Zoology Unit 3: Metazoa, Parazoa & Radiate Animals

Comprehensive vocabulary flashcards covering the theories of multicellular origins, structural grades of organization, developmental patterns, taxonomic groups, Phylum Porifera, and Phylum Cnidaria.

Multinucleated ciliated organisms theory

A theory of multicellular origins suggesting that multicellular organisms evolved from a single cell with multiple nuclei that eventually became compartmentalized, such as Protista.

Colonial flagellated organisms theory

The generally accepted theory suggesting multicellularity arose from a colony of single-celled, flagellated organisms, such as Volvox, that became increasingly interdependent.

Monophyletic

Evolving from one common ancestor phylum.

Polyphyletic

Arising independently from multiple unrelated ancestors.

Protoplasmic grade

Organizational level of unicellular organisms whose protoplasm is differentiated into organelles, such as in Paramecium.

Cellular grade

An aggregate of cells displaying division of labor and distinct differentiation among cells in a colony, such as in Volvox.

Cell tissue grade

An aggregation of similar cells organized to perform a common function within a tissue, as seen in Jellyfish and Hydra.

Tissue organ grade

An organizational grade where more than one tissue type performs a specialized function, such as eye spots or mouth parts in Flatworms and Planaria.

Organ system grade

An organizational level where multiple organs work together to perform functions within complete body systems, as in Humans and Earthworms.

Protostomes

A major developmental group of animals in which the blastopore becomes the mouth.

Lophotrochozoans

A protostome subgroup including segmented worms and mollusks, characterized by a horseshoe-shaped whorl of tentacles and lophophore or trochophore larval stages.

Ecdysozoans

A protostome subgroup including arthropods and roundworms, characterized by the ability to molt or shed their exoskeleton.

Deuterostomes

A major developmental group of animals in which the blastopore becomes the anus.

Osteum

A small side opening in a sponge through which water carrying food particles enters.

Osculum

The large top opening of a sponge through which water is pushed out via flagella.

Mesohyl

The gelatinous matrix layer of a sponge containing specialized cell types such as pinacocytes, choanocytes, and archaeocytes.

Pinacocytes

Outer cells of a sponge that regulate its surface area.

Choanocytes

Inner, flagellated collar cells in sponges that move water and strain food particles.

Archaeocytes

Mobile cells in sponges that digest food and carry out metabolism.

Asconoids

The simplest sponge canal system, where water flows directly through the Osteum, through Choanocytes, and out the Osculum, as seen in Leucosolenia sp.

Synconoids

A sponge canal system with folded outer walls containing Radial canals lined with Choanocytes, connected to Incurrent canals via a Prosopyle and exiting through an Apopyle, as seen in Sycon sp.

Leuconoids

The most complex sponge canal system, where incurrent canals lead to flagellated chambers and excurrent canals exit through the Osculum, as seen in Bath sponges.

Gemmules

Resilient, pear-shaped asexual buds produced by sponges that can survive the death of the parent sponge.

Monoecious

Term describing an organism that possesses both male and female reproductive organs.

Class Calcarea

A class of shallow marine sponges characterized by calcium carbonate spicules with $3$ to $4$ rays, tubular or vase shapes, and possessing all canal types.

Class Hexactinellida

A class of deep-sea sponges, known as glass sponges, with six-rayed silicon spicules and a syncytial multinucleated cell structure.

Class Demospongiae

A sponge class comprising $95$% of all sponges, featuring silicon spicules or spongin, all exhibiting leuconoid body plans, and leaving Gemmules.

Diploblastic

Having two embryonic germ layers, with the mesoderm derived from the ectoderm.

Cnidocytes

Specialized epidermal cells in radiate animals that contain stinging organelles called nematocysts.

Nematocyst

The stinging organelle, consisting of a barb and filament, located within a cnidocyte cell.

Operculum

A lid-like structure on a cnidocyte that opens when triggered to release the barb and filament.

Cnidocil

The trigger mechanism on the end of a cnidocyte cell that causes the operculum to open.

Penetrants

A type of nematocyte equipped with stingers that penetrate prey.

Volvents

A type of nematocyte that functions by entangling prey.

Glutinants

A type of nematocyte that secretes adhesive substances for locomotion and attachment.

Interstitial cells

Stem cells in cnidarians that can differentiate into cnidoblasts, sex cells, nerve cells, or buds, but cannot become epitheliomuscular cells.

Gland cells

Cells in cnidarians that produce adhesives or bubbles for floating.

Hydranth

The feeding and metabolic colony in Obelia, covered by a sac called a Hydrotheca.

Gonangium

The reproductive colony in Obelia, covered by a Gonatheca sac, which releases medusae via a gonnopore.

Perisarc

The dead outer covering that makes up the stem of colonial hydrozoans.

Coenosarc

The living, floating inner tissue inside the stem of colonial hydrozoans, also known as hydrocallous.

Velum

A membrane on the subumbrella surface of Gonionemus medusae that limits size.

Polymorphism

The occurrence of distinct structural forms serving different functions within a single colonial species, such as in Physalia.

Gastrozoite

The specialized feeding colony within a polymorphic hydrozoan like Physalia.

Gonozoide

The specialized reproductive colony within a polymorphic hydrozoan like Physalia.

Dactylozoite

The specialized defensive colony within a polymorphic hydrozoan like Physalia.

Scyphistoma

The sessile polyp stage in the Scyphozoa life cycle that forms after the planula larva settles on a surface.

Strobila

A developmental stage in the Scyphozoa life cycle consisting of about $12$ stacked segments that release ephyra jellyfish.

Ephyra

Small jellyfish released from a strobila that develop into mature medusae.

Valarium

A body structure found in Cubozoa (box jellyfish) that functions similarly to a velum.

Septa

Complete or incomplete partitions within the gastrovascular cavity of Anthozoans.

Pedal laceration

A form of asexual reproduction in Anthozoans involving the detachment of parts of the pedal disc to form new individuals.