5.2.2. Cnidaria Flashcards by Jasmine Marta

_____and ____ are the simplest living animals with true tissues and thus form the base of the evolutionary group _____—the “true animals; nearly all marine, with only a few known freshwater species of cnidarians

Cnidarians and ctenophores

Eumetazoa

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Cnidaria is derived from the unique stinging cells, called ____, present on the body and tentacles of the members of this group.

cnidocytes

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____ are commonly called comb jellies (or comb jellyfish)due to the presence of eight ciliated bands superficially resembling combs that encircle the body.

Ctenophores

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“comb bearers”

Ctenophores

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Ctenophores exchange gas through ___

simple diffusion

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_____

-are nearly all carnivorous but do not actively pursue their prey.
-have ____symmetry
-lack any definite concentration of nervous tissue or sensory organs.
possess a _____ (majority nonpolarized) that connects the uniformly distributed sensory cells and motor neurons to enable a limited number of coordinated movements and behaviors through innervations of the longitudinal and circular “muscle” cells.
-___ arrangement, consisting of an outer epidermis and an inner gastrodermis.

Cnidarians
radial
nerve net
diploblastic

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Cnidarians have two basic body forms____ and ____

polyps and medusae

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gelatinous layer between epidermis and inner gastrodermis

mesoglea

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central digestive cavity in gastrodermis; has only a single opening (mouth) for ingesting and excreting

gastrovascular cavity

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-represented by a cylindrical organism that remains attached to the substrate by a short stalk and has a mouth that faces away from the substrate (usually upward).

polyp

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______- more circular, umbrella shaped form with a mouth on the underside; generally are free floating with tentacles that hang downward, surrounding the mouth; body shape is maintained to some degree by the viscosity of the gelatinous mesoglea and by the regulation of fluid in the gastrovascular cavity, an example of a ____.

medusa

hydrostatic skeleton

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In _____ the polyp is the predominant form in the life cycle

hydrozoans

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Hydrozoans (Class Hydrozoa)

asexual reproduction in the ____ form and sexual reproduction in the ____ form
___ is the predominant body form

polyp; medusa

polyp

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polyps are assembled into colonies

Obelia

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____-do not produce medusae; exist as single, mobile polyps that reproduce either sexually (through production of sperm and eggs) or asexually (through budding) producing a new polyp

Hydra

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the defining characteristics of cnidarians
use these tiny cells both for capturing prey and also as a deterrent to predators
line the tentacles and outer surface of the cnidarian body.

Cnidocytes

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-a stinging capsule within each cnidocyte

Nematocyst

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connected by branches of a common gastrovascular cavity (coenosarc), making them all part of a larger functioning body.

Colonial hydrozoans- Members of the genus Obelia

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This cooperative venture allows certain polyps to develop into highly specialized feeding polyps, and others to lose the ability to feed altogether in exchange for an enhanced ability to reproduce.

Coenosarc

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____illustrates an alternation of the sexual (medusa)and asexual (polyp) stages commonly seen in hydrozoans.

Obelia

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Each zygote develops into a ciliated, swimming ____ that settles to the bottom of the ocean floor, attaches itself to the substrate, and begins to create a new generation of polyps through asexual budding.

planula larva

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thick layer of gelatinous mesoglea

True Jellyfish (Class Scyphozoa)

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largest scyphozoans

Cyanea-

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In _____, the medusa stage is dominant, with the polyp stage relegated to an inconspicuous, short lived larval form that matures quickly into a polyp that buds off young medusae.

Cyanea

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- moon jellyfish; common genus

Aurelia

_____ are represented by sessile organisms in the ____ stage, existing as solitary individuals (sea anemones) or as true colonies of dozens to thousands of individuals (corals) life cycle does not include a free swimming ___ stage. the most numerous and most specialized

Anthozoans polyp medusa

- common North Atlantic sea anemone

Metridium

species of small, marine invertebrates with transparent, bioluminescent, gelatinous bodies commonly referred to as ____” “sea walnuts,” or simply ctenophores.

“comb jellies,

is derived from the unique distinguishing characteristic that all members of the phylum possess—eight rows of evenly spaced ciliated bands (_____) that encircle the body longitudinally most species possess either a pair of tentacles or oral lobes that are used to collect food but lack the ____ these carnivorous predators capture prey by discharging a ____ from specialized cells have a decentralized nerve net without a brain, and the body wall is composed of two layers: an ___ and ___

``` Comb jellies phylum Ctenophora comb plates stinging cnidocytes sticky adhesive outer epidermis and inner gastrodermis ```

Do/Are Comb jellies ____ have a complete digestive system? monoecious (hermaphroditic)/ dioecious?

Yes. they have complete digestive system | monoecious

- gelatinous layer similar to mesoglea sandwiched between the two tissue layers.

collenchyme

-an animal’s response to stimuli in its environment

Behavior

-basic physiological unit of behavior; consists of sensory structures, neurons, and muscles (or glands) whose actions are coordinated to bring about certain behaviors.

motor system

-is the series of immediate physiological events that led up to the specific behavior; explaining how the behavior occurs

proximate cause

-the resultant selective advantages that have promoted that behavior to remain in the animal’s repertoire of possible responses and to evolve over time; explaining why the behavior exists

ultimate cause

Give four major classes of cnidarians

Hydrozoa Scyphozoa Cubozoa Anthozoa

Complete the words (Hint: representatives/examples) Hydrozoa: H___, O____, P____ Scyphozoa: J___ (Aurelia) Cubozoa: Box jellyfish (C____) Anthozoa: S____ (Metridium), c____, sea fans

Hydra, Obelia, Portuguese man of war Jellyfish (Aurelia) (Chironex) Sea anemones (Metridium), corals, sea fans

Alternation of polyp and medusa stages in most species, medusa has velum, mostly marine with a few freshwater species, colonial or solitary

Hydrozoa

Solitary, free floating medusa most prominent form, medusa without velum, mostly marine, mesogleal layer generally thick

scyphozoa

Solitary, free swimming, medusa most prominent form, medusa has velarium (similar to hydrozoan velum), small body (generally 2–3 cm) with square shaped bell, tropical or subtropical

Cubozoa

No medusa stage—polyp stage predominates life cycle, entirely marine, may be colonial or solitary, gastrovascular cavity divided by septa into chambers to increase digestive surface area

Anthozoa

(Hydra anatomy) Defense and prey capture

Tentacles

(Hydra anatomy) Ingestion of food and elimination of indigestible particles (egestion)

Mouth

(Hydra anatomy) Elevated mound of tissue that expands or contracts to regulate size of mouth opening

Hypostome

(Hydra anatomy) Specialized stinging cells located in the epidermal layer of the tentacles and body wall

Cnidocytes

(Hydra anatomy) Chamber within which extracellular digestion of prey occurs; only opening is through the mouth

Gastrovascular cavity

(Hydra anatomy) Product of asexual reproduction; will fall off when mature and become a self sufficient organism

Bud

(Hydra anatomy) Organs for sexual reproduction; Hydra are dioecious, meaning that an organism has either testes or ovaries (male or female), but not both

Gonads (testes and ovaries)

(Hydra anatomy) Specialized region for attachment to the substrate

Basal disc

(Hydra anatomy) Outer tissue layer; specialized for protection

Epidermis

(Hydra anatomy) Inner tissue layer; specialized for digestion

Gastrodermis

(Hydra anatomy) Inert, acellular, jellylike substance that aids in supporting the body

Mesoglea

(Anatomy of Obelia) Polyp specialized for food acquisition

Hydranth (feeding polyp)

(Anatomy of Obelia) Polyp Polyp specialized for reproduction

Gonangium (reproductive polyp)

(Anatomy of Obelia) Polyp Product of asexual reproduction;medusae will be released from the gonangium when mature and will produce either sperm or eggs, which fuse with the respective gamete forming a zygote that will develop into a new polyp

Medusa buds

(Anatomy of Obelia) Polyp Common chamber within which extracellular digestion occurs; nutrients are distributed throughout organism

Coenosarc

(Anatomy of Obelia) Polyp Translucent outer covering of organism; serves protective function

Perisarc

(Anatomy of Obelia) medusae Stalk of fleshy tissue that supports the mouth

Manubrium

State the structures in the Polyp of Obelia (7) and Medusa of Obelia(4)

Polyp: Hydranth (feeding polyp); Tentacles; Hypostome; Gonangium (reproductive polyp); Medusa buds; Coenosarc; Perisarc Medusa: Tentacles: Manubrium; Mouth; Gonads

(Anatomy of Aurelia) Provide sensory information and used in defense and locomotion

Marginal tentacles

(Anatomy of Aurelia) Defense and prey capture

Oral arms

(Anatomy of Aurelia) One of four divisions of the gastrovascular cavity for digestion of food

Gastric pouch

(Anatomy of Aurelia) Extensions of the gastric pouches that radiate outward from the pouches and distribute nutrients through out body

Radial canals

(Anatomy of Aurelia) Circular extension of the gastric pouches that distributes nutrients to outer rim of jellyfish

Circular canal

(Anatomy of Metridium) Raised portion of the mouth (equivalent to the hypostome of hydrozoans)

Oral disc

(Anatomy of Metridium) Pore that allows circulation of fluids between adjacent body sections

Ostium

(Anatomy of Metridium) Muscular portion of the gastrovascular cavity for pulling prey inward and expelling indigestible particles

Pharynx

(Anatomy of Metridium) Expand and contract the body

Retractor muscles

(Anatomy of Metridium) Specialized chamber for extracellular digestion of prey

Gastrovascular cavity

(Anatomy of Metridium) One of six thin, vertical walls that divides body into sections, providing support and increased surface area for digestion

Primary septum

(Anatomy of Metridium) One of several thin, incomplete vertical walls that further subdivides body, providing support and increased surface area for digestion

Secondary septum

(Anatomy of Metridium) Tough, fleshy base that attaches organism to rocks or sandy ocean floor; most anemonescan use this to move slowly, gliding along the ocean floor

Pedal disc

(Anatomy of Metridium) Contain cnidocytes and may be extended through the mouth to aid in subduing live prey or to provide additional defense against predators

Acontia