Chapter 32: Animal Diversity Flashcards
Cleavage
The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.
Radial symmetry
Symmetry in which the body is shaped like a pie (lacking a left side and a right side) and can be divided into mirror-imaged halves by any plane through its central axis.
Blastopore
In a gastrula, the opening of the archenteron that typically develops into the anus in deuterostomes and the mouth in protostomes.
Coelom
A body cavity lined by tissue derived only from mesoderm.
Ectoderm
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.
Gastrulation
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.
Larva
A free-living, sexually immature form in some animal life cycles that may differ from the adult animal in morphology, nutrition, and habitat.
Blastula
A hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals.
Metamorphosis
A developmental transformation that turns an animal larva into either an adult or an adult-like stage that is not yet sexually mature.
Deuterostome development
In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by the radial cleavage and by the body cavity forming as outpockets of mesodermal tissue.
Archenteron
The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal.
Ediacaran biota
An early group of macroscopic, soft-bodied, multicellular eukaryotes known from fossils that range in age from 635 million to 535 million years old.
Endoderm
The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract in species that have these structures.
Eight-cell stage
The stage in embryo development after three rounds of cell division.
Protostome development
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.
Mesozoic era
The geological era known as the “age of reptiles;” includes the Cretaceous, Jurassic, and Triassic periods. Characterized by the origin of mammals and angiosperms and by the extinction of dinosaurs. Approximately 252-66 MYA.
Mesoderm
The middle primary germ layer in a triploblastic animal embryo; develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system in species that have these structures.
Body plan
In multicellular eukaryotes, a set of morphological and developmental traits that are integrated into a functional whole: the living organism.
Cenozoic era
The geological era that includes the Quaternary, Neogene, and Paleogene periods. Characterized by radiation of mammals, birds, and pollinating insects, by angiosperm dominance, by the origin of primate groups, and by the ice ages. Approximately 66-0.01 MYA.
Gastrula
An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.
Pseudocoelom
An animal whose body cavity is lined by tissue derived from mesoderm and endoderm.
Hox genes
A homeobox-containing family of genes that plays an important role in the development of animal embryos and the expression of morphology.
Lophophore
In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.
Tissue
A integrated group of cells with a common structure, function, or both.
Acoelomate
A solid-bodied animal lacking a cavity between the gut and outer body wall.
Lophotrochozoa
One of the three main lineages of bilaterian animals; it includes organism that have lophophores or trochophore larvae.
Paleozoic era
The geological era that includes the Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian periods. Characterized by the Cambrian explosion, the colonization of land, the origin of reptiles, tetrapods, forests of vascular plants, and insects, and a mass extinction at its end. Approximately 541-252 MYA.
