Transcript Chapter 1
Chapter 2 Biological Beginnings The Evolutionary Perspective Natural Selection and Adaptive Behavior ◦ natural selection -- the evolutionary process by which those individuals of a species that are best adapted are the ones that survive and reproduce ◦ survivors are better adapted to their world than are the non-survivors (Darwin, 1859; Johnson & Losos, 2008) Evolutionary Psychology Emphasizes the importance of adaptation, reproduction, and “survival of the fittest” in shaping behavior Fit -- the ability to bear offspring that survive long enough to bear offspring of their own ◦ the ability to pass your genes to the next generation (Promislow, Fedorka, & Burger, 2006) Evaluating Evolutionary Psychology Bandura (1998) rejects what he calls “one-sided evolutionism” An alternative is a bidirectional view, in which environmental and biological conditions influence each other Evolution gave us bodily structures and biological potentialities People have used their biological capacities to produce diverse cultures -aggressive and pacific, egalitarian and autocratic Genetic Foundations of Development Each of us carries a “genetic code” that we inherited from our parents A fertilized human egg carries this human code Fertilized human egg cannot grow into any other species Each of us began life as a single cell which contained our entire genetic code Chromosomes Nucleus of each human cell contains chromosomes Chromosomes -- thread-like structures made up of deoxyribonucleic acid, or DNA DNA is a complex molecule that has a double helix shape, like a spiral staircase, and contains genetic information Genes Genes -- units of hereditary information ◦ short segments of DNA Genes direct cells to reproduce themselves and to assemble proteins Proteins ◦ the building blocks of cells ◦ the regulators that direct the body’s processes (Mader, 2008) Human Genome Project Preliminary map of the human genome -- the complete set of developmental instructions for creating proteins that initiate the making of a human organism ◦ “If I read the genome out to you at the rate of one word per second for eight hours a day, it would take me a century… This gigantic document, an immense book, a recipe of extravagant length, and it all fits inside the microscopic nucleus of a tiny cell that fits easily upon the head of a pin.” (Ridley, 1999, p. 7) Each human has approximately 20,500 genes Human genome consists of many genes that collaborate both with each other and with nongenetic factors inside and outside the body Genetic expression is affected by their environment Questions Would you want yourself or a loved one to be tested for a gene that increases your risk for a disease but does not determine whether you will actually develop the disease? Why or why not? Would you want yourself and your mate tested before having offspring to determine your risk for having a child who is likely to contract various diseases? Why or why not? Should testing of fetuses be restricted to traits that are commonly considered to have negative outcomes, such as Huntington’s disease? Explain. Should altering a newly conceived embryo’s genes to improve qualities such as intelligence, appearance, and strength be allowed? Explain. Should employers be permitted access to your genetic information? Explain. Should life insurance companies have access to your genetic information? Explain. Michael Phelps in the Beginning Fertilization Zygote -- an egg and a sperm fuse to create a single cell In the zygote, the 23 unpaired chromosomes from the egg and sperm combine to form one set of 23 paired chromosomes ◦ One chromosome of each pair is from the mother’s egg and the other from the father’s sperm ◦ Each parent contributes half of the offspring’s genetic material The 23rd Pair of Chromosomes In females, the 23rd pair consists of two chromosomes called X chromosomes (XX) In males, the 23rd pair consists of an X and a Y chromosome (XY) The presence of a Y chromosome is what makes an individual male ◦ Who determines the sex of the zygote? Sources of Variability Combining genes of two parents increases genetic variability in the population Chromosomes in the zygote are not exact copies of the parents Another source of variability comes from DNA ◦ mutated gene -- a permanently altered segment of DNA Genotype and Phenotype Genotype -- all of a person’s genetic material Phenotype -- observable characteristics Phenotypes include ◦ physical characteristics (such as height, weight, and hair color) ◦ psychological characteristics (such as personality and intelligence) Chromosome- and Gene-Linked Abnormalities Down syndrome -- caused by the presence of an extra copy of chromosome 21 ◦ once in every 700 live births ◦ women aged 16 - 34 are less likely to give birth to a child with Down syndrome Behavior Genetics Behavior genetics seeks to discover the influence of heredity and environment on individual differences in human traits and development Behavior geneticists often study either twins or adoption situations (Plomin, DeFries, & Fulker, 2007;Vogler, 2006) Behavior Genetics In a twin study, the behavioral similarities between identical twins is compared with the behavioral similarities between fraternal twins In an adoption study, investigators seek to discover whether the behavior and psychological characteristics of adopted children are more like those of their adopted parents ◦ Examples: Psychological disorders, addiction Behavior Genetics ◦ Multiple Zygotes Monozygotic twins (Identical twins) Dizygotic twins (Fraternal twins) – 2/3 of all twins ◦ From awe to aversion Mythology, ancient Greece and Rome worshiped twin gods Yoruba in Nigeria: twins common and considered a promising sign from the gods Some African tribes: considered bad luck, one or both may be killed American Indian tribes: Akwaala: shown as privileged status Alsea: sometimes killed 2nd born – was not considered a real person North Pomo: killed both twins NW Maidus: mother was sometimes also killed Medieval European cultures: some believed twins were caused by a woman being impregnated by two different men – infidelity The Genetic Code Other possible types of twins (very rare): ◦ Superfecundation: 2 of the mother’s eggs from the same ovarian cycle are fertilized by 2 different men and develop as twins ◦ Mother’s egg divides prior to fertilization and each half is fertilized by different sperm – children are intermediate between fraternal and identical twins The Genetic Code Other differences: ◦ Surrounding membranes Chorion Amnion Fraternal – Both separate Identical – 33% both separate, 61% share chorion w/ separate amnion, 6% share both How could this effect twins? The Epigenetic View Development is the result of an ongoing, bidirectional interchange between heredity and the environment Heredity and environment operate together—or collaborate—to produce a person’s intelligence, temperament, height, weight, ability to pitch a baseball, ability to read, etc. (Gottlieb, Wahlsten, & Lickliter, 2006) The Course of Prenatal Development Fertilization to birth Prenatal development lasts approximately 266 days Three periods ◦ Germinal ◦ Embryonic ◦ Fetal The Germinal Period First two weeks after conception Creation of the fertilized egg (the zygote) Cell division Implantation -- the attachment of the zygote to the uterine wall ◦ takes place about 10 to 14 days after conception The Embryonic Period Occurs from two to eight weeks after conception Rate of cell differentiation intensifies Every body part eventually develops ◦ Neural tube ◦ Organogenesis -- the process of organ formation during the first two months of prenatal development organs are especially vulnerable to environmental influences The Fetal Period Fetal period begins two months after conception (normal gestation is 38-40 weeks) Three months after conception -- fetus is about 3 inches long; weighs about 3 ounces By the end of the fifth month, the fetus is about 12 inches long and weighs close to a pound Vernix Lanugo At birth, the average American baby weighs 7½ pounds and is about 20 inches long Three Trimesters The germinal and embryonic periods occur in the first trimester The fetal period begins toward the end of the first trimester and continues through the second and third trimesters Age of Viability (the chances of surviving outside the womb) occurs at the beginning of the third trimester ◦ About 24-25 weeks after conception Prenatal Tests Ultrasound sonography ◦ non-invasive ◦ high-frequency sound waves Fetal MRI ◦ Used to obtain more detailed images than ultrasound Chorionic villus sampling (CVS) ◦ tiny tissue sample from the placenta is removed and analyzed Amniocentesis ◦ sample of amniotic fluid is withdrawn and tested for chromosome or metabolic disorders Prenatal Tests Maternal blood screening ◦ Identifies pregnancies that have an elevated risk for birth defects such as spina bifida and Down syndrome Triple Screen ◦ Measures three substances in the mother’s blood ◦ If abnormal, ultrasound is performed, then amniocentesis Infertility and Reproductive Technology Approximately 10-15 couples in the United States experience infertility ◦ Defined as the inability to conceive a child after 12 months of regular intercourse without conception In vitro fertilization (IVF) ◦ 25 to 30 percent of pregnancies achieved by fertility treatments result in multiple births Hazards to Prenatal Development A teratogen is any agent that can potentially cause a birth defect or negatively alter cognitive and behavioral outcomes Behavioral teratogen ◦ ◦ ◦ ◦ ◦ Drugs Incompatible blood types Environmental pollutants Infectious diseases Maternal stress, advanced maternal and paternal age Hazards to Prenatal Development The dose, genetic susceptibility, and the time of exposure influence both the severity of damage to an embryo or fetus and the type of defect ◦ Timing of exposure Critical period Example: Third month? ◦ Amount of exposure Threshold effect How much is too much? Interaction effect Examples: Stress & alcohol, poor nutrition & smoking Hazards to Prenatal Development Prescription drugs ◦ Antibiotics ◦ Antidepressants ◦ Hormones ◦ Accutane Psychoactive drugs ◦ Caffeine ◦ Alcohol (Fetal alcohol spectrum disorders, FASD) ◦ Nicotine ◦ Cocaine ◦ Methamphetamine ◦ Marijuana ◦ Heroin Hazards to Prenatal Development Incompatible blood types ◦ Difference in blood groups -- A, B, O, and AB ◦ Rh factor Environmental hazards ◦ Toxic wastes ◦ X-ray radiation Maternal diseases ◦ Rubella ◦ Syphilis, genital herpes, HIV/AIDS ◦ Diabetes Hazards to Prenatal Development Other Parental Factors ◦ ◦ ◦ ◦ ◦ ◦ ◦ Maternal diet and nutrition Sleet deprivation Overweight before and during pregnancy Folic acid is important for normal prenatal development Eating fish -- mercury levels Maternal age -- 35 years or older at risk Emotional states and stress Anxiety Depression ◦ Paternal factors Smoking The Birth Process The Birth Process ◦ first stage -- contractions cause the woman’s cervix to stretch and open ◦ second stage begins when the baby’s head starts to move through the cervix ◦ third stage is afterbirth placenta, umbilical cord, and other membranes are detached and expelled Childbirth Setting and Attendants In the United States, 99 percent of births take place in hospitals Midwives ◦ Practiced throughout the world ◦ 95 percent of the midwives who delivered babies in the United States were certified nurse-midwives Doulas ◦ A caregiver who provides continuous physical, emotional, and educational support for the mother before, during, and after childbirth Breech or Cesarean Delivery Breech position -- buttocks rather than head emerge first ◦ Can prevent the baby from breathing normally Cesarean delivery -- the baby is removed from the mother’s uterus through an incision made in her abdomen ◦ May be lifesaving but carries the risks of major surgery Apgar Scale Used to assess the health of newborns at one and five minutes after birth A score, or reading, of 0, 1, or 2 on each of these five health signs Color (Appearance) Heart rate (Pulse) Reflex irritability (Grimace) Muscle tone (Activity) Respiratory effort (Respiration) Anoxia -- an insufficient supply of oxygen Low Birth Weight and Preterm Infants Low birth weight -- less than 5½ pounds at birth Very low birth weight -- under 3 pounds Extremely low birth weight -- under 2 pounds. Preterm -- born three weeks or more before full term Small-for-date -- birth weight is below normal when the length of the pregnancy is considered Incidence and Causes of Low Birth Weight Incidence of low birth weight varies considerably from country to country ◦ Related to poverty, maternal health status, maternal nutrition More health and developmental problems than normal-weight infants ◦ At school age, more likely to have a learning disability, attention deficit hyperactivity disorder, or breathing problems such as asthma (Moss, 2006;Wocadlo, & Rieger, 2006) Nurturing Low Birth Weight and Preterm Infants Kangaroo care -- a way of holding an infant so that there is skin-to-skin contact for two to three hours per day over an extended time in early infancy Massage therapy -- firm stroking with the palms of the hands three times per day for 15-minute periods Bonding -- formation of a connection, especially a physical bond, between parents and the newborn in the period shortly after birth (Feldman & others, 2003; Field & others, 1986) The Postpartum Period Postpartum period -- lasts for about six weeks after childbirth or delivery or until the mother’s body has completed its adjustment and has returned to a nearly pre-pregnant state Physical and psychological adjustments Involution -- process by which the uterus returns to its pre-pregnant size Emotional and Psychological Adjustments Baby blues -- two to three days after birth, many women begin to feel depressed, anxious, and upset Postpartum depression -- a major depressive episode about four weeks after delivery Fathers also undergo considerable adjustment in the postpartum period, even when they work away from home all day