Cnidarians Phylum Cnidaria: “stinging

cell” Hollow gut- (coel) On earth- since 670 MYA radial symmetry Germ Layers: 2

epidermal (ectoderm)gastrodermal (endoderm)

NO ORGAN SYSTEMS Segmentation: none Movement: sessile or motile predators Have tentacles- stinging cells

(cnidocyts) , nematocysts “thread cells” used as barbs

Structures: One body opening (mouth)

for food to enter and wastes to exit

Gastrovascular cavity: interior cavity where food is digested & nutrients are circulated around the body

Nerve net: net of nerves that allow impulses to travel around the body, senses the environment

Label the hydra on your notes!

http://www.arkive.org/common-jellyfish/aurelia-aurita/video-10.html

Without Body Systems, how do they survive?

Nervous: Cephalization absent; Nerve Net-conducts impulses

Skeleton: Hydrostatic- water pressure maintains shape

Respiration: Oxygen diffuses into body from water

Digestion: mouth, GVC Excretion: simple diffusion into water Circulation: GVC- gastrovascular

cavity Reproduction: asexual and sexual,

alternation of generations

Cnidarians: Body Forms

Polyp: body with tentacles facing upward, sessile

Ex: hydra, sea anenome video polyp predation

Medusa: body with tentacles hanging downward, motile

Ex: jellyfish

Cnidarian Reproduction Asexually: by budding

Sexually: usually in medusa form, sperm and eggs are released into water

(fertilized egg zygote planula larvaadult)

Thousands of gametes are released at a time

Alternation of Generations:Video: medusa releasing from polyp

Checkpoint:1. List 5 traits that cnidarians share.2. How many germ layers do cnidarians

have? ____ Which are they missing?3. Are all cnidarians predators? Motile?4. Describe the specialized cells they

have on their tentacles.5. Describe how a cnidarian consumes

and digests food.6. Describe the two body forms

Cnidarians display, and give examples of each type.

basal disc: sticky structure at the bottom of polyp ; sessile

Epidermis

Mesoglea

Gastroderm

MesogleaGastrovascular cavity

Mouth/anus

Tentacles

Tentacles

Mouth/anus

Gastrovascularcavity

Polyp

Medusa

Structure:The Polyp and Medusa Stages

Diploblastic - 2 germ layers

› Epidermis - outer covering (ectoderm)› Mesoglea - middle non-living jelly-like

layer (missing mesoderm)› gastrovascular cavity (endoderm)

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Classes of Cnidarians

1. Hydrozoa

2. Scyphozoa

3. Anthozoa

Class Hydrozoa Freshwater & marine. Medusa and polyp colonies which

appear to be one organism- different types of polyps work

together to serve the entire colony

Ex: Hydra, Obelia, GonionemusPhysalia (portuguese-man-of-war)36:40 Ocean Drifters

Asexual repro.-budding. Sexual repro. via gametes

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Class Scyphozoa Scyph= “cup” Large- Tentacles

up to 70 meters in length

All marine Independent

medusa forms Lack polyp stage

or have for a very short time

Ex. Box jellyfish12

Class Anthozoa ANTHO=“flower” All polyps-Medusa

stage absent Solitary or colonial Some produce

protective skeletons

All Marine Ex. Sea anemones,

corals 13

Class AnthozoaSea Anemone

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Video jewel anenome

Class AnthozoaMetridiumClass AnthozoaMetridium

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MouthMouth

TentaclesTentacles

PharynxPharynx

SeptumSeptum

Gastrovascular cavityGastrovascular cavity

Symbiosis

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Class AnthozoaCorals

Protective skeleton of calcium carbonate

Polyp retracts when not feeding

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CoralsColony of interconnected polypsCoralsColony of interconnected polyps

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Class AnthozoaMeandrinaBrain Coral

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Class AnthozoaGorgoniaSea Fan

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Class AnthozoaTubiporaPipe Organ Coral

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Class AnthozoaActinodiscusMushroom Coral

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Class AnthozoaAcroporaStaghorn Coral

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Coral Reefs Formed over thousands of

years from successive layers of coral skeleton deposits

The underwater equivalent of the amazon jungle- very high species diversity and biomass

Reefs contain sponges, colonial hydrozoans, anemones, many varieties of coral, fish, many types of worms we’ve not discussed, not to mention bryozoans, ctenophores, protists, bacteria, etc etc..

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Coral Reef Ecosystem

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Photo © McGraw-Hill Higher Education, Barry Barker, Photographer

Cnidarian Cladogram

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AnthozoaScyphozoa Cubozoa

Hydrozoa

Radial symmetry, cnidocytes, planula larva

Septa divide gastrovascular cavity

Medusa cuboidal

Polyp stage reduced

Loss of medusa

Checkpoint

1.Cnidarians are diploblastic, what does this mean?

2.What is the mesoglea? 3.How are Hydrozoans different from other

classes of cnidarians?4.List examples of Hydrozoans.5.What are scyphozoans, do they have a polyp

stage?6.Anthozoans are known as the ______________

animals. Give examples of anthozoans.7.What is an anthozoan’s protective skeleton

made of?8.Why are coral reefs important?

The End

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