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so hello there and welcome to video
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number one in which we're going to be
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looking at adaptation so if we're
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looking at adaptation the first key
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question is what is an adaptation well
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an adaptation so note the an there an
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adaptation is any heritable trait that
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helps an organism such as a plant or an
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animal survive and reproduce in its
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environment so this is a concept that
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spans many different scales of evolution
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so that was the definition for an
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adaptation that I've put on this slide
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for you here this is otherwise or I
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suppose more specifically known as an
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Adaptive trait and it's a feature that
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is common in a population because it
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provides some form of improved function
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adaptations will normally reflect
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whatever that function is and they are
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the result of natural selection they can
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take a bewildering range of forms and on
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this slide I've put three examples of
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behavior
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that allow better evasion of predators
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so these examples on this particular
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slide and I had a great many to choose
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from I can assure you are a praying
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mantis on the left hand side here
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showing a thing called diamatic Behavior
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this is threatening or startling
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Behavior to distract or Scare Predators
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so again if you distract your Predator
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less likely to be eaten that gives you a
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fitness
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advantage in the middle here you can see
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an Impala um and this Impala is um
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engaging in a behavior called stotting
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This is jumping high with stiff legs and
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an arched back and it shows we think the
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high level of Fitness of this individual
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and tells predators that the um that
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individual is likely to be able to
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outrun the Predator so it's a it's a
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tactic to make um Predators less likely
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to try and chase this
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Impala uh the third example on the far
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right hand side here is a thing called
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thanatosis also the name of a metal band
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FYI and this is a this is uh just
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another word for playing dead so if you
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play dead you can avoid predation
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because um many predators will go for
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living food similarly there are um some
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uh species which use uh thanatosis as a
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way to lure in um their prey so as a way
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of catching prey both of those are
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examples of adaptations although towards
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different ends and
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purposes there are also obvious physical
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adaptations that can help avoid
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predation um which
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include uh for example a camouflage you
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can see this in a bird on the left hand
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side here and we've got examples
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throughout the animal kingdom of this
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there's also mimicry you can see a leaf
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insect this is actually an insect it
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looks a lot like a leaf but that's an
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insect um which is camouflaged by
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looking like the plant upon which it
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lives some animals however go go the
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other way and these in this case they
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become really really obvious it's a
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thing called aposematism and this
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advertises Predator that they won't be
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nice to each an example here is this
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fairly garishly colored but super cool
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SE slug um and of course you have
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animals that we're probably familiar
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with in this country that mimic that
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signal as well so you can see an example
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here of a hoverfly that looks like a
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wasp because looking like a wasp means
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that things mistake it for a wasp and
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that gives it a um that helps protect it
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cuz wasps can sting even though this
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creature can't so all of these are
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examples of physical adaptations to help
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you avoid predation whereas in contrast
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the last slide was behavioral
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adaptations to allow you to avoid
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predation all though fantastic examples
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I think that's why I chose them right of
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um an
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adaptation some adaptations of course
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will occur at a molecular l level um so
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this is when um well I suppose
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ultimately because DNA impacts on
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morphology all adaptations occur at
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molecular level so bear that in mind
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that was not a particularly accurate or
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well formulated statement but um I was
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more thinking specifically with this
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statement that um sometimes changes in
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DNA will directly modify proteins that
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will allow a better function in specific
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environments so this isn't filtered so
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much through development um as more
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olical changes would be obvious examples
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occur in the ARA those single cell
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organisms that make one of the two
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fundamental divisions in the tree of
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life um that we met in the first
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lecture so some ARA Thrive at extremes
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of heat cold um extreme phes serenities
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pressures and radiation and as such
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there's loads of really cool evidence in
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this group for adaptations in the
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proteins that they create um as part
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part of their metabolis metabolism um
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you can read about them in this paper
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here um but I wanted to give you just a
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few examples so examples in the group
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include thermophilic proteins um this
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includes those which are um found in the
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bacteria that live in volcanic Waters
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such as Yellowstone shown on the right
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here and these proteins have the ability
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to retain their structure and function
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in extremes of temperature up to about
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105° C which is really quite impressive
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there are also examples that we know
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from this group of pilic proteins these
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are changes to proteins that allow them
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to function and thus for their organisms
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to live under extremely high hydrostatic
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pressure so at Great depths um of rock
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or of water for example there are um
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proteins that work in uh PHS as low as
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one these are acid acidophilic proteins
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um and they remain catalytically active
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down to low phes there are halophilic
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proteins these are for organisms that
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like living in um in waters for example
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with high salt con concentrations so
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salt has a significant effect on the
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solubility stability and confirmation of
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a protein so proteins in salty
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environments need to be especially
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formed and there are a load more
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examples in the paper that I put here if
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you're interested in reading about
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them but I wanted to finish talking
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about physical adaptations um these
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adaptive traits by giving you one
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example that shows you just how complex
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they can become and how cool they are
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but I first wanted to put this warning
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um that you may want to skip over the
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next slide if you don't like snakes or
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spiders and you may want to skip over it
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if you really like birds so consider
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that a fair warning and you can just
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skip forward in the video if that
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doesn't sound like your bag but this
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video is an example of how complex
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adaptations can get and as you can see
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you've just got a spider here half
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happily wandering around a
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rock so happily wandering spider all is
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good spider's now sitting still wanding
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again wanding again just a spider on a
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rock oh NOP nope turns out that was
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actually the tail of a snake so this is
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a lure on the tail of a snake that looks
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like a spider the snake waves it around
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and that attracts birds that predate
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spiders but when they uh try and pick up
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the tail that allows this snake to
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attack that bird this is a really good
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example of the complexities of
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adaptations that can build up over
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hundreds of millions of years of
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evolution isn't that fantastic Isn't
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that cool obviously not for the bird I
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mean that kind of sucks for the bird but
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you know pretty neat huh so I think
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that's really fantastic example of uh of
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the complexity of
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adaptations so those are adaptations or
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adaptive traits but adaptation is also
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the name for the process by which Things
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become
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adapted so Rob had a section uh I think
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it was section 2.3 on the scale of
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evolution and how small things scale up
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the big ones and he highlighted in that
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the random nature of genetic changes so
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at the genetic level when we're talking
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about DNA um changes are based on
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mutations and those are primarily random
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and he mentioned as part of that the
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theory of neutral Evolution or I sorry I
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should say the neutral theory of
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evolution and this kind of posits the
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random or stochastic changes of genomes
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within a population are kind of like one
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of the primary factors and that these
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random changes add variation that's not
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part of the neutral Theory that's just a
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statement that this is where variation
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comes from but the uh the neutral theory
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of evolution kind of maximizes or
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emphasizes the importance of these
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random
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changes but we can contrast this idea of
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neutral Evolution the neutral theory of
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evolution with that of adaptive
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Evolution adaptive Evolution happens
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when trait differences impact upon
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reproductive success when that is the
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case when the changes um
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that occur um within individuals um
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impact on their Fitness and thus their
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ability to reproduce we have adaptive
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Evolution we've also learned about
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Fitness and selection so that was um
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part of Rob's lectures and it's this
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that drives adaptation so there's a a
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definition of adaptation on this slide
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it's any change in the structure or
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functioning of successive Generations so
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through time of a population that makes
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that population better see to
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environments natural selection of
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heritable adaptations ultimately leads
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to the development of new species and
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increasing adaptation of a species to a
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particular environment tends to diminish
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its ability to adapt to any sudden
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changes in the environment that last bit
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I think it's a nice addition but that
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isn't actually really um part um
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strictly of the definition of adaptation
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but I left it in because I thought it
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was an interesting
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point so in other words within a
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population um changes may be stochastic
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so stochastic means random like this
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image on the left here those uh green
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and black dots are all random that's a
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example of a stochastic image and in
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this case um the changes are
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representing drift within the
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population but Fitness and based on
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Fitness um we have selection can
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make adaptation um which is a non-random
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process arise from this random process
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so my green and blacks on this image on
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the right from the Matrix are no longer
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random and that's fundamentally the
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difference between those two we've got a
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random process and this random process
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is always happening um Fitness and then
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selection uh leads to adaptation and
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that is fundamentally a
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non-random process so in what
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circumstances we seen neutral versus
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adaptive radiation sorry adaptive
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Evolution um
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depends on many different
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things um and
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indeed on a small scale um the kind of
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the balance between neutral and adaptive
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evolution is the subject of lots and
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lots of ongoing research there's loads
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of reading that you could do on this but
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I think it's fair to summarize based on
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the reading that I have done that
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neutral forms of evolution such as drift
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such as mutations that um that uh kind
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of are fundamentally random has a bigger
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imp impact on smaller scales so talking
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about DNA level changes or shorter time
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periods than on bigger scales so changes
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in morphology or over many generations
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of
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time so I hope that's a useful insight
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into what an adaptation is then into
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adaptation the process and I want to
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finish by highlighting um this on this
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slide that adaptation occurs through
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adaptive Evolution but given what we
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know we should remember that not
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everything is an adaptation I think for
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for us as evolutionary biologists if we
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consider ourselves such um it's very
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easy to assume everything is down to
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adaptation but some things can just be
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the result of chance um pass down
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because they have no effect on Fitness
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and furthermore um the heritable traits
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that we uh have and we see in in the
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world around us could be linked to
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another character that is being selected
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selected for so they may just be
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they could even be slightly dilar but
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not but the um the trait with which they
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are associated is highly um beneficial
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to an
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organism or um we could be looking at
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adaptations towards previous
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environments if the environment has
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changed we could be looking at a
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situation where adaptations have not
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managed to keep track with the
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environment so adaptation is important
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but it's not the be all and N all of
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evolution there are lots of things to
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consider basically what I'm telling you
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is evolution is a complex topic and I
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think by this point you probably know
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that right that's what makes it so
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exciting and
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cool
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cool so adaptations themselves can
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evolve and change through time in
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numerous ways and I have chosen not to
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focus in on this too much for for needs
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of keeping this less than a less than a
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3 or 4 Hour lecture for you all but a
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common and interesting process in the
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evolution of complex traits that I
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wanted to finish this video on is a
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thing called exaptation so I've put this
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word here for you so you can see how
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it's
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spelled and this is just a fancy word
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for a shift in the function of a
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trait there are loads of really cool
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examples of this um and a really neat
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one that I've chosen to to highlight in
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this slide and to finish this video for
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you today is an example that's seen in
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the evolution from non-avian dinosaurs
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into birds so the dinosaur these big
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lumbering creatures that were around in
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the um Mesozoic definitely evolved into
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Birds there's no question about that um
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so you know all is good but the latest
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research shows that a large range of
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feathers or feather-like morphologies
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morphotypes we may call them were
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present in the dinosaurs that were most
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closely related to birds that's really
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interesting this work suggests that they
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already fulfilled a really wide array of
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of biological roles prior to the
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evolution of flight within this group
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The the posited roles for the early
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feathers include Thermo regulation and
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visual display and this all occurred
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this Evolution all occurred prior to
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their co-option for flight so this is
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what you can see on this tree on the
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right hand side here that I took from
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this really interesting book that we can
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get three through as an ebook through
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our Li if you want to learn more about
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this I was super pleased to know it was
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available when I was writing this
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lecture and here you can see um the
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changing uh morphologies of feathers
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that we see within the evolution of the
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dinosaurs on the way to the birds and on
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this particular tree of the birds and
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their closest relatives you can see a
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number of um major
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changes within the feather morphology
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based on this philogyny now as Rob has
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already mentioned a philogyny is just a
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hypothesis so bear in mind some elements
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of this tree may be wrong but as tree is
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drawn what it suggests is that you start
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off with a filamentous morphology for
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feathers you then start having a primary
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branching and a PL of morphology um
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slightly further up the tree you then
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start getting secondary branching um in
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this clave called The Man Manor
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rapor and then you get a closed vein uh
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once you get really close to the birds
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and that's reflected in this the
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evolution from 1 to 11 across
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here so it's really important important
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to note that this is an exaptation
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because these things were not adapted
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for flight at first um there were
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several aerodynamic Innovations and
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flight related morphological adaptations
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that were probably independently
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experimented with within the uh Cade
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that is most closely related to the
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origins of birds but flight had nothing
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to do with the earliest evolution of
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these structures they were exapted they
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are an exaptation feathers are
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acceptation and I've put some examples
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in case you don't believe me because why
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would you right I'm a longe head hippie
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talking about evid biology on the left
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hand side here you can see some examples
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of these um of these nonavian dinosaurs
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where they have preserved feathers if
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you look along the back of this creature
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here and around the throat of this one
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here you can clearly see um the remnants
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of feathers in organisms that didn't
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have a forearm that was adapted to be a
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wing so we know they couldn't fly and
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that is a super cool example of an
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acceptation and that brings me to the
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end of video number one hope it's been
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interesting and I'll be back very
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shortly in video number two thank you
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for listening to me ramble
