Cnidaria

Question 1

Hydrostatic skeleton

Answer 1

Formed from a fluid filled and closed cavity surrounded by a body wall containing muscles oriented in different directions. Muscular contractions maintain the rigid form or change the shape of the organisms allowing movement.

Question 2

Hydrozoa

Answer 2

class of organisms that have the polyp and medusa, hydromedusae, in their life cycle. Almost all are carnivorous marine animals and they form colonies of interconnected polyps encrusted on the substrate making them appear more like plants than animals.

Question 3

Incomplete digestive system

Answer 3

An incomplete digestive system consists of a digestive cavity with one opening. The single opening serves as both mouth and anus.

Question 4

Incomplete septa

Answer 4

when one end of the septa attaches to the body wall but their free ends are suspended and are armed with cnidocytes to help immobilize ingested prey.

Question 5

Medusa

Answer 5

The freeswimming, mobile stage of the cnidarian life cycle. This stage, when present, is reproductive and mature gonads form on either male or female medusae. A common example is the jellyfish.

Question 6

Mesoglea

Answer 6

The jellylike layer found between the ectodermal and endodermal cell layers of diploblastic organisms. It acts as a type of cement holding the two layers together but, unlike mesenchyme, has few, if any, cells.

Question 7

Myoneme

Answer 7

Strands of contractile myofibers found in single cells. These allow the cell, or a portion of the cell, to contract in length and change its shape.

Question 8

Nematocyst

Answer 8

This organelle is part of the cnidocyte unique to the Cnidarians. It is the stinging, or eversible, portion of the cell, and it can drill into, entangle, and or stick to potential prey.

Question 9

Nerve net

Answer 9

The nerve net is the simplest form of a nervous system found in multicellular organisms. Unlike central nervous systems where neurons are typically grouped together, neurons found in nerve nets are found spread apart. This nervous system allows cnidarians to respond to physical contact.

Question 10

Nutritive muscular cells

Answer 10

inner circular muscle of the hydroskeleton.

Question 11

Oral surface

Answer 11

surface of the oral opening

Question 12

Oral aboral axis

Answer 12

The axis of the body down which symmetry is defined.

Question 13

Pedalia

Answer 13

The flat, enlarged base of the tentacles in some cnidarians, usually the cubozoans.

Question 14

Pigment cup

Answer 14

contains photoreceptors that are sensitive to light. The organisms uses this to tell the direction of the light.

Question 15

Planula larva

Answer 15

A planula is the solid, free swimming larval stage of cnidarians consisting of two cell layers an outer ciliated ectoderm and an inner endoderm.

Question 16

Polyp

Answer 16

The sessile, asexual stage in the cnidarian life cycle. In some species they are independent organisms. In others, they form colonies where some polyps are involved in food gathering (gastrozooids) and other polyps (gonozooids) produce the reproductive stage.

Question 17

Rhopalium

Answer 17

These sensory structures are found around the bell margin of the jellyfish medusa. They always contain a statocyst for balance and sometimes an ocelli for light detection.

Question 18

Schyphozoa

Answer 18

Class of animal. Jellyfish. Most of the scyphozoan life cycle is spent as a medusa, the short lived polyp is represented in the life cycle by the schyphostome that undergoes transverse fissions, strobilization, to form the strobila from which ephyrae, small immature medusae, are formed.

Question 19

Scyphistoma

Answer 19

The jellyfish, class Scyphozoa, get their name from this unique stage in the life cycle. It is a small polyp existing for only for a short time before developing into a strobila, which then produces the medusa.

Question 20

Septa

Answer 20

Sheets of tissue that separate two compartments or cavities. Singular is septum.

Question 21

Siphonoglyphs

Answer 21

Single or paired ciliated grooves in the oral opening of anthozoans that, along with other features, create the biradial symmetry of the group. The cilia propel water into the gastrovascular cavity.

Question 22

Spermaries

Answer 22

an organ in which spermatozoa are generated.

Question 23

Statocyst

Answer 23

A balance organ that senses gravity. It consists of at least one solid statolith surrounded by sensory cilia. As the position of the organism changes the statolith rolls, stimulating different cilia.

Question 24

Strobilia

Answer 24

Stage in the life cycle of scyphozoan cnidarian formed from transverse fission of the scyphostome and producing the small medusoid ephyra.

Question 25

Strobilization

Answer 25

The process that converts the scyphistoma into a strobila during the life cycle of scyphozoans, jellyfish. Transverse divisions of the strobila produce the small, disc shaped ephyra that develop into the adult jellyfish.

Question 26

Tissue grade

Answer 26

Animals that have tissues but no organ systems. Cnidaria and Ctenophora are examples.

Question 27

Triploblastic

Answer 27

Organisms formed from the three cell layers. (endoderm, ectoderm, and mesoderm.)

Question 28

Velum

Answer 28

A thin flap of tissue found around the inner surface of the bell of a hydrozoans medusa or surrounding the mouth of a cephalochordate.