Cnidarians

History: Found all over the world, but only in the sea.

Characteristics:

Body structure: Soft bodied animals with stinging tentacles arranged in a circle around their mouth. - ___________ symmetry-Specialized

cells and tissues

-Individual

and colonial

Feeding: Capture and

eat small animals by using stinging “whips” or ________________ found in tentacles (each is a poison filled sac with a spring-loaded dart)

- ______________ then push food through the mouth into the ________________ cavity.- Food is then broken up into tiny pieces, and the fragments are digested further by specialized cells in

the ________________- Nutrients are transported to rest of body by diffusion- Any materials that can’t be digested are passed back out through the mouth.

Respiration and Excretion: By _______________ directly through their body walls into the water- They get O2 and give CO2 to the symbiotic ___________ that live in their _____________

Response: Lack a _____________________________ (CNS) and Brain- Have a simple nervous system called “_____________” concentrated around the mouth but also

spread throughout body in the mesoglea- Specialized sensory cells in ____________ detect chemicals in food and the touch of foreign objects- Medusa have organs for proprioception called _______________ (balance) and __________ (eyespots)

that detect light

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Movement: They lack specialized muscle cells but they do have cells that that change shape when stimulated by the nervous system

- Polyps are sessile but they move their tentacles by relaxing and contracting their _____________ cells- In medusa contracting the epidermal cells change the bell shape and cause it to close like an umbrella,

this causes water to push out and move the medusa in by jet propulsion

Reproduction: - Life cycle has 2 stages: polyp (sessile) and medusa (motile)- Both _____________ and ____________- Polyps can make new polyps and medusa by _____________ - Mature medusa reproduces _____________ by producing ___________ into water (there are male and

female medusa)- Fertilization can occur inside the body or outside (depending on the species)- ___________ grows into a ciliated larva that swims around until it settles down, attaches to a hard

surface, and becomes a ___________

Internal transport: Most have not developed a system of transport but some have branching gastrovascular cavities that help carry partially digested food through their bodies.

Examples of Cnidarians:

1. Hydrozoa - Spend most of their lives as __________ - Hydras lack a medusa stage and can move in a somersault motion in polyp stage, reproduce

asexually by budding or sexually by producing either eggs or sperm (some produce both) in their body walls.

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- example: “Portuguese man of war”

2. Scyphozoa: Jellyfish

- Same life cycle as hydras except the __________ is large and long lived and __________ is restricted to a tiny larval stage.

- examples: the “lion’s mane” 2m in diameter- Some nematocysts are not harmful, others can sting, others can cause death in 3-20 min.

3. Anthozoa: Sea Anemones and Corals- Only have ___________ stage - Adults reproduce ___________ by producing eggs and sperm that are released into the water- Zygote forms a ciliated larva that settles to the ocean bottom and forms a new polyp- Many also reproduce by ____________ by budding.- Sea Anemones: live in the sea from low tide to great depths, and depend heavily on

photosynthetic symbionts, can grow up to 1m in diameter.- Corals: grow in shallow tropical water in the world, polyps are similar to SA’s but they produce

skeletons of Calcium carbonate or limestone. Most are colonial and the colonies grow slowly but may live for 100s of years, with each bud more limestone is put down

- Example: great barrier reef in Australia.

How they fit into the world:

1. Symbiotic relationships: - Fish, shrimp, and other animals live in __________ giving protection and providing food and

help clean the SA and protect it for certain _____________ - Corals provide homes for many organisms such as fish and organisms that produce shells and

pearls2. Reefs protect the land from the action of waves.3. Fossil reefs offer important clues to geologists about locations of oil deposits4. Large blocks of coral have been used to build houses and to filter drinking water5. Coral are used for jewelry and decorations.6. Cnidarians have been used for __________ __________:

- Corals produce chemicals to protect themselves from being infected, overgrown or settled upon by other organisms.

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- Some provide anti-cancer drugs- Nerve toxins are powerful research tools

WORD BANKGastrovascular cavityTentacleCnidocyteEctodermEndodermMesogleaOvary/TesteBudNematocystMouthBasal Disk

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