Chapter 31- Protostome Animals

Insects

________ have three tagmata- a head, thorax, and abdomen.

Roundworms

________ are unsegmented worms with a pseudocoelom, a tube- within- a- tube body plan, no appendages, and an elastic cuticle that is molted during growth.

Chelicerates

________ are named for a pair of claw like appendages called chelicerae, located near the mouth.

trochophore larva

A(n) ________ has a ring of cilia around its middle.

anterior end

At the ________ of the visceral mass, the mouth has a unique molluscan feeding structure called a radula, which functions like a rasp or file.

digestive tract

Unlike flatworms, most annelids have a coelom, a fully developed ________ with a mouth and an anus, and a segmented body.

compound eye

A(n) ________ contains many lenses, each associated with a light- sensing, columnar structure.

Flatworms

________ are named for the broad, flattened shape of their bodies.

Protostomes

________ such as mollusks and arthropods have relatively compartmentalized body plans- their bodies are divided into different regions with different functions.

Lophophore

________ is a specialized structure that rings the mouth and functions in suspension feeding.

Mollusks

________ are a highly diverse monophyletic group of lophotrochozoans, comprising more than 85, 000 species.

visceral mass

The mantle, an outgrowth of the body wall that covers the ________, forming an enclosure called the mantle cavity.

bivalves

In ________, the mantle is lined with muscle and forms tubes called siphons.

Myriapods

________ have relatively simple bodies- a head region and a long trunk featuring a series of many segments, each bearing either one pair of legs or two pairs of legs.

ecdysozoans

All ________ grow intermittently by molting- that is, by shedding an exoskeleton or external covering.

Crustaceans

________ live primarily in marine and freshwater environments, where they play important ecological roles.

cuticle

During a molt, an individual sheds its outer layer, or ________- called an exoskeleton if it is hard- and slips out of it.

Adaptation

________ is a heritable trait that increases the fitness (reproductive success) of individuals in a particular environment.

Adaptive radiation

________ is a period of rapid speciation resulting in a large number of descendant species that have adapted to a variety of habitats.

visceral mass

The ________ often includes one or two external gas exchange structures called gills.

Visceral mass

________, the region containing the main organ systems.

The common ancestor of the annelids had a key synapomorphy in addition to segmentation

bristle-like extensions called chaetae that extend from lobe-like appendages called parapodia