Unit 8 Human Reproduction and Development ........................................ 732 Chapter 21 The Beginning of Life ................................................................... 734 Lesson 21.1 The Male Reproductive System ..................................... 736 Lesson 21.2 The Female Reproductive System .................................. 741 Lesson 21.3 Conception, Pregnancy, and Birth .................................. 750 Lesson 21.4 Teen Pregnancy and Parenthood .................................... 758 Chapter 22 Health Across the Life Span ........................................................... 770 Lesson 22.1 Understanding Development ......................................... 772 Lesson 22.2 Health During the Childhood Years ................................ 777 Lesson 22.3 Adolescence and Puberty .............................................. 782 Lesson 22.4 Adulthood and the Nature of Aging ................................ 788 Background Lesson 1 The Body Systems ................................................. 800 Background Lesson 2 Personal Hygiene .................................................. 812 Background Lesson 3 Sleep .................................................................. 817 Glossary/Glosario .................................................................................. 819 Index ................................................................................................... 857 xii