Invertebrate Diversity and Classification

These flashcards provide definitions for key vocabulary terms and concepts related to invertebrate biology, classification, and anatomy based on the lecture transcript.

Diploblast

An organism that develops from two embryonic germ layers: the endoderm and ectoderm.

Triploblast

An organism that develops from three embryonic germ layers: the endoderm, ectoderm, and mesoderm.

Protostomes

A group of animals in which the blastopore, or the point of invagination of the ectoderm, becomes the mouth.

Deuterostomes

A group of animals in which the blastopore becomes the anus, and the mouth develops secondarily.

Acoelomate

An organism that lacks a body cavity between the digestive cavity and the outer body wall, such as flatworms.

Eucoelomate

An organism with a true coelom (body cavity) completely lined with mesoderm, such as annelids, mollusks, and arthropods.

Pseudocoelomate

An organism with a body cavity that is not completely lined by tissue derived from mesoderm, such as roundworms.

Segmentation

The repetition of body segments, which serves as a gateway to more diverse body plans, as seen in the human vertebral column or the $170$ segments of the female Illacme plenipes.

Hox genes

Homeotic genes that provide genetic control over early embryonic development and determine the identity of body segments.

Cephalization

The evolution of a concentration of nervous tissues and sensory organs at the anterior end of a bilaterally symmetrical organism.

Lophophore

A feeding apparatus consisting of a ring of cilia around the mouth, found in some members of the superphylum Lophotrochozoa.

Trochophore

A larval stage characterized by two bands of cilia around the body, found in certain members of the superphylum Lophotrochozoa.

Flame cells

A synapomorphy of the Phylum Platyhelminthes used for physiological processes in these acoelomate worms.

Monoecious

An organism possessing both male and female reproductive organs; also known as a hermaphrodite.

Visceral mass

The region in mollusks that contains most of the internal organs.

Mantle

A fold of tissue over the visceral mass in mollusks that secretes a calcium-carbonate-hardened shell for protection.

Radula

An abrasive tongue-like structure used by most mollusks to scrape up food particles.

Polyplacophora

A class of marine mollusks, commonly called chitons, characterized by a shell made of eight plates.

Bivalvia

A class of mollusks, including clams and oysters, that are enclosed in two-part valves or shells and are mostly sessile filter-feeders.

Cephalopoda

A class of exclusively marine mollusks, including octopuses and squids, featuring a prominent head and tentacles modified from the foot.

Setae (or chaetae)

Bristle-like structures made of chitin found in the Phylum Annelida.

Clitellum

A specialized, protruding segment with different coloration in earthworms that aids in reproduction.

Ecdysis

The physiological process of shedding the old outer cuticle or exoskeleton, which occurs in the superphylum Ecdysozoa.

Chitin

A complex carbohydrate found in the cuticle of nematodes and the exoskeleton of arthropods.

C. elegans

A free-living soil nematode used as a model organism in cell biology, notable for being the first multicellular organism to have its entire DNA sequenced.

Tagmata

Functional groups of body segments in arthropods, such as the head, thorax, and abdomen.

Hemocoel

The central body cavity in arthropods where hemolymph bathes the cells in an open circulatory system.

Malpighian tubules

Excretory structures used by insects to remove nitrogenous waste and regulate salt concentration.

Hexapoda

A subphylum of arthropods, including insects, characterized by having three pairs of jointed appendages.

Myriapoda

A subphylum of arthropods including centipedes (Chilopods) and millipedes (Diplopoda), characterized by numerous legs.

Biramous

Two-branched appendages typical of crustaceans and trilobites, considered the ancestral condition in arthropods.

Chelicerae

The first pair of appendages in the subphylum Chelicerata, which serve as specialized claw-like or fang-like mouthparts.

Pentaradial symmetry

The symmetry found in adult echinoderms where arms are arrayed in multiples of five around a central axis.

Water vascular system

A network of fluid-filled canals in echinoderms derived from the coelom that controls gas exchange, feeding, and locomotion via tube feet.

Notochord

A flexible, rod-like structure found in all chordates at some point during their life cycle.