Campbell Biology Chapter 32: An Overview of Animal Diversity

Vocabulary practice flashcards covering animal characteristics, embryonic development, geological eras, body plans, tissue layers, body cavities, and major phylogenetic clades from Chapter 32.

Heterotroph

An organism that obtains energy and nutrients by eating other living or nonliving organisms, rather than producing its own organic molecules.

Tissue

A group of similar, specialized cells that act together as a functional unit to carry out specific functions.

Collagen

A structural protein that provides support and tensile strength to animal cells, which lack rigid cell walls.

Cleavage

A succession of mitotic cell divisions in an early animal zygote that occurs without cell growth between divisions.

Blastula

An early multicellular embryonic stage produced by cleavage, typically taking the form of a hollow ball of cells surrounding a central cavity called the blastocoel.

Gastrulation

The developmental process following blastula formation in which layers of embryonic tissues are produced, transforming the blastula into a gastrula.

Gastrula

The embryonic stage formed by gastrulation that possesses distinct embryonic tissue layers (germ layers) and an archenteron.

Blastocoel

The fluid-filled internal cavity of an animal blastula.

Archenteron

The endoderm-lined blind pouch formed during gastrulation that develops into the digestive tract (gut).

Blastopore

The indentation or opening in the gastrula surface that leads into the developing archenteron.

Larva

A sexually immature animal developmental stage that is morphologically and behaviorally distinct from the adult form.

Metamorphosis

A developmental process that transforms an animal larva into a juvenile that resembles the adult but remains sexually immature.

Hox genes

A unique family of developmental regulatory genes shared by most animals that control the expression of many other genes influencing body morphology.

Choanoflagellates

Colonial or solitary flagellated protists supported by morphological and molecular evidence as the closest living relatives to animals.

CCD domain

A specific cadherin protein domain found exclusively in animals that is involved in cell adherence.

Ediacaran biota

An early group of macroscopic, mostly soft-bodied animal fossils dating from approximately 560 million years ago, first discovered in the Ediacara Hills of Australia.

Cloudina

A small shelled organism from the Ediacaran period whose fossilized shells show bore holes, providing early evidence of predator attacks.

Cambrian explosion

A period of rapid animal diversification occurring 535–525 million years ago, marking the first appearance of large animals with mineralized skeletons.

Hallucigenia

A 508-million-year-old animal from the Cambrian explosion characterized by pairs of elongate spines and walking appendages.

Body plan

A set of morphological and developmental traits integrated into a functional whole that characterizes an animal group.

Radial symmetry

A body arrangement around a single central axis such that any imaginary slice through the central axis divides the animal into mirror images.

Bilateral symmetry

A body plan arranged around two axes (anterior-posterior and dorsal-ventral) in which only one imaginary slice divides the organism into mirror-image right and left halves.

Dorsal

Pertaining to the top side of a bilaterally symmetrical animal.

Ventral

Pertaining to the bottom or belly side of a bilaterally symmetrical animal.

Ectoderm

The outermost germ layer covering the embryo's surface, which gives rise to the outer body covering and, in some phyla, the central nervous system.

Endoderm

The innermost embryonic germ layer that lines the archenteron and gives rise to the digestive tract lining and associated organs.

Mesoderm

The middle germ layer in triploblastic animals situated between the ectoderm and endoderm that gives rise to muscles and most internal organs.

Diploblastic

Having a body plan derived from only two embryonic germ layers: ectoderm and endoderm (e.g., cnidarians).

Triploblastic

Having a body plan derived from three embryonic germ layers: ectoderm, mesoderm, and endoderm (characteristic of all bilaterians).

Body cavity

A fluid- or air-filled space positioned between the digestive tract and the outer body wall that cushions organs and allows internal movement.

Coelom

A body cavity that is completely lined by tissue derived from mesoderm, with mesoderm forming structures that suspend internal organs.

Hemocoel

A body cavity formed between mesoderm and endoderm that is filled with hemolymph to circulate nutrients and waste products.

Hemolymph

A circulatory fluid that transports nutrients and metabolic waste throughout a hemocoel.

Protostome development

A developmental mode typically characterized by spiral, determinate cleavage, coelom formation via the splitting of solid mesoderm masses, and the mouth developing from the blastopore.

Deuterostome development

A developmental mode characterized by radial, indeterminate cleavage, coelom formation from mesodermal folds budding from the archenteron wall, and the anus developing from the blastopore.

Spiral cleavage

An embryonic cleavage pattern common in protostomes where the planes of cell division are diagonal to the vertical axis of the embryo.

Determinate cleavage

A cleavage type in protostomes wherein the developmental fate of each embryonic cell is rigidly fixed very early in development.

Radial cleavage

An embryonic cleavage pattern typical of deuterostomes where the planes of cell division are parallel or perpendicular to the embryo's vertical axis.

Indeterminate cleavage

A cleavage type in deuterostomes where early embryonic cells retain the developmental capacity to each differentiate into a complete, viable embryo.

Eumetazoa

A clade of animals ('true animals') that possess true tissues, comprising all animals except sponges and a few other basal lineages.

Invertebrates

Animals that lack a backbone or vertebral column, accounting for the vast majority of extant animal species.

Vertebrates

Animals that possess a backbone or vertebral column, belonging exclusively to the phylum Chordata.

Deuterostomia

A major bilaterian clade defined by molecular phylogeny that includes hemichordates, echinoderms, and chordates.

Ecdysozoa

A clade of entirely invertebrate bilaterians (such as nematodes and arthropods) that secrete an external skeleton that must be shed during growth.

Ecdysis

The process of molting or shedding an external skeleton (cuticle or exoskeleton) to permit organismal growth.

Lophotrochozoa

A clade of invertebrate bilaterians named for possessing either a lophophore feeding crown or a trochophore larval stage.

Lophophore

A crown of ciliated tentacles surrounding the mouth used for filter-feeding in groups such as ectoprocts.

Trochophore larva

A distinctive ciliated larval developmental stage observed in molluscs, annelids, and other lophotrochozoan lineages.