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Unformatted text preview: PowerLecture: Chapter 43 Principles of Animal Reproduction and Development Section 43.0: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Impacts, Issues: Sex and the Mammalian Heritage Lioness gives birth to cubs less than 4 months after mating Cubs depend on mother about 16 months 80% die before 16 months, usually from starvation Impacts, Issues: Sex and the Mammalian Heritage Males are larger, compete for dominance of females When new male assumes power, he kills all cubs he can catch Females collectively ovulate, get pregnant, bear and defend cubs Impacts, Issues: Sex and the Mammalian Heritage In nature, the main function of sex is to perpetuate one’s genes Perpetuation of life includes reproduction and development Section 43.1: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Modes of Reproduction Sexual reproduction Meiosis, gamete formation, and fertilization Offspring show genetic variation Asexual reproduction Single parent produces offspring Offspring are genetically identical Cost of Sexual Reproduction Specialized cells and structures must be formed Special courtship, and parental behaviors can be costly Nurturing developing offspring, either in egg or body, requires resources from mother Cost of Sexual Reproduction Early Development Where embryos develop Section 43.2: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Stages of Development Gamete formation Fertilization Cleavage Gastrulation Organ formation Growth, tissue specialization Stepped Art Life Cycle of a Leopard Frog Leopard frog life cycle Life Cycle of a Leopard Frog Stages of development Section 43.3: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Maternal Instructions The egg cytoplasm contains enzymes, mRNA transcripts, etc. These materials are not randomly distributed throughout the egg The egg also contains yolk, which inﬂuences cleavage patterns Experimental Evidence of Localized Differences Experimental Evidence of Localized Differences Cytoplasmic localization Cleavage Patterns Vary Complete or incomplete Radial or rotational Section 43.4: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Gastrulation Blastula is ball of cells During gastrulation, some cells move inward Produces a three-layered embryo Ectoderm Mesdoderm Endoderm Gastrulation Gastrulation Cell Differentiation Certain groups of genes are activated in some cells but not in others Genes are not lost, just inactivated Gurdon showed frog intestinal cell still had all the genes needed to make a new individual Morphogenesis Orderly changes result in specialized tissues and early organs Cells migrate Whole sheets of cells expand and fold Programmed cell death sculpts body parts Morphogenesis Neural tube formation Section 43.5: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Cytoplasmic Localization Development fate of embryonic cell lineages changes upon exposure to gene products from adjacent tissues Cells behave as if they have positional memory Demonstrated experimentally by transplanting embryonic cells Signal Transduction Pathways Dorsal Lip Transplant Dorsal Lip Transplant Embryonic induction Morphogens Dorsal lip (embryonic signaling center) Influences other cells by producing a morphogen Diffusion of morphogen creates gradient that influences differentiation; influences which genes are turned on or off AER Transplant AER transplant Pattern Formation Starts with cytoplasmic localization Classes of master genes activated in sequence Interactions among master genes are guided by regulatory proteins Gene products are spatially organized in the embryo Similar Master Genes Diverse animals use similar or the same master genes to govern development May help explain why there are so few body plans The relatively small number of master genes constrains variation To Know a Fly Drosophila used to study development Fate map Egg is polar Gradients of gene products influence expression of other genes Section 43.6: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Videos: CNN Ask your Thomson Sales Representative for these volumes on CD or VHS Genetics, 2003, Vol. 1, Fountain of Youth (1:32) Biology, 2004, Vol. 8, Is Aging Treatable? (2:25) Why Do Animals Age? Programmed life span hypothesis Cumulative assaults hypothesis Gray Crescent Formation of gray crescent Blastomere Blastomere separation I Blastomere Blastomere separation II Section 43.7: Weblinks and InfoTrac See the latest Weblinks and InfoTrac articles for this chapter online Dying in the Open Everything in the world dies, but we only know about it as a kind of abstraction Animals seem to have an instinct for performing death alone, hidden If…all the dying were done in the open, with the dead there to be looked at, we would never have it out of our minds …we take [deaths] to be unnatural events, anomalies, outrages We will have to give up the notion that death is a catastrophe, or detestable, or avoidable, or even strange Everything that comes alive seems to be in trade for everything that dies… There might be comfort in the recognition of synchrony, in the information that we all go down together, in the best of company - Lewis Thomas, 1973 Leading cancer specialist before his own death from cancer Coral Spawning Salamander Salmon Upstream Tadpoles ...
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