1. A Topical Approach to LIFE-SPAN DEVELOPMENT
Chapter Two:
Biological Beginnings
John W. Santrock

2. The Evolutionary Perspective
Natural selection
Evolutionary process where the best adapted individuals in a species survive and reproduce
Natural selection and adaptive behavior
Darwin: On the Origin of Species (1859)
All organisms must adapt in life

3. The Evolutionary Perspective
Evolutionary psychology
Emphasizes adaptation, reproduction, and survival of the fittest in shaping behavior
Evolution explains human physical features and behaviors

4. The Evolutionary Perspective
Evolutionary developmental psychology
Explaining humans and their behavior
Larger brains and more complex societies
Takes longest of all mammals to mature
Some evolved mechanisms of adaptation not compatible with modern society

5. The Evolutionary Perspective
Evolution and life-span development
Natural selection
Benefits decrease with age
Failures: harmful conditions and non-adaptive characteristics
As adults weaken biologically, culture-based needs increase
Alternative: bi-directional view

6. Baltes’ View of Evolution and Culture Across the Life Span
Fig. 2.2

7. Genetic Foundations of Development
The collaborative gene
Nucleus of a human cell:
Chromosomes — thread-like structures
DNA — double helix-shaped molecule
Genes — units of hereditary information
Human Genome Project
20,500 genes in humans
Genetic expression and inherited traits

8. Cells, Chromosomes, Genes, and DNA
Nucleus (center of cell) contains chromosomes and genes
Chromosomes are threadlike structures composed of DNA molecules
Gene: a segment of DNA (spiraled double chain) containing the hereditary code
Fig. 2.3

9. Genetic Foundations of Development
Genes and chromosomes
Mitosis — cell nucleus duplicates
Meiosis — cell division forms gametes
Fertilization — egg and sperm form zygote
Genetic variability in the population
X and Y chromosomes determine sex

10. Genetic Foundations of Development
Genes and chromosomes
Sources of variability
Each zygote is unique
Identical and fraternal twins
Muted genes due to environmental agent
Genotype: all of one’s genetic makeup
Phenotype: observable characteristics

11. Genetic Foundations of Development
Genetic principles
Dominant and recessive genes
Sex-linked genes
X-linked inheritance for males and female
Genetic imprinting
Imprinted gene dominates
Poly-genetically determined characteristics
Many genes interact to influence a trait

12. Father B b Mother B b B B B b B b b b
How brown-haired parents can have a blond-haired child: the gene for blond hair is recessive B
Brown hair
Blond hair b
Father
B b
Mother
B b
B B
B b
B b
b b

13. Genetic Foundations of Development
Chromosomal and gene-linked abnormalities
Down syndrome: 2 copies of chromosome 21
Sex-linked abnormalities
Klinefelter syndrome: XXY instead of XY
Fragile X syndrome: X in boys is fragile, breaks
Turner syndrome: girl is XO instead of XX
XYY syndrome: link to criminal males unproven

14. Genetic Foundations of Development
Chromosomal and gene-linked abnormalities
Gene-linked abnormalities
Phenylketonuria (PKU) – treated by diet
Sickle-cell anemia – red blood cells affected
Cystic fibrosis, diabetes, hemophilia, spina bifida, Tay-sachs and Huntington diseases
Can sometimes be compensated for by other genes or events

15. Heredity and Environment Interaction: The Nature-Nurture Debate
Behavior genetics
Studies genetic impact on traits and development
Tests for genetic/environmental influences
Twin studies
Shared and nonshared factors
Adoption studies
Effects of biological and adoptive parents

16. Heredity and Environment Interaction: The Nature-Nurture Debate
Heredity-environment correlations
Passive genotype-environment
Parents provide/guide child’s interests
Evocative genotype-environment
Some traits elicit more adult responses
Active (niche-picking) genotype-environment
Child seeks/selects favorable environments

17. Heredity and Environment Interaction: The Nature-Nurture Debate
Heredity-environment correlations
Heredity directs environmental experiences
In infancy, environment mostly parent-controlled
As child ages, experiences extend beyond family
Some environments can mute or strengthen genetic traits
Critics: heredity gets too much credit

18. Heredity and Environment Interaction: The Nature-Nurture Debate
Epigenetic view
Development is ongoing
Bi-directional interchange of heredity/environment
Infancy
Positive and negative environmental experiences can modify genetic activity

19. The Heredity-Environment and Epigenetic Views
Fig. 2.9

20. Prenatal Development Course of prenatal development
Germinal period: creation of fertilized egg
Embryonic period: cell differentiation of embryo
Endoderm – digestive/respiratory systems
Ectoderm – nervous system, sensory receptors
Mesoderm – circulatory, bones, muscles, excretory and reproductive systems
Organagenesis: organ formation

21. Prenatal Development Course of prenatal development
Fetal period: lasts for 7 months, 3 trimesters
Brain:
100 billion neurons (nerve cells)
Neural tube formed from ectoderm
Birth defects can cause death, retardation
Neurogenesis – new cells formed
Neuronal migration – cell specialization

22. The Three Trimesters of Prenatal Development
First trimester
0-4 weeks
Less than 1/10th of inch long
8 weeks
Less than 1 inch long
12 weeks
3 inches long, wt: 1 ounce
Second trimester
16 weeks
5.5 inches long, wt: 4 ounces
20 weeks
10-12 inches, wt: ½ -1 lbs
24 weeks
11-14 inches, wt: 1-1½ lbs
Third trimester
28 weeks
14-17 inches, wt: 2½ -3 lbs
32 weeks
16½ -18 inches, wt: 4-5 lbs
36-38 weeks
19 inches, wt: 6 lbs
Fig. 2.10

23. Prenatal Diagnostic Tests
Tests for abnormality
Ultrasound sonography
Fetal MRI: better than ultrasound
Chorionic villus sampling: samples placenta
Amniocentesis: samples amniotic fluid
Maternal blood screening (triple screen test)
Noninvasive prenatal diagnosis (NIPD): tests fetal cells (DNA) in mother’s blood

24. Hazards to Prenatal Development
Teratogens
Agents causing birth defects
Severity of damage affected by
Dose
Genetic susceptibility
Time of exposure
Prescription, nonprescription drugs

25. Hazards to Prenatal Development
Teratogens
Psychoactive drugs
Caffeine, cocaine, methamphetamines, marijuana, and heroin
Alcohol and fetal alcohol syndrome (FAS)
Nicotine’s link to SIDS, ADHD, low birth weight
Paternal smoking during pregnancy

26. Teratogens and Timing of Their Effects on Prenatal Development
Fig. 2.12

27. Hazards to Prenatal Development
Other prenatal factors
Incompatible blood types (Rh factor)
Maternal diseases
STDs, HIV and AIDS; Rubella measles
Diet and nutrition (vitamins, folic acid); weight
Toxins in foods, mercury in fish
Maternal age, emotional states, and stress
Environmental hazards (toxins, waste)

28. Prenatal Care Prenatal care varies around the world
Quality of medical care visits, education
Low-birth weight and infant mortality rates
Outside the United States: free/low cost prenatal care, liberal maternity leave
Impact of cultural/ethnic beliefs about pregnancy

29. Birth Birth process Stages of birth
Labor occurs in three stages:
Uterine contractions
Baby’s head begins to enter birth canal
Afterbirth (shortest stage)
Birth attendants vary across cultures
Midwifery
Doula

30. Birth Methods of childbirth
Natural childbirth: reduce maternal pain through education (breathing, relaxation techniques)
Prepared childbirth: Lamaze method
Nonmedicated techniques to reduce pain
Waterbirth
Massage, acupuncture, hypnosis
Music therapy

31. Birth Methods of childbirth From fetus to newborn
Cesarean delivery (surgical procedure)
Breech position birth
Benefits and risks continue being debated
From fetus to newborn
Vernix caseosa (protective skin grease at birth)
Baby must withstand stress of birth

32. Birth Assessing the newborn Apgar Scale: heart, reflexes, and color
Brazelton Neonatal Behavioral Assessment Scale (BNBAS)
A sensitive index of neurological competence
Neonatal Intensive Care Unit Network Neurobehavioral Scale (NNNS)
Analysis of behavior, neurological and stress responses, and regulatory capacities

33. The Apgar Scale
Fig. 2.14

34. Birth Low birth weight and preterm infants
Low birth weight: less than 5 ½ lbs at birth
Very low: less than 3 lbs at birth
Extremely low: under 2 lbs at birth
Preterm: born in 35 weeks or less after conception
Small for date (small for gestational age infants)
Birth weight below normal for gestational age

35. Birth Low birth weight Incidences
Not all preterm babies are low birth weight
High rates in developing countries from poverty
Rates increasing in the United States in last two decades
Lowest rates in Nordic countries

36. Birth Low birth weight Causes Consequences
Poor maternal health and nutrition
Maternal diseases and infections
Cigarette smoking is leading cause
Weekly hormone injections can lower rates
Consequences
Learning difficulties, more behavioral problems

37. Birth Nurturing preterm infants
Intensive enrichment (medical, educational)
Neonatal Intensive Care Unit (NICU) interventions
Kangaroo care: skin-to-skin contact
Stabilizes bodily functions (ie: breathing)
Better sleep, weight gain, more alertness
Massage therapy

38. Birth Bonding Special part of parent-infant relationship
Needs to occur shortly after birth
Early emotional attachments may create healthy interactions after leaving hospital
Rooming-in arrangements offered
Massages and tactile stimulation for premature infants affect development

39. The End