hi everyone! Welcome. Today we'll be
talking about natural selection so
whenever I'm learning something i always
like to know the "what"
and so afterwards it's easier to answer
the "why" and the "how"
what exactly is natural selection?
natural selection is one of the
processes that causes evolution
it does so by increasing certain traits
that contribute to the reproductive
success in a particular environment
so for example if having large colorful
feathers is advantageous in a particular
environment then we would expect to see
an increase in this trait overtime so
this might sound a little overwhelming
so i have a broken natural selection
into different parts
so the first part is a variation
ok so when I talk about variation
I would like to think about it in
this way. Basically if all individuals in
a population are exactly the same in
every way
no one individual has an advantage over
another
so let's use this example right here. We
have a crop of corns and let's say they
are all genetically identical. Something
breaks out in the crop, like a disease or pest
if all corns are susceptible to this
disease or pest
then all of them died and none of them
survived
so therefore variation is very important
in a population to ensure the survival
of at least some of the individuals in
the population
now the second part is heritable traits
right there
if we want to see changes in the
population
we need traits that can be passed from
one generation to the next
now we can we have right here the Weasley family from Harry Potter and they all
have red hair
if red hair was not a heritable trait
then the children wouldn't get that from
their parents and lastly we have
differential reproductive success
now it might sound a little complicated
but it totally isn't, it just means that
some individuals have higher chances of
reproducing than others
so for instance we have right here
antlers on dears and the size of anglers
is different for every individual the
larger the antlers
the more successful they are at fighting
and finding a potential mate
so all individuals in that population
have different reproductive success and
based on the size of the antlers
now I have a very cool example for you
to better understand natural selection
ok so this example is an antibiotic
resistant
now you've probably heard about this in
the news or even in your daily life
so let's say the first step we have
right here we have a population of
bacteria and some of them are resistant
to antibiotic
ok and some are not resistance
so basically there's variation in the
population
so there is non resistant bacteria and
there is resistant bacteria and an
important thing to note is that in step
1
there is no antibiotics there's only
resistant individuals
ok so in step two we have the
antibiotics administered and it kills
all but the resistant individuals
resistant individuals
I survived reproduce and pass on their
traits to the next generation and over
time
there are more and more individuals with
the resistant gene now and like i said
in step 1
there was no antibiotics there was only
resistant individuals
likewise natural selection does not
create new traits new alleles it simply
act on it on the pre-existing our
variation in the population
ok so i hope that makes sense
and so now we'll talk about this
now when i was a student I still am i
came across a lot of misconceptions
regarding evolution and natural
selection as a whole
so I'm going to ask you these questions
right here and answer them in your head
it's natural selection creating more
complex organisms from simple to complex
is natural selection only about survival
of the fittest would we expect the
largest the strongest and the fastest
individuals to succeed and reproduction
now when I asked these questions I would
like to think about the environment
what do we know about the environment
that it changes the environment always
changes right it does not stay the same
and basically it can select for or
select against a trait
depending on the situation so what may
be advantages in one instance might not
be so advantages in another so to hit
this point across
I'm giving you a real life example we
have right here the peppered moths in
England in the 19th century
so there are two kinds of of peppered
moths light gray and the dark great
variant the light grade version used to
be more common but between 1848 and
eighteen nineties the dark colored mods
were becoming more common now
coincidently this happened at the same
time of industrial revolution in the
industrial revolution there are burning
large amounts of coal which produce
large amounts of soot soot is just this
dark colored substance and it covered
basically everything even tree trunks
the tree trunks covered in soot became
darker and therefore they were able to
hide the dark colored mods better than
the light colored months
the light colored months were basically
I eaten by predators more
and the dark colored wants survived and
reproduce and pass on their traits to
the next generation
so over time you saw an increase in the
dark colored ah you know month and saw
decreased in the light colored months
not surprisingly in non-industrialized
areas
you saw a light colored wats were still
a more common than dark colored months
and this was because there was no suit
and up and light-colored months were
more advantages in that environment
so you can see that in one environment
it was more advantages to be a
dark-colored months and and another it
was more advantages to be the light
colored mods so everything depends on
the environment and the and the
pre-existing conditions
so I hope that makes sense and i hope
that i had cleared some of your
confusions misconceptions and so I hope
to make more videos like this and thank
you so much for watching and have a
great day
