Print this Web Links Activity Log to record your findings. In order to view and print these activities, it is necessary to have Adobe Acrobat Reader. If you do not have this, get the free download now.   Click the Techie Toolbox for tips and help to make the most of your time on the Web. Chapter 41: Reproduction and Development  Human Reproduction Problem Set, The Biology Project, Human Biology This site provides problems designed to help students understand the human reproductive system. What hormone is released by the hypothalamus at the onset of sexual maturity? Welcome to Developmental Biology Follow the link to this site to learn more about embryological development. Click on the tutorials to learn about development in a variety of species and body structures. Visible Embryo This site provides information and photographs that illustrate the first four weeks of human development. What event occurs in the fourth week after fertilization?