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Cellular Interactions in the Regulation of Development in Annelids and Molluscs

1971; Elsevier BV; Linguagem: Inglês

10.1016/b978-0-12-028609-6.50006-6

0065-2962

James N. Cather,

Microplastics and Plastic Pollution

This chapter presents an evaluation of the regulatory mechanisms, which form the basis for the development of the spiralian organism, its organs and organ systems, its tissues and cells, and its molecular specificity. The significance of the larval form lies in its adaptability to the environment and its role in evolution. The form of the larva can be understood by analysis of the organs present and through comparison of the presumptive areas. The theory of variable gene activity is being subjected to a critical analysis in spiralians, as in other organisms. This theory expresses the concept that a portion of the cell's genome functions at any particular time and that the active portion differs between different cell types. The activation of specific genes is a result of the cytoplasmic niche in which a particular nucleus finds itself. That niche quality is because of molecular configurations established in oogenesis and through the interactions of cells and tissues in the developing embryo. Fertilization, which forms the basis for embryogenesis and the establishment of diploidy, is one of the major cellular interactions and plays a significant role in the reorganization of the cytoplasm of the egg and the initiation of metabolic changes.