Sponges, Cnidarians, and Ctenophores
Chapter 33
Phylum Porifera
Section 33.1
Phylum Porifera
Latin for “Pore-Bearing”
Asymmetric Body Structure
Sponges
• Aquatic animals
• Represent transition from unicellular to
multicellular life
• No true tissue or organs
• 5,000 species (most marine)
• Various colors, shapes, sizes, etc.
• Adults are sessile
Sponge Body Plan:
• Two layers of cells separated by
mesohyl (jellylike substance)
• Body wall forms a hollow cylinder that
is open at the top
More Sponge Parts:
• Choanocytes (collar cells): flagellated
cells that draw water into the sponge
• Ostia (pores): pores that penetrate the
body wall that allow water into the
sponge
• Osculum: opening at the top of the
sponge
• Water leaves the sponge through this
structure
Water Flow:
Sponge Support System
• Simple skeleton made up of spongin
and/or spicules
• Spongin: tough, flexible protein fibers
• Spicules: tiny, hard particles of calcium
carbonate or silicon dioxide
• shaped like spikes
Spicules
Spongin
Sponge Anatomy
Feeding & Digestion
Filter feeders of plankton and other small
organisms
Steps in feeding & digestion:
1. Choanocytes beat & draw water into ostia
• Then collect food from water
2. Nutrients pass from choanocytes to
amoebocytes
• Crawling cells that deliver nutrients to rest of
the body
3. Wastes and CO2 diffuse into the water and
goes out the osculum
Asexual Reproduction
• Regeneration:
• regrowth of missing cells
• Budding:
• sometimes the bud breaks off the parent
and becomes a new organism
• or it may remain attached to the parent
and develop into a sponge colony
Environment gone bad?
Gemmules: food filled ball of
amebocytes protected by protein
& spicules
• Can survive harsh conditions
• Similar to endospore of bacteria
Sexual Reproduction
1. Sperm of one sponge enters pores of
a different sponge
2. Choanocytes engulf the sperm
3. Sperm transferred to amebocytes
4. Then transferred to egg in mesohyl
5. Egg is fertilized
6. Swimming larva leaves the sponge
and settles on an object to become
an adult
Hermaphrodites
• Why doesn’t self-fertilization usually
occur in an hermaphroditic species?
• Answer:
• Less genetic diversity thus less of a
change to survive an environmental
change (evolution would not occur as
much)
Phyla Notecards:
• First side:
• Phylum name
• Example organisms
• Drawing of organism
• With color!
• Opposite side:
• Body symmetry
• Mobility (adult & larval
stages)
• Feeding methods
• Reproductive methods
• Defense mechanisms
• Environment/habitat
Cnidaria & Ctenophora
Section 33.2
Phylum Cnidaria
General Characteristics:
• Radial symmetry
• Have tissues and simple organs
• Aquatic (mostly marine)
Phylum Cnidaria
Body Plans:
• Medusa: bell-shaped specialized for
swimming
• Polyp: vase-shaped specialized for
sessile living
More Body Parts:
• Two cell layers:
•Epidermis: outer layer
•Gastrodermis: inner
layer
• Mesoglea:
• jellylike material
between two layers
Continued…
• Gastrovascular cavity: center of body
with a hollow gut and mouth
• Tentacles: flexible extensions
surrounding the mouth
• Moves food in
Feeding & Defense:
• Cnidocytes: specialized cells used for
defense and capturing prey
• Gives the phylum its name!
• Nematocyst: organelle within
cnidocyte with a long filament and a
poison tip
2nd Video
• Trigger response
Video
Nervous System:
• Nerve net: diffused web of interconnected
nerve cells
• No brain
• No cephalization
• Can respond to stimuli
• Nerve net  contractile cell  contraction of
whole body
• Can control swimming & feeding
Classification:
Four classes:
1. Class Hydrozoa
2. Class Cubozoa
3. Class Scyphozoa
4. Class Anthozoa
Class Hydrozoa:
• Colonial organisms (combo of polyp & medusa
form)
• Each organism has a specialized function for the
colony
• Exception: hydras – only polyps, NOT colonial
• Examples: Portuguese man-of-war, hydra, and
Obelia
Video
Class Cubozoa:
• Commonly known as box jellies
• Cube shaped medusa
• Some have cnidocytes that can cause
death to humans
• Example: Sea wasps
Class Scyphozoa:
• Commonly known as jellyfish
• The medusa form is dominant
• Some have poisonous nemotocytes
that can cause pain and death
• Biotechnology with Jellies video
Class Anthozoa:
• Meaning: flower animals
• Dominant form = polyp
• Examples: coral & sea anemone
• Some have symbiotic relationships with
other species:
• Coral with algae
• Sea anemone with clownfish
Coral
And
Algae
Video
Nemo!
Phylum Ctenophora
Distinguishing Characteristics:
• Meaning: comb holder
• Commonly called comb jellies
• Move by beating cilia
• Contain colloblasts that secrete a sticky
substance that blinds prey
• Do not have cnidocytes (like other jellies)
Continued…
• Apical organ: sensory structure that
determines orientation in the water
• Bioluminescence: production of light
through chemical reactions
Phyla Notecards:
• First side:
• Phylum name
• Example organisms
• Drawing of organism
• With color!
• Opposite side:
• Body symmetry
• Mobility (adult & larval
stages)
• Feeding methods
• Reproductive methods
• Defense mechanisms
• Environment/habitat
Class Notecards:
• First side:
• Class name
• Example organisms
• Drawing of organism
• With color!
• Opposite side:
• Unique characteristics
• Description of
representative organism
• Info about an organism
listed in the book
• Environment/habitat