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cleavage
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(1) The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. (2) The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.
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spiral cleavage
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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.
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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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Arthropods
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A group of organisms that have jointed appendages, an exoskeleton, bilateral symmetry, and reproduce sexually; insects, arachnids, millipedes and cenitpedes, and crustaceans
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Gastrulation
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In animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo, the gastrula.
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acoelom
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has endoderm, mesoderm, and ectoderm, but no body cavity
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pseudocoelom
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A body cavity that is not completely lined by tissue derived from mesoderm
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lophotrochozoans
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Member of a group of animal phyla identified as a clade by molecular evidence. Lophotrochozoans include organisms that have lophophores or trochophore larvae.
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pluripotent
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Stem cells with the potential to differentiate into most any type of cell
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Gastrula
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An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.
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ectoderm
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The outermost of the three primary 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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Porifera
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coextensive with the subkingdom Parazoa: sponges
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protostome development
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In animals, a developmental mode distinguished by the development of the mouth from the blastopore; often also characterized by spiral cleavage and by the body cavity forming when solid masses of mesoderm split.
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mesoderm
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the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue
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Evo-devo
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Evolutionary developmental biology; a field of biology that compares developmental processes of different multicellular organisms to understand how these processes have evolved and how changes can modify existing organismal features or lead to new ones.
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diploblastic
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having 2 germ layers: ectoderm and endoderm.
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archenteron
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The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
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mollusks
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Invertebrates with soft, unsegmented bodies that are often protected by a hard outer shell
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Ecdysozoans
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Animals that have an exoskeleton that is a thick non living covering. It provides protection and support, it does not grow with the organism. Some exoskeletons contain chitin and the exoskeleton allows for new mechanisms for locomotion and respiration.
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radial symmetry
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a body plan in which the body parts are arranged in a circle around a central point
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differentiation
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process in which cells become specialized in structure and function
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chordata
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phylum characterized by a dorsal nerve chord, notochord, post anal tail and pharyngeal slits
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Eumetazoa
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Members of the subkingdom that includes all animals except sponges. (true tissues)
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blastula
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The hollow ball of cells marking the end stage of cleavage during early embryonic development
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coelom
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a body cavity completely lined with mesoderm.
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endoderm
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the inner germ layer that develops into the lining of the digestive and respiratory systems
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echinoderms
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invertebrates with an internal skeleton and a system of fluid-filled tubes called a water vascular system
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deuterostome development
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In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by radial cleavage and by the body cavity forming as outpockets of mesodermal tissue.
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Metazoa
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first real animal, multicellular animals having cells differentiated into tissues and organs and usually a digestive cavity and nervous system
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radial cleavage
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A type of embryonic development in deuterostomes in that 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.
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nematodes
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roundworms
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annelida
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segmented worms: earthworms
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flatworms
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A group of often parasitical worms that have bilateral symmetry, a one opening digestive system, and the beginnings of a brain; tapeworm
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triploblastic
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Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoa are triploblastic.
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blastopore
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The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes
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