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competition

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    So...
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    in your book in Chapter 17
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    the importance of wolves to the
    Yellowstone ecosystem
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    is the main topic.
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    And we have talked already about
    the connections between living things
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    and their environment;
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    and how there are different
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    types of interactions.
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    We also found out that wolves fulfill
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    a very important role in the community:
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    they're a keystone species.
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    Which means that they have a really
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    big influence for their population size
    on the community structure;
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    and their presence or absence can really
    change that community structure.
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    Wolves occupy
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    a very important niche in the
    Yellowstone ecosystem.
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    And a niche simply refers to,
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    what is an organisms role in
    its environment?
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    What does it do?
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    Who does it interact with, and how?
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    What are its needs?
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    So, really, the needs and the...
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    interactions of an organism
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    in an ecosystem
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    describe this concept of a niche.
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    Basically, everything about how
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    it acts in that ecosystem.
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    If there is overlap of a niche,
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    a place where needs and roles overlap,
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    then we get our last type of biological
    interaction: competition.
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    Competition is going to take place
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    when two organisms,
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    two species,
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    or two members of the same species
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    are interacting in a way that indicates
    that they are competing for a resource.
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    So, for example, here we have a
    little parakeet
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    and a starling that are fighting
    over a french fry.
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    Now, hypothetically...
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    in the case of competition,
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    one competitor will usually manage to
    exclude the other competitor for that
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    --from that resource--
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    and we refer to this as
    competitive exclusion.
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    Organisms can compete for lots of things.
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    They can compete for space,
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    like these corals.
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    Um...
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    the corals are also competing
    for sunlight.
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    There is some algae sort of growing
    here in the corner of the picture;
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    and as that algae grows over the coral
    it takes up the sunlight and the coral
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    can't get it.
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    So organisms can compete for physical
    resources like:
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    space, sunlight, nutrients,
    water, things like that.
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    Organisms can compete for food.
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    The lions and hyenas are competing
    for food here.
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    You saw some competition in the
    "Battle At Krueger" video.
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    There was some very interesting
    competitive interactions taking place.
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    Organisms can compete for mates.
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    These are two male elephant seals,
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    uh, who are competing to become
    the "beach master."
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    And that is a real term that describes the
    male elephant seal that has control of
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    all the females on the beach.
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    Elephant seals have a harem mating system
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    where one male mates with the females,
    and, of course,
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    for that evolutionary fitness, for that
    reproductive success,
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    that is a very hotly contested position.
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    You can see they are battling pretty hard.
    They are bloody and fighting, uhm...
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    What's really interesting about the
    elephant seal situation is that you do
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    have a little bit of disruptive selection.
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    There are "sneaker males," as well,
    in that system.
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    But, there is very intense competition
    for mates.
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    When organisms compete
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    they can compete in different ways.
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    Some organisms compete by taking up,
    using up a resource.
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    And we refer to this as exploitation
    competition.
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    Now, this is different from the
    exploitation that we talked about earlier
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    when we talked about how parasites
    and predators exploit other organisms.
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    In the case of exploitation competition,
    you can also think of it as "scramble."
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    This squirrel is hoarding nuts.
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    He's gathered up nuts and he is sitting
    on them and he's com--com--com...
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    um, taking up that resource and
    keeping other organisms from getting it.
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    So exploitation competition can happen
    when an organism uses up a resource
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    and doesn't allow other organisms to
    access it.
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    Interference competition,
    on the other hand,
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    is when you have organisms that are
    physically competing, or interfering,
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    with one another for a resource.
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    This is sometimes referred to as
    "contest competition."
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    So, in this case you have a, uh...
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    a little ground squirrel and some
    starlings that are competing for nuts.
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    And, instead of--instead of the ground
    squirrel hogging all the nuts
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    and just setting them aside,
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    instead what we have is an actual,
    physical altercation,
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    a fight if you will, for that resource.
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    So, exploitation competition:
    using up the resources.
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    Interference competition: physically
    competing over them and--and
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    physically keeping other organisms from
    having them.
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    So those are two different strategies
    for competition.
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    And depending on the organism and
    the resource, you might see either
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    of those take place.
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    The coral example here, we have the
    algae is engaging
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    in exploitation competition by
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    covering up the coral and keeping it
    from getting light.
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    The elephant seals are engaging in
    interference competition
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    by physically battling one another
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    for the mates.
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    Okay...
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    When competition occurs
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    one of the things that we see
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    is that one competitor,
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    if they have the same exact needs,
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    will often out compete the other
    predator.
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    So here are two protists.
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    Um , Paramecium aurelia and
    Paramecium caudatum.
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    That, if grown in separate flasks,
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    in separate conditions,
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    we see almost the exact same
    population growth curves.
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    They grow in the same way.
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    If, however, we put them in the same flask
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    Paramecium aurelia ultimately out competes
    Paramecium caudatum
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    because two organisms cannot occupy
    the same niche simultaneously
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    and continuously.
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    This is known as competitive exclusion.
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    So, the parrot and the starling competing
    for a french fry,
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    if they lived in the exact same
    environment and only ate the same
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    food, over time what we would see
    is one competitor would be a superior
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    competitor; out compete the other one.
    and we would get competitive exclusion.
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    How organisms get around this is through
    resource partitioning.
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    For example:
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    this is a group of birds, warblers,
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    a closely related species,
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    that are engaging in
    resource partitioning.
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    They use different resources
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    to allow them
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    to effectively coexist.
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    So, some of the warblers use
    different parts of the tree.
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    The myrtle warbler, for example, is found
    in the mid-section, the lower mid-section
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    of the tree.
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    While the cape may warbler is found
    at the tops of the trees.
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    They eat different things.
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    Black throated warblers that live sort of
    near the tops are eating
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    small worms and grubs.
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    Where cape may warblers are actually
    uh, eating flying insects.
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    So we have different forms of competition
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    different types of resources being
    used here.
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    Different spaces, different food items...
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    And so these birds have engaged
    in resource partitioning
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    where they take advantage of
    different resources
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    so that they can still gain a foothold
    in the ecosystem.
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    One of the things we might see
    here though is that
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    some areas of this tree, or some types of
    insect prey may not be as desire--
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    as desirable as others.
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    So that when one resource is
    removed, or one competitor is removed
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    we might see changes.
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    And so competition really can
    influence distributions in time and space.
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    Here is an example from the
    Oregon Coast.
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    We have two different species that are
    living on the coastline here,
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    we have barnacles
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    and we have mussels.
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    And these two organisms both like to
    live in the inner tidal zone.
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    This is an area between the high and low
    tides that is partially covered by water
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    during a portion of the day .
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    And mussels tend to be very quickly
    growing.
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    They grow fast, they are a little
    bit bigger, and they can actually
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    -and you see this happening here-
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    they can crush and squeeze out barnacles.
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    They are engaging in some exploitation
    competition where they are physically
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    taking up a resource and keeping other
    organisms from getting it.
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    The problem that mussels have
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    is that...
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    while they are competitively excluding
    these barnacles
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    they are limited to the area
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    that is covered by water for much
    of the day.
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    They have a much lower tolerance
    for drying out than the barnacles do.
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    And so we see this very distinct,
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    what's called a zonation line,
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    that's separating the mussels and the
    barnacles
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    because barnacles can live in those
    higher, inner tidals
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    where there is less wave splash,
    but mussels can't survive.
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    So this is a good example of resource
    partitioning.
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    The mussels have excluded the barnacles
    from the--the wet zone down here
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    but he barnacles, because they can last
    a little bit longer out of water,
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    have been able to engage in resource
    partitioning and use this space up
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    in the high inner tidal.
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    What's kind of exciting
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    is that if mussels are removed in some way
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    then barnacles will spread
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    to fill the available space.
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    So perhaps we have a sea star predator
    that comes up here,
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    removes and eats the mussels,
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    barnacles will then spread to fill
    that available space
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    and this is known as
    "competitive release."
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    Basically if a superior competitor
    is removed
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    then the other competitor may take
    advantage of that better resource.
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    They don't have to resource partition
    anymore.
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    And so this the reason that sea stars
    are, themselves, considered a keystone
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    species on the Oregon Coast
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    and throughout the Pacific Northwest
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    because they wipe out big mussel
    populations and allow other kinds of
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    organisms to live in the inner tidal.
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    So, competition has a really big
    influence here,
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    but if our sea star comes along and
    removes that superior competitor,
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    it changes the community--
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    making the sea star another example
    of a keystone species.
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    And you can see that here in this
    actual picture of the, um, these sea stars
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    that come up to a certain level of the
    inner tidal
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    they've eaten a whole bunch
    of these mussels.
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    Remember from our example of
    co-evolution,
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    sea stars are great at eating shellfish
    because they pry open that shell
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    just a little bit
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    and push their stomachs inside out and
    inside that shell and--and dissolve those
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    nutrients in there and then
    [clicks tongue]
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    pull their stomachs back into their
    bodies.
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    So, here they have created this
    line of mussels and if you look below
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    the mussel line you can see all these
    different kinds of seaweed,
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    there's some other shells downs here,
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    some barnacles.
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    And they have really changed the
    community.
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    And we have different populations
    taking part in that community.
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    We have mussels,
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    we have sea stars,
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    we have barnacles,
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    we have algae,
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    all of those populations,
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    all the members of a species that are
    living together in a place
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    are interacting...
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    in this community.
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    And what we are going to see
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    is that competition
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    can occur between members of a
    community.
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    Like a lion and a crocodile.
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    And, in this case, what are a lion and
    a crocodile gonna compete for?
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    Well, they're certainly competing for
    food.
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    But, they may not be competing for
    all of the same things.
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    So here we have niche overlap that is
    just partial .
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    In this case, the lion and the crocodile
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    they're not competing for the same
    place to live;
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    the crocodile prefers an aquatic
    environment, the lion does not.
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    They're certainly not competing for mates.
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    However...
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    lions are going to have 100% niche overlap
    with other members of the same species.
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    And so competition tends to be much
    more intense between members
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    of the same species.
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    That's the difference between
    interspecific competition:
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    competition that takes place between
    members of a different species
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    and intraspecific competition that takes
    place between members of the same species.
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    And the real difference here is
    complete niche overlap.
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    If you're in the same species
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    you're competing for food,
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    for living space,
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    for mates,
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    because you have the exact same needs.
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    So one of the things that we see with
    competition that's really interesting
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    is that intraspecific competition tends to
    be the most intense competition
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    and is going to be much more intense,
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    in many cases,
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    than interspecific competition.
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    We are going to be focusing more next
    week on other kinds of dynamics that
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    influence the shape,
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    and size of these pop...
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    We are going to be looking in much
    more detail next week at other kinds
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    of interactions that influence the shape
    and size of these populations.
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    In the meantime, don't forget to do the
    "Battle At Krueger" online exercise for
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    your 5 activity points
    and to also participate in the discussion
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    forum for this week where you can ask
    and answer questions.
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    I will also be asking and
    answering questions
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    and that is going to help us
    keep up on these community interactions.
Title:
competition
Video Language:
English
Duration:
13:39
odscaptioning edited English subtitles for competition

English subtitles

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