Chapter 28 Vocabulary Life 103

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cleavage

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The process of cytocinesis in animal cells sharacterized by pimching of the plasma membrane: the succesion of rapid cell divisions eithout groeth during the early embrionic development that converts the zygote into a ball of cells

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Blastula

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The hollow ball of cells making the end stage of cleavage during early embrionic development

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Grastulation

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the formation of the Gastula from a bastula

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Gastrla

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the three layered, cup shaped embrionic stage

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Larva

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

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metaporphosis

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The resurgence of development in an animal latca that transforms it in to a secially mature adult.

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Ediacran Fauna

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Earliest generally accepted animal fossils datingfrom about 575 MYA

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Cambrian Explosion

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A burst of evolutionary orgins when most of the majority of animals appeared in a realitive breif time in geologic history; recirded in fossil record 542-525 MYA

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Grade

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Group of animal species that share the same level of organization complexity

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Body Plan

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In animals, the set of morphological and developmental traits that define a grade (a level of organizational complexity)

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radial Symmetry

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Characterizing a body shape like a pie or barrel, with many equal parts radiating outwards like the spokes of a wheel; present in CNIDARANS and ECHINODERMS

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Bilateral Symmetry

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Characterizing a body form with a central longitudinal plane that divides the body into two equal but opposite halves

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Dorsal

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Referrers to the BACK of a bilaterally symmetrical animal

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Ventral

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Pertaining to the underside or bottom of a bilaterally symmetrical animal

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Anterior

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Referring to the head of a bilaterally symmetrical animal

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Posterior

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

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Cephalization

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An evolutionary trend towards the concentration of sensory equipment on the anterior end of the body

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germ layers

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The three main layers that form the various tissues and organs on an animal body

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Ectoderm

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The outer most of the three germ layers in animal embryos; gives rise to the outer covering and , in some phyla the nervous system, inner ear and lens of the eye

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Endoderm

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The inner most of the three germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas lungs and lining of the digestive tract

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Archenteron

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The endoderm lined cavity, form during he gastualation process, that develops into the digestive tract of an animal

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Diploblastic

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of having two germ layers

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Mesoderm

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The middle primary germ layer that develops into the notocord, the lining of the coelom, muscles, skeleton, gonads, kidneys and most of the circulatory system

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Triploblastic

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Processing tree germ layers; the ectodermis, mesodermis and endodermis. Most EUMETAZOANS are triploblasts

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Body cavity

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A fluid-containing space between the digestive tract and the body wall

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Coelom

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A body cavity completely lined with mesoderm

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Coelomates

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Animal that posses a true coelom

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Pseudococlamates

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An animal whose body cavity is not completely lined with mesoderm

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acoclomates

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

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protostome development

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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

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Deuterosome Devlopment

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A developmental mode distinguished by the development of the anus from the blastopore; often characterized by ENTEROCOELOUS development of the body cavity by radial cleavage

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Spiral Cleavage

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A type of embryonic development in protosomesin which the planes of division that transforms the zygote into a ball of cells occur obliquely to the polar axis, resulting in cells of each tier sitting in the groves btw cells of adjacent teirs.

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Determinate Cleavage

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a type of embryonic development in protosomes that rigidly casts development fate of each embryonic cell very early

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Radial Cleavage

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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, therby aligning tiers of cells one above the other

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Indeterminate cleavage

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

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Schizocoelous

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pattern of formation of the body cavity common in protosome develop in which initially solid masses pf mesoderm split, forming the body cavity

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Enterocoelus

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Pattern of formation of the body cavity common in deuterosome development, in which the mesoderm buds

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Blastopore

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The hallow ball of cells marking the end stage of cleavage during early embryonic development

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Parazoan

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Animal belonging to the grade of organization of lacking true tissues
A SPONGE

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Eumetazoan

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Member of the clade EUMETAZOA, animals with true tissue (all animals except sponges)

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Bilaterians

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Member of the clade bilateria, animals with bilateral symmetry

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Ecdysozoans

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member of the animal group phyla with protostome development that some systematists hypothesize form a clade, including many molting animals.

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Lophotrochozoans

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Member of the animal group phyla with protostome development that some systematist hypothesized form a clade by lophophores or tropchophore larva

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Lophophore

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a horse-shoe shaped pr circular fold of the body wall bearing ciliated tenticles that surround the mouth

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Trochophore Larva

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Distinctive larval stage observed in certian invertabrates, including some annelids and molluscs