Download Phylum Cnidaria - Mahtomedi Middle School

Phylum Cnidaria
(ny DEHR ee a)
The Highlights of Jellyfish and
Hydra life
Video below
http://marinebio.org/oceans/coral-reefs/
Examples of Cnidarian
 Jellyfish
 Hydra
 Coral
 Sea
Anemone
Cnidarians (ny DEHR ee unz) and
Characteristics
 Invertebrates
 Stinging
Cells
 Have a central
body cavity
 Radial symmetry
– more than one
line of symmetry
& parts arranged
in a circle
Pretty Radial Symmetry pics:
BODY STUCTURE:
 Polyp:
vase-shaped body plan (like a sea
anemone, coral or hydra)
 Medusa:
jellyfish)
Bowl-shaped body plan (like a
Polyp
 Mouth
opens at the top of its body
 Tentacles surround the mouth
 Attach themselves to an underwater
surface
More on Medusa
 Adapted
to a life of swimming
 Mouths open downward (at the bottom)
and is surrounded by tentacles that dangle
Which came first: Polyp or
Medusa??
 Brooks
(1886) proposed a theory still
widely accepted – however, being
studied (DNA evidence, etc.)
 •Ancestral cnidarian was a medusa
Life Cycle
 Some
Cnidarians have both body plans in
their life cycle…
 Sexual
 Asexual
(budding)
Obtaining FOOD!!!
 Same
way for polyps and medusa
 Use their stinging cells to catch prey
 Some have sharp spines with venom
 Venom paralyzes them – pull prey into
their mouths with tentacles
 Prey goes into hollow central body cavity
to be digested
 Waste goes out of mouth.
Movement
 Many
Cnidarians can move to escape
 Jellyfish swim
 Hydra turn slow somersaults
 Sea Anemones bend from side to side,
stretch out, shrink down or move slowly
 Nerve net – nerve cells arranged like a
basketball net – help with this movement
Life in a Colony
 Some
species of Cnidarians spend life in a
colony – a group of many individual
animals
 Examples: Coral and Portuguese man-ofwar
Coral Reefs
 Found
in warm shallow water
 Built by cnidarians
 A coral polyp attaches to a solid surface
(broken shell, sunken ship, rock or reef
ball)
 Polyp produces a hard, stony skeleton
around its soft body
 Home to more species of fishes and
invertebrates than any other environment
https://www.youtube.com/watch?v=eIul2ObvKV8
on Earth - video
Coral Reefs in Danger
 More
than 1.5 million recreational divers
 Divers can cause damage by standing on
or even touching fragile reefs
 Collecting coral for jewelry or decoration
(now illegal)…should they ban diving all
together?
 Oil spills, tropical storms, changes in sea
level and temperature, and illegal fishing
can also harm reefs
Portuguese Man-of-War
 Contains
as many as 1,000 individuals
that function together as one unit
 Top of medusa is a gas-filled chamber that
allows the colony to float
 Various polyps with different functions drift
below by the tentacles
 Some polyps catch prey and others digest
the prey…some are adapted for
reproduction
https://www.youtube.com/watch?v=sQyByfmKGJs
https://www.youtube.com/watch?v=NbpB5F9CcLc