trait that's how peppered
moths changed from mostly having light
wings to mostly having dark wings but
the story doesn't end there when people
realized what the new factories were
doing to the air eventually they figured
out new and better ways of making stuff
without making the air as dirty over
time the air got cleaner again and guess
what happened the bark on the birch
trees got lighter again and the lichen
started to grow back those moths with
darker wings started to stick out again
and the moss with lighter wings have an
easier time hiding from the birds
natural selection happened all over
again and today the peppered moths with
lighter wings are much more common than
the ones with darker wings and that's
where our story ends but this was just
one example of how one type of animal
changed over time because there was
something that helps some of them
survive natural selection happens with
all types of living things all the time
it just usually takes too long for us to
notice it as it's happening one great
example of this is how a long time ago
humans became very good at running the
people who were good at running had an
easier time finding food and running
away from animals they were trying to
eat them so they had more babies and
pretty soon lots of humans could run
really fast
natural selection is also how wrasse
became so good at smelling things they
can smell animals that want to eat them
from far away so they have time to run
and hide there are examples of this type
of change everywhere we look in a way
the story of the peppered moth is
lot like the story of how all life on
Earth has come to be thanks for joining
us if you want to keep learning all
sorts of amazing things about our
incredible world and all the animals in
it hit the subscribe button and we'll
see you next time here at the fort
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