Theme 1 | Page 140

CURRICULUM GUIDE FOR S.C. TEACHER CADET COURSE | EXPERIENCING EDUCATION, TENTH EDITION Physical Development Theme I: Experiencing Learning Unit 3: Growth and Development Principles of Growth for All Stages of Development Human growth and development is based on a combination of genetics and environment. Environmental factors, such as maternal nutrition, stress, diseases, age, and use (or nonuse) of cigarettes, alcohol, and drugs, affect development and birth size. In all stages of development, humans follow four main principles of growth Four Main Principles of Growth From Birth to Age Two Zygote (from conception to two weeks) This new life has inherited 23 chromosomes from each parent, 46 in all, creating the complex genetic blueprint for every detail of human development—sex, hair and eye color, height, and skin tone. Embryo (from two to eight weeks) Foundations of the brain, spinal cord, and nervous system are already established. The heart begins to beat; backbone and muscles are forming; and arms, legs, eyes, and ears have begun to show. Fetus (from eight to thirty-eight weeks) Everything is now present that will be found in a fully deve