ABCS 101: Animal Classification and Phylum Platyhelminthes

Vocabulary practice flashcards covering fundamental zoological classification criteria and the detailed anatomy, physiology, and pathology of Phylum Platyhelminthes (Turbellaria, Trematoda, and Cestoda).

Taxonomy

The science of identifying and naming species, and arranging them into a classification; derived from Ancient Greek taxis ('arrangement') and nomia ('method').

Binomial nomenclature

A two-name naming system developed in 1758 by Swedish biologist Carolus Linnaeus to classify organisms by genus and species.

Diploblastic

Characterized by having two embryonic germ layers (ectoderm and endoderm) separated by a non-living layer.

Triploblastic

Characterized by having three embryonic germ layers: ectoderm, mesoderm, and endoderm.

Acoelomate

An animal that lacks an internal body cavity (coelom), where the interior region between the gut and skin is completely filled in with tissue.

Pseudocoelomate

An animal possessing a body cavity that is not completely lined or surrounded by mesodermal muscles or tissues (e.g., roundworms).

Coelomate

An animal possessing a true body cavity (coelom) entirely surrounded by muscle and other mesodermal tissues.

Radial symmetry

A body plan arrangement that can be divided into equal halves by multiple longitudinal planes passing through a central axis (e.g., starfish).

Bilateral symmetry

A body plan arrangement that can be divided into mirror-image right and left halves along only a single longitudinal plane.

Endoskeleton

An internal skeletal support structure found within an animal's body, composed of bone or cartilage.

Exoskeleton

A rigid external body covering providing support and protection, commonly composed of chitin in arthropods.

Parenchyma

A specialized connective tissue filling the body interior of flatworms in which organs are embedded.

Class Turbellaria

A class of mostly free-living, carnivorous flatworms within Phylum Platyhelminthes that possess a ciliated epidermis and move using cilia and muscles.

Ocelli

Light-sensitive pigmented eyespots located on the triangular head region of planarians.

Auricles

Earlike lateral projections on the head of a planarian that are sensitive to touch and chemical stimuli.

Flame cells

Specialized protonephridial excretory cells in flatworms that eliminate unwanted liquid wastes by moving fluid through ducts to dorsal excretory pores.

Neoblasts

Pluripotent cells in planarians that enable regeneration of missing or detached body parts during asexual reproduction.

Class Trematoda

A class of flatworms commonly called flukes, characterized by flattened, leaf-like unsegmented bodies and oral and ventral suckers for attachment.

Miracidium

The free-swimming, ciliated larval stage that hatches from a trematode egg and penetrates an intermediate snail host.

Cercaria

A free-swimming larval stage of flukes released from snails into water that penetrates the definitive host or encysts on vegetation.

Metacercaria

The encysted, resting infective stage of hermaphroditic flukes (such as Fasciola hepatica) formed on aquatic plants.

Gynaecophoral canal

A large ventral groove found in the broader, heavier male Schistosoma worm that holds the female worm during mating.

Schistosomiasis

A human parasitic disease caused by blood trematodes of the genus Schistosoma, acquired from water infested with infected snails.

Hepatosplenomegaly

An enlargement of both the liver and spleen resulting from a fibrotic tissue reaction induced by trapped Schistosoma eggs.

Praziquantel

An anthelmintic medication effective in treating all human-infecting species of Schistosoma.

Class Cestoda

A class of endoparasitic flatworms (tapeworms) that completely lack an alimentary canal and absorb all nutrients across a specialized tegument.

Scolex

The anterior attachment organ or head of an adult tapeworm, equipped with sucking disks, grooves, or hooks.

Proglottid

An individual reproductive segment forming the ribbon-like chain (strobila) of a tapeworm, containing both male and female organs.

Rostellum

A small button-like, often retractable structure on the scolex of armed tapeworms from which attachment hooks protrude.

Glycocalyx

A layer of carbohydrate covering the outer surface of a tapeworm's tegument that enhances nutrient absorption and protects against host digestive enzymes.

Cysticercus

The encysted larval stage of tapeworms (such as Taenia solium) that develops in muscles, skin, or brain tissue.