Campbell Biology Chapter 32: An Overview of Animal Diversity

Comprehensive vocabulary flashcards covering anatomical terminology, developmental modes, germ layers, body plans, and major phylogenetic lineages of animals from Chapter 32 of Campbell Biology.

Anterior

Pertaining to the front, or head, of a bilaterally symmetrical animal.

Posterior

Pertaining to the rear, or tail end, of a bilaterally symmetrical animal.

Dorsal

Pertaining to the top side of an animal with radial or bilateral symmetry.

Ventral

Pertaining to the underside, or bottom side, of an animal with radial or bilateral symmetry.

Radial symmetry

Symmetry in which the body is shaped like a pie or barrel (lacking a left side and a right side) and can be divided into mirror-imaged halves by any plane through its central axis.

Bilateral symmetry

Body symmetry in which a central longitudinal plane divides the body into two equal but opposite halves, giving the organism two axes of orientation: front to back and top to bottom.

Cephalization

An evolutionary trend associated with bilateral symmetry toward the concentration of nervous and sensory equipment at the anterior end of the body.

Body plan

In multicellular eukaryotes, a set of morphological and developmental traits that are integrated into a functional whole—the living organism.

Tissue

An integrated group of specialized cells with a common structure, function, or both, isolated from other tissues by membranous layers.

Cleavage

The succession of rapid mitotic cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.

Blastula

A multicellular, hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals.

Gastrulation

A series of cell and tissue movements in animal development in which the blastula folds inward, producing a three-layered embryo called the gastrula.

Gastrula

An embryonic stage in animal development encompassing the formation of three primary germ layers: ectoderm, mesoderm, and endoderm.

Archenteron

The endoderm-lined blind pouch formed during gastrulation that develops into the digestive tract of an animal.

Blastopore

The indentation or opening of the archenteron formed during gastrulation that typically develops into the anus in deuterostomes and the mouth in protostomes.

Ectoderm

The outermost primary germ layer in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.

Endoderm

The innermost primary germ layer in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract.

Mesoderm

The middle primary germ layer in a triploblastic animal embryo; develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system.

Diploblastic

Having two germ layers (ectoderm and endoderm), as seen in animals such as cnidarians and comb jellies.

Triploblastic

Possessing three primary germ layers: ectoderm, mesoderm, and endoderm. All bilaterian animals are triploblastic.

Body cavity

A fluid- or air-filled space located between the digestive tract and the outer body wall that cushions organs and can function as a hydrostatic skeleton.

Coelom

A body cavity lined completely by tissue derived only from mesoderm.

Coelomate

An animal that possesses a true coelom lined completely by tissue derived from mesoderm.

Pseudocoelomate

An animal whose functional body cavity is lined by tissue derived from both mesoderm and endoderm.

Acoelomate

A solid-bodied animal lacking a body cavity between the gut and the outer body wall.

Grade

A group of organisms that share similar morphological and developmental body plans (e.g., coelomates or pseudocoelomates), which is not necessarily equivalent to a monophyletic clade.

Protostome development

A developmental mode distinguished by the development of the mouth from the blastopore; often characterized by spiral cleavage and by the coelom forming when solid masses of mesoderm split.

Deuterostome development

A developmental mode distinguished by the development of the anus from the blastopore; often characterized by radial cleavage and by the coelom forming as outpockets of mesodermal tissue from the archenteron.

Spiral cleavage

A type of embryonic development in protostomes in which the planes of cell division are diagonal to the vertical axis of the embryo, causing the cells of each tier to sit in the grooves between cells of adjacent tiers.

Radial cleavage

A type of embryonic development in deuterostomes in which the cleavage planes are either parallel or perpendicular to the vertical axis of the embryo, aligning tiers of cells one directly above the other.

Determinate cleavage

A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early.

Indeterminate cleavage

A type of embryonic development in deuterostomes in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo.

Larva

A free-living, sexually immature form in some animal life cycles that may differ from the adult animal in morphology, nutrition, and habitat.

Metamorphosis

A developmental transformation that turns an animal larva into either an adult or an adultlike stage that is not yet sexually mature.

Hox genes

A unique homeobox-containing family of developmental genes in animals that controls the expression of dozens or hundreds of other genes influencing morphology and axis formation.

Collagen

An extracellular structural protein unique to animals that holds multicellular animal bodies together in the absence of cell walls.

Ediacara biota

An early group of macroscopic, soft-bodied, multicellular eukaryotes known from fossils ranging in age from $635\text{ million}$ to $535\text{ million years old}$.

Cambrian explosion

A relatively brief time in geologic history ($535\text{--}525\text{ million years ago}$) when many present-day phyla of animals first appeared in the fossil record, including the emergence of the first large, hard-bodied animals.

Eumetazoan

A member of a clade of animals with true tissues. All animals except sponges and a few other groups are eumetazoans.

Bilaterian

A member of a major animal clade characterized by bilateral symmetry and triploblastic organization with three germ layers.

Invertebrate

An animal without a backbone; invertebrates make up approximately $95\%$ of all animal species.

Vertebrate

A chordate animal possessing vertebrae, the series of bones that make up the backbone.

Lophophore

In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.

Trochophore larva

A distinctive ciliated larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.

Lophotrochozoa

One of the three main lineages of bilaterian animals; identified by molecular data, its members often develop lophophores or trochophore larvae.

Ecdysozoa

One of the three major clades of bilaterian animals, which includes nematodes and arthropods, characterized by secreting and molting an exoskeleton through ecdysis.

Ecdysis

The process by which an ecdysozoan animal molts its old external skeleton (exoskeleton) and secretes a new, larger one as it grows.

Deuterostomia

One of the three main clades of bilaterian animals, which includes chordates, echinoderms, and other related phyla sharing a deuterostome developmental mode.

Acoela

A lineage of basal bilaterians (acoel flatworms) possessing a simple nervous system, a saclike gut with a single opening, and no excretory system, demonstrating traits resembling ancestral bilaterians.