Phylum Cnidaria

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

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

Phylum Cnidaria Body Plan Cnidarians generally have _______ symmetry. radial

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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