Section II Beginnings

Chapter 3 Biological Beginnings

Summary

1.0 Images of Life-Span Development: The Jim and Jim Twins

The Minnesota Study of Twins Reared Apart investigates various aspects of the lives of identical twins and fraternal twins from all over the world. Although the study's conclusions must be evaluated in light of several methodological criticisms, the more important point is that this study illustrates a growing interest in the genetic basis of human development.

2.0 The Evolutionary Perspective

Natural Selection. Natural selection is an evolutionary process that favors individuals within a species best adapted to survive and reproduce. Darwin believed that evolutionary change occurs at a slow pace. Although no dramatic evolutionary changes have occurred since the human lineage (род родословная, потомство) appeared in the fossil record about 50,000 years ago, there have been sweeping (быстрый) cultural changes. Biological evolution shaped humans into a culture-making species for whom change can occur rapidly.

Sociobiology. Sociobiology is an evolutionary view that argues behavior is motivated by a desire to dominate the gene pool (генофонд). Sociobiology is controversial. Critics say that Sociobiology ignores the environmental determinants of behavior, lacks predictive power, and manifests a bias against (смещение) females.

3.0 Heredity

What Are Genes? Human development begins with the genetic code we receive from our parents. The nucleus of each human cell contain 46 chromosomes, composed of DNA, that provide the blueprint for the development of an individual. Genes are the building blocks of chromosomes. Gametes are human reproductive cells.

Reproduction. Genes are transmitted from parents to offspring by gametes, the ovum or egg from the female and sperm from the male. The process of meiosis produces the gametes. In human beings each gamete has 23 chromosomes. Reproduction occurs when a sperm fertilizes an ovum, producing a zygote. Male and female sperm can be separated by a centrifuge, making it possible to control the sex of the offspring. Approximately 10-15 percent of American couples are infertile. In vitro fertilization, conception outside the body, allows otherwise infertile couples to bear children; however, adoption provides an alternative choice.

Abnormalities in Genes and Chromosomes. A number of genetic problems can occur. PKU syndrome is a genetic problem resulting in the failure to produce an enzyme necessary for metabolism and can cause severe mental retardation if not treated by dietary restrictions. Down syndrome is a form of mental retardation caused by the presence of an extra choromosome, and is accompanied by physical abnormalities. Sickle-cell anemia is a disease of the red blood cells, existing primarily among blacks, and causes early death. Several disorders are associated with sex chromosome abnormalities. These include Klinefelter syndrome, males with an extra X chromosome; Turner syndrome, females missing an X chromosome; and XYY syndrome, males with an extra X chromosome. Genetic counseling provides information to couples about the risks of having a genetically defective child. Four procedures can be used to determine the presence of genetic defects: amniocentesis, ultrasound sonography, the chorionic villus test, and the maternal blood test.

4.0 Genetic Principles and Methods

Some Genetic Principles. Genetic transmission is a complex process because the underlying genetic structure, or genotype, must be inferred from the actual physical characteristics of a person, the phenotype. Nonetheless, some general principles have been identified. Some genes are dominant, and will always be expressed phenotypically when present, whereas other genes are recessive, and will be expressed phenotypically only when paired with another recessive gene on the other chromosome, the principle of dominant-recessive genes. Some characteristics are determined by the interaction of many different genes, the principle of polygenetic inheritance. The reaction range refers to the possible extent of phenotypes that could be expressed by a given genotype. The genetic codes set broad limits on the range of possible outcomes, which are then affected by the environment. Canalization refers to the extent to which certain genotypes might be immune to environmental influences.

Methods Used by Behavior Geneticists. The field of behavior genetics studies the nature and degree of the hereditary basis for behavior. Twin studies examine identical and fraternal twins for the degree of similarity. Adoption studies compare the adopted child with both the adoptive and biological parents.

Heredity's Influence on Development. The two most widely investigated aspects of heredity's influence on development concern intelligence and temperament. Jensen argues that intelligence is primarily inherited and that environment and culture play minimal roles. Jensen reviewed twin studies and claimed that the heritability of intelligence, as measured by IQ, is about 80 percent. Criticisms of Jensen's work include: (a) 10 tests measure only a narrow range of intelligence, and (b) investigations do not include environments that differ radically.

5.0 Heredity-Environment Interaction and Development

Behavior geneticists study the influences of both genes and environment on development, the heredity-environment interaction.

Passive Genotype-Environment, Evocative Genotype-Environment, and Active Genotype-Environment Interactions. Sandra Scarr believes that parental genotypes influence the environment they provide for their children. Three ways behavior geneticists believe that heredity and environment interact in this manner are passively, evocatively, and actively. Passive genotype-environment interactions occur when parents, who are genetically related to the child, provide a rearing environment for the child. Evocative genotype-environment interactions occur because a child's genotype elicits certain types of physical and social environments. Active (niche-picking) genotype-environment interactions ocur when children seek out environment they find compatible and stimulating. The relative importance of these three forms of interaction changes as children develop.

Shared and Nonshared Environmental Influences. Shared environmental experiences are children's common experiences, such as their parents' personalities and intellectual orientation, the family's social class, and the neighborhood in which they live. Nonshared environmental experiences refer to the child's own unique experiences both within a family and outside the family, that are not shared with another sibling. Robert Plomin argues nonshared environmental experiences produce different personalities for siblings.

The Contemporary Heredity/Environment Controversy. Sandra Scarr's view that genotypes drive experience have been criticized by Baumrind, Maccoby, and Jackson who stress the role of experience as the primary determinants of development.

Conclusions about Heredity-Environment Interaction. Both genes and experience are necessary for development. The two factors are said to interact because the environmental effects depend on individual's genetic endowment.

6.0 Contemporary Concerns

Sociocultural Worlds of Development 3.1: The Human Species is a Culture-Making Species. The biological evolution of humans is quite slow relative to cultural evolution. Cultural evolution makes it possible for humans to shape the world to fit human needs.

Perspectives on Parenting and Education 3.1: The Effects of Early Intervention on Intelligence. Early intervention programs try to provide favorable outcomes early in the life of children who are judged at risk for impaired intelligence. One study of the babies of mothers with IQs averaging 80 produced higher IQs at age three for children who attended an educational day-care center as compared to home-reared children. A second study demonstrated a successful intervention for Mexican American families who received parent education and educational day care when compared to control families.

Life-Span Practical Knowledge 3.1: Being Adopted. The authors review the influence of being adopted on people's lives and explore the relationship between being adopted and Erik Erikson's stages of psychosocial development.

Life-Span Practical Knowledge 3.2: Prenatal Tests. Robin Blatt's book is a comprehensive guide to the benefits and risks of various prenatal tests. It also addresses emotional and ethical issues facing couples who consider prenatal testing.

Life-Span Health and Well-Being: Genetic Counseling. Genetic counselors are typically physicians or biologists who are versed in medical genetics. These individuals are familiar with the potential genetic problems, their likelihood, and ways to minimize their effects. Final decisions always depend on a couple’s ethical and religious beliefs.

Key Terms

1.0 Images of Children: The Jim and Jim Twins

Minnesota Study of Twins Reared Apart

fraternal twins

identical twins

2.0 The Evolutionary Perspective

natural selection

evolutionary change

cultural change

sociobiology

altruism

genetic determinism

3.0 Heredity

chromosomes

DNA genes

gametes meiosis

reproduction

zygote зигота оплодотворенная клетка

in vitro fertilization экстракорпоральное оплодотворение

infertility бесплодие

phenylketonuria (PKU) оксифенилкетонурия, фенилпировиноградная олигофрения, болезнь Феллинг, синдром Феллинга

Down syndrome

sickle-cell anemia серповидно-клеточная анемия

Klinefelter syndrome синдром Клайнфелтера (Рейфенштейна - Олбрайта) хромосомная болезнь мужчин

Turner syndrome

XYY syndrome

genetic counselor

amniocentesis пункция, прокол

ultrasound sonography ультразвуковая эхография

chorionic villus test

maternal blood test

4.0 Genetic Principles and Methods

dominant-recessive genes principle

polygenetic inheritance

genotype

phenotype

reaction range

canalization

behavior genetics

twin study

monozygotic twin

identical twin

dizygotic twin

fraternal twin

adoption study

intelligence

5.0 Heredity-Environment Interaction and Development

interaction

passive genotype/environment interactions

evocative genotype/environment interactions

active (niche-picking) genotype/environment interactions

shared environmental influences

nonshared environmental influences

6.0 Contemporary Concerns

early intervention

prenatal tests

Essay and Critical Thinking Questions

Comprehension and Application Essay Questions

We recommend that you follow either our guidelines for "Answering Essay and Critical Thinking Questions,” or those provided by your instructor, when preparing your response to these questions. Your answers to these kinds of questions demonstrate an ability to comprehend and apply ideas discussed in this chapter.

1. Explain the concept of natural selection. Also explain the relationship between natural selection and sociobiology.

2. Explain the relationship among genes, chromosomes, and DNA. Also indicate how these entities function in reproduction.

3. What is infertility? What causes infertility? Explain what an infertile couple can do to have a baby.

4. Indicate and explain at least three examples of abnormalities in genes and chromosomes.

5. Assume that you have received a number of tests to assess fetal abnormalities. Identify and explain each procedure and what you would learn from it.

6. In your own words, what is a genotype and phenotype? Also explain how these concepts relate to the concepts of dominant and recessive genes.

7. Compare and contrast the concepts of reaction range and canalization.

8. Describe the methods used by behavior geneticists to study heredity's influence on behavior.

9. Indicate how you would explain to a friend that heredity and environment interact in various ways to produce development. Also provide an example of each of the three types of interaction and shared and nonshared environmental influences that you would use to help your friend understand this concept.

10. Imagine that you want to start a family. Explain what you would do before attending a session with a genetic counselor and what kinds of questions you would ask during the meeting.

Chapter 4 Prenatal Development and Birth

Summary

1.0 Images of Life-Span Development: Jim and Sara, an Expectant Couple

Couples expecting their first child spend much time preparing for the birth and face many difficult questions.

2.0 Prenatal Development

The Course of Prenatal Development. Prenatal development includes the germinal, embryological, and fetal periods. Conception usually occurs when a sperm cell unites with an ovum in the female's fallopian tube. The first two weeks of gestation is the germinal period, during which the zygote, a structure of 100 to 150 cells forms. The inner layer is the blastocyst that later develops into the embryo. The outer layer is the trophoblast that later develops into the placenta.

The implantation of the blastula marks the beginning of the embryological period. During the next six weeks, the embryo differentiates into an outer layer (ectoderm), a middle layer (mesoderm), and an inner layer (endoderm). The ectoderm becomes the hair, skin, nails, nervous system, and sensory receptors. The mesoderm becomes the muscles, bones, circulatory, and excretory systems. The endoderm develops into the digestive and respiratory systems. During the embryological period, a primitive human form takes shape, and the basic parts of the body can be identified. The placenta, umbilical cord, and amnion form and serve as a life-support system. The process of organ formation during the embryological period is called organogenesis. The embryological period ends at about eight weeks after conception.

The remaining seven months until birth is the fetal period. During this time, fetal size increases, the organs start functioning, reflexes appear, and there is sexual differentiation.

Miscarriage and Abortion. Miscarriages, or spontaneous abortions, happen when pregnancy ends before the developing organism is mature enough to survive outside the womb. Most occur within the first trimester without the mother's knowledge. Estimates indicate that 15 to 20 percent of pregnancies end in miscarriages. Deliberate termination of pregnancy is legal in the United States and can be done up until the end of the second trimester. The issue of induced abortion raises many medical, psychological, and social concerns and questions. Although abortion policies differ throughout the world, there is approximately one abortion for every two births. An unwanted pregnancy is stressful for the woman regardless of how it is resolved.

Teratology and Hazards to Prenatal Development. Teratology is the field that investigates the causes of congenital (birth) defects. Any agent that causes birth defects is called a teratogen; teratogens have their greatest effects during organogenesis.

Maternal diseases can cross the placental barrier or act at the time of birth. The maternal diseases and conditions believed to be involved in possible birth defects include rubella, syphilis, genital herpes, AIDS, the mother's age, nutrition, and emotional state and stress.

In the early 1960's mothers who took thalidomide, a tranquilizer for morning sickness, subsequently bore many deformed babies and demonstrated the powerful effects of drugs on prenatal development. Women who consume alcohol during pregnancy increase the likelihood of producing offspring with fetal alcohol syndrome. Smoking cigarettes is associated with adverse prenatal development, birth, and postnatal development. In addition, women who smoke during pregnancy experience more fetal and neonatal deaths, and have more preterm and low-birthweight infants. Other hazardous drugs include marijuana, heroin, and cocaine. Recent attention has centered on babies born to mothers who use cocaine.

Various environmental hazards can endanger the fetus. For example, exposure to radiation can cause chromosomal abnormalities. Pollutants and toxic wastes such as pesticides, carbon dioxide, mercury, and lead pose dangers to fetuses. A newer concern is with the effects of electromagnetic radiation from video display terminals. Toxoplasmosis produces coldlike symptoms in adults, but acts as a teratogen for a developing fetus. Saunas and hot tubs that raise the mother's body temperature can produce fevers that endanger the fetus.

3.0 Birth

Stages of Birth. The birth process has been divided into three stages. In the first stage, uterine contractions dilate the woman's cervix so that the baby can move from the uterus into the birth canal. The second stage begins when the baby's head starts to move through the birth canal and ends when the baby is born. The third stage, called afterbirth, involves the detachment and expulsion of the placenta.

Delivery Complications. A baby can move through the birth canal too rapidly or too slowly. A delivery that is too fast is called precipitate; when delivery is too slow, anoxia may result. The breech position occurs when the baby's head does not emerge from the vagina first. Surgical removal of the baby from the uterus is called a cesarean section.

The Use of Drugs During Childbirth. Drugs can aid deliveries by relieving pain or anxiety. Drugs such as the hormone oxytocin can speed the process of delivery. It is difficult to make clear statements about drug effects because birth weight and social class are better predictors of problems than drugs. Some medications are thought to have negative effects on the infant; others are thought to have no effect; however, the amount of medication is quite an important variable.

Childbirth Strategies. Expectant parents can choose from a number of childbirth strategies. In standard childbirth, an expectant mother goes to a hospital where a doctor becomes responsible for the baby's delivery. The birth usually takes place in a space resembling an operating room, and medication is commonly administered to the mother. Critics of this method point out that other individuals important to the mother are excluded from the process, the infant is separated from, the mother shortly after birth, and giving birth is treated like a disease. The LeBoyer method, often deemed "birth without violence," was intended to make the process of birth less stressful for infants. Prepared, or natural childbirth, is a process in which the mother is informed about what will happen during the procedure and about how she may best remain comfortable during childbirth, entails little medication, and involves parents in making decisions about any complications that arise. Although there are variations (e.g., the Lamaze method), all share common concerns for making parents confident, providing self-help tools for normal childbirth, and explaining how the medical system functions. This approach endorses both the teaching and taking of childbirth classes. The most current trend in the 1990's shifts emphases, offers new choices, and encourages understanding of obstetrical terminology.

Fathers now increasingly participate in the childbirth process. A cultural change in America encourages fathers to meet with caregivers, attend childbirth classes, and participate in the care of infants. Parents expecting a second or subsequent child often prepare older children for the birth of a sibling. The older child learns about pregnancy, birth, and life with a newborn in a developmentally appropriate fashion.

Preterm Infants and Age-Weight Considerations. Normal gestation is 38 to 42 weeks from conception. Infants born earlier than 38 weeks after conception are called preterm babies. Full-term infants born after a normal gestation period but who weigh less than 5.5 pounds are called low-birth,.lit infants. Intervention programs now improve the developmental outcomes for low-birthweight infants. Preterm infants have a different profile than that of full-term infants.

Care of the preterm infant is much too complex to be described only in terms of amount of stimulation. The conceptual age, illness, and Individual make of preterm infants affect their responses to stimulation. The appropriate stimulation changes as the preterm infant becomes less fragile and approaches full-term. Intervention programs should entail individual developmental plans.

Four important conclusions about preterm infants include: (a) advances in intensive care technology have reduced the likelihood of serious consequences for preterm infants, (b) outcomes for infants born with an identified problem are likely to be worse than for those born without a recognizable problem, and (c) more favorable outcomes for preterm infants are associate.with higher socioeconomic status.

Measures of Neonatal Health and Responsiveness. The Apgar Scale is a quick screen of inf. r.status that assesses heart rate, respiratory effort, muscle tone, body color, reflex irritability at one and five minutes after birth. The Brazelton Neonatal Assessment Scale is a more detailed long-term neurological evaluation, typically given on the third day of life and repeated later. It evaluates 20 reflexes and an infant's reactions to 27 different circumstances involving both physical and social stimulation. Brazelton training involves using the Brazelton Scale to show parents how their newborn responds to people. The training may be of help with high-risk infants.

4.0 The Postpartal Period

The Nature of the Postpartal Period. The postpartum period, usually lasting about six weeks after birth, comprises a time in which a woman's body adjusts both physically and psychologically to the process of childbearing. The term "fourth trimester" conveys the idea of continuity and the importance of this period for the mother.

Physical Adjustments. Physical adjustments include fatigue, involution (the process by which the uterus returns to its prepregnant size), consideration of when to resume sexual intercourse, and participation in exercises to recover former body contour and strength.

Emotional and Psychological Adjustments. Emotional fluctuations are common for recent mothers during the postpartal period. A special interest in the parent-infant relationship concerns bonding, the development of an emotional tie between parents and infant. In recent years, a critical-perk hypothesis has been advanced, suggesting that bonding must occur within the first few days of life. Although the exact time period has been questioned, this view has led to a revision of hospital procedures, allowing mothers and fathers more access to their infants in hospitals than was previously permitted.

5.0 Contemporary Concerns

Sociocultural Worlds of Development 4.1: Prenatal Care in the United States and around the World. The effectiveness of prenatal care is reflected by the percentage of low-birthweight infants. The United States has the highest percentage of low-birthweight infants among the economically and technologically advanced countries of the world. This outcome likely results from a lack of a national health care policy that ensures care for pregnant women.

Sociocultural Worlds of Development 4.2: To Work or Not to Work. New babies prompt families to consider whether and when a recent mother should go back to work. Guidelines for making the decision to work or not to work exist.

Perspectives on Parenting and Education 4.1: Becoming Knowledgeable about Pregnancy, Prenatal Development, and Childbirth Strategies. Learning about pregnancy and prenatal development and learning about childbirth strategies are two important aspects of education for expectant parents. Expectant parents often can benefit from parent education classes that cover topics such as self-care, fetal development, sexuality, nutrition, rest, and exercise. Childbirth class help an expectant couple learn about labor, birth, and how to cope with the final stage of pregnancy.

Life-Span Practical Knowledge 4.1: What to Expect when You're Expecting. This book provides a step-by-step guide to pregnancy and childbirth. This book is excellent and reassuring to expectant parents.

Life-Span Practical Knowledge 4.2: Will it Hurt the Baby? Richard Abrams book discusses how to use medicines safely during pregnancy and breast feeding.

Life-Span Health and Weil-Being: The Power of Touch and Massage in Development. Research by Tiffany Field has produced interest in the roles of touch and massage in improving the growth, health, and well-being of infants and children. Massage facilitates weight gains for preterm babies. Touch has been helpful also with children and adolescents who have touch aversions deriving from sexual abuse, autism, and eating disorders.

Key Terms

1.0 Images of Life-Span Development: Jim and Sara, An Expectant Couple

Prenatal Development

germinal period

blastocyst

trophoblast

implantation вживление

embryonic period

endoderm

ectoderm

mesoderm

placenta

umbilical cord пуповина

amnion водная оболочка плода

organogenesis органогенез – формирование органов в период роста

fetal period внутриутробный период

miscarriage выкидыш

abortion

teratogen (пороки, уродство)

teratology наука, изучающая пороки развития и уродства

ectopic pregnancy внематочная беременность

rubella краснуха

sexually transmitted diseases (STDS)

fetal alcohol syndrome (FAS) плодный алкогольный синдром

environmental hazards вредные факторы окружающей

toxoplasmosis токсоплазмоз (паразитарный болезнь из группы протозойных зоонезов)

2.0 Birth

dilation дилатация расширение

birth

afterbirth послед

precipitate преципитат, осадок

anoxia гипоксия (кислородная недостаточность)

breech position положение ягодиц

cesarean section

tranquilizer

sedative успок средство

analgesic

oxytocin окситоцин (для стимуляции родов)

standard childbirth

Leboyer method

prepared, or natural, childbirth

Lamaze method

sibling брат, сестра

full-term infant

preterm infant

low-birthweight infant

stimulation

Apgar Scale

Brazelton Neonatal Behavioral Assessment Scale

4.0 The Postpartal Period

pospartal period постнатальный, послеродовой

involution дегенерация, инволюция, сокращение

bonding связь

5.0 Contemporary Concerns

health care circle

massage

Essay and Critical Thinking Questions

Comprehension and Application Essay Questions

We recommend that you follow either our guidelines for "Answering Essay and Critical Thinking Questions," or those provided by your instructor, when preparing your response to these questions. Your answers to these kinds of questions demonstrate an ability to comprehend and apply ideas discussed in this chapter.

1. Describe development during the germinal, embryological, and fetal periods. Also indicate and explain what factors might contribute to complications at specific times during gestation.

2. What is organogenesis, and why is this concept important to the process of development?

3. Discuss medical, ethical, psychological, and personal issues pertinent to the decision to have an abortion.

4. What is a teratogen? Also indicate at least two examples of teratogens and their specific effects.

5. Compare and contrast the risks to expectant mothers who are either teenagers, twenty-something, or thirty-something.

6. Describe the stages of birth, and also explain three birth complications.

7. Imagine that you are about to give birth. What questions about cesarean sections and the use of drugs during delivery would be important to you? What reasons would lead you to accept or reject a cesarean section and drugs such as tranquilizers, sedatives, and analgesics during delivery?

8. Imagine that you are an expectant parent. What would you do and learn in a parent education class on pregnancy, prenatal development, and the three most common childbirth strategies?

9. Why and how have fathers and siblings become more involved in childbirth? Also discuss the pros and cons of this involvement.

10. How do preterm and low-birthweight infants differ?

11. What would you learn about your newborn from the Apgar and Brazelton Neonatal Behavioral Assessment Scales?

12. Explain why some claim that the postpartal period should be termed the fourth trimester.

13. A newborn baby often raises a question as to whether the mother will return to work outside the home or stay home with the baby. Explain how the advice of Eisenberg, Murkoff, and Hathaway would help you make this decision.

14. Summarize the evidence for and against the claim that touch and massage improves the growth, health, and well-being of infants and children.

Section III Infancy

Дата добавления: 2015-11-16