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Campbell Biology Chapter 32
Intro to Animal Diversity
48
Biology
Undergraduate 2
02/23/2008

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Term
Cleavage
Definition
A succession of mitotic cell divisions without cell growth between division cycles.
Term
Blastula
Definition
The hollow ball of cells marking the end stage of cleavage during early embryonic development.
Term
Gastrulation
Definition
The formation of a gastrula from a blastula; during which layers of embryonic tissues that will develop into adult body parts are produced.
Term
Gastrula
Definition
The three-layered (endoderm, exoderm and mesoderm), cup-shaped embryonic stage.
Term
Larva
Definition
A sexually immature form of an animal that is morphologically distinct from the adult stage; usually eats different food and may have a different habitat than the adult.
Term
Metamorphosis
Definition
A resurgence of development that transforms a larva into an adult.
Term
Hox Genes
Definition
Homeoboxes; common modules of DNA sequences that are responsible for assigning specific regional identities on body parts.
Term
Choanoflagellate
Definition
Protists that are the closest living relatives of animals.
Term
Ediacaran Fauna
Definition
The first generally accepted fossils of animals dating back 575 million years ago.
Term
Cambrian Explosion
Definition
A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 542-525 million years ago. Possibly due to predator-prey relations, changes in atmposphere and genetic flexibility.
Term
Niche
Definition
The position or function of an organism in a community; its functional role.
Term
Grade
Definition
A group of animal species that share the same level of organizational complexity.
Term
Body Plan
Definition
In animals, the set of morphological and developmental traits that define a grade.
Term
Radial Symmetry
Definition
Characterizing a body shaped like a pie or barrel, with many equal parts radiating outward like the spokes of a wheel; present in cnidarians and echinoderms.
Term
Bilateral Symmetry
Definition
Characterizing a body form with a central longitudinal plane that divides the body into two equal but opposite halves.
Term
Dorsal
Definition
Pertaining to the back (top) of a bilaterally symmetrical animal.
Term
Ventral
Definition
Pertaining to the front (bottom) of a bilaterally symmetrical animal.
Term
Anterior
Definition
Referring to the head end of a bilaterally symmetrical animal.
Term
Posterior
Definition
Referring to the tail end of a bilaterally symmetrical animal.
Term
Cephalization
Definition
An evolutionary trend toward the concentration of sensory equipment on the anterior end of the body.
Term
Germ Layer
Definition
Concentric layers of tissue that form the various tissues and organs of the body.
Term
Ectoderm
Definition
The germ layer covering the surface of the embryo that gives rise to the outer covering of the body; in some cases, to the central nervous system.
Term
Endoderm
Definition
The innermost germ layer that line the embryonic digestive tube (archenteron) and gives rise to the lining of the digestive tract and organs derived from it (liver, lungs, etc).
Term
Archenteron
Definition
The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
Term
Diploblastic
Definition
Having two germ layers.
Term
Mesoderm
Definition
The middle primary germ layer of an early embryo that develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys and most of the circulatory system.
Term
Triploblastic
Definition
Having three germ layers.
Term
Body Cavity
Definition
A fluid-filled space separating the digestive tract from the outer body wall.
Term
Coelom
Definition
A body cavity completely lined with mesoderm.
Term
Coelomate
Definition
Animal that possess a true coelom.
Term
Pseudocoelomate
Definition
An animal whose body cavity is not completely lined by mesoderm.
Term
Acoelomate
Definition
An animal that lacks any body cavity.
Term
Protostome Development
Definition
In animals, a developmental mode distinguished by the development of the mouth from the blastopore; often also characterized by schizocoelous development of the body cavity and by spiral cleavage.
Term
Deuterostome Development
Definition
In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by enterocoelous development of the body cavity and by radial cleavage.
Term
Spiral Cleavage
Definition
A type of embryonic development in protostomes, in which the planes of cell division that transform the zygote into a ball of cells occur obliquely to the polar axis, resulting in cells of each tier sitting in the grooves between cells of adjacent tiers.
Term
Determinate Cleavage
Definition
A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early.
Term
Radial Cleavage
Definition
A type of embryonic development in deuterostomes in which the planes of cell division that transform the zygote into a ball of cells are either parallel or perpendicular to the polar axis, thereby aligning tiers of cells one above the other.
Term
Indeterminate Cleavage
Definition
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.
Term
Schizocoelous
Definition
Pattern of formation of the body cavity common in protostome development in which intially solid masses of mesoderm split, forming the body cavity.
Term
Enterocoelous
Definition
Pattern of formation of the body cavity common in deuterostome development, in which the mesoderm buds from the wall of the archenteron and hollows, forming the body cavity.
Term
Blastopore
Definition
The indentation that during gastrulation leads to the formation of the archenteron.
Term
Major Features of Animal Phylogeny
Definition
1) All animals share a common ancestor.
2) Sponges are basal animals.
3) Eumetazoa is a clade of animals with true tissues.
4) Most animal phyla belong to the clade Bilateria.
5) Vertebrates and some other phyla belong to the clade Deuterostomia.
Term
Eumetazoans
Definition
True animals; characterized by possessing true tissues.
Term
Bilaterians
Definition
Animals with bilateral symmetry.
Term
Ecdysozoans
Definition
Bilateral animals with protostome development that secrete external skeletons (exoskeleton).
Term
Lophotrochozoans
Definition
Members of a bilateral group of animal phyla with protostome development that some systematists hypothesize from a clade characterized by lophophores or trochophore larvae.
Term
Lophophore
Definition
A horseshoe-shaped or circular fold of the body wall bearing ciliated tentacles that surround the mouth.
Term
Trochophore
Definition
Distinctive larval stage observed in certain invertebrates including some annelids and molluscs
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