phylum cnidaria 1

7/27/2019 Phylum Cnidaria 1

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Phylum Cnidaria


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Phylum Cnidaria

Cnidarians have special stinging cells calledcnidocytes. They have long flexible

tentacles and usually live in sea water.Because they have a hollow gut calleda__________, they are known as

____________ as well as Cnidarians.


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Phylum Cnidaria

Characteristics of Cnidarians

Body plan

Two cell layers

Specialized structures

Nerve net Sexual and asexual reproduction


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Phylum Cnidaria

Body Plan

Cnidarians generally have _______

symmetry.


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Phylum Cnidaria

Body Plan

Cnidarians live in the ocean and can have

one of two different body plans:

1._______ free swimming

2.______- sessile


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Phylum Cnidaria

Two Cell Layers

Cnidarians are advanced beyond sponges

in the development of their cell layers.Although sponges also have two celllayers, in cnidarians the cell layers are

organized into ______. These tissues havespecific functions and serve specificpurposes.


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Phylum Cnidaria

Two Cell Layers

A jelly-like substance, the__________, separates the twocell layers. The three together make up a body wall

called a _____________cavity that surrounds a centralcavity.


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Phylum Cnidaria

Specialized Structures

Cnidarians are aggressive hunters for food.

They have strong _________ cells whichshorten and lengthen to allow _________of the organism. This movement allows

the tentacles to capture food and allowsthe cnidarian to swim and actively seekprey.


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Phylum Cnidaria


Cnidarians also have specialized stinging cellscalled _________. Cnidocytes contain a coiled

protein strand called a __________. The strandhas poison barbs or spines on it.


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Phylum Cnidaria


When Cnidarians encounter prey, the

cnidocyte fires the nematocyst. Thepoison on the barb of the nematocystparalyzes or kills the prey. The Cnidarian

then draws the strand back in and haulsthe prey in to be digested.


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Phylum Cnidaria

Nerve Net

Cnidarians lack a sophisticated

nervous system but possess a

________. Nerve nets are

considered to be the_______form of a nervous system.


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Phylum Cnidaria

Nerve Net

Nerve impulses cause cell contractions,

but no center for control exists with anerve net. There is _______ or centralnervous system in cnidarians.


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Phylum Cnidaria

Sexual and Asexual Reproduction

Sexual reproduction in the common jellyfish

1. The adult female medusa (free-swimmingform) releases ____ into the water. The adultmale medusa releases ______ into the water.Fertilization is _______.


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Phylum Cnidaria


2. Fertilization results in formation of a________. This stage is sometimes called

the larva or _______. The planula is free-swimming due to the presence of cilia.


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Phylum Cnidaria

Sexual and Asexual Reproduction 3. The planula settles to the ocean floor or any sturdy

surface and develops into a sessile stage called the________.

4. The polyp matures by developing a ________ and__________. As it grows, layers of __________ forminside the ring of tentacles.


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Phylum CnidariaSexual and Asexual Reproduction

5. Medusa _______ and swim off in thewater to mature and release more eggs

and sperm.


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Phylum Cnidaria


Asexual Reproduction in Cnidarians

Asexual reproduction is usually by

_______. Hydra reproduce in thismanner. Small buds are formed on the

exterior of their body.

The buds grow, mature within a few

_____, and fall off the adult form. They

then begin life as independent new

individuals.


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Phylum Cnidaria

Classes of Cnidarians

1. Class Hydrozoa

These include the _____ and the obelia.


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Phylum Cnidaria


2. Class Scyphozoa

This class is composed of ________. The_______ is the dominant body form.


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Phylum Cnidaria


3. Class Anthozoa

____________ and _______ compose Class Anthozoa. The

_______ is the only body form present. Polyps grow assolitary individuals or in colonies.

phylum cnidaria 1

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