Hi all I am back and today for gym bio
we're going to talk about natural
selection okay last time we talked about
this man on the Left Charles Darwin and
today we're going to talk a little bit
about the man on the right which is
Alfred Russel Wallace together both
these individuals came up with the
theory of evolution by means of natural
selection Darwin gets most the credit
and I'll tell you you know potentially
why that is but nonetheless Alfred
Russel Wallace deserves some credit for
at least coining the term natural
selection but for his findings when it
came to natural selection okay so the
theory of natural selection remember
where I said before that Darwin when he
was suggesting natural selection he was
saying that organisms over reproduce and
they had the capacity to do so
so not all their offspring are going to
survive only the ones that are best
suited for the current environment that
concept is often referred to as the
survival of the fittest
now fittest has a couple different
meanings in some cases it does mean you
actually are the most physically fit
so you're physically fit for that
environment you can swim the fastest run
the fastest climb the fastest jump the
highest
etc but in other cases it has nothing to
do with the actual fit of the individual
but it's rather what we call biological
Fitness biological fitness is very
different than say you know like modern
sociological fitness biological fitness
refers to an individual's capability of
passing on genetic material to the next
generation
so if you have children you have Fitness
if you have grandchildren you have more
fitness if you know your brother sister
siblings have children you have more
fitness if they have grandchildren
you're more fitness and so fitness is a
variable of how much of your genes how
many you know like how what percent of
your genes are being passed on to the
next generation and the next generation
and so you have to look at fittest in a
couple ways one it's not always
referring to the biggest and strongest
in today's society it's not the biggest
and strongest individuals that get to
reproduce typically if we're talking
about human societies in human societies
mainly it's the individuals that are
most financially stable that are going
to reproduce this is why you see that
people are waiting much later in life to
reproduce is because they're obtaining
financial stability before they
reproduce so it's not always about the
biggest and strongest now in some
species it has to be about the biggest
and strongest because only the large
individuals might reproduce or only the
fast individuals might reproduce and so
it depends on the organism for sure
survival of the fittest however this
concept has been taken out of context in
many ways to either say that darn wood
would have been in support of things
like genocide or things like
concentration camps and things like that
because the fittest individuals and ones
that have the biggest guns etc are the
ones that are going to survive but that
is not the case Charles Darwin would
have said that that is not
natural selection nature's not doing the
selection humans are doing the selection
that's artificial selection and it's not
part of the theory of natural selection
it's has its own premise and its own
regulations and Charles Darwin for
information - that's probably not common
knowledge even in the 1800s when slavery
was very very common Charles Darwin did
not have slaves and was opposed to
slaves and writes about and many times
in his different books including a
motion of man that there is no
difference between individuals with
black skin or white skin and so Charles
Darwin was against slavery and therefore
would probably not been for things like
concentration camps or genocide and
things like that it's hard to ask him
he's been dead for 200 years or so not
quite all right
so Fitness is based on evolutionary
theory it's based on organisms having
the capability of passing their genes on
to the next generation now again I have
to remind you that Charles Darwin did
not know there was such thing as
genetics genes or or anything like that
he didn't actually know the method by
which material got passed on to the next
generation but he did know that
characteristics that were favourable in
the parent could get passed on to the
offspring and make it favourable in the
offspring so Charles Darwin drafted his
ideas in 1842 is when his pretty much
the entire manuscript of the Origin of
Species by means of natural selection
was finished in 1842
but he sat on it and he did not publish
it for 16 years now there are you know a
lot of different people out there that
suggest reasons why etc I think probably
one of the main reasons that is accepted
is that Charles Darwin his wife Emma
Darwin was devout Christian and she was
extremely religious and Charles Darwin
didn't want to disappoint his wife that
had nothing really to do with it per se
but he knew that when he published this
and it had nothing to do with religion
but he knew that when he published it
that the church would not accept it and
that he would be outcasted and his
family would be probably outcasted also
with this publication so I think that is
a lot of the reason why Charles Darwin
sat on on this for 16 years on top of
that though he also sat on it for 16
years and it wasn't like it just sat on
the shelf he sat on it so he could
develop even more evidence so the the
period between 1842 and 1858 was not
just Layton like it sat on the shelf and
he worked on something else he was still
working he was still working on this
book and other books for that matter but
he was still working on it
and collecting more data and writing
more letters and things like that he
wanted this to be as sound as possible
so it's the scientific community because
of such a big idea the scientific
community would not reject it but his
hand was kind of forced in 1858 when
Alfred Russel Wallace sent Charles
Darwin an outline of the theory of
evolution by natural selection and in
fact like I said before Wallace coined
the term natural selection now
this is just a brief essay kind of
outlying lining what Darwin had been
writing about for roughly 16 years now
there are some people that will say that
Wallace gave Darwin the idea and then
Darwin ran with it there are some people
that will say that Darwin because he was
writing letters to everyone all over the
world could have let some of those
information slip and Wallace read one of
those letters or got one of those
letters and that's where how Wallace
came up with natural selection and
evolution but right now it's hard to say
we do know that Charles Darwin in 1842
had already drafted his ideas and it
wasn't until 1858 that Wallace came up
with natural selection so for the most
part we just assume that they came to it
independently and they both came up with
a max mechanism by which evolution can
occur Darwin being a gentleman in in my
opinion decided that the best thing to
do was for both individuals to read or
present their material to the Linnaean
Society in London so the the the purpose
or the point was for both of these
individuals Wallace and Darwin to
present their own ideas to the Linnaean
Society and let the Linnaean Society
make a judge on who who's got more
evidence or who came up with it first or
how they want to proceed
well Wallace couldn't make it to London
and therefore he didn't present he just
sent his manuscript he just sent his
paper to the Linnaean Society and Darwin
couldn't make it either because prior to
this presentation
Darwin daughter died
and he you know he was heartbroken and
so he sent his ideas to and they were
read to Linnae in society and as far as
we can tell based on what's been written
no one really cared it didn't cause much
of a out cried and cause much thinking
and no one really made a decision
so Charles Darwin decided to publish on
the Origin of Species by means of
natural selection in 1859 now this on
the other hand did create a controversy
so when the publication came out you got
to remember this during this time period
there's no radio no TV nothing like that
so you get all your information from
books and so anytime a new book was
published everyone read it and including
this book and it sold out many many
copies continuously sold out and people
were at it a lot but it created a huge
controversy and mainly the controversy
came around a single kind of passage
near the end of the book where Darwin
suggested that like all organisms humans
have a common ancestor and that is Apes
and didn't say monkeys
he said Apes and cartoonists and
religious entities came out and out
cried and bashed Charles Darwin in
public and in writing for the book that
he published but it wasn't long and the
scientific community accepted Darwin's
argument and then started working on
either trying to refute it by developing
experiments to test it or trying to
support it by developing experiments in
support of it
you know 200 years later there's really
been no documented scientific study
that's ever refuted Charles Darwin's
theory of natural selection
so where did a lot of this information
come from a lot of the evidence come
from it really came from what we call
Darwin's finches or the Galapagos
finches we know that on the Galapagos
Islands there are a lot of finches
they're distinct species but they are
closely related their similarities are
pretty much everything except for their
bill shape and Darwin noticed this after
he was told that they were all finches
okay that wow this is this is a great
deal of evidence here that these birds
have different shaped bills but they
create similar massive similar calls or
similar plumage it's really just the
beak and he assumed that they were
eating separate things and we'll get to
that in a second we now know because of
modern genetics we now know the exact
cause of the differences in beaks and
that is a gene that we call bmp4
which codes for protein that lays down
material on on the beak of birds and so
birds with larger beats thicker beaks
will have more bmp4 turned on or more
protein turned on and typically turned
on at an earlier time in their life and
then individuals then birds with smaller
bills and so we can manipulate this you
can turn this gene off or turn it on and
you can create different bill shapes
sizes etc and because we now know the
gene that causes these these differences
so here you can see on a single Island
you might have eight to ten different
finches and so some that are feeding on
things like
and others that might be feeding on
insects and some that might be feeding
on like vegetation but nonetheless they
all all have very different bill shapes
right but the rest of the organism is
very so they all have different build
shapes but the rest of the organism is
very similar now you might say oh but
look at this one here he's got a much
bigger head than this one yes because if
you have a giant bill you're gonna need
to have much more muscle mass to work
that bill and that's that's pretty much
a given we know that based on the
physics of you know action or bill
action in that case so an organism over
here will probably have less muscle mass
due to work a smaller bill that's that's
a given now the bill itself is what
we're interested in actually the head or
the muscle mass because the muscle mass
can change over time okay so it was this
bill size that was really interesting to
researchers even after Darwin's time so
Darwin suggested in Darwin presented it
and really Darwin's finches was it was a
guess though on Darwin's part because he
shot all these birds and he sent them
off to be identified and then he said
that they all had a common ancestor that
occurred on the mainland yeah he said
that all of them you know must be eating
different things but he never actually
checked and so when Darwin proposed this
that the birds were evolving to eat
separate foods different foods and that
they evolved from a single ancestor on
the mainland it was all still just a
hypothesis no one had tested until David
lack study
in 1938 david black came along went to
the Galapagos Islands shot a bunch of
birds and looked at what they had been
eating and what he found was that they
all pretty much eat the same kinds of
seeds so now here's this study by lack
in 38 that suggests well maybe maybe
they're not specialized on particular
foods they're eating the same feed same
kind of seed no matter what the size of
their bill is and so the question really
came about well it's Darwin's theory of
evolution by means of natural selection
at least for finches is it wrong well
Along Came to researchers Peter and
Rosemary grant and they decided that
they're going to look into lacs issue or
lacks research and they're going to do
an extensive study of the medium ground
Finch on Daphne major in the Galapagos
and definitely majors Island and when I
say extensive study we're talking
roughly 40 years of studying the medium
ground Finch and it's probably more than
40 years because they're grad students
and other other individuals that are
associated with them have picked up the
research Peter and Rosemary grant are
fairly old right now but others have
picked up their research and and have
continued these studies on Daphne major
so what do they do they went to the
island and this is crazy they went to
the island they stayed there for 3
months or so 4 months at a time they'd
live in caves there's no electricity on
the island so they had to bring their
own food to bring their own watering and
it would capture birds and they measure
their beak and they do all kinds of
things look at what they were eating
look at how many offspring
is measure the calls look at the nesting
material all kinds of things and they
just kept track of these birds year
after year after year and what they
found was indeed just like lack study
which was a very short period of time
fetches do prefer small tender seeds but
when drought periods come on when those
small tender seeds go away the finches
that have the capability they will
switch to larger harder to crack seeds
and the individuals that can't make that
switch die off so the beak depth or the
size of the bill increased with the
increase in those larger harder seeds
and if you know much maybe you don't
know much but seeds soft seeds tender
seeds typically are that way because
they house a lot of water and they occur
in wet environments but if you want hard
seeds and drought resistant seeds
they're gonna have a hard shell on the
outside and then the fleshy seed in the
inside so the more arid or drier the
environment the more hard seeds you're
going to see than saucy soft seeds will
dry up the tender seeds will lose a lot
of water and they won't be in existence
so what they found is as you get dry
years about every three three years or
so you get these dry year periods where
big depth on average is deeper than
during what years and remember we're
talking about evolution here not
individuals changing okay so evolution
is
population genetic change not an
individual change so it's not like the
birds are increasing their bills so it's
not like the birds are increasing their
bill depth or decreasing their bill but
they're providing or producing offspring
that either have deeper bills or smaller
bills and this fluctuates across years
depending on the environment
that is a bill so grants work with the
medium ground Finch was the first
example first document an example of
what we call evolution in action it was
a way which we could finally see
evolution population genetic change or
population change over a human's
lifespan and so it took a long time it
took many years of Peter and Rosemary's
life to document this but nonetheless
they did document that these populations
were changing their genetics were
changing their beak depths were changing
Hey and it was evolution in action
we now have lots and lots of examples of
evolution in action due to Peter and
Rosemary grants work right but
nonetheless it was one of the very first
research projects to do this ok again
what they found was that the average
beak depth increases after a drought and
that's because these small seeds are
gone and there's only large sheets left
so individuals that can break those
seeds can eat those seeds they can pass
on their genes to the next generation
when wet periods return the small B
beaks come back because small beaks are
easier to use to handle smaller seeds
and so they can out-compete the large
beak individuals and so the population
flux
it's overtime so from that we can then
suggest something called adaptive
radiation and Darwin's finches are a
good example of this adaptive radiation
is when you get an ancestral species or
an ancestral population moving or
migrating to a new region a different
habitat and it doesn't mean that they
have to move it could be that we have
you know some kind of tropical storm or
you could have a volcano explode you
could have some kind of natural disaster
that changes in the environment but at
any rate a lot of times the populations
migrate to a different habitat and then
when in that different when they're in
that different habitat they have the
ability to change rapidly and they adapt
to the different habitats very quickly
causing one species or maybe a couple
species to become lots of species now
what they're adapting to is what we call
ecological niches an ecological niche is
a region in which a species can and have
it and is specialized to or has adapted
to okay a niche it consists of both
abiotic or nonliving things like
temperature humidity and the days of
frost and you know these kind of things
but it also includes biotic community so
what are the plants available what are
the microbes what are other animals
doing and so you take into account both
biological and a biological and you can
get these little micro habitats which we
call niches
and species will adapt to a given niche
and so when we look at evolution
evolution occurs around niches small
inhabited places where species can adapt
to and we'll talk about niche
competition and things like that when we
talk about ecology but you know there's
some things around niches that are
important like for example no two
organisms can occupy the same niche
because of competition so you'll get
competition around that niche and and
you get organisms that move move away
they'll go to a new niche and and
develop around that toward adapt to that
new niche the other thing that this is
done a modern technology has allowed us
to do is examine the phylogenetic
linkage between Galapagos finches so
Darwin suggested that Galapagos finches
are the result of a single ancestor
making it to the opticals Islands and
then giving rise to all these other
birds but it was a hypothesis until
modern technology came around and we can
look at the genetics of these mechanisms
and we can see that indeed the base of
the tree is in an ancestral Finch that
occurs in Ecuador the rest of these
organisms that are very similar they may
belong together so the ground finches
and the cactus patches they lump
together the tree finches off together
the Warbler French is lumped together
and then the vegetarian French is off on
its own so you see that modern genetics
which you know is very useful in
evolutionary
studies has basically just reiterated
that Darwin was correct his hypothesis
was correct that these organisms indeed
went through an adaptive radiation they
came from an ancestral species on the
mainland somehow they got to the island
tropical storm probably and then they
adapted and the adaptation is coming
around ecological niches so if you have
a cactus Finch it's because that niche
was open and that bird took advantage of
it and on and on and on okay so with
that next time we're going to talk about
evidence for evolution where and talk
about what was the evidence that Charles
Darwin put forth but also what is modern
evidence so Darwin had a quite a bit of
evidence but remember Darwin didn't know
anything about genetics he didn't know
anything about proteins and that's some
of the the greatest evidence for
evolution that we have comes in the
genes the genetics and the proteins that
are coded for it alright next time we'll
talk about evidence of evolution
