Lab 8 Handout

Muchofthe

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Unformatted text preview: r,
not
a
monophyletic
group.
There
are
two
 classes:
the
ray‐finned
fish
(Class
Actinopterygii)
and
the
lobe‐finned
fish
(Class
Actinista).
 Nearly
all
living
vertebrates
actually
belong
to
the
class
of
ray‐finned
fish.
In
this
group
of
 fish,
lungs
were
present
primitively
and
have
either
been
retained
or
modified
into
swim
 bladders
(for
buoyancy

 
 control)
in
modern
species.
They
have
unjointed
appendages
(pelvic
and
pectoral
fins),
 whereas
the
lobe‐finned
fish
and
lungfish
have
jointed
appendages.

 There
are
three
extant
species
of
lungfish
(class
Dipnoi)
which
all
live
in
stagnant
 freshwaters
in
tropical
Southern
Hemisphere.
Lungfish
have
both
lungs
and
gills.
This
group
 of
fish
is
believed
to
be
sister
taxon
of
the
terrestrial
tetrapods
and
therefore
characteristic
 of
our
distant
ancestors.

 
 1.
What
is
meant
by
the
following
statement
–
“We
are
all
fish
to
a
cladist”?
 2.
Notice
the
number
and
placement
of
the
fins
on
the
fish
body.
What
purpose
do
you
 think
the
fins
serve
in
the
aquatic
environment?
 
 Transition
to
Land:
Evolution
of
Tetrapods

 As
mentioned
earlier,
evidence
strongly
suggests
that
tetrapods
(Superclass
Tetrapoda)
 evolved
from
lungfish
ancestry.
Amphibians
were
the
first
to
move
into
terrestrial
 environments.
Over
evolutionary
time,
reptiles
and
mammals
evolved,
each
group
 exhibiting
different
adaptations
for
terrestrial
life.
As
you
go
through
the
different
stations,
 consider
the
adaptations
that
allowed
for
greater
success
at
each
evolutionary
“step.”

 
 Transition
to
Land

 As
we
also
saw
in
plant
evolution
and
in
protostome
evolution
(especially
in
the
 arthropods),
eventually
chordate
animals
began
transitioning
to
land.
Chordates
solved
 problems
associated
with
the
same
selection
pressures
that
we
saw
in
each
of
those
other
 groups:
preventing
desiccation,
body
support
in
air,
and
protection
of
gametes
(and
 developing
young).
There
are
several
traits
that
become
increasingly
modified
in
different
 groups
of
chordates,
allowing
these
animals
to
reduce
their
dependence
on
water.

 1 Skin:
The
skin
provides
a
layer
(associated
with
mucus
in
the
amphibians
and
other
 structures
in
the
amniotes)
that
provides
protection
from
desiccation.

 2 Lungs:
Lungs
provide
an
ability
to
manage
gas
exchange
internally.
They
evolved
in
a
 tetra...
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