Animal Kingdom Classification – Vocabulary Review

A set of 60 English vocabulary flashcards summarizing essential terms and definitions from the lecture on animal classification and major phyla.

Cellular level of organization

Body is a loose aggregation of cells with no true tissues; seen in Porifera.

Tissue level of organization

Similar cells combine to form tissues, but organs are absent; found in Cnidaria and Ctenophora.

Organ level of organization

Different tissues organize into discrete organs that perform specific functions; starts from Platyhelminthes upward.

Organ system level of organization

Organs work together as systems to carry out major physiological tasks; characteristic of higher animals.

Incomplete digestive system

Alimentary canal with only one opening acting as both mouth and anus; present in Cnidaria and Platyhelminthes.

Complete digestive system

Alimentary canal with separate mouth and anus allowing one-way food flow.

Open circulatory system

Blood (hemolymph) flows through open sinuses and is not confined entirely to vessels.

Closed circulatory system

Blood remains within vessels throughout its circuit; typical of Annelida and vertebrates.

Asymmetrical body

Body cannot be divided into two equal halves in any plane; common in many sponges and some snails.

Radial symmetry

Body can be divided into equal halves by multiple vertical planes along the oral-aboral axis; seen in Cnidaria, Ctenophora, adult Echinodermata.

Bilateral symmetry

Only one plane divides the body into mirror-image right and left halves; characteristic from Platyhelminthes to Chordata.

Diploblastic

Embryos form two germ layers—ectoderm and endoderm—with mesoglea between; found in Cnidaria and Ctenophora.

Triploblastic

Embryos possess three germ layers—ectoderm, mesoderm, and endoderm; present from Platyhelminthes onward.

Coelom

Mesoderm-lined body cavity situated between body wall and gut wall.

Acoelomate

Animals lacking a body cavity; space between gut and body wall filled with parenchyma, e.g., Platyhelminthes.

Pseudocoelomate

Body cavity not completely lined by mesoderm; mesoderm appears as scattered pouches, e.g., Aschelminthes.

Coelomate

Animals with a true, mesoderm-lined coelom, e.g., Annelida to Chordata.

Metamerism

Serial repetition of similar body segments (metameres) both externally and internally; seen in Annelids and Arthropods.

Notochord

Flexible, mesodermal, dorsal supporting rod present during embryonic development of chordates.

Water canal system

Network of ostia, canals, and osculum that drives water flow for feeding, respiration, and excretion in sponges.

Choanocytes

Flagellated collar cells lining spongocoel and canals of Porifera, responsible for driving water flow and capturing food.

Cnidoblasts

Specialized stinging cells containing nematocysts used for defense, anchorage, and prey capture in cnidarians.

Polyp

Sessile, tubular, asexual body form of cnidarians with upward-directed mouth and tentacles (e.g., Hydra).

Medusa

Free-swimming, umbrella-shaped, sexual body form of cnidarians with downward-directed mouth and tentacles (e.g., Aurelia).

Alternation of generation (Metagenesis)

Life cycle in which asexual polyps produce sexual medusae and vice versa, as in Obelia.

Bioluminescence

Ability of some animals, notably Ctenophora, to emit light from their bodies.

Flame cells (Protonephridia)

Excretory and osmoregulatory cells possessing cilia, found in Platyhelminthes.

Syncytial epidermis

Multinucleate outer covering without distinct cell boundaries; typical of Aschelminthes.

Setae

Chitinous bristles on each annelid segment used for anchorage and locomotion (absent in leeches).

Parapodia

Fleshy, lateral appendages bearing setae in polychaete annelids such as Nereis, aiding in swimming.

Malpighian tubules

Excretory organs opening into the gut of terrestrial arthropods like insects and spiders.

Mantle (Pallium)

Dorsal fold of body wall in molluscs that secretes the shell and forms the mantle cavity.

Radula

File-like rasping organ in the mouth of most molluscs used for feeding.

Water vascular system

Network of hydraulic canals and tube feet in echinoderms functioning in locomotion, feeding, respiration, and excretion.

Madreporite

Porous, sievelike plate on echinoderms through which seawater enters the water vascular system.

Stomochord

Proboscis-derived, hollow outgrowth in Hemichordata once thought homologous to notochord.

Cyclostomata

Jawless vertebrate class of ectoparasitic lampreys and scavenging hagfishes with circular, sucking mouths.

Placoid scales

Pointed, toothlike dermal scales characteristic of cartilaginous fishes (Chondrichthyes).

Operculum

Bony gill cover protecting each side of the head in bony fishes (Osteichthyes).

Air bladder (Swim bladder)

Gas-filled sac in most bony fishes providing buoyancy regulation.

Poikilotherm

Cold-blooded animal whose body temperature varies with the environment.

Homoiotherm

Warm-blooded animal capable of maintaining a constant internal body temperature, e.g., birds and mammals.

Tympanum

External eardrum visible as a circular patch in amphibians and reptiles, serving as auditory organ.

Crop and gizzard

Additional storage and grinding chambers in the digestive tract of birds.

Cloaca

Common chamber for digestive, urinary, and reproductive tracts opening to the exterior in amphibians, reptiles, and birds.

Heterodont dentition

Possession of teeth of different shapes and functions (incisors, canines, premolars, molars) as in mammals.

Thecodont dentition

Condition where teeth are embedded in sockets in the jaw bone, typical of mammals.

Diphyodont dentition

Having two successive sets of teeth in a lifetime—deciduous (milk) and permanent; seen in mammals.

Pneumatic bones

Lightweight, air-filled bones of birds that aid in flight.

Mammary glands

Milk-producing glands unique to mammals, nourishing the young.

Ecdysis (Skin casting)

Shedding of outer skin layers by reptiles such as snakes and lizards.

Autotomy

Self-amputation of body parts, notably seen in echinoderms for defense or escape.

Regeneration

Ability to regrow lost body parts, highly developed in echinoderms and planarians.

Exoskeleton (Chitinous cuticle)

Hard, external protective covering secreted by arthropods composed mainly of chitin.

Compound eyes

Multi-faceted visual organs of many arthropods providing a broad field of vision.

Statocysts

Balance-sensory organs in crustaceans and some other invertebrates detecting orientation.

Book lungs

Stacked, leaf-like respiratory structures in some arachnids allowing gas exchange on land.

Proboscis gland

Excretory organ located in the proboscis of hemichordates.

Spicules

Microscopic skeletal elements made of calcium carbonate or silica supporting sponge bodies.

Spongin fibres

Flexible protein fibers forming part of the supportive skeleton in many sponges.