Chapter 3– Biological Beginnings

Chapter 3– Biological Beginnings
A Topical Approach to Life-Span Development, 7th edition John W. Santrock Chapter 3– Biological Beginnings Copyright McGraw-Hill Education, 2014

The Evolutionary Perspective
Natural Selection Individuals best adapted to their environment are most likely to survive and reproduce Their characteristics are passed on to the next generation Over generations, organisms with characteristics best suited for survival make up an increased percentage of the population Copyright McGraw-Hill Education, 2014

Evolutionary psychology Emphasizes adaptation, reproduction, and survival of the fittest in shaping behavior Evolution explains human physical features and behaviors Evolutionary developmental psychology Extended childhood evolved for human beings Evolved characteristics are not always adaptive in contemporary society Copyright McGraw-Hill Education, 2014

Evolution and life-span development Evolution favors longevity? Natural selection operates primarily on characteristics tied to reproductive fitness Extends through the first half of life As older adults weaken biologically, the need for culture- based resources increases Copyright McGraw-Hill Education, 2014

Copyright McGraw-Hill Education, 2014

Bidirectional view Alternate view that evolution does not dictate behavior Evolutionary pressures created changes in biological structures Allowed use of tools, enabling ancestors to manipulate environment and construct new environmental conditions Environmental innovations produced new selection pressures Led to evolution of specialized biological systems for consciousness, thought, and language Copyright McGraw-Hill Education, 2014

Genetic Foundations of Development
Chromosomes Threadlike structures located in the nucleus of each human cell Made up of deoxyribonucleic acid (DNA) DNA Complex molecule with a double helix shape Contains genetic information Copyright McGraw-Hill Education, 2014

Genes Basic units of hereditary information Short segment of the DNA strand Direct cells to reproduce and assemble proteins that direct body processes Copyright McGraw-Hill Education, 2014

Human Genome Project Mapping of complete set of developmental instructions for creating proteins to create human organism Humans have about 30,000 genes Genes collaborate with each other and with nongenetic factors in and outside of body Gene activity is affected by environment Turns genes “on” or “off” Copyright McGraw-Hill Education, 2014

All cells in the human body have 23 pairs—or a total of 46—chromosomes All cells—except the sperm and egg—reproduce through mitosis Cell’s nucleus, including chromosomes, duplicates itself and divides Two new cells formed with identical DNA makeup Copyright McGraw-Hill Education, 2014

Meiosis Specialized process of cell division in which egg and sperm cells are created Cell’s nucleus duplicates and divides twice, producing four cells Each cell contains 23 unpaired chromosomes Half of the genetic material of parent cell Copyright McGraw-Hill Education, 2014

Fertilization Egg and sperm cells fuse to create a single cell Newly fertilized cell is called a zygote Each zygote has 23 unpaired chromosomes from egg and another 23 unpaired chromosomes from sperm Copyright McGraw-Hill Education, 2014

Genetic variability Combining genes of two parents in offspring increases genetic variability in the population Mutated genes, or permanently altered segments of DNA, form by chance or environmental damage Copyright McGraw-Hill Education, 2014

Genotype A person’s actual genetic material Phenotype Observable and measurable characteristics of an individual Height Hair color Intelligence Range of phenotypes can be expressed for each genotype Copyright McGraw-Hill Education, 2014

Dominant-recessive genes Dominant gene overrides the expression of the recessive gene Recessive gene exerts its influence only if both genes in the pair are recessive Sex-linked genes X-linked inheritance results when a mutated gene is carried on the X chromosome Females are carriers, while males may exhibit an X-linked disease Copyright McGraw-Hill Education, 2014

Genetic imprinting Occurs when genes have differing effects depending on whether inherited from mother or father Chemical process “silences” one member of the gene pair Polygenetic inheritance Most human characteristics are determined by interaction of several genes Copyright McGraw-Hill Education, 2014

Genetic counselor Physicians or biologists Provide clients with information on chromosome or gene- linked abnormalities, odds of encountering them, and helpful strategies for offsetting their effects Copyright McGraw-Hill Education, 2014

Heredity and Environment Interaction
Behavior genetics Investigates the influence of heredity and environment on individual differences in human traits and development Twin study Behavioral similarity of identical twins compared with fraternal twins Identical twins share 100% of DNA, while fraternal twins share 50% Copyright McGraw-Hill Education, 2014

Adoption study Seek to discover whether adopted children’s behavior and psychological characteristics are more like adoptive or biological parents May also compare adoptive and biological siblings Copyright McGraw-Hill Education, 2014

Heredity-environment correlations Individuals’ genes may influence environments to which they are exposed As child ages, experiences extend beyond family Some environments can mute or strengthen genetic traits Copyright McGraw-Hill Education, 2014

Passive genotype-environment correlations Biological parents, who are genetically related to child, provide rearing environment Evocative genotype-environment correlations Child’s characteristics elicit certain types of characteristics Active (niche-picking) genotype-environment correlations When children seek out environments they find compatible and stimulating Copyright McGraw-Hill Education, 2014

Shared environmental experiences Siblings’ common experiences Nonshared environmental experiences Child’s own unique experiences, both within and outside of family, not shared by sibling Experiences occurring within the family may be part of nonshared environment Copyright McGraw-Hill Education, 2014

Epigenetic view Development is the result of an ongoing, bidirectional interchange between heredity and environment Copyright McGraw-Hill Education, 2014

Copyright McGraw-Hill Education, 2014
Prenatal Development Conception When a single sperm cell unites with an ovum in a process called fertilization Prenatal development Lasts for approximately 266 days Beginning with fertilization and ending with birth Further divided into three periods Copyright McGraw-Hill Education, 2014

Prenatal Development Germinal period Takes place during the first two weeks after conception Creation of fertilized egg Cell division Attachment of zygote to uterine wall Copyright McGraw-Hill Education, 2014

Prenatal Development Embryonic period Occurs from two to eight weeks after conception Rate of cell differentiation intensifies Support systems for cells form Organs appear Copyright McGraw-Hill Education, 2014

Prenatal Development Fetal period Lasts about seven months until birth Fetus is viable at about 6 months after conception Can survive outside of the womb if born At birth, the average American baby weighs 7½ pounds and is about 20 inches long Copyright McGraw-Hill Education, 2014

Prenatal Development Brain development Basic architecture of the brain takes place prenatally during first two trimesters Neurons move to specific locations and start to become connected Third trimester and first two years of life are characterized by increased brain connectivity and functioning At birth, babies have approximately 100 billion neurons Copyright McGraw-Hill Education, 2014

Prenatal Development Anencephaly Head of the neural tube fails to close Highest regions of the brain fail to develop Spina bifida Incomplete development of spinal cord Results in varying degrees of paralysis of lower limbs Neural tube defects can be prevented by consuming adequate amounts of folic acid Copyright McGraw-Hill Education, 2014

Prenatal Development Ultrasound sonography Noninvasive procedure in which high-frequency sound waves are directed into pregnant woman’s abdomen Echo from sounds creates a visual representation of fetus Fetal MRI Magnetic resonance imaging uses a powerful magnet and radio waves to generate detailed image of body’s organs and structures Clearer, more detailed image than ultrasound Copyright McGraw-Hill Education, 2014

Prenatal Development Chorionic villus sampling Tiny tissue sample is removed from the placenta Analyzed for genetic defects and chromosome abnormalities Amniocentesis Sample of amniotic fluid withdrawn by syringe and tested for chromosome or metabolic disorders Maternal blood screening Triple screen blood test used to determine elevated risk for birth defects Copyright McGraw-Hill Education, 2014

Prenatal Development Teratogen Any agent that can potentially cause a birth defect or negatively alter cognitive or behavioral outcomes Severity of damage from teratogens depends on: Dosage Genetic susceptibility Time of exposure Maternal Diseases *Rubella, CMV, Syphilis, Toxoplasmosis, HIV, & Chronic Illness Copyright McGraw-Hill Education, 2014

Prenatal Development Common teratogens: Drugs Incompatible blood types Environmental pollutants Infectious diseases Nutritional deficiencies Maternal stress Advanced maternal and paternal age Copyright McGraw-Hill Education, 2014

Prenatal Development Prenatal Care Defined schedule of visits for medical care Screening for manageable conditions and treatable diseases that can affect baby or mother Often includes comprehensive education, social, and nutritional services Especially valuable for first-time mothers and women in poverty Copyright McGraw-Hill Education, 2014

Birth and Postpartum Period
Stages of Birth Beginning of uterine contractions 15 to 20 minutes apart Cervix stretches and opens to 10 centimeters Baby begins to move through birth canal Contractions come almost every minute Mother bears down to push the baby out Afterbirth Placenta, umbilical cord, and membranes detached and expelled Copyright McGraw-Hill Education, 2014

In United States, 99% of births take place in hospitals Mothers receive assistance from fathers/birth coaches Midwifery Midwives, rather than doctors, deliver babies Doulas Caregiver who provides physical, emotional, and educational support for mother before, during, and after childbirth Copyright McGraw-Hill Education, 2014

Analgesia Drugs used to relieve pain Anesthesia Used late in first-stage labor and during delivery Epidural block – regional anesthetic that numbs body from waist down Oxytocin Synthetic hormone used to stimulate contractions Copyright McGraw-Hill Education, 2014

Natural childbirth No drugs given to relieve pain or assist in birth process Mother uses breathing and relaxation techniques during delivery Prepared childbirth Developed by French obstetrician Lamaze Special breathing technique to control pushing in final stages of labor More detailed education about anatomy and physiology Nonmedicated techniques to relieve pain Waterbirth Massage Acupuncture Copyright McGraw-Hill Education, 2014

Caesarean delivery Normally, baby’s head is delivered first When baby is in breech position, its buttocks are the first to emerge from birth canal Breech births can cause respiratory problems for baby In a caesarean delivery, the baby is removed from uterus through an incision in mother’s abdomen Copyright McGraw-Hill Education, 2014

Apgar Scale Used to assess the health of newborns at one and five minutes after birth Heart rate, respiratory effort, muscle tone, body color, and reflex irritability evaluated Copyright McGraw-Hill Education, 2014

Low birth weight infants Infants that weigh less than 5½ pounds at birth Preterm infants Infants born three weeks or more before pregnancy has reached full term Small for date infants Infants whose birth weights are below normal when the length of pregnancy is considered May be preterm or full term Copyright McGraw-Hill Education, 2014

Kangaroo care Skin-to-skin contact in which the baby, wearing only a diaper, is held upright against the parent’s bare chest Neonatal intervention practiced with preterm infants Bonding Forming a close connection, especially a physical bond between parents and their newborn, in the period shortly after birth Copyright McGraw-Hill Education, 2014

Period after childbirth that lasts for about six weeks or until mother’s body has returned to a pre-pregnancy state Fatigue Loss of sleep Hormonal changes Involution Uterus returns to pre-pregnancy size five or six weeks after birth Copyright McGraw-Hill Education, 2014

Postpartum Blues Feelings of anxiety, upset, or depression that come and go for several months following birth Without treatment, feelings go away after a few weeks Postpartum Depression Major depressive episode that occurs about 4 weeks after delivery Strong feelings of sadness, anxiety, despair, trouble coping with daily tasks May worsen without treatment Copyright McGraw-Hill Education, 2014

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