Biology Essay

1996 Words Feb 20th, 2015 8 Pages
Chapter 4 * Figure 4-2 * Modification of a germ cell to form a mammalian sperm. (A) The centriole produces a long flagellum at what will be the posterior end of the sperm, and the golgi apparatus forms the acrosomal vesicle at the future anterior end. The mitochondria collect around the flagellum near the base of the haploid nucleus and become incorporated into the midpiece ("neck") of the sperm. The remaining cytoplasm is jettisoned and the nucleus condenses. The size of the mature sperm has been enlarged relative to the other stages. (B) Mature bull sperm. The DNA is stained blue with DAPI, the mitochondria are stained green, and the tubulin of the flagellum is stained red. (Q Acrosome of mouse sperm, …show more content…
* Egg jelly- attracts or activates sperm. The egg is specialized for receiving sperm and initiating development. * Sea urchin egg cell surface. (A) Scanning electron micrograph of an egg before fertilization. The cell membrane is exposed where the vitelline envelope has been torn. (B) Transmission electron micrograph of an unfertilized egg, showing microvilli and cell membrane, which are closely covered by the vitelline envelope. A cortical granule lies directly beneath the cell membrane. * Figure 4-7 * Zona pellucida- the extracellular envelope is a separate and thick matrix * Cumulus- a layer of cells that nurture the egg from the time of release from the ovary. * The hamster egg, or ovum, is encased in the zona pellucida
. This in turn, is surrounded by the cells of the cumulus. A polar
 body cell, produced during meiosis, is also visible within the zona pellucida. (B) At lower magnification, a mouse oocyte is shown surrounded by the cumulus. * Figure 4-5 * Stages of egg maturation at the time of sperm entry in different animal species. Note that in most species, sperm entry occurs before the egg nucleus has completed meiosis. The germinal vesicle is the name given to the large diploid nucleus of the primary oocyte. The polar bodies are nonfunctional cells produced by meiosis * Figure 4-8 * (A) Sea urchin fertilization is external. (1)The sperm is chemotactically attracted to and activated

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