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2.Biological-PhysicalDev.pptxA Topical Approach to Life-Span Development, 7th edition John W. Santrock
Physical & Biological Development
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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
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The Evolutionary Perspective
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
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The Evolutionary Perspective
Bidirectional view
Alternate view that evolution does not dictate behavior
Biology and environment simultaneously influence each other
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
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Genetic Foundations of Development
Genes
Basic units of hereditary information
Short segment of the DNA strand
Direct cells to reproduce and assemble proteins that direct body processes
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Genetic Foundations of Development
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
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Genetic Foundations of Development
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
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Genetic Foundations of Development
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
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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%
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Heredity and Environment Interaction
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
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Heredity and Environment Interaction
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
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Heredity and Environment Interaction
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
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Heredity and Environment Interaction
Epigenetic view
Development is the result of an ongoing, bidirectional interchange between heredity and environment
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Heredity and Environment Interaction
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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
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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
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Prenatal Development
Embryonic period
Occurs from two to eight weeks after conception
Rate of cell differentiation intensifies
Support systems for cells form
Organs appear
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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
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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
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Prenatal Development
Common teratogens:
Drugs
Incompatible blood types
Environmental pollutants
Infectious diseases
Nutritional deficiencies
Maternal stress
Advanced maternal and paternal age
Environmental pollutants
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Birth and Postpartum Period
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
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Body Growth and Change
Hormones
Powerful chemical substances secreted by endocrine glands and carried through bloodstream
Hypothalamus
Brain structure involved in eating and sexual behavior
Testosterone
Hormone associated in boys with genital development, increased height, deepening voice
Estradiol
Hormone associated in girls with breast, uterine, and skeletal development
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The Brain
Brain physiology
Two brain hemispheres
Cerebral cortex responsible for 80% of brain’s volume
Critical in perception, thinking, language, etc.
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The Brain
Frontal lobes
Voluntary movement, thinking, personality, emotion, memory, attention, intentionality, or purpose
Occipital lobes
Vision
Temporal lobes
Hearing, language processing, and memory
Parietal lobes
Spatial location, attention, and motor control
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The Brain
Myelination
Encasing of axons with a myelin sheath
Helps increase the speed and efficiency of information processing
Lateralization
Specialization of function in one hemisphere of the brain
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The Brain
Infancy
Brain development occurs extensively during prenatal period
Infant’s head should be protected from fall or other injuries
Shaken baby syndrome can produce brain swelling and hemorrhaging
Infant’s brain is waiting for experiences to determine how neural connections are made
Children who grow up in deprived environments exhibit depressed brain activity
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The Brain
Adolescence
Brain is still growing in adolescence
Adolescents have fewer, more selective, more effective neural connections than children
Corpus callosum
Band of fibers that connects brain’s left and right hemispheres
Thickens during adolescence, improving ability to process information
Amygdala
Brain’s center for emotions, such as anger
Matures earlier than prefrontal cortex
Capable of strong emotion but may lack self-control
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The Brain
Activities older adults engage in influence brain’s development
Aerobic fitness linked with better memory function
Neurogenesis
Generation of new neurons
Dendrite growth can occur in human adults, possibly older adults
“Rewiring” to compensate for loss
Less lateralization with age, more adaptation
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Sleep
Infancy
Newborns sleep 16-17 hours per day
By 6 months of age, infants have moved closer to adult-like sleep patterns
Longest span of sleep at night and longest span of waking during the day
Nighttime waking is most common infant sleep-related problem
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Sleep
Childhood
Experts recommend young children get 11-13 hours of sleep each night
Sleep throughout night with one daytime nap
Inadequate sleep linked to depression, school problems, disagreeable families, living in unsafe neighborhoods, father in poor health
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Sleep
Many adolescents exhibit inadequate sleep patterns
Less than 8 hours a day
Linked to fatigue, moodiness, depression, more caffeine beverage use, falling asleep in school
Adolescents sleep an average of 9 hours, 25 minutes when given opportunity to sleep as long as desired
Sleep debt created when adolescents do not get enough sleep
Hormonal shifts in biological clock cause later waking
Delay in nighttime presence of hormone melatonin
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Sleep
Average American adult gets just under 6 hours of sleep per night
Work and school pressures, family and social obligations lead to long hours of wakefulness and irregular sleep/wake schedules
Beginning in forties, wakeful periods during the night become more frequent
Shorter periods of deep sleep
Older adults go to bed earlier and wake earlier in morning
Approximately 50% of older adults complain of difficulty sleeping
Lack of sleep linked to health problems
Can produce lower level of cognitive function and can lead to earlier death
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Longevity
Life span
Maximum numbers of years an individual can live
Maximum life span of humans is about 120 years
Life expectancy
Number of years lived by the average person in a specific year
Improvements in medicine, nutrition, exercise, and lifestyle have increased life expectancy
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