BIOLOGY 101 Study Guide - Midterm Guide: Homeosis, Model Organism, Ontogeny
Document Summary
By these terms we mean the differentiation from egg to mature individual. Among animals and plants there is a wide variety of developmental patterns. B/c of this difference in ontogenies we will concentrate on two quite different organisms, humans and insects. We do this because we want to stress both the differences as well as fundamental similarities in two distantly related groups. Fertilization: sperm contacts jelly layer, acrosomal reaction begins, digestion of jelly layer, binding to vitelline envelope, sperm iyses hole in vitelline envelope. Fusion of acrosomal process membrane and egg membrane: sperm nucleus and centriole enter egg. Cleavage is set of rapid cell divisions (w/o growth) that follows fertilization. Cells created by cleavage are called blastomeres. Cleavage results in solid cells called a morula: w/ further cell division a hollow sphere called a blastula is formed. Gastrulation involves production of 3 embryonic layers and elongation of developing embryo called a gastrula.
