Animals: Protostomes and Ecdysozoa

These flashcards cover key vocabulary terms and definitions related to animals classified within protostomes, particularly focusing on the characteristics and classification of ecdysozoans.

Ecdysozoa

A superphylum that includes animals undergoing molting, characterized by a tough cuticle.

Molting (Ecdysis)

Periodic shedding of the cuticle, allowing for growth, regulated by hormones.

Cuticle

A tough, flexible exoskeleton secreted by the outermost cell layer that prevents desiccation and protects from predators.

Nematodes

Also known as roundworms, a phylum within Ecdysozoa with over 28,000 species, many of which are parasitic.

Pseudocoelomates

Organisms with a body cavity that is not completely lined with mesoderm, as seen in nematodes.

Dioecious

Species that have separate male and female organisms.

Monoecious

Species that have both male and female reproductive organs in the same individual.

Arthropoda

The most diverse animal phylum, characterized by jointed appendages and an exoskeleton.

Chelicerata

A subphylum of arthropods including horseshoe crabs and spiders, defined by the presence of chelicerae.

Biramous appendages

Appendages that are forked into two branches, characteristic of crustaceans.

Hexapoda

A subphylum of arthropods that includes insects, characterized by three body segments and six legs.

Incomplete metamorphosis

A life cycle in which insects develop through nymph stages resembling adults without a pupal stage.

Complete metamorphosis

A life cycle with distinct stages: egg, larva, pupa, and adult, involving significant morphological change.

Endopterygota

A clade of insects undergoing complete metamorphosis, such as butterflies and beetles.

Jointed appendages

Characteristic limbs of arthropods that provide flexibility and mobility, absent in other ecdysozoans.

Epicuticle

The thin, waxy outer layer of the arthropod cuticle that prevents water loss.

Chitin

The primary component of the exoskeleton in arthropods, providing strength and protection.

Fossil Ecdysozoan

Remains of animals from the Cambrian period, dating back to 535 million years ago.

Common ancestor

The hypothetical shared ancestor from which all ecdysozoans are believed to have evolved.

Gas exchange in crustaceans

Small crustaceans diffuse gas through their cuticle, while larger ones utilize gills for respiration.

Terrestrial adaptation of grasshoppers

Grasshoppers exhibit internal fertilization and incomplete metamorphosis, adapting them to life on land.