Exam 7: Cnidarians and Ctenophores

The tall secretory cells around the pedal disc and mouth of Hydra are the ___________ cells.

All ctenophores are marine,and most of them are free-swimming forms.

Most of the hydrozoans are colonial marine animals with both an asexual polyp and a sexual medusa stage in their life cycle.

The neuromuscular system first evolved in the cnidarians.

The medusa of Obelia is the

Coral reefs are limited to areas

The morphological type adapted to a sedentary or sessile life is the _________,and that adapted for floating or free-swimming existence is the _____________.

The radiate animals represent the tissue-organ level of organization.

Ctenophores capture prey by use of

The ______________ are often bioluminescent.

Octocorallian corals include soft corals,sea pansies,sea pens,and sea fans and other gorgonian corals (horny corals).All of these are characterized by strict _________________ symmetry.

In cnidarians,extracellular digestion occurs in the

Radial symmetry benefits animals that actively move in certain directions because they approach their environment from all sides equally.

Most of the zooids of Obelia are feeding polyps called ____________________.

The long threadlike structures that help to overcome prey and provide defense in sea anemones are called _______________.

The central nervous system of cnidarians includes a brain.

Digestion in cnidarians is

The body wall of a Hydra consists of an outer epidermis and an inner gastrodermis with ______________ between them.

Molecular evidence suggests that hydrozoans,scyphozoans,and cubozoans shared a common ancestor with an anthozoan life cycle and a ___________ form later to the life cycle.

A distinguishing characteristic of cubozoan medusae is the presence of a flattened blade called a _________________ at the base of the tentacles.