architecture in this ancient mutualistic relationship
relationship
so that means that each one of these
mitochondria is going to have its own
circular DNA the mitochondrial DNA which
looks a lot like bacterial DNA because
these were once Free Living bacteria but
this mitochondrial DNA is separate from
the nuclear DNA so it's really nice
because it's only about 16 000 base
pairs and then further the protein
coding genes in the mitochondria
mitochondrial DNA are highly conserved
meaning they don't mutate very often
that said there are other loci in the
mitochondrial DNA that evolve very
rapidly so this means mitochondrial DNA
is very uh diverse in terms of the scale
of the questions that you can ask you
can use mitochondrial DNA to ask
intra-specific questions so looking at
populations within a species all the way
up to intra ordinal questions and I
might point out that it was actually
mitochondrial DNA analysis uh that first
mapped out human migrations around the
globe and what's called the human
genographic project so looking at
mitochondrial DNA we will we were able
to determine uh that Africa was the
birthplace of humans the first wave
leaves Africa travels across southern
Asia there's India across Indonesia and
settles in Australia becoming the
Aboriginal Australians another wave as
we mentioned several slides ago settles
in Kazakhstan and then moves over into
Europe to encounter the Neanderthals
still another wave waves really uh
spread out across Asia eventually move
across the Bering land bridge populate
North America the Native Americans and
then down into South America so these
routes were all established looking at
increasingly evolutionary geneticists
are now employing next Generation
sequencing so this is a really powerful
method which is going to determine
millions of short and by short I mean
like 50 to 750 bases they're going to
determine millions of these sequence fragments
fragments
simultaneously these fragments are then
assembled into larger sequences by
linking them together using regions of
overlap using high-speed computational methods
methods
these reconstructed genomes are then
compared against a reference genome
reference genomes are really important
because they're going to make the
analysis of new genomic data sets much
easier and more robust
so I'm super stoked to report that there
are hundreds of these reference genomes
that are now uh openly available in Open
Access databases like the National
Institutes of Health they have Gene bank
and you can download uh and analyze this
data there's another project known as
zoonomia and you can see all of these
species for which uh reference genomes
exist it's a really wide variety from
carnivores like the arctic fox to the
III which is a lemur from Madagascar a
primate so a wonderful variety of
mammalian reference genomes that have
allowed us to build uh to build the most
uh precise
phylogenetic tree of mammalian
relationships to date all right let's
conclude with a bit of History
George Gaylord Simpson was a professor
of zoology at Columbia and a curator at
the American Museum of Natural History
he was a prominent evolutionary
biologist he contributed to the great
synthesis in biology he was a
paleontologist and a taxonomist in fact
George Gaylord Simpson he really laid
the taxonomic foundation for our modern
science of mammology with his Landmark
publication entitled the principles of
classification and a classification of
mammals which was published in 1945.
as you may recognize at right many of
the orders that George Gaylord Simpson
described uh are still in use today so
uh he recognized the order mono tremada
the marsupials the primates the
chiroptera road and slagomorphs
carnivores so on and so forth so these
orders have survived Decades of
subsequent research
so George Gaylord Simpson he didn't have
next Generation sequencers okay so he
realized at the time that some of his orders
orders
um like the order
insectivora here were and I quote
something of a scrap basket for small
animals of a generally primitive
character that are not clearly referable
to some more distinctive order so in
short he's going to lump the Hedgehogs
the shrews the ten racks the golden
moles he's going to put them all in this
catch-all order that he calls the
insectivora using modern molecular
methods phylogenetic systematists now
split the insectivora into the orders
macro Scalia day which includes the elephant
elephant
trues the order afro psoricidae which
includes the tenrex Shrew 10 Rex and
Otter shrews we'll be covering both of
those orders in our next lecture so
that's why we're covering classification
now as well as the EULA pot phyla which
is the selenodons true shrews moles
hedgehogs we'll cover them in week five
and then the order scandencia which are
the tree shrews and we'll cover
scandincia in week four this represents
the best phylogenetic tree of mammalian
orders that we have to date so this uh
has been presented before it's in
chapter three the phylogeny and
diversification of mammals this is figure
figure
3.1 but this is going to map out those
phylogenetic relationships and remember
Sister taxa they are most closely
related to each other so the macro
Scalia day and the afro-cericidae they
are what we would consider sister taxa
because they share a most recent common
ancestor here some 75 million years ago
so these are the orders that we're going
to be covering in ABS
470. we've already covered a good chunk
of them here's our monotreams and our
marsupials so you remember that new
world opossums
um the um
uh dazzy urads which includes the
Tasmanian devil and the thylacine so
these have already been covered and then
in our next lecture we're going to cover
these three uh orders within this super
order the
afrotheria so we're going to be coming
back to this figure again and again
because in uh mammology in all the
biological sciences it only makes sense
to see things through an evolutionary lens
lens
with that uh short lecture I told you it
was short
um just a handful of references cited in
this lecture and uh just one more
lecture to go in this module before your
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