L18 reproduction II

L18 reproduction II - Chapters 51 52 Lecture Guide...

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Chapters 51 & 52 Lecture Guide Intro: Single Cell to Multicellular Organism A single fertilized egg has to give rise to different cell types. Each type of cell has a different structure and corresponding function. Cells of similar types are organized into tissues, tissues into organs, organs into organ systems, and organ systems into the whole organism. The challenge: To give rise not only to cells of different types but also to higher- level structures arranged in a particular way in three dimensions. Development: A Three-Step Process Cell division Cell differentiation—cells become different in structure and function controlled at the level of transcription cytoplasmic determinants induction Morphogenesis—“creation of form,” gives an organism shape. Limited to embryonic and juvenile periods in animals Occurs throughout lifetime in plants—meristemic (embryonic) regions Cytoplasmic Determinants Regulate the expression of genes that affect the developmental fate of the cell After fertilization, the cell nuclei resulting from mitotic division of the zygote are exposed to different cytoplasmic environments. Induction Caused by signal molecules from nearby cells which trigger observable cellular changes through gene expression in the target cell The Egg and Extraembryonic Membranes Fish and amphibians Eggs are laid in water; no special water-filled enclosure required Reptiles, birds, and mammals are amniotes Shelled egg Uterus Marsupial and placental mammals 1
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Chapters 51 & 52 Lecture Guide Three Phases of Early Development Cleavage Gastrulation Cleavage and Gastrulation=embryogenesis Organogenesis: organs begin to form Meroblastic cleavage: Holoblastic cleavage: Division Into Smaller Cells Called Blastomeres Cleavage in an echinoderm (e.g., sea urchin) Cleavage in a frog embryo Gastrulation: layers 2
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Lecture Guide Gastrulation Process By the End of Gastrulation The three embryonic tissues are arranged in layers
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L18 reproduction II - Chapters 51 52 Lecture Guide...

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