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Chapter 17 Extended Lecture Outline

Chapter 17 Extended Lecture Outline - Chapter 17 Extended...

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Chapter 17 Extended Lecture Outline Chapter Outline INTRODUCTION All Cells in a Multicellular Organism Descend From a Single Cell The Developmental Program Unfolds With Precision fig 17.1 DEVELOPMENT IS A REGULATED PROCESS Multicellular Cell Specialization Controlled Via Gene Expression ` In fungi only reproductive cells are specialized Plant development is flexible and influenced by the environment Animal development is rigidly controlled with less influence by environment fig 17.2 Vertebrate Development Dynamic series of stages of cell movement and formation of organs fig 17.3 Cleavage Zygote is the initial vertebrate being One cell divides rapidly forming blastomeres fig 17.4 Embryo stays same size, cell number increases, cell size decreases Cells at animal pole form external body tissues Cells at vegetal pole from internal tissues Formation of the blastula Outer blastomeres connected by tight junctions Cell mass effectively separated from environment At sixteen-cell stage cells at interior pump Na+ to outside Forms osmotic gradient in intercellular spaces Water moves from cells to enlarging intercellular spaces Spaces combine to form a cavity in cell mass 17.3b Resulting hollow ball of cells is the blastula Gastrulation Gastrula forms when wall of blastula at vegetal pole pushes inward fig 17.3c Cell extensions called lamellipodia help in cell movement Process called gastrulation, embryo becomes bilaterally symmetrical Embryo develops three germ layers Endoderm forms tube of primitive gut, most internal organs Outer cells are ectoderm form skin and nervous system Mesoderm forms notochord, bones, blood vessels, connective tissue, muscles Neurulation Presence of notochord triggers thickening of an ectodermal zone fig 17.3d Cells elongate, form wedge shape and roll into a tube Neural tube formed through this process of neurulation Cell migration Variety of cells migrate to form distant tissues fig 17.3e Neural crest pinches off from neural tube forms sense organs Somites migrate from central blocks of muscle forming skeletal muscles Receptor proteins of migrating cells interact with destination tissues to cease movement Organogenesis and growth Basic vertebrate plan established when body is only a few millimeters long Tissues develop into organs size increases enormously fig 17.3f Insect Development Insects possess two distinctly different body forms Changes from a tubular eating machine to a form with wings and legs Change in body form called metamorphosis
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Exemplified by the fruit fly, Drosophila fig 17.5,6 Maternal genes Construction of egg begins development before fertilization Nurse cells move their mRNA into end of egg nearest them fig 17.6a After divisions daughter cells contain different maternal products Action of maternal, not zygotic, genes controls initial development Syncytial blastoderm Nuclear divisions without cytokinesis produce syncytial blastoderm fig 17.6b Produce 400 nuclei within a single cytoplasm Nuclei communicate freely, but experience different maternal products
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Chapter 17 Extended Lecture Outline - Chapter 17 Extended...

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