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Chapter 33
Porifera (Sponges),
Cnidarians (hydra, jellyfish, sea anemone, some corals)
Ctenophores ( comb jellies)
pictures from: &
Animalia: A Progression of Complexity
• As we begin discussing the animal kingdom-Consider
that as animal phyla diverge, organs and organ
systems are added, increasing complexity.
Tissues ( # germ layers)
Body symmetry
Internal body cavity
Organs and Organ systems:
integumentary system - protection (injury, infection, water loss)
digestive system - food processing
nervous system - coordination; response to environment
reproductive system – asexual or sexual, external or internal
excretory system - removal nitrogenous waste from body fluid
skeletal system - structural support
circulatory system - internal distribution of materials
respiratory system - gas exchange (O2 in, CO2 our)
Noted from:
I. Porifera
Invertebrate (no backbone)
No true tissues or organs
No gastrula stage (embryonic development)
Less cell specialization than other animals
All species -Aquatic
• Adult is Sessile (attach to surface, do not move)
Why are sponges considered animals?
• Early biologists thought they were plants.
• BUT- Have 2 key characteristics of animals:
– (Reproduction is asexual or sexual)
– (Mobility- adults are sessile- but some species can
move up to 4mm/day (
*larvae have flagella.)
• Represent transition from unicellular to
multicellular life.
A. Basic Body plan of a Sponge
1. Asymmetrical
2. Sessile
3. Vocabulary of sponge parts:
Hollow cylinder shape, closed at bottom, opening
at top called Osculum.
Interior lined with Choanocytes – flagellated
cells that draw water into the sponge through
pores in the body wall called Ostia.
2 layers of cells separated by mesohyl
(a jelly like substance)
Sponge Skeleton
2 types support- (different
sponges use one or both):
• Spongin - tough,
flexible protein fibers
• Spicules – hard
calcium carbonate
(like in limestone,
teeth & bones) or
hard silicon dioxide
(quartz, glass)
Picture from:
B. Digestive System/Wastes
1. Filter Feeding- bits of organic matter or
2. Amoebocytes- crawling cells that
deliver nutrients from choanocytes to the
rest of the body
3. Digestion is Intracellular
-wastes & CO2 expelled with water as it
passes through osculum
C. Reproductive System
1. Asexual
a. Budding- part of the parent pinches off & forms a
new organism
b. Gemmules – a reproductive structure in sponges,
-produced in harsh conditions
-a food-filled ball of amoebocytes in a protective coat
c. Regeneration- regrowth of missing cells.
2. Sexual
a. Sperm are released into water, enters next sponge
through pores, choanocytes engulf sperm. Carry to
ameobocytes, carry them to egg in mesophyl. Produces a
flagellated Larvae (immature form)
b. Hermaphrodite- each sponge has both eggs &
II. Cnidaria (Hydra, Jellyfish,
Sea Anemones, some corals)
A. Body Plan
1. Stages:
Medusa –bell shaped, swims
Polyp – vase-shaped, sessile
2. 2 cell tissue layersEpidermis outside layer
Gastrodermis inside layer
-with Mesoglea in between)
3. Gastrovascular cavity (gut)
4. Tentacles
B. Digestive System/Waste
1. Cnidocytes (special defensive cell) have
Nematocysts (coiled organelle with stinging
2. Tentacles push
prey through mouth &
into gastrointestinal cavity
3. Digestion is
Extracellular, wastes
expelled through mouth.
C. Nervous System
1. Nerve Net -Nerve cells located below
epidermis near the mesoglea interconnect and
form a nerve net throughout the body.
Cnidarians have both muscle fibers and nerve
fibers, making these animals capable of
directional movement.
2. Movement – using pulsing tentacles
D. Classes
1. Hydrozoa ( 3,700 species) ex- Obelia,
Portuguese Man-O War.
2. Cubozoa ex- box jellies, sea wasp
3. Scyphozoa “cup-animals” jellyfish
4. Anthozoa (6,100 species) “flower animals”
like sea anemones, corals
• Use your book to describe one organism from
each of the 4 classes.
• List & diagram the steps in describing the
cnidarian hunting & feeding process (use
terms for special parts.)
E. Reproductive Systems• Some reproduce asexually (see Hydrabudding) especially in warmer
• Sexual reproduction– lower temps
– hermaphrodites.
– Motile sperm, egg in ovary.
III. Ctenophora (100 species)
Ctenophora means “comb holder”- named
for the 8 comb-like rows of cilia that run
along outside of these animals
How are they different than jellyfish?
A. Movement - beating cilia
B. Digestive
-ctenophores are voracious predators.
-Unlike cnidarians, they lack stinging cells.
(no cnidocytes)
-Instead,to capture prey, have sticky cells
called colloblasts. located on ends
of 2 tentacles.
-In a few species, special cilia in the mouth
are used for biting gelatinous prey.
C. Nervous- have an apical organ for
sensing environment.
D. Bioluminescence –glow with light they
produce with chemicals