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- When I say animal,

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what is the first one that comes to mind?

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I can bet it was something
cute and furry, right?

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However, furry mammals only
account for about 5,400

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of the species found in kingdom animalia,

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which is pretty small given that we have

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around a million plus species
of animals on our planet,

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and there are a huge number left

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that we haven't discovered or described.

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In order to be in the
kingdom animalia club,

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you need a few basic
requirements that must be met.

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You have to be multicellular eukaryotic,

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in that you have to lack a cell wall.

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You need to be heterotrophic,

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meaning that you ingest other organisms,

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and you are going to
bring them into your body

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and then have an ability
to harness their energy

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and nutrition by breaking
them down in your body

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in some way, shape, or form,

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through an internal digestion process.

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Adult animals are going to be diploid,

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meaning they have a
full set of chromosomes

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in a number that is
appropriate for their species.

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And in order to be in kingdom animalia,

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you must produce gametes,
otherwise known as sex cells,

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from reproductive organs
referred to as gonads

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in order to create the next generation,

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which is going to arise
from the fusion of gametes.

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Now, we generally call
these sperm and egg.

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Many animals have distinctive attributes

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on their left and right sides.

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And most times you can tell the difference

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between the front end,
which we call the anterior,

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the rear end, which we call the posterior,

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and the back, or dorsal surface,

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and then finally the belly,

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which is going to be what
we call the ventral surface.

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This is helpful when identifying

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an individual animal or
discussing a species.

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And last but not least,
you need to be able to move

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from place to place at
some stage in your life,

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an act we call motility.

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Since most, although not all,
adult animals are motile,

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then this is going to increase the amount

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of feeding mechanisms that
we see in this kingdom,

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and it's gonna be a much
larger range of diversity

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in terms of structure and
function in kingdom animalia

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than you see in kingdom plantae.

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In order to deal with all that diversity,

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scientists, like we do, have created

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a system of classification
to group together those

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that are similar and to
have a really quick way

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of discussing large groups of species.

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We need to whittle our way
down to the species level

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by sorting out organisms based on traits.

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The first big sorting moment
is to separate those animals

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that have a backbone, or a
vertebrae, and those that do not.

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If we have a really, really
old book in front of us,

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then we might see some references

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to animals being higher or lower,

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but that is really outdated.

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Now, we use terms like
simple versus complex

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to describe organisms based on
their biological attributes,

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since the terms higher
and lower really imply

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that one species has more of
a right to live than another.

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When actually, there is not
one that is better than others.

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There's just going to be differences.

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In terms of survival, complex organisms

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are not guaranteed a better chance.

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In fact, when the environment
gets really tough,

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it's usually the big, complex organisms

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that go extinct first,
not the simple ones,

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because the complex organisms usually need

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a lot more of everything
in order to survive.

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When we think about animal survival,

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we can figure out their
biggest problems in life

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by thinking about our
own survival problems.

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We need air that contains oxygen.

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We need to find and
process food and water.

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We need to live at the right temperature

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in our little home habitat

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that's not too hot and not too cold.

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And we need to get rid of waste products.

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And we have to have
enough of our individuals

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to reproduce to pass on
genes to the next generation.

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And this is going to be the same problems

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that you see in all animal species,

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and they've had to evolve
physiological, anatomical,

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and behavioral methods
of dealing with them.

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These different attributes
is what helps us

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sort them into their different phyla.

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Each phylum contains species

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that share a common evolutionary history

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and some features that
have evolved in response

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to those various environmental challenges.

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Phyla are a classification grouping

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that is going to be more inclusive,

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meaning it contains more diversity,

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than the species level,
but far less inclusive

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than the domain or kingdom level.

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So it goes domain, kingdom, phyla,

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class, genus, species, in terms of size.

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There are other classification
levels mixed in there,

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but those are going to be the major ones

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that we're going to interact
with in this series.

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So the major phyla we are
going to briefly touch upon

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in kingdom animalia, in the
order from simple to complex,

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are going to be Phylum
Porifera, Phylum Cnidaria,

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Phylum Platyhelminthes, Phylum
Nematoda, Phylum Annelida,

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Phylum Arthropoda, Phylum Mollusca,

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and Phylum Echinodermata,
and finally, Phylum Chordata.

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Now that we've had our quick
lesson in ancient languages,

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jump into the next video where we examine

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a little more of each of these phylums.

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Until next time, thank you for joining me

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on exploring environmental biology.