1. Phylum Cnidaria

2. Phylum Cnidaria
Cnidarians have special stinging cells called cnidocytes. They have long flexible tentacles and usually live in sea water. Because they have a hollow gut called a__________, they are known as ____________ as well as Cnidarians.
coelenteron
Coelenterates

3. Phylum Cnidaria Characteristics of Cnidarians Body plan
Two cell layers
Specialized structures
Nerve net
Sexual and asexual reproduction

4. Phylum Cnidaria Body Plan Cnidarians generally have _______ symmetry.
radial

5. Phylum Cnidaria Body Plan
Cnidarians live in the ocean and can have one of two different body plans:
_______– free swimming
______- sessile
Medusa
Polyp

6. Phylum Cnidaria Two Cell Layers
Cnidarians are advanced beyond sponges in the development of their cell layers. Although sponges also have two cell layers, in cnidarians the cell layers are organized into ______. These tissues have specific functions and serve specific purposes.
tissues

7. Phylum Cnidaria Two Cell Layers
A jelly-like substance, the__________, separates the two cell layers. The three together make up a body wall called a _____________cavity that surrounds a central cavity.
mesoglea
gastrovascular

8. Phylum Cnidaria Specialized Structures
Cnidarians are aggressive hunters for food. They have strong _________ cells which shorten and lengthen to allow _________ of the organism. This movement allows the tentacles to capture food and allows the cnidarian to swim and actively seek prey.
contractile
movement

9. Phylum Cnidaria Specialized Structures
Cnidarians also have specialized stinging cells called _________. Cnidocytes contain a coiled protein strand called a __________. The strand has poison barbs or spines on it.
cnidocytes
nematocyst

10. Phylum Cnidaria Specialized Structures
When Cnidarians encounter prey, the cnidocyte fires the nematocyst. The poison on the barb of the nematocyst paralyzes or kills the prey. The Cnidarian then draws the strand back in and hauls the prey in to be digested.

11. 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.
nerve net
simplest

12. Phylum Cnidaria Nerve Net
Nerve impulses cause cell contractions, but no center for control exists with a nerve net. There is _______ or central nervous system in cnidarians.
no brain

13. Phylum Cnidaria Sexual and Asexual Reproduction
Sexual reproduction in the common jellyfish
1. The adult female medusa (free-swimming form) releases ____ into the water. The adult male medusa releases ______ into the water. Fertilization is _______.
eggs
sperm
external

14. Phylum Cnidaria Sexual and Asexual Reproduction
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.
blastula
planula

15. 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 __________ form inside the ring of tentacles.
polyp
mouth
medusae
tentacles

16. Phylum Cnidaria Sexual and Asexual Reproduction
5. Medusa _______ and swim off in the water to mature and release more eggs and sperm.
break free

17. Phylum Cnidaria Sexual and Asexual Reproduction
Asexual Reproduction in Cnidarians
Asexual reproduction is usually by
_______. Hydra reproduce in this
manner. 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.
budding
days

18. Phylum Cnidaria Classes of Cnidarians 1. Class Hydrozoa
These include the _____ and the obelia.
hydra

19. Phylum Cnidaria Classes of Cnidarians 2. Class Scyphozoa
This class is composed of ________. The _______ is the dominant body form.
jellyfish
medusa

20. Phylum Cnidaria Classes of Cnidarians 3. Class Anthozoa
____________ and _______ compose Class Anthozoa. The _______ is the only body form present. Polyps grow as solitary individuals or in colonies.
Sea anemones
corals
polyp