Phylum Cnidaria

General Characteristics About 9000 species _____________________ Simple nervous system

__________________ Diploblastic organization

EndodermEctoderm

General Characteristics Cont’d-• Either tubular or bell shaped• _______________________• Only animal with

cnidocytes• Cnidocytes-specialized

stinging cells (on tentacle)• _______________________• All marine (aquatic)

____________________________

• Cnidarians’ bodies are organized around the gastrovascular cavity, where digestion takes place• GV has a single opening

that serves as both mouth and anus

2 Layers of Cells

–Diploblastic: •__________________________

–Gastrodermis: lines GV cavity–Epidermis: lines the outside of

the body (the skin)

• In between the two layers is the _________- a jelly-like substance.

Cnidarian Body Wall

Stinging Cells• Have Cnidocytes–________________–Contain nematocysts: barbed

thread-like structures inside the cnidocyte that shoots out and can puncture and poison or entangle prey

Cnidocyte

Feeding

• _______________________________

• Inner gastrodermis secretes digestive juices into gastrovascular cavity which digests food and circulates nutrients

Feeding Cont.

Nervous and Movement

•_________________ & sensory receptors

•Muscles help in directional movement & capturing prey

Life Cycles

• Cnidarians have two body forms that are representative of the sexual and asexual life cycles that they undergo.

–_______–Medusa

Polyp

–_______–_______–Usually attaches to a substrate

at the aboral end–Oral end is surrounded by

feeding tentacles

Medusa

_________________________Sexual (dioecious)Shaped like an upside-down bowlTentacles surround the mouth

that is housed underneath the bell

• When cnidarians display both forms at some point in their lives, they are said to display an __________________________

_________________________ Both sexual and asexual Sexual

Gametes released into waterFertilization takes place to

create free-swimming planula Asexual

By budding

Generalized Cnidarian Life Cycle

__________________________

• Scyphozoa: Jellyfish

• Anthozoa: Sea anemones & Corals

• Hydrozoa: Hydra

• Cubozoa: Box Jellies

Class Hydrozoa

• Ex. Hydras

http://upload.wikimedia.org/wikipedia/commons/0/07/Millepora_fire_coral.JPG

• __________________• Includes hydras, fire corals, and

Portuguese Man of War• Display alternation of generations–Polyp –Medusa

Class Scyphozoa

• True Jellyfish• ___________________________–Small polyp stage during life

cycle

_____________________

• Similar to Scyphozoans, except that their medusa is cuboidal• Includes the box jellyfish–1 of the 10 most venomous

animals on the planet–Kills 12 people per year

http://animals.nationalgeographic.com/animals/enlarge/box-jellyfish_image.html

Class Anthozoa

• Polyps that are flower-like• ___________________• Includes sea anemones, corals,

sea whips, and sea fans