Studied by 2 peopleInsects
________ 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
Note 
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