Biology: Spermatogenesis: Meiosis in Males

http://www.mindbites.com/lesson/1471 This lesson covers the biological explanation of how sperm is created. It discusses both meiosis in the male that create sperm (spermatogenesis) and an explanation of why sperm are structured as they are and a description of where each of these processes take place anatomically. Additionally, there is a discussion of how developing sperm cells receive nurtrients. Sperm are produced in the seminiferous tubules of the testis. These tubules are arranged in layers that parallel the stages of meiosis. Germ cells produce primary spermatocytes which divide to produce secondary spermatocytes, which divide to produce spermatids, which develop into sperm. The process of sperm creation is called spermatogenesis. It is basically the type of meiosis that occurs in males (where oogenesis is the type of meiosis that occurs in females). Meiosis is the division of a diploid cell (has a diploid number of chromosomes) into 4 haploid cells (gametes). In the process of spermatogenesis, a diploid cell sees a doubling of chromosomes and then is divided into two separate diploid cells in Meiosis I. Following this is a second division in which the outcome is four cells with exactly half of the number of chromosomes as there were in the original cell that divided in Meiosis I. Last, Professor Wolfe will explain why men don't 'run out' of sperm cells while women do run out of eggs during the course of their life (because the germ cells that go through meiosis to create sperm also can undergo mitosis, or cell division, to reproduce though the equivalent cells in women cannot undergo mitosis). Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis. George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science. Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel. His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp. He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.