Heredity and Enviornment

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11 Genetic and Environmental Influences on Human Development



We may often wonder about the reasons and forces which shape our personality and character. Each one of us has a specific kind of nature which takes that particuler form because of the effect of two major factors. The first is the genetic make-up which we inherit from our parents, and the second influence comes from the various experiences we have in our interaction with our surrounding environment. This includes all the things we see and hear from the time of birth and all the interactions we have with other people as we grow up. In this lesson the influences of genetic as well as environmental factors on human development will be discussed. The joint influence of these two factors will also be discussed in detial.



After reading this lesson you will be able to : apprise the intendependence of genetic and vironment on human development; explain the development of human life from the time of conception; illustrate the effects of environmental conditions on pre-natal development; define socialization;

Genetic and Environmental Influences on Human Development :: 119

List the agents of socialization.


Human life from the time of Conception
Environmental Influences on the unborn child Two types of environmental conditions are important to note. Some maternal characteristics and external harmful agents can cause considerable risk for the developing embryo or fetus. Very young mothers, particularly those under 17, and mothers over 35 years of age have greater risk of prenatal and birth complications and death of the fetus or the new born (neonate). Inadequate diet and nutritional deficiency of the mother increases the risk of congenital defects, still birth and infant mortality during the first year. Prolonged and severe emotional stress of the pregnant mothers increases the chances of miscarriage, premature delivery and temperamental state of the babies.

As described in the last lesson an individual life begins when the female ovum (egg) is fertilized by the male sperm. At this moment of conception human life begins, when the zygote is formed. This single fertilized cell divides into many cells, and these cells have the capacity to deal with specialized functions. In the early stage of development, the organism is called a fetus. Behaviour in the form of bodily movements starts at the beginning of the fetal period, that is 8-9 weeks after conception. The fetal development of human behaviour takes place according to the growth and readiness of the nervous system. At the end of the second month, the size of the head is half of the total body. The head becomes smaller in proportion as age increases. The functions that deal with information coming form the sensory channels and that relate to movement (motor), first develop in the head region of the fetus, and later develop in body parts away from the head.

Besides the maternal characteristics, a number of environmental agents such as diseases, viruses, drugs, chemicals and radiation can adversely affect the prenatal development and produce birth defects. Such external harmful agents are known as teratogens. Maternal diseases such as rubella (German measles), syphilis, genetal herpes, AIDS (Acquired Immune Deficiency Syndrome), chicken pox, cholera, diabetes, hapatitis, mumps, tuberculosis and influenza etc., several drugs such as alcohol, marijuana, tobacco, cocaine, heroin, LSD, some antibiotics and medicines in excess doses and X-ray and other exposure to radiation and several other chemicals and environmental pollutions are known teratogens which cause birth defects increasing the risk in the development of the embryo, the fetus or the new born. Some behaviours which occur in the human infant are not caused by external stimulation. The internally caused actions are crying, stretching, sneezing, chewing, and smiling. At the time of birth, certain...
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