Chapter 33 - An Introduction to Invertebrates

Digestion

________ starts in the gastrovascular cavity and ends inside food vacuoles in the gastrodermis cells.

Nematocysts

________ are specialized cnidae with a stinging thread that may pierce the body wall of the cnidarian's victim.

hard calcareous plate

A thin skin covers a(n) ________ endoskeleton, and most species are prickly due to skeletal ridges and spines.

mesoglea

The ________ is a gelatinous layer that sits between the epidermis and the gastrodermis.

Bundles of microfilaments

________ organized into contractile fibers are seen in the epidermis (outer layer) and gastrodermis (inner layer) cells.

exterior components

Most adult echinoderms 'internal and ________ radiate from the center, generally in the form of five spokes.

sexual reproduction

Echinoderm ________ often involves distinct male and female individuals who release their gametes into the sea.

water vascular system

The ________ is unique to echinoderms, consisting of a network of hydraulic canals branching into tube feet that act in movement and feeding.

Sea stars

________ (also known as starfish) and the majority of other echinoderm groupings (from the Greek urchin, spiny, and derma, skin) are slow- moving or sessile aquatic creatures.

Cnidarians

________ come in polyp and medusa forms.

fundamental body design

A cnidarian's ________ is a sac containing a central digestive compartment, the gastrovascular cavity.

Echinoderms

________ originated from bilaterally symmetrical ancestors, although most species seem to be radially symmetrical at first glance.

Hydras

________ and sea anemones are two examples of polyps.

larva

A(n) ________ grows into a sessile adult after landing on a suitable substrate.

gastrovascular cavity

The ________ serves as a hydrostatic skeleton against which the contractile cells can function.

sequential hermaphroditism

Almost all sponges display ________, which means they operate as one sex first and subsequently as the other.

Water

________ is pulled into a central cavity through the pores.

nematocyst

The ________, which includes a coiled thread, is found in this kind of cnidocyte.

Cnidarians

________ have contractile tissues and nerves in their most basic forms.

Sponges

________ are filter feeders, meaning they filter out food items floating in the surrounding water as they pull it through their body, which resembles a sac perforated with holes in certain species.