Invertebrate Diversity and Classification

Comprehensive practice flashcards covering terms, definitions, and synapomorphies of invertebrate phyla and developmental biology based on the lecture notes.

Synapomorphy

A shared derived character or trait that distinguishes a clade from other organisms.

Diploblast

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

Triploblast

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

Protostomes

A group of animals in which the blastopore develops into the mouth.

Deuterostomes

A group of animals in which the blastopore develops into the anus.

Acoelomate

An animal that lacks a body cavity, such as flatworms.

Eucoelomate

An animal with a true coelom (body cavity) lined by mesoderm, found in annelids, mollusks, arthropods, echinoderms, and chordates.

Pseudocoelomate

An animal with a body cavity that is not completely lined by mesoderm, such as roundworms.

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, characteristic of some Lophotrochozoans.

Trochophore

A larval stage characterized by two bands of cilia around the body.

Phylum Platyhelminthes

A phylum of flatworms characterized by bilateral symmetry, cephalization, spiral cleavage, and the presence of flame cells.

Flame cells

A synapomorphy of Phylum Platyhelminthes used for excretion or osmoregulation.

Monoecious

Organisms that are hermaphroditic, possessing both male and female reproductive organs.

Radula

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

Mantle

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

Setae (or chaetae)

Bristle-like structures made of chitin found in annelids.

Clitellum

A specialized protruding segment in earthworms that aids in reproduction.

Ecdysis

The physiological process of shedding the old exoskeleton, often called molting.

Phylum Nematoda

True roundworms that are non-segmented, possess a chitinous cuticle, and have a complete digestive system.

C. elegans

A free-living soil nematode used as a model organism to study cell biology, genetics, and development; the first multicellular organism to have its entire DNA sequenced.

Tagmata

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

Hemolymph

The analogue of blood in arthropods that circulates through an open circulatory system and bathes the cells.

Hemocoel

The central body cavity in arthropods containing hemolymph.

Biramous

A type of appendage that is two-branched, considered the ancestral condition in arthropods.

Chelicerae

Specialized claw-like or fang-like pinching mouthparts found in the subphylum Chelicerata.

Pentaradial symmetry

A form of radial symmetry found in adult echinoderms where body parts are arrayed in multiples of five around a central axis.

Water vascular system

A network of hydraulic fluid-filled canals used by echinoderms for locomotion, gas exchange, and feeding.

Phylum Chordata Synapomorphies

The four features all chordates possess at some point: dorsal hollow nerve cord, notochord, post-anal tail, and pharyngeal gill slits.

Urochordata (Tunicata)

A subphylum of chordates commonly called sea squirts, which are marine filter feeders with sac-like bodies and siphons.

Cephalochordata

A subphylum of chordates commonly called lancelets, in which adults retain all four chordate characteristics.