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BIOL 303
Bruce Reed

BIOL 303 STUDY QUESTIONSLECTURE SET 1 1What do we mean when we refer to the development of an organism The process of progressive and continuous change that generates a complex multicellular organism from a single cell Development occurs throughout embryogenesis maturation to the adult form and continues into senescence 2Define the following terms oGamete a specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring a sperm or an egg oZygote a fertilized egg with a diploid chromosomal complement in its zygote nucleus generated by fusion of the haploid male and female pronuciei oCleavage a series of rapid mitotic cell divisions following fertilization in any early embryos cleavage divides the embryo without increasing its mass oBlastomere a cleavagestage cell resulting from mitosis oMorula mulberry vertebrate embryo of 1664 cells precedes the blastula or blastocyst stage Blastula earlystage embryo consisting of a sphere of cells surrounding an inner fluidfilling cavity the blastocoeloblastocoel A fluidfilled cavity that forms in the animal hemisphere of early amphibian and echinoderm embryos or between the epiblast and hypoblast of avian reptilian and mammalian blastodermstage embryosogastrulation a process involving movement of the blastomeres of the embryo relative to one another resulting in the formation of the three germ layers of the embryo ogastrula a stage of the embryo following gastrulation that contains the three germ layers that will interact to generate the organs of the body ogerm layer one of the three layers of the vertebrate embryo generated by the process of gastrulation that will form all of the tissues of the body except for the germ cells otriploblastic three germ layersodiplobasltic lack a true mesoderm oectoderm the cells that remain on either the outside amphibian or dorsal avian mammalian surface of the embryo following gastrulation Of the three germ layers the ectoderm is the one that forms the nervous system from the neural tube and neural crest and also generates the epidermis covering the embryo omesoderm the middle of the three embryonic germ layers laying between the ectoderm and the endoderm The mesoderm gives rise to muscles and skeleton connective tissue the reproductive organs and to kidneys blood and most of the cardiovascular tissue oendoderm the innermost germ layer forms the epithelial lining of the respiratory tract the gastrointestinal tract and the accessory organs of the digestive tract oorganogenesis interactions between and rearrangement of cells of the three germ layers to produce tissue and organs ogerm cells a group of cells set aside from the somatic cells that form the rest of the embryo for reproductive function Consists of the cells of the gonads ovary and testis that undergo meiotic cell divisions to generate the gametes osomatic cells cells that from the body all cells in the organism that are not germ cells 3What is holoblastic cleavage meroblastic cleavageHoloblastic refers to a cell division cleavage pattern in the embryo in which the entire egg is divided into smaller cells as it is in frogs and mammals Meroblastic refers to the cell divisions pattern in zygotes containing large amounts of yolk wherein only a portion of the cytoplasm is cleaved The yolk serves as nutrition for the embryo as in insects fish reptiles and birds 4What were the tenets of the epigenesis and preformation theories of embryogenesis oAristotle and Hervey in examining their developing chicken embryos asserted that organs of the embryo were formed from scratch or de novo each generation epigenesis theory of embryogenesis oKaspar Friedrich Wolff supports epigenesis but without the concept of cells and the cell doctrine Wolff postulated an unknown force vis essentialis that directs embryogenesis oEpigenesis established by Christian Pander Karl Ernst von Baer and Herinrich Rathke There were better microscope and stains described the concept of germ layers discovery of the notochord discovered the mammalian egg and concept of induction tissues construct organs through interactions with other tissues oMalpighi despite the fact that he was using a microscope concluded that organs were already present in miniature form preformation theory 5What are von Baers lawsThe laws argue against the flawed view of recapitulation Recapitulation is the idea that ontogeny growth and development occurs through a variety of stages that are representative of the evolutionary phylogeny of a particular species 1all embryos go through a similar stage 2generalized features appear early in development 3specialized features arise from generalized ones4adult forms of lower animals are not embryos of higher animals 6How are epithelial and mesenchymal cells differentEpithelial cellsoform sheets connected by functional complexes that communicate with each otherosheets act as a barrieromove in harmony ohave a clear polar character from one side to anotherobasal lamina is a foundation contacts only one surface of the cell mesenchymal cells oloosely organized and loosely attached cells more like bold individuals ocan migrate as individual cells ocan also adhere in 3D clumps obasal lamina may surround the cells 7What is meant by the term morphogenesisThe organization of the cells of the body into functional structures via coordinated cell growth cell migration and cell death ocell division direction and amount of ocell shape changescan also involve change in character from epithelial to mesenchymal ocell movement or migration ocell growth some cells become smaller sperm cells or larger egg cells ocell death programmed removal of superfluous cells or entire tissues ochanges in composition of cell membrane or secreted products extracellular matrix can influence whether neighbouring cells migrate 8What is a fate map and how would a fate map be constructed using todays technology ie with transgenic organisms andor fluorescence microscopesFate map A map of the developmental fate of a zygote or early embryo showing the adult organ that will develop from material at a given position on the zygote or early embryo
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