Animal Evolution & Diversity: Invertebrates Part II

Flashcards covering the diversity and biological features of invertebrates, including Lophotrochozoa, Ecdysozoa, and Deuterostomia, based on lecture notes.

Lophophore

A ciliary feeding structure possessed by some members of the Lophotrochozoa, such as Bryozoans, Brachiopods, and Rotifers.

Trochophore

A distinct swimming larval stage characteristic of certain Lophotrochozoa, including Mollusks, Annelids, and Platyhelminthes.

Phylum Platyhelminthes

Flatworms that are acoelomate, lack specialized respiratory or circulatory systems, and possess an incomplete digestive system where one opening serves as both mouth and anus.

Gastrovascular cavity

The structure in Platyhelminthes where food is digested.

Phylum Rotifera

Microscopic, mostly freshwater animals with a pseudocoelom, an alimentary canal (separate mouth and anus), and a ciliated crown called a corona.

Corona

A ciliated crown in Rotifers that creates water currents to propel the animal and bring food toward the mouth.

Bryozoa

Small ($0.5\,mm$) colonial animals with a lophophore and a true coelom that are important reef builders.

Brachiopods

Small ($1\text{-}8\,cm$) bottom-dwelling marine organisms that possess a lophophore and two shell halves similar to clams.

Muscular foot

One of the three major body sections of a mollusk, usually used for movement.

Visceral mass

The section of a mollusk body that contains the internal organs and rests atop the foot.

Mantle

A fold of skin over the visceral mass in mollusks that secretes a shell in species where they are present.

Radula

A unique tongue-like organ found in the mouth of many mollusks.

Hemolymph

The body fluid pumped by the heart through vessels and into sinuses in the open circulatory system of most mollusks and arthropods.

Cephalopods

The most complex group of mollusks ($780$ species), including squid and octopus, which possess a closed circulatory system.

Phylum Annelida

Segmented worms that possess a closed circulatory system, a complete unsegmented digestive system, and a double transport system using both blood and coelomic fluid.

Cuticle

A nonliving cover, such as an exoskeleton, that supports and protects animals in the clade Ecdysozoa.

Ecdysis

The periodic molting of the cuticle, characteristic of Ecdysozoans.

Phylum Nematoda

Roundworms characterized by a tough collagen cuticle, a pseudocoelom, and a complete digestive tract; they are often parasitic.

Tagmata

Functional units formed by the fusion of body segments in arthropods, such as the head or thorax.

Tracheal system

The respiratory system of terrestrial arthropods consisting of a network of tubes with openings called spiracles.

Subphylum Chelicerata

Arthropods including spiders and scorpions that have two tagmata (cephalothorax and abdomen) and six pairs of appendages including chelicerae (fangs).

Subphylum Myriapoda

Arthropods including millipedes (two pairs of legs per segment) and centipedes (one pair of walking legs per segment).

Subphylum Hexapoda

Insects and their relatives, characterized by three tagmata, three pairs of walking legs, and wings developed as outgrowths of the body wall cuticle.

Complete metamorphosis

A developmental process in insects comprising four distinct stages: egg, larva, pupa, and adult.

Incomplete metamorphosis

A developmental process in insects comprising three stages: egg, nymph, and adult.

Subphylum Crustacea

Arthropods such as crabs and lobsters that possess two pairs of antennae and a cephalothorax.

Autotomy

The ability of most echinoderms to regenerate from a detached body part or limb.

Water vascular system

An adaptation of the coelom in echinoderms that functions in movement, gas exchange, feeding, and excretion.

Madreporite

The opening through which water enters the water vascular system of an echinoderm.

Ampulla

A muscular sac at the base of each tube foot in echinoderms that stores water and contracts to extend the tube feet.

Notochord

A single flexible rod lying between the digestive tract and nerve cord; one of the four critical innovations of chordates.

Dorsal hollow nerve cord

A tube-like structure that develops into the brain and spinal cord in vertebrates; a defining feature of chordates.

Pharyngeal slits

Slits that open to the outside near the mouth; a defining feature of chordates present at some stage of development.

Postanal tail

A tail that extends posterior to the anal opening; one of the four critical innovations of chordates.

Subphylum Cephalochordata

Invertebrate chordates known as lancelets, which are marine filter feeders that possess all four chordate characteristics.

Subphylum Urochordata

Invertebrate chordates known as tunicates; the larvae display all four chordate features, while adults only retain pharyngeal slits.