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Ch. 35 Porifera
 Invertebrates
 Animals without a
backbone
97% of all species
 Simplest is sponge
Sponges
Sponge
*Phylum: porifera
*Show transition
from
unicellular to
multicellular life.
*Have no tissue or
organs.
*Less cell
specialization.
* 10,000 species,
most in salt water.
* Adult form is
sessile.
* Attaches itself
firmly to some
surface.
* Range from 1cm
to 2 m.
Body Plan
ody wall is 2 layers
with jellylike substance
between.
Surrounds hollow
cylinder that is closed at
bottom and open at top.
Interior of cylinder is
lined with collar cells.
*they beat their
flagella and draw water
in through pores.

Sponge Body Plan
Body Plan
Water pumped in
is pumped out
through osculum.
Skeleton is made
up of spongin
(protein fibers) or
spicules (calcium
carbonate) or both.
Feeding and Digestion
Filter feeders.
*filter food out of
water that is
pumped through
pores by collar
cells.
 Food is bacteria,
protozoa and
unicellular algae.

Food digested by
collar cells then
nutrients passed on to
amebocytes which
are crawling cells
which take nutrients
to all cells.
Waste materials are
then carried out by
water through
osculum.
Feeding and Digestion
Reproduction
 Asexual by buds.
*Buds fall off and live
separately.
 Gemmules are formed
during droughts or cold
weather.
*Food filled ball of
amebocytes.
*When conditions
improve, sponge cells
emerge from gemmules
and grow into new
sponge.
Reproduction
 Regeneration
*Grow missing parts.
*Sponges can regenerate complete sponges.
 Sexual (see transp. 145)
*Sperm released into water from 1 sponge enters
pore of another sponge.
*Collar cells in second sponge engulf sperm,
transfer it to amebocyte which takes it to an egg.
*Egg fertilized, develops into larva, larva attach to
an object and grows into adult sponges.
Hermaphrodites

Some species have separate sexes
but most species produce both egg
and sperm. These are known as
hermaphrodites. They do not self
fertilize. This is most common in
invertebrates that are sessile, move
slowly or live in low-density
populations.