Chapter 31 Protostome Animals

Protostome

An organism whose first embryonic opening, the blastopore, becomes the mouth, characterized by bilateral symmetry and three germ layers.

Lophotrochozoan

A monophyletic group within protostomes that includes phyla such as mollusks and annelids, characterized by the presence of lophophores.

Ecdysozoan

A group of protostomes that grow by molting, shedding their old cuticle to allow for growth.

Lophophore

A feeding structure used in suspension feeding in adults of certain protostome groups.

Trochophore

A type of larva commonly found in marine mollusks and annelids, characterized by a band of cilia.

Metamorphosis

The developmental process in insects involving stages of juvenile forms (nymphs or larvae) and adults.

Coelom

A fluid-filled body cavity lined by mesoderm found in some animal phyla, including annelids.

Hemocoel

An extensive body cavity found in arthropods that acts as part of the circulatory system.

Spiral Cleavage

A type of embryonic development seen in lophotrochozoans, where cell divisions occur at angles to each other.

Radula

A feeding structure found in mollusks, often used for scraping food off surfaces.

Annelids

Segmented worms that are distinguished from flatworms, containing a coelom and a fully developed digestive tract.

Cestoda

A class of flatworms that includes endoparasitic tapeworms, absorbing nutrients through their body wall.

Bivalvia

A class of mollusks that includes clams and oysters, characterized by two-part shells and suspension feeding.

Gastropoda

A class of mollusks including snails and slugs, known for their diverse feeding strategies.

Cephalopoda

A class of mollusks that are intelligent predators with modified feet as arms and tentacles, capable of jet propulsion.

Incomplete Metamorphosis

A form of insect development where juveniles (nymphs) resemble smaller adults.

Complete Metamorphosis

A form of insect development characterized by a distinct larval stage that differs significantly from the adult form.

Ecdysozoan Growth

The process by which ecdysozoans grow by molting their outer cuticle or exoskeleton.

Nematoda

A phylum of roundworms, many of which are parasitic.

Adaptation Radiation

The evolution of diverse forms from a common ancestor in response to the development of new habitats or environmental changes.

Body Compartmentalization

The division of an organism's body into distinct regions that can evolve and function independently.