Transcript Slide 1 - SchoolRack

Mr. Gibson
Lecture Room 213/Labs 214
w/o March 28th & April 11th
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
This week we are
building upon your
prior knowledge
regarding embryonic
development & the
transition of zygote
cells [from]
“undifferentiated”
[to] “differentiated”.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
In particular the
differentiation as it
pertains to:
Ectoderm (outer)
Mesoderm (middle)
Endoderm (inner)
Cells.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Even more specific to
our studies over the
next two weeks is the
further differentiation
of
Ectoderm/Mesoderm
/Endoderm cells into
specific structures
regarding
Invertebrates (no
spinal column or
backbone)
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The first of our
invertebrates for our
developing
Protostome
Embryos will be
“worms”.
And of the worms, we
will be dealing with
“Flatworms” first.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Flatworms are the
“simplest” of the
worm invertebrates
[as] they have tissues
and internal organs
[as well as] the three
embryonic
differentiated cells:
Ecto/meso/endoderm
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The invertebrate
“Flatworms” are
studied first due to
the fact; biologists
state their overall
development &
structures are less
complex than their
more evolved
“cousins”.
But don’t be confused…
[…] by “less complex” it does
NOT imply “simplistic”.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Flatworms have
Bilateral symmetry.
By that we mean they
have a body plan in
which only a single,
imaginary line can
divide the body into
two equal halves. This
is a characteristics of
worms.
Plane of symmetry
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Flatworms have an
area of
Cephalization
By that we mean they
have an area on their
body that has a
concentration of their
sensory organs
(allowing for
interacting with their
surrounding
environment)
Various flatworms &
their areas of
cephalization
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Flatworms are also
called
Acoelomates
(ay-SEE-luh-mates)
Usually in biology if
you see the letter “a”
in front of a term it
means “without”.
Flatworms are
without a coelom
coelom
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The “Flatworms” we
will study have a
much less complex,
digestive system and
neurosystem… and no
real circulatory”
system;
As these systems have
arisen from further
differentiation of
Ecto/meso/endoderms cells.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The further
differentiation of
“Flatworm”
endoderm cells.
Once the protostome
develops for the
invertebrate flatworm
the endoderm cells
continue to further
differentiate into a
digestive system.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The invertebrate
flatworm’s
differentiated
endoderm cells
become a “simple”
digestive system. For
the planeria @ the
right it is nothing
more than an
endoderm lined cave
or cavity called a
“gastrovascular
cavity”
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
The invertebrate
flatworm’s endoderm
lined “gastrovascular
cavity”
Is really a “tube” that
runs through the
middle of the animal
where secreted
enzymes break down
ingested food for
cellular nutrient
needs.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Food intake
The flat worm…
because it IS flat
doesn’t really need all
that sophisticated of a
digestive system.
The “flatness” of the
worm allows it to act
like a sponge…
It can readily
“absorb” materials
through the
endoderm cells.
pharnyx
mouth
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Food intake
By the time the
ingested food reaches
the other end of the
gastrovascular track
what is needed will
be absorbed into the
animal’s body feeding
all the other cells.
Anything not needed
plus waste coming
out of the cells will
empty out of the
animal.
pharnyx
mouth
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Cell boundary
Materials such as
oxygen & nutrients
move into a
flatworm’s interior
(meso/ectoderm)
Cells in-spite of the
fact the flatworm has
NO circulatory
system. This is done
by diffusion.
Waste materials
to leave the cell
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Cell boundary
Diffusion also
removes carbon
dioxide and other
wastes from their
body.
Because their bodies
are so thin and flat,
many flatworms do
not need a circulatory
system to transport
materials.
Waste materials
to leave the cell
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
There is another
structure that the
flatworm uses to
remove waste
material and excess
water.
That structure is
called a FLAME CELL
Waste materials also leave the cell
via Flame Cells
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
In addition to
handling materials
into and out of the
animal;
The animal must be
able to find the food
too (as well as be
aware of predators
and not become food
itself).
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
To help in finding food
while avoiding
becoming food the
animal uses light
sensing areas called
EYESPOTS
And
It uses CHEMICAL
SENSORY organs that
detect good/bad
chemicals in the
water.
Eye spots are light sensing cells
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
And to process all this
information while
handling all the
interior signals
running the animal’s
systems;
The neural impulses
to/from activities
route through groups
of cells not complex
enough to be called a
brain -- GANGLIA
A group of nerve cells that
process electrical impulses.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
From the ganglia are a
pair of long nerve
chords that run either
side of the body.
These are called
Ventral Chords.
The long chords that run the
length of the animal’s body
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
And the series of
much smaller nerve
chords that run
laterally (side-to-side)
of the animal’s body
serving the ganglia
are:
TRANSVERSE NERVES
The much shorter nerves that run
side to side of the animal’s body –
serving the ganglia
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
In terms of
reproduction…
Flatworms are QUITE
versatile!
They can reproduce:
•Sexually as
hermaphrodites (have
both sex organs);
•Asexually via fission
(splitting in half);
•Asexually via
fragmentation
Sexual reproduction
of hermaphrodites
Asexual reproduction
by fission
reproduction by
fragmentation
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
And speaking of food;
Free living flatworms
obtain their nutrients
[as] heterotrophic
carnivores that feed
on tiny aquatic
animals, or they can
be scavengers that
feed on recently dead
animals.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Flatworms that are
“parasitic” (means
they live off another
living organism).
A flatworm with
another parasitic
flatworm feeding
off of it.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
There are three types
of Flatworms:
Turbellarians: freeliving flatworms of
which most of them
live in marine or fresh
water.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
There are three types
of Flatworms:
Flukes: parasitic
flatworms that are
generally found
infecting the internal
organs of their host
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
There are three types
of Flatworms:
Tapeworms: long,
flat, parasitic worms
that are adapted to
life inside the
intestines of their
hosts
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Some special features
of the ectoderm
structures worth
noting with
flatworms.
Scolex (SKOH-lex): A
structure that can
contain suckers or
hooks and is the head
of an adult worm
belonging to the
parasitic flatworms
group.
Embryonic Development
& Cellular Differentiation
Invertebrate Flatworms
Some special features
of the ectoderm
structures worth
noting .
Proglottids (proGLAHT-tidz):
Segments that make
up most of the worm’s
body. Located behind
the scolex and
belongs to the
parasitic flatworms
group.