10 Unit 1 Children and Families in Today’s World Copyright Goodheart-Willcox Co., Inc. Environment All people live in both a physical and social environment. The unborn baby lives primarily in a physical environment that is almost totally dependent on the mother’s physical condition. This environment may be benefi cial due to proper prenatal care or harmful due to the lack of such care. After birth, physical conditions, such as food and rest, are part of the environment. Beyond physical conditions, all other experi- ences are part of a person’s social environment. To some degree, even unborn babies have a social envi- ronment. They can hear outside-the-womb sounds, especially the mother’s voice that may be soothing or startling due to fear or anger. These sounds are reinforced by physical signals sent to the unborn by the mother—changes in blood pressure, breathing rate, and hormones. After birth, the social environ- ment affects the way a child grows and develops in every developmental domain (Figure 1.4). that identical twins, who have the same structural genome, were more alike in physical traits and intellectual abilities than are brothers and sisters or other family members. The same similarities were found in identical twins reared apart. Researchers also study the effects of heredity in virtual twins. Virtual twins are unrelated children of almost the exact same age raised by the same parents. Although the environment would be very similar for both children, virtual twins often are very different in most traits. Thus, heredity has a major impact in growth and development. Today, most of the studies of heredity are con- ducted in a laboratory. Genetics (juh-NET-iks) is the study of the factors involved in the passing of traits in living beings from one generation to the next. In short, genetics is the study of heredity. Geneticists (biologists who study heredity) continue to make strides in learn- ing which traits pass from parents to child. Almost every physical, intellectual, and social-emotional trait is affected by genes. Thus, genes infl uence your growth and development in many ways. The follow- ing points are known about heredity: • Genes affect some parts of growth and development more than others. Genes determine body features, such as blood type, facial structure, and color of hair, eyes, and skin (Figure 1.3). Other traits, such as intellectual ability and social-emotional traits, are affected by both genes and the environment. Some genes determine whether a person will have a trait. For example, a person either is or is not an albino. (An albino is a person with white skin, almost white hair, and pink irises.) This is determined by genes. • Other genes affect the range of a trait. Traits such as height (very short to very tall) and athletic ability (almost no ability to greatness) come from these genes. These genes determine a trait’s potential. (Potential is the greatest amount or level possible.) Whether a person will show or use that trait to its potential depends on the person’s life. For instance, a healthful diet will help a child reach his or her height potential. The child cannot grow, however, beyond this potential. On the other hand, children with poor nutrition may not achieve their full potential. Figure 1.3 Because they share genes, parents and children often look alike. What physical traits do this mother and daughter have in common?