Phylum: CnidariansPhylum: Cnidarians

What is a Cnidarian?What is a Cnidarian?

A cnidarian is an A cnidarian is an invertebrateinvertebrate

It uses It uses stinging stinging cellscells to capture to capture preyprey

Examples:Examples:– JellyfishJellyfish– CoralsCorals– Sea AnemonesSea Anemones

Body StructureBody Structure

All cnidarians have the following All cnidarians have the following characteristics:characteristics:– Radial symmetryRadial symmetry– A hollow central cavityA hollow central cavity– Tentacles with stinging cellsTentacles with stinging cells

However, cnidarians can have one of 2 However, cnidarians can have one of 2 different body plans. different body plans. – PolypPolyp– MedusaMedusa

Body PlansBody Plans PolypPolyp

– Mouth opens at Mouth opens at toptop– Vase-shapedVase-shaped– Attached to a Attached to a surfacesurface– Examples: Examples: Hydra, Sea Hydra, Sea

anemone, Coralanemone, Coral

MedusaMedusa– Mouth opens Mouth opens downdown– Tentacles point Tentacles point downdown– Adapted for a Adapted for a

swimming life swimming life – Examples: Examples: JellyfishJellyfish

Activity: Color Code a Activity: Color Code a CnidarianCnidarian

Tentacle

Ectoderm Tentacle

Jelly-like layer (Mesoglea)

Endoderm

Obtaining FoodObtaining Food

Stinging cells inject Stinging cells inject venomvenom which paralyzes which paralyzes the preythe prey– THINK!THINK! – Why are clown fish resistant to the – Why are clown fish resistant to the

toxins given off by sea anemones?toxins given off by sea anemones?

TentaclesTentacles pull the prey into the mouth pull the prey into the mouth

Digestion happens in the Digestion happens in the body cavitybody cavity

Waste is expelled back out through the Waste is expelled back out through the mouthmouth

MovementMovement

Cnidarian movements are directed by Cnidarian movements are directed by nerve cellsnerve cells that that spread throughout the cnidarians body like a spread throughout the cnidarians body like a basketball netbasketball net

Jellyfish Jellyfish swim through waterswim through water

Hydras can be found in freshwater and turn Hydras can be found in freshwater and turn somersaults or use their tentacles to movesomersaults or use their tentacles to move– Watch these Hydra MoviesWatch these Hydra Movies

http://micro.magnet.fsu.edu/optics/olympusmicd/http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/moviegallery/pondscum/coelenterata/galleries/moviegallery/pondscum/coelenterata/hydra/index.htmlhydra/index.html

Sea anemones Sea anemones stretch out, shrink down, and bend stretch out, shrink down, and bend slowlyslowly from side to side from side to side

ReproductionReproduction

AsexualAsexual– Budding is most common in hydras, Budding is most common in hydras,

corals, sea anemones where corals, sea anemones where these these polyps just pull apart forming two new polyps just pull apart forming two new polyps.polyps.

SexualSexual– Can occur during the life cycle of Can occur during the life cycle of

certain cnidarians certain cnidarians such as the jellyfishsuch as the jellyfish

Life Cycle of A Jelly Life Cycle of A Jelly FishFish

Life on a Coral ReefLife on a Coral Reef

Coral polyps produce a Coral polyps produce a hard, stony hard, stony skeletonskeleton around its soft body once around its soft body once attached to a hard surface.attached to a hard surface.

Coral polyps then continue to Coral polyps then continue to reproduce asexuallyreproduce asexually

Over time, reefs build up from the sea Over time, reefs build up from the sea floor and make floor and make great homes for other great homes for other sea lifesea life

Video QuizVideo Quiz

Watch the following clip:Watch the following clip:– Coral Ecosystems (5:59) Coral Ecosystems (5:59)

There will be a short video quiz There will be a short video quiz following the clip. following the clip.

Make sure to take good notes! You Make sure to take good notes! You can use your notes for the video can use your notes for the video quiz!quiz!