Transcript Phylum Cnidaria - Welcome to Cherokee High School

Phylum Cnidaria
Cnidarians Include Hydras, jellyfish, sea anemones & corals
Radially symmetrical
Acoelomate
Two basic forms:
–Polyp: Cylindrical form which attach bases to substratum
–Medusa: Flattened, mouth down version of the polyp. Moves freely
Forms of Cnidarians
Body Plan
Basic Body Plan:
Has an outer epidermis
Has an inner
gastrodermis which
forms a gastrovascular
cavity
Has a middle "jelly filled"
layer called mesoglea
Cnidocytes
Cnidarians are predators which have tentacles possessing batteries of special cells
called Cnidocytes
Cnidocytes contain special stining capsules called nematocysts.
When triggered, these cells shoot out a discharge thread which can entangle
and/or poison it's intended prey
Reproduction
– Reproduction can occur sexually by
fertilization of egg and sperm forming
larvae.
– Reproduction can also occur asexually
through budding
3 Major classes
– Class Hydrozoa: Hydras
– Class Scyphozoa: Jellyfish
– Class Anthozoa: Anemones and corals
Class Hydrozoa: The Hydras
Polyp phase is
dominant
Generally microscopic
Generally freshwater
Class Scyphozoa: The Jellies
Generally refered tro
as jellies
Medusa stage is
dominant
Come in a variety of
forms
Aggressive
predators, and can
be dangerous to
humans
Jelly
Portugese
Man-o-war
Class Anthozoa: Anemones & Corals
Appear like plants but are
animals.
Polyp form is dominant.
Corals build calcium
shells to protect
themselves
Anemone
– Have symbiotic relationship
with algae.
Can build extensive
masses which can form
land masses.
Coral Polyps
Coral Reefs
Clownfish living in
An anemone