In this lecture we'll be answering the
question "What is evolution" or "What is
evolutionary biology?"
We'll start off first with a brief
overview about different areas of
interest to evolutionary biologists; the
general goal of this is for students to
just become familiar with broad areas of
evolutionary research and what types of
questions evolutionary biologists
investigate more specifically after this
and the next lecture you should be able
to differentiate different types of
evolutionary research and what they are
focusing on and what their purpose is
for example phylogenetics paleontology
or the evolution of different types of
traits or phenotypes so we're gonna
start off with a question from mr.
Darwin here I'm always curious what
things do students associate with the
word evolution when you hear the word
evolution either in the media or in
conversation or posed by a professor in
biology class what do you associate with
evolution and go ahead and take a minute
to think and I would encourage you to
actually write down some of your
thoughts here go ahead and pause the
video if you want and just brainstorm
when you hear or when you hear me say
evolution what do you associate with
that so evolutionary biologists are
interested in a large number of things
and evolutionary biologists work closely
with a lot of the similar disciplines
and often people might call themselves
an evolutionary biologist but they also
might call themselves something else
like a paleontologist or evolutionary
ecologist or an ecologist an
anthropologist so here I'm going to go
over some of the major themes and quest
types of questions that evolutionary
biologists are investigated
one big question is of course where did
life begin how did life even get started
for example did life originate as RNA or
DNA
most people think now it's RNA and also
where on earth or in what environment or
what ecological conditions did life
originate many people have proposed that
in conditions such as deep-sea vents or
hydrothermal vents perhaps that is where
life originated well this is a really
interesting question it's not always
very easy to pursue this experimentally
and most people who work as evolutionary
biologists don't work in this field
though a similar fields a related field
to evolutionary biology astrobiology
considers the question from a different
angle which is how my life have emerged
on other planets once we have the origin
of life we often consider how life
evolved and changed over time or the
evolutionary history of life so once we
had conditions to create our first
organisms or our first cells whether
they were RNA based or DNA based once we
had single-celled life how do we how did
organisms change over time how did they
develop the ability to photosynthesize
how did you carry oats with
membrane-bound organelles develop how
did multicellular life develop and that
how did all of the diversity all the
many types of animals multicellular
complex animals we have a multicellular
complex plants and other organisms
evolved over time so what is the broad
evolutionary history of life again this
is a field that's not necessarily that
open to experimentation and most people
who call themselves evolutionary battle
just don't work necessarily on this
question though it's always an
interesting question to consider and
there's always new research coming out
especially as we gain more understanding
genomes
the ability to understand how different
genes functioned and where they may have
originated deep in the history of life
another big consideration of
evolutionary biologists and this is a
field that is quite large and many
people are engaged in is what is the
role of thaws the fossil record in
understanding the history of life and
and understanding the evolution of life
so this includes paleontologists and to
some extent archaeologists once we get
and anthropologists once we get to the
history of humans so once we have
multicellular life once we start having
animals we can start to develop fossils
and we can use that to piece together
our understanding of how life changed
over time and what are the origins of
the organisms that are alive now a major
tool used by many evolutionary
biologists also by many ecologists is
phylogenetics this is the tools and
techniques and area of study to
understand the relationships of
organisms often focusing on organisms
that are alive today such as primates
but also often trying to understand the
relationship to extinct organisms or
theoretical common ancestors that
existed in the past a key question that
is considered often when we use
phylogenetics is - what
how did groups of organisms evolve or
what how does the process of clay to
genesis occur so a clade is a distinct
group of organisms that are evolutionary
related for example we can consider how
in the history of the evolution of
primates did the clade of the group of
great apes evolve which includes Gibbons
and orangutans gorillas chimps and
ourselves we're a coherent evolutionary
group that shares numerous interesting
traits how did we split off as a group
and then diversify from other primates
similar to the topic at played as
Genesis and one which is many biologists
are engaged on is the study of
speciation so how did individual
populations change over time or split
off into different groups for example
there are new there are several species
that are considered grape Apes and how
did for example very similar organisms
that are still considered to be separate
species such as chimpanzees and bonobos
how did they split off and change so
that they no longer interbreed another
consideration that many evolutionary
biologists work on is what is the origin
of novel traits or novelties phenotypes
that are new to a group of organisms
often we consider them as something that
is typical or indicative an organism
like the orange fur of an orangutan or
especially interesting are traits that
allow organisms to survive better or do
better than other organisms similar to
the emergence of novel traits or things
by novel traits I mean things that
didn't formerly exist within an
evolutionary exists lineage or didn't
exist at all talk more about that in the
next lecture similar related to this is
the topic of trait evolution so once a
trait evolves how does it change over
time within a species or between species
for example all vertebrates have complex
nervous systems and primates have very
sophisticated nervous systems and
abilities to communicate to take in
visual and auditory information
communicate vocally but there is a large
difference between the the cognitive
abilities of monkeys great apes and
especially humans so this phylogeny here
underneath some of the names
it says ec this stands for
encephalization quotient it's basically
the relative size of the
taking into account the size of the
organisms so monkeys gorillas and chimps
all have ec values that are 2.2 or less
so all of these organisms have a similar
ratio between the size of their brain
and the rest of their body humans
however have a very large and
cephalization climatic ocean an EC of
7.4 this is a difficult
relative to our bodies and this
correlates with our capacity for
language for communication for being
able to communicate locally build
sophisticated tools etc so all of these
organisms from monkeys on up to humans
have have brains have sophisticated
nervous systems but in humans this trait
has evolved and changed to become very
sophisticated so evolutionary biologists
often study how a single trait like a
brain or a nervous system can change
between organisms or change over time
another consideration that many
evolutionary biologists and many
evolutionary ecologists are interested
in is how treats vary within a species
so most of the great apes are dark
colored so gorillas chimpanzees bonobos
most Gibbons have black fur humans don't
have fur we have hair on our heads in
other parts of our bodies but it's very
much less sparse and we also have skin
color that varies considerably from
light to dark this is a trait that has
several adaptive reasons for it related
to vitamin D and cancer prevention so
what causes trait to evolve why does it
vary so much within humans how did it
change over time from our ancestors
unifying most of these considerations
and something many evolutionary
biologists study is what is the genetic
basis for different traits how do
different species vary genetically or
genomically how do
what is the genetic basis what are the
genes and underline new traits what
genes have changed as traits evolved or
what genes are different what alleles
are different that drive variation for
example it's often quoted that around 15
or 20 different genes are involved in
human skin color each one of them has
different alleles and the combination of
all of those alleles and on those all
those different genes results in the
broad variation of skin color so many
evolutionary biologists want to know
genetically what leads to variation in
traits of the evolution of traits
