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| A succession of mitotic cell divisions without cell growth between division cycles. |
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| The hollow ball of cells marking the end stage of cleavage during early embryonic development. |
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| The formation of a gastrula from a blastula; during which layers of embryonic tissues that will develop into adult body parts are produced. |
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| The three-layered (endoderm, exoderm and mesoderm), cup-shaped embryonic stage. |
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| 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. |
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| A resurgence of development that transforms a larva into an adult. |
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| Homeoboxes; common modules of DNA sequences that are responsible for assigning specific regional identities on body parts. |
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| Protists that are the closest living relatives of animals. |
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| The first generally accepted fossils of animals dating back 575 million years ago. |
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| 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. |
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| The position or function of an organism in a community; its functional role. |
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| A group of animal species that share the same level of organizational complexity. |
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| In animals, the set of morphological and developmental traits that define a grade. |
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| 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. |
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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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| Pertaining to the back (top) of a bilaterally symmetrical animal. |
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| Pertaining to the front (bottom) of a bilaterally symmetrical animal. |
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| Referring to the head end of a bilaterally symmetrical animal. |
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| Referring to the tail end of a bilaterally symmetrical animal. |
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| An evolutionary trend toward the concentration of sensory equipment on the anterior end of the body. |
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| Concentric layers of tissue that form the various tissues and organs of the body. |
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| 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. |
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| 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). |
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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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| 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. |
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| Having three germ layers. |
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| A fluid-filled space separating the digestive tract from the outer body wall. |
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| A body cavity completely lined with mesoderm. |
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| Animal that possess a true coelom. |
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| An animal whose body cavity is not completely lined by mesoderm. |
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| An animal that lacks any body cavity. |
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| 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. |
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| 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. |
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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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| A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early. |
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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, thereby aligning tiers of cells one above the other. |
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| 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. |
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| Pattern of formation of the body cavity common in protostome development in which intially solid masses of mesoderm split, forming the body cavity. |
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| 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. |
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| The indentation that during gastrulation leads to the formation of the archenteron. |
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| Major Features of Animal Phylogeny |
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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. |
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| True animals; characterized by possessing true tissues. |
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| Animals with bilateral symmetry. |
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| Bilateral animals with protostome development that secrete external skeletons (exoskeleton). |
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| Members of a bilateral group of animal phyla with protostome development that some systematists hypothesize from a clade characterized by lophophores or trochophore larvae. |
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| A horseshoe-shaped or circular fold of the body wall bearing ciliated tentacles that surround the mouth. |
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| Distinctive larval stage observed in certain invertebrates including some annelids and molluscs |
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