Evolution - Heredity & Evolution - Science Video Lecture - Class 10

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Stated Clearly Presents
What is Evolution?
In biology,
the Theory of Evolution doesn't tell us
exactly how life began on earth -
but it helps us understand how life -
once it came into existence -
diversified into the many incredible
forms we see now and in the fossil
record.
It also helps us make sense of the way
in which modern creatures
continue to adapt and change today.
In biology,
evolution can be defined as any changed
in the heritable traits
(those are physical traits like fur color in mice
spots on the wings of butterflies
or instinctive behaviors like the way
in which dogs greet their friends with a sniff)
within a population
across generations.
This definition can be a bit confusing
so let's see how it works
all healthy living things from
single celled amoebas to
flowers to dolphins
are capable
of reproduction.
We have children,
we make copies of ourselves.
We do this by duplicating DNA
and passing that DNA on to future
generations.
DNA is a chain like chemical stored
inside each one of your cells
which tells them how to grow and
function.
Your DNA contains coded information
on how to build you.
Tthe information in your DNA is different
than that of say a daffodils DNA,
which is why you look and function
differently than a daffodil.
The information in your DNA is
slightly different
than that of Elvis Presley,
which is one of many reasons you don't
look a and act quite like he did.
Single celled amoebas and
other simple creatures
reproduce by copying their DNA - inside
their guts -
moving both copies to either side of
their body,
splitting in two right down the middle
and then growing back to full size.
If all goes well the two new amoebas will be exact copies of each other.
But in nature things aren't always
perfect.
When DNA is being copied,
errors can occur
which modify the DNA code.
This is what we call a DNA mutation.
These mutations,
which happened completely on accident
and
randomly to any part of a DNA
strand,
can produce variation in the body shape
and function of the creature who inherits
the modified DNA.
In this case,
our new little friend has an arm that
stretches extra long.
If he survives long enough to grow and
reproduce
that extra stretchy arm (which
is now coded for his DNA)
will be passed on to his children.
Evolution:
any change in the heritable traits
within a population
across generations
has officially occurred.
reproduction for dolphins and badgers
and people
is a little more complicated.
we have to find ourselves a partner.
When to a badgers get together and
you know...fall in love
a sperm cell from the father which contains
a copy of half of his DNA
- only half -
combines with the egg cell of the mother
which contains half a copy of her DNA
the result is a brand new cell with a
complete set of DNA instructions
all the information needed to divide and
grow up
into a brand new badger
the new child matures to be similar
to her parents
but also unique
because she developed some traits from her
mother's DNA
and some from her father
her new combination of traits can be
passed on to her children and again
Evolution: any change in the heritable
traits
within a population
across generations
has officially occurred
Besides the unique recombination of her
parents traits
she might also have developed some
completely new traits of her own due to
DNA mutations
maybe extra hairy ears for example
if she survives long enough to have kids
her DNA will combine with the DNA of her partner
and she'll pass on those extra hairy ears to
at least some of her children
again
Evolution has officially occurred
so there you have it
evolution is really pretty simple
scientists and normal folks everywhere
witness evolution happening all the time
small changes like the ones we've seen
here can add up over multiple
generations to create dramatic
changes
if you were to go back in time just a
few thousand years
you'd find that all dogs for example
originally evolved from an ancestral
group of gray wolves
the evolution of those wolves from
generation to generation
was guided
by humans
people were selecting wolves with the
traits they liked
letting them breed
and then only keeping the puppies with
the most desirable traits
as time went on
different breeders preferred dogs with
different features
some selected from large size
some for small size, some for brains
others for brawn
today wolves have branched out into hundreds of breeds
very few of which look and behave much like
their ancestors
a massive amount of observable evidence
from many different fields such as
Genetics
chemistry, paleontology, and mathematics
overwhelmingly suggest just like all
dogs share a common ancestor
all living things
me,
you, puffer fish
banana trees, if you go back far enough
also share a common ancestor
we are literally related
we don't know what the first life form
was or exactly how it came to be
but the simple process of reproduction
with variation over billions of years
looks to be responsible for all the
diversity of life we see today
now you might be saying wait a minute,
hold on here -
isn't evolution
random?
To do something functional like turn a
wolf into an adorable
mini poodle
random evolution had to be carefully
guided
by an intelligent dog breeder
researchers claim that all mammals
evolved from an ancient shrew-like
creature
but the difference between a shrew
and an elephant
is far greater than that of a wolf
and a poodle
who guided that process?
who
was the breeder
in the mid eighteen hundreds two men
Charles Darwin
and Alfred Russel Wallace independently
discovered
that a breeder is not necessarily needed
there is another force capable of guiding
random evolution
to produce order and complex function
they called it natural selection
(Which happens to be the entire topic of
our next video)
but before you move on
let's recap what we've learned so far:
Biological evolution
is any change in the heritable traits
within a population
across generations.
All healthy living things can make
copies of themselves -
but they do so imperfectly.
Small variations can build up over
generations to create dramatic
differences
in the body form and function
of living creatures.
Evidence overwhelmingly suggests that
all life on earth is related.
So remember -
next time you invite family and friends
over for a holiday feast
you're actually just inviting family!
That includes the turkey,
and the pumpkin
in the pumpkin pie.
I'm Jon Perry and that's evolution
Stated Clearly
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until next time, Stay Curious