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Slide 1
A Topical Approach to
Life-Span Development 6e
Chapter Two:
Biological Beginnings
John W. Santrock
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Slide 2
The Evolutionary Perspective
• Charles Darwin: On the Origin of Species (1859)
– All organisms must adapt to survive
• Natural selection
– Evolutionary process where the best adapted (“fittest”)
individuals in a species survive and reproduce
• Adaptation = ability to meet the demands of one’s
environments and respond to changes in them
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Slide 3
Reproductive Fitness
• Possession of characteristics that give one the
ability to survive long enough to reproduce
– Goal =
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Slide 4
Evolutionary Psychology
• Emphasizes:
– Evolution can explain certain human physical features,
behaviors, emotions, and cognitive abilities
– Biological certainty associated with increased
nurturing of genetically-related offspring
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Slide 5
Mating Strategies & evolution:
Why do men “play the field?”
• Mating strategies differ by gender
– Men seek:
• Best strategy:
– Women seek:
• Best strategy:
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Slide 6
Evolutionary developmental psychology
• Adaptations to increasingly complex societies
– Humans take longest of all mammals to sexually mature
• Extended childhood & adolescence to learn rules of society,
survival & thriving skills
– Largest brains of all mammals
• Brains continue to develop into young adulthood
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Slide 7
Evolutionary developmental psychology
• Why do humans outlive their reproductive capacity?
– Paul Baltes’ theory of natural selection
• Operates primarily on characteristics tied to reproductive
fitness in youth
• Harmful conditions, non-adaptive traits common in elderly
• As adults weaken biologically, culture-based needs increase
– Give more back to society in turn?
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Slide 8
Bi-directional view
• Alternative to one-sided biological evolution
• Social behavior is not just the product of biology
• Environmental & biological conditions influence each other
Biology
Environment
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Slide 9
Genetic Foundations of Development
• Genes carry a code for physical/psychological
characteristics inherited through:
• generations of evolution (shared by all humans)
• our parents (family traits)
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Slide 10
Genetic Foundations of Development
• Genetic expression =
– Collaborative and environmentally influenced
– Direct cells to reproduce and to assemble proteins
• Proteins form cells and direct biological processes
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Genetic Foundations of Development
Figure 2.3 - Cells, Chromosomes, Genes, and DNA
Nucleus (center of
cell) contains
chromosomes and
genes
What is DNA?
Chromosomes are
threadlike structures
composed of DNA
molecules
Gene: a segment of DNA
(spiraled double chain)
containing the hereditary code
Slide 12
Cell Reproduction
• Mitosis: Cell nucleus duplicates and cell divides
• mitosis video
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Slide 13
Sexual Reproduction
• Meiosis: Cell division forms
gametes (sex cells)
– egg & sperm
• 23 unpaired chromosomes
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Slide 14
Sexual Reproduction
• Fertilization: egg and sperm form zygote
– Contains 23 chromosomes from each parent, re-paired
– On 23rd pair, X and Y chromosomes determine sex
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Male and female chromosome pairs
Slide 16
Genetics
• “We are all 99.9 percent genetically equal. It
is one one-hundredth of one percent of
genetic material that makes the difference
between any one of us.” (Barry Schuler)
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Slide 17
Sources of Genetic Variability
1. Each zygote is unique in chromosomal pairings
2. DNA mutations occur by chance or damage
3. Genotypes and phenotypes
– Genotype:
• sets up a range of potential phenotypes
– Phenotype:
• may be influenced by environmental factors
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Slide 18
Poly-genetic determination
• Poly-genetically determined characteristics
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Slide 19
Behavior Genetics
• Study of:
– Twin studies
• Identical twins compared to fraternal twins
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Slide 21
Heredity and Environment Interaction:
Behavior Genetics
– Shared and nonshared environmental experiences
• Variability in psychological traits is more linked to:
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Slide 22
Heredity and Environment Interaction:
The Epigenetic View
• Epigenetic view
– Development is ongoing
– Bi-directional interchange of heredity/environment
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Slide 23
Prenatal Development Stages
• Germinal period:
• Embryonic period:
• Fetal period:
http://www.ted.com/talks/alexander_tsiaras_conception_to_birth_visualized.html
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Slide 25
Hazards to Prenatal Development
• Teratogens
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Slide 26
Teratogens
• Prescription, nonprescription drugs
• Psychoactive drugs
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Figure 2.12 - Teratogens and Timing of Their
Effects on Prenatal Development
Slide 28
Hazards to Prenatal Development
• Incompatible blood types (Rh factor)
• Maternal diseases
• Diet and nutrition
• Maternal age, weight, emotional states, stress
• Environmental hazards (toxins, waste)
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Slide 29
Birth
• Low birth weight and preterm infants
– Low birth weight: Less than 5 ½ lbs at birth
– Preterm: Born in 35 weeks or less after conception
– Small for date
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Slide 30
Birth
• Low birth weight
– Causes
• Cigarette smoking
• Poor maternal health and nutrition
– Maternal diseases and infections
– Consequences
• Learning difficulties, more behavioral problems
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