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5 Written questions

5 Matching questions

  1. Yolk sac
  2. From cleavage to blastula
  3. Embryology
  4. Organogenesis
  5. Amnion
  1. a (membrane of eggs) this membrane encloses the amniotic fluid; amniotic fluid provides an aqueous environment that protects the developing embryo from shock
  2. b the body organs begin to form; in this process, the cells interact, differentiate, change physical shape, proliferate, and migrate
  3. c (membrane of eggs) encloses the yolk; blood vessels in the yolk sac transfer food to the developing embryo
  4. d the first complete cleavage of the zygote occurs approximately 32 hours after fertilization; the second cleavage occrus after 60 hours, and the third cleavage after approximately 72 hours, at which point the eight-celled embryo reaches the uterus; as cell division continues, a solid ball of embryonic cell, known as teh morula, is formed; blastulation begins when teh morula develops a fluid-filled cavity called the blastocoel, which by the fourth day becomes a hollow sphere of cells called the blastula; the blatula is the stage of teh embryo that implants in the uterus
  5. e the study of the development of a unicellular zygote into a complete, multicellular organism; in the course of nine months, a unicellular human zygote undergoes cell division, cellular differentiation, and morphogenesis in preparation for life outside teh uterus; much of what is known about mammalian development stems from the study of less complex organisms such as sea urchins and frogs

5 Multiple choice questions

  1. the fluid-filled cavity that forms in the center of a blastula
  2. fter the initial cell division the fate of the resulting daughter cells is not determined -- each has the potent ial to develop into an entire organism. Sometimes this occurs; resulting individuals are genetically identical (in humans, they are called identical twins)
  3. a longitudinal, flexible rod made of tightly packed mesodermal cells that runs along the anterior-posterior axis of a chordate (member of the phylum chordata) in the dorsal part of teh body
  4. a tube of infolded ectodermal cells that runs along the anterior-posterior axis of a vertebrate, just dorsal to the notochord; it will give rise to teh nervous system
  5. during the first weeks, the major organs begin to develop; the heart begins to beat at approximately 22 days, and soon afterwards, the eyes, gonads, limbs, and liver start to form; by five weeks the embryo is 10mm in lenght; by six weeks the embryo has grown to 15mm; the cartilaginous skeleton begins to turn into bone by the seventh week; by the end of eight weeks, most of teh organs have formed, the brain is fairly developed, and the embryo is referred to as a fetus; at teh end of teh third month, the fetus is about 9 cm long

5 True/False questions

  1. Cleavageeach embryonic development is characterized by a series of rapid mitotic divisions knows as cleavage; these divisions lead to an increase in cell number without a corresponding growth in cell protoplasm (i.e., the total volume of cytoplasm remains constant); thus, cleavage results in progressively smaller cells, with an increasing ratio of nuclear-to-cytoplasmic material; cleavage also increases the surface-to-volum ration of each cell, thereby improving gas and nutrient exchange; this early developmental process consists of a series of very rapid, synchronous mitotic divisions that converts the zygote's single large cell into a solid ball of cells, known as teh morula, then into the blastula


  2. Gastrulaa hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals


  3. Second trimesterthe fetus does a tremendous amount of growing; it begins to move around in teh amniotic fluid; its face appears human, and its toes and fingers elongate; by the end of the sixth month, the fetus is 30-36 cm long


  4. Chorion(membrane of eggs) lines the inside of the shell; it is a moist membrane that permits gas exchance


  5. Blastulaan embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm


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