Page 1

AP
Biology
Notes
 Unit
9:
Structure
and
Function
of
Animals
 
 Introduction
to
Vertebrates
 
 A.


Chordate
Characteristics
 





All
chordates
are
bilaterally
symmetrical
deuterosomes
that
have
four
anatomical
 





structures
that
appear
at
some
point
during
the
animal’s
lifetime.
Often
these
 





structures
only
appear
during
the
embryo
stage.
 
 





1.


Notochord
 










A
longitudinal,
flexible
rod
located
between
the
gut
and
the
nerve
chord.
It
is
 










composed
of
large,
fluid‐filled
cells
encased
in
a
stiff
fibrous
tissue.
The
notochord
 










extends
through
most
of
the
length
of
the
animal
as
a
simple
skeleton.
Chordates
are
 










named
after
this
structure.
In
simple
chordates,
the
notochord
supports
the
adult.
 










In
more
complex
vertebrates,
a
jointed
skeleton
develops
and
the
notochord
exists
 










as
the
gelatinous
material
of
the
disks
between
vertebrae.
 
 





2.


Dorsal,
Hollow
Nerve
Chord
 











This
develops
from
the
neural
plate
ectoderm
that
rolls
into
a
tube
dorsal
to
the
 











notochord.
The
dorsal,
hollow
nerve
chord
forms
the
central
nervous
system.
 
 





3.


Pharyngeal
Slits
 











The
lumen
of
the
digestive
tube
of
almost
all
chordates
opens
to
the
outside
 











through
slits
located
on
the
side
of
the
pharynx.
They
have
been
modified
for
gas
 











exchange,
or
other
functions
in
chordates.
 
 





4.


Muscular
Postanal
Tail
 











Most
chordates
have
a
tail
extending
beyond
the
anus.
The
tail
contains
skeletal
and
 











muscle
elements.
 
 B.


Phylum
Chaetognatha
(Arrow
Worms)
 





There
are
60
species
of
this
arrow
shaped
hermaphrodite.
Although
the
arrow
worm
is
 





only
1‐10
cm
in
length,
it
is
the
most
abundant
predator
of
marine
plankton.
 
 C.


Phylum
Hemichordata
(Acorn
Worms)
 





Although
the
anterior
end
of
the
acorn
worm
has
a
probiscus,
the
acorn
worm
has
 





pharyngeal
gill
slits.
Water
goes
through
the
mouth,
through
the
gills
and
oxygen
is
 





removed.
The
larval
forms
of
acorn
worms
resemble
larval
form
of
echinoderms.
 
 D.


Phylum
Chordata
(Divided
into
Three
Subphyla)
 





Urochordata,
Cephalochordata,
and
Vertebrata
 
 





1.


Subphylum
Urochordata
 










The
most
common
examples
of
urochordates
are
tunicates
and
sea
squirts.
They
are
 










chordates
because
their
tadpole‐like
larvae
have
a
notochord,
a
hollow
dorsal
nerve
 










chord,
gill
slits
and
a
postanal
tail.
However,
they
only
exist
in
this
form
for
a
day
or
 










two.
The
larvae
attach
to
a
substrate
and
become
adults.
They
are
filter
feeders,
 










have
an
open
circulatory
system,
and
secrete
cellulose,
a
rarity
in
animals.
 
 





2.


Subphylum
Cephalochordata
(Lancelets)
 











These
organisms
resemble
fish.
They
have
a
prominent
notochord,
obvious
 











pharyngeal
gill
slits,
and
a
hollow
dorsal
nerve
chord.
Cephalochordates
move
like



fish
and
are
filter
feeders.
 
 





3.


Subphylum
Vertebrata
 











All
vertebrates
have
several
traits
in
common:
 
 











a.


Backbone
or
vertebral
column
 











b.


Cranial
brain
development
 











c.


Closed
circulatory
system
with
a
dorsal
aorta
and
ventral
heart
 











d.


Gaseous
exchange
in
gills
and
lungs
 











e.


Two
pair
of
limbs
 











f.


One
pair
of
image
forming
eyes
 











g.


Excretory
system
consolidated
in
a
pair
of
kidneys
 











h.


Separate
genders
 
 











Ectothermic
(poikilothermic):
These
organisms
cannot
regulate
their
own
internal
 











temperature.
The
temperature
of
the
organism
is
determined
by
the
environment.
 











They
are
called
‘cold
blooded’.
This
group
includes
all
invertebrate
phyla
and
 











vertebrate
groups
except
birds
and
mammals.
 

 












Endothermic
(homeothermic):
These
organisms
maintain
a
constant
internal
 












temperature,
regardless
of
the
environment.
They
are
‘warm
blooded’.
This
group
 












includes
birds
and
mammals.
 
 E.


Classes
of
Vertebrates
 





There
are
eight
classes
of
living
vertebrates
and
one
class
of
extinct
vertebrate.
 
 





1)


Class
Agnatha
(Jawless
fish;
lampreys
and
hagfish)
 





2)


Class
Placodermi
(first
fish
with
jaws;
extinct)
 





3)


Class
Chondrichthyes
(cartilagineous
fish;
sharks,
skates,
and
rays)
 





4)


Class
Osteichthyes
(bony
fish)
 





5)


Class
Amphibia
(frogs,
toads,
and
salamanders)
 





6)


Class
Reptilia
(turtles,
snakes,
lizards
and
crocodilians)
 





7)


Class
Aves
(birds)
 





8)


Class
Mammalia
(mammals)
 
 





1.


Class
Agnatha
(Jawless
Fish)
 










There
are
about
60
modern
species
of
jawless
fish.
 










There
are
fossils
of
some
jawless
fish
that
are
as
old
as
one
half
billion
years
old.
 










Some
agnathans
suck
up
nutrients
from
sediments.
Lampreys
and
hagfish
are
modern
 










day
agnathans.
They
have
long
cylindrical
bodies,
simple
fins
that
are
adapted
for
 










wriggling
along
the
bottom,
and
feed
using
a
rounded
sucker
mouth
with
horny
spikes
 










and
a
raspy
tongue.
Hagfish
lack
sucking
mouths
and
bore
into
bodies
of
dead
or
 










dying
animals.
Lampreys
are
parasitic
and
attach
to
a
body,
bore
into
the
skin
and
 










suck
out
blood
or
body
fluids.
The
mouth
is
used
for
feeding
and
for
the
intake
of
 










water
that
passes
over
the
gills.
 

 





2.


Class
Placodermi
(Extinct
Jawed
Fish)
 











Placoderms
became
extinct
150
million
years
ago.
This
armored
group
had
hinged
 











jaws,
could
swim
better
than
agnathans,
and
were
predators.
The
hinged
jaw
is
an
 











important
evolutionary
structure.
From
placodermi,
chondrichthyes
and
osteichthyes
 











arose.
 
 





3.


Class
Chondrichthyes
(Sharks,
Skates,
and
Rays)



There
are
about
750
species
of
chondrichthyes.
They
have
a
stiff
caudal
tail
for
 











propulsion,
dorsal
fin
for
stabilizer,
pectoral
and
hind
fins
to
provide
lift
in
the
 











water.
Chondrichthyes
are
cartilaginous
fish;
the
skeleton
is
made
of
cartilage.
 











Instead
of
armor,
they
have
tough
skin.
The
skin
and
teeth
of
sharks
consist
of
 











placoid
scales
which
are
made
continuously.
 
 





4.


Class
Osteichthyes
(Bony
Fish)
 











There
are
36,000
species
of
osteichthyes.
The
fins
are
finer
than
previous
classes
 











of
fish,
and
provide
greater
maneuverability.
They
have
an
air
bladder
that
allows
 











the
fish
to
remain
stationary
at
any
depth.
The
body
is
covered
with
flattened
 











scales.
The
skin
contains
numerous
mucous
glands
which
makes
the
fish
slimy.
 











Osteichthyes
have
taste
buds,
but
their
tongue
is
immovable.
There
are
balance
 











centers
in
their
inner
ear.
They
have
a
closed
circulatory
system
with
a
two
 











chambered
heart.
Osteichthyes
are
able
to
suck
water
over
their
gills
with
their
 











mouth
parts,
and
each
gill
has
a
food
raker
which
keeps
the
food
out
of
the
gills.
 











Most
osteichthyes
are
oviparous.
 
 





5.


Class
Amphibia
 











There
are
4,000
species
of
modern
amphibians,
represented
by
three
orders:
 
 











a.


Urodela
 

















Salamanders
 
 











b.


Anura
 

















Frogs
and
toads
 
 











c.


Apodia
 

















Worm‐like
caecilians
 
 











Nearly
all
amphibians
reproduce
and
develop
in
aquatic
habitats.
They
have
moist
 










and
highly
vascularized
skin.
The
skin
is
the
most
important
organ
of
the
respiratory
 










exchange
in
spite
of
the
presence
of
lungs
in
most.
They
have
a
three
chambered
 










heart.
Most
frogs
and
toads
are
external
fertilizers,
but
salamanders
and
caecilians
 










are
internal
fertilizers.
Most
amphibians
are
oviparous
with
external
fertilization.
 










However,
some
are
viviparous
or
ovoviparous.
 
 





6.


Class
Reptilia
 











There
are
7,000
species
of
reptiles
which
are
represented
by
three
important
 











orders.
 
 











a.


Chelonia
 

















Turtles
 
 











b.


Crocodilian
 

















Crocodiles,
alligators,
and
relatives.
 
 











c.


Quamata
 
















Lizards
and
snakes.
 
 











Reptiles
are
conceived,
live
and
die
on
land.
Since
they
are
the
first
fully
terrestrial
 











group
of
vertebrates
and
therefore,
have
specialized
organs
for
life
on
land.
The
 











female
reptiles
retained
a
cloaca,
but
the
male
has
developed
a
penis
for
copulation
 











and
internal
fertilization.
The
amniote
egg
is
porous,
leathery
and
complete
with



food
and
fluids
(parts:
yolk,
allantois,
chorion,
embryo).
 
 











Reptiles
convert
nitrogenous
wastes
to
uric
acid
rather
than
ammonia.
Ammonia
is
 











less
toxic,
but
requires
a
large
amount
of
water.
The
skin
is
dry
with
protective
 











scales,
reducing
water
loss.
There
are
few
mucous
secreting
glands.
Most
have
a
 











three
and
half
or
four
chambered
heart,
with
two
atria
and
a
ventricle
with
a
partial
 











septum.
The
crocodile
has
a
complete
septum
and
a
four
chambered
heart.
Most
 











reptiles
are
carnivorous.
They
locate
food
by
sight,
heat
detecting,
olfactory
and
 











hearing.
 
 





7.


Class
Aves
(Birds)
 











There
are
8,600
species
of
birds.
They
have
a
light
skeleton
with
many
hollow
bones.
 











The
reptilian
teeth
have
been
replaced
by
a
light
horny
beak,
the
neck
is
long
and
 











flexible,
the
bones
of
the
trunk
are
fused
together,
and
their
breast
bone
is
 











enlarged
which
acts
as
a
large
keel
for
the
attachment
of
flight
muscles.
The
bird
 











tail
is
small
made
of
only
four
vertebrae;
legs
are
adapted
for
perching
and
grasping.

 











Feathers
evolved
from
reptilian
scales.
The
feathers
are
strong
for
their
weight
 











because
of
their
interlocking
barbs.
Birds
have
a
complicated
respiratory
system
 











and
lack
a
urinary
bladder;
both
solid
waste
and
liquid
waste
are
added
together.
 










The
female
has
only
one
ovary
to
produce
eggs.
Birds
have
a
four
chambered
heart.
 
 8. Class
Mammalia
(Mammals)
 Mammals
are
furry
or
hairy
animals
that
produce
milk.
There
are
three
groups
of
mammals:
 monotremes
(egg
laying,
mono
=
single,
treme
=
holed.
Monotremes
have
retained
the
cloaca.),
 marsupials
(pouched
mammals,
most
of
embryonic
development
occurs
outside
of
the
womb
 and
in
the
pouch)
and
placental
(development
of
embryo
occurs
in
womb).
 
 Mammals
use
a
muscular
diaphragm
to
move
air.
They
have
a
four
chambered
heart
and
lungs.
 Fertilization
and
development
is
usually
internal
(except
for
monotremes).
Females
have
 separate
urinary
and
reproductive
tracts.
Mammals
may
have
specialized
teeth.
Milk
is
modified
 sweat
which
provides
the
young
with
high
protein,
high
caloric
nutrients.
 
 


/AP_Bio_Notes_31_Intro_to_Vertebr  

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