Intro To Animal Diversity

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Metamorphosis

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when an organism changes from a juvenile to an adult form

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Metazoa

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collective term/group of all animals

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Parazoa

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animals that do not posses specialized tissue types or organs; single phylum (Porifera)

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Eumetazoa

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animals that have one or more types of tissue and, for the most part, different types of organs

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Radiata

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symmetric animals that can be divided equally by any longitudinal plane passing through the central axis; often circular or tubular in shape

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Bilateria

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symmetric animals that be divided along a vertical plane at the midline to create two halves

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Dorsal

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upper sideof animal body plan

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Ventral

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lower side of animal body plan

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Anterior

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side of animal body plan where the head is found

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Posterior

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tail end of animal body plan

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Cephalization

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the localization of sensory structures at the anterior end of the body

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Germ layers

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Embryonic layer

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Gastrulation

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process in which the growing embryo of animals develops different layers of cells

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Cleavage

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a succession of rapid cell divisions with no significant growth that produces a blastula

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Blastula

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a hollow sphere of cells

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Gastrula

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a structure created through gastrulation where an area of the blastula folds inward

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Endoderm

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the innermost layer of cells formed during gastrulation; lines the primitive digestive tract

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Ectoderm

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the outermost layer of cells formed during gastrulation that covers the surface of the embryo and differentiates into the epidermis and nervous system

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Mesoderm

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a layer of cells formed during gastrulation that develops between the ectoderm and endoderm; gives rise to the skeleton, muscles, and much of the circulatory system; only found in Bilateria

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Triploblastic

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animals having three distinct germ layers; bilateral animals

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Diploblastic

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animals that only have an endoderm and ectoderm; radial animals

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Blastopore

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the opening of the primitive digestive tract (archenteron) to the outside

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Protostomes

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animals where the blastopore becomes the mouth and, if present, the anus form from a secondary opening

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Deuterostomes

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animals where the blastopore becomes the anus and the mouth is formed from the secondary opening

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Determinate cleavage

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when the fate of each embryonic cell is determined very early on; if one of the cells is removed from a four-cell protostome embryo, neither the single cell nor the remaining three-cell mass can form viable embryos and development stops

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Indeterminate cleavage

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each cell produced retains the ability to develop into a complete embryo; deuterostome development; in humans if individual embryonic cells separate from one another early in development, twins can result

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Coelom

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fluid-filled body cavity

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Coelomates

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animals with a (true) coelem completely lined with a mesoderm

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Pseudocoelomates

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animals with a fluid-filled cavity that isn't completely lined by tissue derived from a mesoderm

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Acoelomates

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animals that lack a fluid-filled body cavity

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Hydrostatic skeleton

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a fluid-filled body cavity surrounded by muscles that gives support and shape to the body of organisms; muscle contractions at one part of the body pushes this fluid toward another part of the body; observed in earthworms

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Hox genes

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involved in determining the spatial patterning of the body and appendages; present in all animals

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Ecdysozoa

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a clade of animals that secrete a nonliving cuticle that they molt when it becomes too small before secreting a new, larger one; consists of nematodes and arthropods

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Lophotrochozoa

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a major protostome clade encompassing mollusks, annelids, and many other phyla

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Lophophore

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a horseshoe-shaped crown of tentacles used for feeding; found in rotifers, bryozoans, and brachiopods

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Trochophore larva

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a distinct larva stage characterized by a band of cilia around its middle that is used for swimming