Cnidaria. General Information Eumetazoans (true animals) all animals other than sponges-have both tissues and symmetry When eumetazoans develop-they.

CnidariaCnidaria

General InformationGeneral Information

EumetazoansEumetazoans (true animals) all animals (true animals) all animals other than sponges-have both tissues and other than sponges-have both tissues and symmetrysymmetry

When eumetazoans develop-they develop When eumetazoans develop-they develop three embryonic tissue typesthree embryonic tissue types

EctodermEctoderm outer layer-gives rise to outer covering of outer layer-gives rise to outer covering of body and nervous systembody and nervous system

MesodermMesoderm middle layer-gives rise to skeleton and middle layer-gives rise to skeleton and musclesmuscles

EndodermEndoderm inner layer-gives rise to digestive organs inner layer-gives rise to digestive organs

Cnidaria CharacteristicsCnidaria Characteristics

Includes jellyfish, hydra, sea anemones, and Includes jellyfish, hydra, sea anemones, and coralscorals

All radially symmetricalAll radially symmetrical All are carnivorous-capture prey with tentacles All are carnivorous-capture prey with tentacles

around the moutharound the mouth Evolved a digestive cavityEvolved a digestive cavity Two body formsTwo body forms

MedusaMedusa (sexual) free floating, umbrella shape (sexual) free floating, umbrella shape PolypPolyp (asexual) cylindrical, attached to rocks (asexual) cylindrical, attached to rocks

Cont…Cont…

Single opening (mouth/anus) to Single opening (mouth/anus) to gastrovascular cavity where food & gastrovascular cavity where food & water enter & wastes leave; called water enter & wastes leave; called one-way digestive systemone-way digestive system

Have a simple nerve net (only travels Have a simple nerve net (only travels one way) to help with movement & one way) to help with movement & sensessenses

Reproductive Life CycleReproductive Life Cycle

Alternate generations between polyp and Alternate generations between polyp and medusa formmedusa form

Planula (larval form)

Polyp

Medusa

Egg

SpermZygote+

Asexual - budding

Sexual

Stinging CellsStinging Cells

Tentacles have stinging Tentacles have stinging cells called cnidocytescells called cnidocytes

Each cnidocyte has Each cnidocyte has nematocyst that are barbed nematocyst that are barbed and are used to spear the and are used to spear the preyprey

FeedingFeeding

Use cnidocytes to stun or kill Use cnidocytes to stun or kill preyprey

Tentacles contract to bring Tentacles contract to bring food to mouthfood to mouth

Food is digested in Food is digested in gastrovascular cavitygastrovascular cavity

Three Classes of CnidariaThree Classes of Cnidaria

HydrozoaHydrozoa Polyp dominant which is larger than medusaPolyp dominant which is larger than medusa

ScyphozoaScyphozoa Medusa dominant and it is larger than polypMedusa dominant and it is larger than polyp

AnthozoaAnthozoa Only polyps no medusa formsOnly polyps no medusa forms

HydrozoaHydrozoa

HydrozoansHydrozoans Have both medusa and polyp stagesHave both medusa and polyp stages

EX: HydraEX: Hydra freshwater- no medusa stage- solitary freshwater- no medusa stage- solitary polyp- lives in quiet ponds, lakes, and streams-polyp- lives in quiet ponds, lakes, and streams-attaches to rocks with sticky basal diskattaches to rocks with sticky basal disk

EX: Portuguese Man of WarEX: Portuguese Man of War marine-medusa and marine-medusa and polyps- colony of organisms-gas filled balloon floats on polyps- colony of organisms-gas filled balloon floats on surface and dangling below are the tentacles with surface and dangling below are the tentacles with stinging cells-prey is entangled in the tentaclesstinging cells-prey is entangled in the tentacles

Hydrozoan ReproductionHydrozoan Reproduction

Most hydrozoan reproduce asexually by Most hydrozoan reproduce asexually by forming small buds on the outside of forming small buds on the outside of their bodies-these buds develop into their bodies-these buds develop into miniature polyps-miniature polyps-

Hydrozoan can also reproduce Hydrozoan can also reproduce sexually-the polyps produces male and sexually-the polyps produces male and female medusa that release egg and female medusa that release egg and sperm in water-the egg and sperm form sperm in water-the egg and sperm form a larvae called a planulae the eventually a larvae called a planulae the eventually settles to the bottom and forms a polyp.settles to the bottom and forms a polyp.

Bud

ColonizationColonization

Some Hydrozoans produce colonies in Some Hydrozoans produce colonies in which different polyps have a different which different polyps have a different specialization.specialization. Some specialized in feeding, reproduction, Some specialized in feeding, reproduction,

and protectionand protection

ScyphozoanScyphozoan

ScyphozoanScyphozoan cup animal cup animal JellyfishJellyfish live most of their life as live most of their life as

medusamedusa Active predators-hunt foodActive predators-hunt food Sea wasp-deadlySea wasp-deadly Reproduce much like hydrozoans but male Reproduce much like hydrozoans but male

and female medusa mate and form planulae and female medusa mate and form planulae which settles to bottom and forms polyp. which settles to bottom and forms polyp. Polyp grows it and buds off to form medusaPolyp grows it and buds off to form medusa

AnthozoansAnthozoans

AnthozoansAnthozoans largest class of Cnidaria – largest class of Cnidaria –name means flower animal-DO NOT name means flower animal-DO NOT form medusa – Show neoteny (sexual form medusa – Show neoteny (sexual maturity during the larval stage) maturity during the larval stage)

Sea AnemonesSea Anemones soft bodied polyps-coastal- soft bodied polyps-coastal-feed on fish-when touched they retract their feed on fish-when touched they retract their tentacles-Symbiotictentacles-Symbiotic

CoralsCorals live in colonies-polyp secretes a hard live in colonies-polyp secretes a hard outer covering which make up coral reefs-outer covering which make up coral reefs-

Three types of ReefsThree types of Reefs

Fringing-close to beach-FloridaFringing-close to beach-Florida

Barrier-form in deeper water farther out Barrier-form in deeper water farther out from the shore-Great Barrier Reef in from the shore-Great Barrier Reef in AustraliaAustralia

Atoll-coral island that form far out at sea Atoll-coral island that form far out at sea and grow into a ring shape with a lagoon and grow into a ring shape with a lagoon in the center.in the center.

HomeworkHomework

1.1. What are some differences between the What are some differences between the three different classes discussed?three different classes discussed?

2.2. Why would it be of an advantage to Why would it be of an advantage to switch from polyp to medusa for vise switch from polyp to medusa for vise verse?verse?

3.3. Why would it be of an advantage to Why would it be of an advantage to have specialization in colonies?have specialization in colonies?