Chapter 33: Invertebrates

Question 1

Choanocyte

Answer 1

A flagellated feeding cell found lining the spongocoel in sponges. Also called a collar cell, it has a collar-like ring that traps food particles around the base of its flagellum. By beating flagella, they create a current that draws water in through the pores and out through the osculum.

Question 2

Incomplete metamorphosis

Answer 2

A type of development in certain insects, such as grasshoppers, in which the young (called nymphs) resemble adults but are smaller and have different body proportions. The nymph goes through a series of molts, each time looking more like an adult, until it reaches full size.

Question 3

Complete metamorphosis

Answer 3

The transformation of a larva into an adult that looks very different, and often functions very differently in its environment, than the larva.

Question 4

Radula

Answer 4

A straplike scraping organ used by many molluscs during feeding.

Question 5

Chelicerate

Answer 5

An arthropod that has chelicerae and a body divided into a cephalothorax and an abdomen.

Question 6

Chelicera

Answer 6

One of a pair of clawlike feeding appendages characteristic of chelicerates.

Question 7

Arachnid

Answer 7

A member of a subgroup of the major arthropod clade Chelicerata. They have six pairs of appendages, including four pairs of walking legs, and include spiders, scorpions, ticks, and mites.

Question 8

Myriapod

Answer 8

A terrestrial arthropod with many body segments and one or two pairs of legs per segment.

Question 9

Pancrustacean

Answer 9

A member of a diverse arthropod clade that includes lobsters, crabs, barnacles and other crustaceans, as well as insects and their six-legged terrestrial relatives.

Question 10

Molting

Answer 10

A process in ecdysozoans in which the exoskeleton is shed at intervals, allowing growth by the production of a larger exoskeleton.

Question 11

Invertebrate

Answer 11

An animal without a backbone, making up 95% of animal species.

Question 12

Porifera

Answer 12

The phylum informally called sponges, which are sessile animals that lack tissues. They live as filter feeders, trapping particles that pass through the internal channels of their body. Due to their lack of tissues, sponges are said to be basal animals. 5,500 known species.

Question 13

Cnidaria

Answer 13

The phylum that includes corals, jellies, and hydras. These animals have a diploblastic, radially symmetrical body plan that includes a gastrovascular cavity with a single opening that serves as both mouth and anus. 10,000 known species. Composed of two major clades, Medusozoa and Anthozoa.

Question 14

Spongocoel

Answer 14

The central cavity of a sponge into which water is drawn.

Question 15

Osculum

Answer 15

A large opening in a sponge that connects the spongocoel to the environment.

Question 16

Amoebocyte

Answer 16

An amoeba-like cell that moves by pseudopodia and is found in most animals. Depending on the species, it may digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, or change into other cell types.

Question 17

Mesohyl

Answer 17

A gelatinous region between the two layers of cells of a sponge.

Question 18

Totipotent

Answer 18

Capable of becoming other types of cells.

Question 19

Hermaphrodite

Answer 19

An individual that functions as both male and female in sexual reproduction by producing both sperm and eggs.

Question 20

Sequential hermaphroditism

Answer 20

The alternating function of an organism as either female or male in sexual reproduction.

Question 21

Eumetazoa

Answer 21

The clade of animals with tissues; members are referred to as “true animals.” It includes Cnidaria, Lophotrochozoa, Ecdysozoa, and Deuterostomia.

Question 22

Gastrovascular cavity

Answer 22

A central cavity with a single opening in the body of certain animals, including cnidarians and flatworms, that functions in both the digestion and distribution of nutrients.

Question 23

Polyp

Answer 23

The sessile variant of the cnidarian body plan.

Question 24

Medusa

Answer 24

The floating, flattened, mouth-down version of the cnidarian body plan.

Question 25

Cnidocyte

Answer 25

A specialized cell unique to the phylum Cnidaria; contains a capsule-like organelle housing a coiled thread that, when discharged, explodes outward and functions in prey capture or defense.

Question 26

Nematocyst

Answer 26

In a cnidocyte of a cnidarian, a capsule-like organelle containing a coiled thread that when discharged can penetrate the body wall of the prey.

Question 27

Medusozoa

Answer 27

Subphylum under Cnideria that consists of scyphozoans, cubozoans, and hydrozoans.

Question 28

Anthozoa

Answer 28

Subphylum under Cnideria that consists of anemones and corals. Occur only as polyps, and many secrete a hard exoskeleton.

Question 29

Scyphozoa

Answer 29

Class of true jellies under Medusozoa (Cnideria).

Question 30

Cubozoa

Answer 30

Class of box jellies and sea wasps under Medusozoa (Cnideria).

Question 31

Hydrozoa

Answer 31

Class of organisms that alternate between polyp and medusa forms under Medusozoa (Cnideria).

Question 32

Bilateria

Answer 32

Clade of animals whose members exhibit bilateral symmetry and triploblastic development. Most also have a digestive tract with two openings and a coelom. It includes Lophotrochozoa, Ecdysozoa, and Deuterostomia.

Question 33

Trochophore larva

Answer 33

Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.

Question 34

Lophophore

Answer 34

A crown of ciliated tentacles that function in feeding.

Question 35

Lophotrochozoa

Answer 35

Animal superphylum whose members have a true mouth/anus and most a true coelom. It includes Platyhelminthes, Syndermata, ectoprocts, brachiopods, molluscs, and annelids.

Question 36

Platyhelminthes

Answer 36

Phylum under Lophotrochozoa that consists of flatworms and rhabitiphores. Characterized by being acoelomates, triploblastic, having a gastrovascular cavity with one opening, gas exchange on the surface, and no cardiovascular system.