Download chapter 1 book 2 Sponges, Cnidarians

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Section 3
Sponges and Cnidarians
• Live mostly in oceans, but in
some rivers and lakes
• Water currents carry food
and oxygen to them and take
away their waste products.
Body Structure
• Invertebrates that have no body
symmetry and never have tissues
or organs
• Belongs to phylum Porifera, which
means “having pores”
• Has spikes for support and for
Obtaining Food and Oxygen
• Eats tiny single celled organisms
• The collar cells that line the central
cavity trap tiny organisms
• Jelly-like cells inside the sponge
then digest the food
• Gets oxygen from the water
• Can reproduce either sexually or
• Asexually – budding – new
sponges grow from the sides of an
adult sponge
• Sexually – sponges produce both
sperm cells and egg cells
• Examples: jellyfishes, corals, sea
• Invertebrates that have stinging
cells and take food into a central
body cavity.
• They use stinging cells to capture
food and defend themselves.
Body Structure
• Has 2 different body plans: one looks like a
vase and the other looks like an upsidedown bowl.
• Vase shaped is called a polyp
• A polyp’s mouth opens at the top and its
tentacles spread out from around the mouth.
• Adapted for life attached to a surface
Body Structure
• Bowl-shaped is called a medusa
• Is adapted for swimming
• Have mouths that open downward
and tentacles that trail down
• Some cnidarians go through both
stages during their lives.
Obtaining Food
• Both types obtain food in the same way
• Use stinging cells to catch the animals they
• Stinging cell contains a threadlike structure
which has many sharp spines.
• When this stinging cell touches its prey, this
threadlike structure explodes
• Can move to escape danger and to
obtain food
• Some have muscle-like tissues that aid
in movement
• Jellyfishes swim through the water,
and hydras turn slow somersaults
• Movement is directed by nerve cells
• Reproduce both asexually and
• Polyps: asexual (budding is most
• Sexual: some produce both male
and female sex cells; some are
specifically male or female
Life in a Colony
• Some cnidarians live in a
colony – group of many
individual animals.
• Examples: Stony corals,
Portuguese man-of-war
Stony Corals
• A coral reef is built by cnidarians
• A coral polyp attaches to a solid
surface, it produces a hard, stony
skeleton around its soft body.
• Coral polyp reproduces asexually –
when they die, their skeletons
remain behind.
Portuguese man-of-war
• It contains as many as 1,000
individuals that function together
as one unit
• Top has a gas filled chamber that
allows it to float on the top of the
• Various polyps drift below
Learning Log
•What are two
examples of asexual
reproduction seen in
•Pulling apart