Question 1

The nervous system of enteropneusts is __________ in origin.

Accepted Answer

The nervous system of enteropneusts (acorn worms) is ectodermal in origin, meaning it develops from the ectoderm, the outermost layer of cells or tissue of an embryo in early development.

Question 2

The common name acorn worm is derived from the appearance of the __________ of these worms.

Accepted Answer

The common name "acorn worm" comes from the shape of the proboscis of these worms, which resembles an acorn.

Question 3

The circulatory system of enteropneusts sends blood anteriorly into a series of sinuses called the __________,that may filter excretory wastes.

Accepted Answer

The circulatory system of enteropneusts sends blood anteriorly into a series of sinuses called the glomerulus, which may filter excretory wastes.

Question 4

The ciliated larva of an acorn worm is called the

Accepted Answer

The ciliated larva of an acorn worm is called a tornaria. The other options are larval stages of other marine invertebrates.

Question 5

The water vascular system of echinoderms carries out many functions that are distributed through multiple systems in other animals.Which of the statements below are valid comparisons between the functions of the water vascular system and similar functions in arthropods? Check all that apply.

Accepted Answer

The water vascular system of echinoderms carries out many varied functions that are distributed through multiple systems in most other animals.These functions include attachment,locomotion,exchange of gases and wastes,sensory perception,and feeding.

Question 6

Ambulacrarians and chordates are united into the clade Deuterostomia.In addition to sharing deuterostome characters like radial cleavage and an anus that forms in the region of the embryonic blastopore,the validity of the clade is supported by a wealth of molecular evidence.Another synapomorphy was once considered to be uniquely chordate,but now it is thought to have evolved very early in the deuterostome lineage and then lost in the echinoderm branch.This character is

Accepted Answer

Pharyngeal slits are a synapomorphy once considered unique to chordates, but it is now believed to have evolved early in the deuterostome lineage and later lost in the echinoderm branch.

Question 7

Echinoderms and hemichordates are more closely related to mammals than to crabs and shrimp.Indicate below if this statement is True or False,followed by the correct reasoning for that answer.Check all of the answer choices that apply.

Accepted Answer

Echinoderms,hemichordates and chordates (including mammals)share deuterostome characteristics including radial cleavage and an anus that forms in the region of the blastopore.The relationship is also supported by molecular evidence.

Question 8

Enteropneusta are wormlike as adults and pterobranchia live attached to the substrate.Which of the following are similarities that warrant their inclusion in the common phylum Hemichordata? Check all that apply.

Accepted Answer

Enteropneusta and pterobranchia are taxa within the Hemichordata.Even though they are superficially dissimilar in adult body forms they share the following characters: ciliated pharyngeal slits,tripartite coelom,dorsal nervous system,and bodies divided into three regions.Their feeding mechanisms are quite different.Pterobranchs are ciliary suspension feeders,and enteropneusts use their proboscis (and the mucus it secretes)to feed on detritus within the substrate.

Question 9

Synchronous spawning by enteropneusts suggests the presence of

Accepted Answer

Synchronous spawning suggests that the enteropneusts are communicating with each other through the use of pheromones, indicating the presence of some sort of chemical signaling for reproduction. This makes choice E, "pheromones," the best answer option. The other choices are not as applicable or relevant to this situation.

Question 10

Nutritionally,pterobranchs are

Accepted Answer

Pterobranchs are filter feeders, which means they obtain their nutrition by filtering tiny particles and microorganisms from the water. They have specialized structures called tentacles that are used to capture food, similar to other filter feeders like barnacles and bivalves.

Question 11

Exchange of respiratory gases in enteropneusts is accomplished at the pharyngeal slits and by

Accepted Answer

Enteropneusts do not possess specialized respiratory organs like lungs or gills. Instead, they exchange respiratory gases by simple diffusion across their body wall and also through the pharyngeal slits. These pharyngeal slits are openings in the pharynx (throat) which function in feeding as well as gaseous exchange. Therefore, option C, diffusion across the body wall, is the best choice.

Question 12

Coiled masses of fecal material called __________ are deposited on the substrate at one of the openings of the burrow of an enteropneust.

Accepted Answer

Castings are coiled masses of fecal material that are a characteristic after-effect of enteropneust burrowing.

Question 13

Sea daisies were formerly assigned to a class of their own.They have been recently assigned to the echinoderm class

Accepted Answer

Sea daisies have been reclassified into the class Asteroidea, which is the same class as starfish. This reclassification is based on similarities in their morphology and genetic makeup, aligning them more closely with starfish than with other echinoderm classes.

Question 14

Enteropneusta and Pterobranchia are classes of animals within the phylum Hemichordata.Which of the following characters could be used to distinguish between members of these two classes?

Accepted Answer

Enteropneusta (acorn worms) are primarily deposit feeders, ingesting sediments and extracting nutrients, while Pterobranchia (pterobranchs) are filter feeders, using their tentacles to capture food particles from the water. This feeding method is a key distinguishing characteristic between the two classes within the phylum Hemichordata.

Question 15

Most modern echinoderms assume a mouth-down feeding and locomotion posture.Members of the class Crinoidea are an exception.They are attached,mouth-up,and feed using tube feet to trap food from the water column.Recent molecular analyses show the Crinoidea to be basal to other extant classes.Which of the following help to explain these observations?

Accepted Answer

The observation that members of the Crinoidea class have a mouth-up posture and feed using tube feet to trap food from the water column can be explained by the possibility that this is an ancestral character, and the mouth-down posture evolved secondarily in other echinoderm classes. This is supported by recent molecular analyses that show the Crinoidea to be basal to other extant classes.

Question 16

Members of the phylum __________ include acorn worms and pterobranchs.

Accepted Answer

Acorn worms and pterobranchs belong to the phylum Hemichordata. Echinodermata includes starfish, sea urchins, and sea cucumbers. Echiura is a phylum that includes spoon worms. Chordata includes vertebrates such as mammals, birds, and reptiles. Pogonophora is a phylum that includes deep-sea tube worms.

Question 17

Which of the following is a characteristic of animals in the phylum Hemichordata?

Accepted Answer

Animals in the phylum Hemichordata possess ciliated pharyngeal slits, which are a synapomorphy for all members of the deuterostome lineage.

Question 18

Which is the only class of echinoderms where the oral surface is not oriented to the substrate?

Accepted Answer

Crinoidea, which includes sea lilies and feather stars, is the only class of echinoderms where the oral surface (the mouth side) is oriented upwards rather than towards the substrate. This is unlike other echinoderms, where the oral surface typically faces the substrate.

Question 19

Acorn worms belong to the class

Accepted Answer

Acorn worms belong to the class Enteropneusta, which are a group of worm-like marine animals that have a unique feeding structure called a proboscis. Ascidacea, Pterobranchia, and Thaliacea are all different classes of marine animals. Concentricycloidea is a recently discovered class of deep-sea echinoderms and not related to acorn worms.

Question 20

The anterior region of the digestive tract of enteropneusts contains the gill slits.This region is called the

Accepted Answer

The pharynx is the region of the digestive tract in enteropneusts that contains the gill slits. The buccal cavity is the mouth, the esophagus is further down the digestive tract, the atrium is a chamber for collecting excretory products, and the stomach is posterior to the pharynx.

Quiz 16: Ambulacraria: Echinoderms and Hemichordates