Chapter 33: Invertebrates Flashcards
Choanocyte
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.
Incomplete metamorphosis
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.
Complete metamorphosis
The transformation of a larva into an adult that looks very different, and often functions very differently in its environment, than the larva.
Radula
A straplike scraping organ used by many molluscs during feeding.
Chelicerate
An arthropod that has chelicerae and a body divided into a cephalothorax and an abdomen.
Chelicera
One of a pair of clawlike feeding appendages characteristic of chelicerates.
Arachnid
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.
Myriapod
A terrestrial arthropod with many body segments and one or two pairs of legs per segment.
Pancrustacean
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.
Molting
A process in ecdysozoans in which the exoskeleton is shed at intervals, allowing growth by the production of a larger exoskeleton.
Invertebrate
An animal without a backbone, making up 95% of animal species.
Porifera
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.
Cnidaria
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.
Spongocoel
The central cavity of a sponge into which water is drawn.
Osculum
A large opening in a sponge that connects the spongocoel to the environment.
Amoebocyte
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.
Mesohyl
A gelatinous region between the two layers of cells of a sponge.
Totipotent
Capable of becoming other types of cells.
Hermaphrodite
An individual that functions as both male and female in sexual reproduction by producing both sperm and eggs.
Sequential hermaphroditism
The alternating function of an organism as either female or male in sexual reproduction.
Eumetazoa
The clade of animals with tissues; members are referred to as “true animals.” It includes Cnidaria, Lophotrochozoa, Ecdysozoa, and Deuterostomia.
Gastrovascular cavity
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.
Polyp
The sessile variant of the cnidarian body plan.
Medusa
The floating, flattened, mouth-down version of the cnidarian body plan.
Cnidocyte
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.
Nematocyst
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.
Medusozoa
Subphylum under Cnideria that consists of scyphozoans, cubozoans, and hydrozoans.
Anthozoa
Subphylum under Cnideria that consists of anemones and corals. Occur only as polyps, and many secrete a hard exoskeleton.
Scyphozoa
Class of true jellies under Medusozoa (Cnideria).
Cubozoa
Class of box jellies and sea wasps under Medusozoa (Cnideria).
Hydrozoa
Class of organisms that alternate between polyp and medusa forms under Medusozoa (Cnideria).
Bilateria
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.
Trochophore larva
Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.
Lophophore
A crown of ciliated tentacles that function in feeding.
Lophotrochozoa
Animal superphylum whose members have a true mouth/anus and most a true coelom. It includes Platyhelminthes, Syndermata, ectoprocts, brachiopods, molluscs, and annelids.
Platyhelminthes
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.
