Download Sponges and Cnidarians

Learning Goal:
 Describe the main characteristics of
cnidarians
 Explain why coral reefs are important
Warm up:
What makes up a coral reef?
Homework:


Finish all questions on packet pages 6, 7, 8, & 9
TEST on Wednesday on Ch. 9 Sec 1 & 3
MONDAY 2/29/16
Cnidarians
Chapter 9 Section3
Jellyfish, corals, and sea anemones
 Invertebrates that have stinging cells
to capture food and protect themselves
 Take food into central body cavity

Cnidarians
 Two
different body plans
(vase and bowl)
 Radial symmetry
 Central hollow cavity
 Tentacles containing
stinging cells
Cnidarians: Body Structure

Radial symmetry - symmetry around a
central axis, as in a starfish
 Vase-shaped body plan is a POLYP
 Sea anemone
 Mouth opens at top
 Tentacles spread out from around
mouth
 Most are attached to underwater
surface
Body Structure:
Polyp
 Bowl-shaped
body plan is a
MEDUSA
 Jellyfish
 Adapted for a swimming life
 Mouths open downward and
tentacles trail down
Body Structure:
Medusa
 Use
stinging cells to catch animals
they eat (prey)
 Contains threadlike structure with
spines
 Uses tentacles to pull prey to
mouth
 Takes food into central body cavity
 Expels undigested food through
mouth
Obtaining Food

Unlike adult sponges, many
cnidarians move to escape danger
and to obtain food

Jellyfish
◦ Swim through the water
◦ Hydras turn slow somersaults

Sea Anemones
◦ Stretch out, shrink
down, bend slowly
from side to side
Movement
 Asexual
Reproduction
◦ Hydras, corals, and sea anemones
 Sexual
Reproduction
◦ Jellyfish
Reproduction
 Colony
◦ a group of many individual animals
 Stony corals and Portuguese man-ofwar
Life in a Colony
a
coral reef is built by cnidarians
 coral reefs are home to more species
of fishes and invertebrates than any
other environment on Earth
 Coral polyps produce hard, stony
skeletons around their soft
bodies
Stony Coral
 Contains
as many as 1,000
individuals that function together
as one unit
 Top: gas filled chamber, allows
colony to float
 Bottom: polyps with different
functions drift below
◦ Some catch prey and help with digestion
and reproduction
Portuguese Man-of-War