Lab 8 Handout

Inadditiontoneural

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: erm
“Craniata”
is
used
to
designate
a
larger
clade
which
includes
the
vertebrates,
along
 with
hagfish
and
lampreys.
The
craniates
are
distinguished
by
having
a
cranium:
a
skull
 made
of
cartilage
or
bone
that
protects
the
brain.
Vertebrates
can
then
be
classified
as
 animals
with
a
backbone
composed
of
vertebrae.

 
 Craniates
also
share
the
character
of
neural
crest
tissue,
the
chunk
of
neural
ectoderm
that
 rolls
up
to
form
the
dorsal
nerve
tube.
Craniate
embryos
form
this
neural
crest
tissue,
and
 no
other
animal
group
does.
The
brain
tissue
develops
embryologically
to
form
just
about
 the
entire
vertebrate
head,
including
most
of
the
brain,
the
central
nervous
system,
the
 brain
case,
most
of
the
sense
organs,
cartilaginous
gill
arches
(which
becomes
parts
of
the
 circulatory
system,
middle
ear
bones,
and
jaws),
and
teeth.
The
evolution
of
neural
crest
 tissue
and
its
derivatives
has
been
called
the
evolution
of
a
“new
head,”
because
it
adds
 many
new
features
to
the
anterior
part
of
a
fundamentally
primitive
chordate
body.

 The
increased
cephalization
probably
resulted
from
an
evolutionary
switch
from
filter‐ feeding
to
active
predation.
Most
of
the
“new
head”
structures
were
adaptive
because
they
 enhanced
prey
detection
or
active,
energy
expensive
prey
capture.
In
addition
to
neural
 crest
tissue,
there
are
several
characteristics
that
are
shared
by
many,
but
not
all,
 vertebrates.

 
 1.
Vertebral
column:
This
gives
the
phylum
its
name
and
is
commonly
known
as
the
 “backbone.”
The
vertebral
column
is
the
dorsal
part
of
the
endoskeleton
that
functionally
 replaces
the
notochord
and
surrounds
the
dorsal
hollow
nerve
tube.
The
lampreys
and
 retain
the
notochord
but
have
no
vertebrae.

 2.
Two
pairs
of
appendages:
These
appendages
are
the
pectoral
and
pelvic
fins
which
are
 attached
to
the
vertebral
column.
They
evolved
from
flaps
of
flesh
associated
with
lateral
 spines
in
early
fishes
and
further
evolved
to
the
four
limbs
in
tetrapods.
Lamprey
and
 hagfish
lack
these
appendages.

 3.
Bone:
This
contains
a
calcium
phosphate
salt
found
in
no
other
group
of
animals.
Bone
 makes
up
the
endoskeleton
of
most,
but
not
all,
vertebrates.

 4.
Neural
Crest
Tissue:
This
is
the
brain
case
which
provides
support
for
sensory
organs
and
 the
large
brain.
Lampreys
and
hagfish
also
lack
this
structure...
View Full Document

Ask a homework question - tutors are online