Deuterostomes, Hemichordates, and Echinoderms Practice Flashcards

A set of vocabulary flashcards based on the lecture notes regarding the characteristics and classification of Deuterostomes, specifically Hemichordates and Echinoderms.

Bilateria

A group of animals characterized by bilateral symmetry, being generally triploblastic, and possessing a complete digestive tract with a mouth and an anus.

Protostomes

Animals in which the blastopore formed during gastrulation develops into the mouth; the name means "mouth first."

Deuterostomes

Animals in which the blastopore formed during gastrulation develops into the anus; the name means "mouth second."

Coelom

An internal body cavity full of fluid that is lined with a layer of tissue called peritoneum.

Peritoneum

A layer of tissue that lines the coelom and also covers the internal organs.

Hemichordates (Hemichordata)

A phylum of bilaterally symmetrical animals containing approximately $120$ species, divided into classes Enteropneusta and Pterobranchia.

Enteropneusta

A class of Hemichordates known as acorn worms that live in marine muddy substrates and can grow up to $2$ meters long.

Proboscis

A sticky structure in acorn worms used to capture prey, which is then conveyed to the mouth using cilia.

Echinoderms (Echinodermata)

A phylum of marine animals whose larvae have bilateral symmetry but whose adults typically exhibit pentaradial symmetry.

Pentaradial symmetry

Symmetry in $5$ or multiples of $5$, which is characteristic of adult echinoderms.

Water vascular system

Also called the "ambulacral system," this is a network of water-filled canals in echinoderms used for gas exchange, locomotion, and feeding.

Madreporite

The structure through which water enters the water vascular system of an echinoderm.

Crinoidea

A class of echinoderms including sea lilies and feather stars that are suspension feeders and can be sessile or vagile.

Asteroidea

A class of echinoderms known as starfish, which typically have $5$ arms, a mouth facing downward, and often act as keystone species.

Keystone species

A term coined by Robert Paine referring to a species that has a large ecological effect relative to its abundance, such as the starfish $Pisaster ochraceus$.

Trophic cascades

Strong but indirect top-down effects in a community, a term named by Robert Paine following his starfish removal experiments at Mukkaw Bay.

Ophiuroidea

A class including brittle stars and basket stars characterized by a disk containing all internal organs, $5$ toothed jaws, and the absence of an anus.

Echinoidea

A class including sea urchins and sand dollars, featuring a test composed of fused plates of calcium carbonate.

Aristotle’s lantern

The specialized jaw apparatus found in the mouth of sea urchins.

Holothuroidea

A class of echinoderms known as sea cucumbers that are detritivorous or suspension feeders and have the mouth and anus at opposite poles.

Cuvierian tubules

Sticky tubules that some sea cucumbers can expel through their anus as a defense mechanism when they come in contact with seawater.

Holothurin

A toxic saponin compound found in many sea cucumbers that helps reduce predation.