Ch 32 Intro to Animal Evolution
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eagleswings59 Plus on February 14, 2012
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41 terms
Terms | Definitions |
|---|---|
 cleavage | (embryology) the repeated division of a fertilised ovum |
| blastula | The hollow ball of cells marking the end stage of cleavage during early embryonic development |
| gastrula | An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm. |
| larva | the immature free-living form of most invertebrates and amphibians and fish which at hatching from the egg is fundamentally unlike its parent and must metamorphose |
| metamorphosis | the marked and rapid transformation of a larva into an adult that occurs in some animals |
| grade | A group of organisms that share the same level of organizational complexity or share a key adaptation. |
| parazoans | phylum porifera (sponges) |
| eumetazoans | member of the clade of 'true animals', the animals with true tissues (all animals except sponges) |
| radiata | Members of the radially symmetrical animal phyla, including cnidarians. |
| radial symmetry | the property of symmetry about an axis |
| bilateria | Members of the branch of eumetazoans possessing bilateral symmetry. |
| bilateral symmetry | arrangement of body parts so there are distinct left and right halves that mirror each other |
| dorsal | back |
| ventral | Front |
| germ layers | Tissue layers in the embryos of all animals except sponges, ectoderm, mesoderm, endoderm |
| 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 |
| 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 |
| archenteron | The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal. |
| diploblastic | Having two germ layers. |
| triploblastic | has three germ layers: the ectoderm, endoderm, and mesoderm. |
| mesoderm | the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue |
| acoelomate | an animal that lacks a coelom, or body cavity |
| body cavity | A fluid-containing space between the digestive tract and the body wall. |
| pseudoceolomate | an organism in which the ceolom is not completely covered by the mesoderm |
| coelomates | An animal that possesses a true coelom (a body cavity lined by tissue completely derived from mesoderm). |
| coelom | a body cavity completely lined with mesoderm |
| protostomes | Organisms that first forms a mouth when it develops from the blatopore. |
| deuterostomes | Undergoes radial cleavage and the anus forms before the mouth. |
| spiral cleavage | 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. |
| determinate cleavage | A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early. |
| radial cleavage | 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. |
| indeterminate cleavage | 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. |
| schizocoelous | In protosomes, a pattern of development in which a solid mass of mesoderm cells splits to form the cavity that becomes the coelom. |
| enterocoleous | in deuterostomes when development begins as buds from the archenteron |
| blastopore | The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes |
| Lophotrochozoa | a clade that encompasses the annelids, mollusks, and several other phyla, they are distinguished by two morphological features, the lophophore, a crown of tentacles used for feeding,and the trochophore larva, a distinct larval stage |
| Ecdysozoa | One of two distinct clades within the protostomes. It includes the arthropods and animals that molt as they grow. |
| trochophore larva | Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs. |
| Ediacaran period | the last period during the Precambrian period, when there was extensive glaciation, which delayed further evolution on earth |
| Cambran explosion | 545 to 525 mya all major body plans evolved examples are in the fossils of the Burgess Shale |
| lophopore | water is circulated and food removed through a funnel fringed with cilia |
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