chapter 3: biological beginnings
TRANSCRIPT
Chapter 3:
Biological
Beginnings
McGraw-Hill © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
The
Evolutionary
Perspective
• Natural selection is evolutionary
process
– Based on Darwin’s theory
– Best-adapted members of species survive
to reproduce
– Survival characteristics passed on in genes
– Ideas explain behavior in evolutionary
psychology approach
– David Buss: evolution shapes our physical
features and how we make life decisions
• Evolutionary developmental psychology:
– Extended juvenile period allows brain to develop
and learn complexity of social interactions
– Many aspects of childhood are preparation for
adulthood evolving over time
– Some childhood characteristics promote adaptation
during development before reaching adulthood
– Many evolved psychological mechanisms are
domain-specific or specific to environmental needs
– Evolved mechanisms are not always adaptive in
contemporary society
Figure 3.2
Life span (in years)
Life span (in years)
0 100 0 100
Need for culture increases with age
Evolutionary selection benefits decrease with age
Baltes’ View of Evolution and Culture Across the Life Span
• Currently:
– There is great interest in evolutionary
explanations of aging
– Natural selection has not weeded out harmful
conditions or diseases and nonadaptive
characteristics associated with reproduction
– Evolutionary psychology approach has its
limitations and weaknesses, and its critics
Genetic
Foundations
• Genetic process:
– Human life begins as a single cell
– Nucleus of each cell contains DNA
– DNA carries genetic information in double-helix
– Genes are units of hereditary information in
each chromosome
– Human Genome Project mapped the
human genome and found that it included
only about 30,000 genes
Figure 3.3
Cells, Chromosomes, Genes, and DNA
Chromosomes are threadlike structures
composed of DNA molecules
Nucleus (center of cell) contains chromosomes and genes
A gene, a segment of DNA (spiraled
double chain) containing the
hereditary code
The body contains trillions of cells
• All cells in human body (except the sperm and egg)
have 46 chromosomes arranged in 23 pairs
• Meiosis forms sperm and eggs (gametes)
• Fertilization: fusing of sperm and egg to form one set
of paired chromosomes (offspring gets half of its
genes from each parent)
• Child’s sex determined by 23rd pair of chromosomes
• Genotype: a person’s genetic material
containing
– Phenotypes: observable or physical
characteristics such as height, body style and
psychological characteristics like personality
and intelligence
– Dominant genes in each pair have the most
influence on characteristics unless the pair
contains two recessive genes which will
have a dominant effect
• Sex-linked genes:
– X-linked diseases and mutations such as
hemophilia and fragile-X syndrome
– Females have a second X chromosome so
chances of having mutation or disease are
less, BUT they are carriers of it
– Males have no second chance; more males
than females have X-linked diseases
b B B b b b B B
Mother
B b
Father
B b
b
B
Blond hair
Brown hair
How Brown-Haired Parents Can Have a Blond-Haired Child
Figure 3.6
The gene for blond
hair is recessive.
• Chromosome abnormalities usually arise in meiosis when chromosomes do not properly separate
• Sex-linked abnormalities:
– Klinefelter syndrome: males born with XXY mutation instead of XY
– Fragile X syndrome: occurs more often in males than females; X chromosome constricted or breaks off
– Turner syndrome: females born with XO rather than XX, sometimes causing infertility
– XYY syndrome: males with extra Y chromosome
• Gene-linked abnormalities:
– PKU: occurs in 1 out of 10,000-20,000
births but can be treated if detected
early enough
– Sickle-cell anemia: impaired red blood
cells die more quickly; more often found
in African Americans
– Other abnormalities: cystic fibrosis,
diabetes, spina bifida, Huntington disease,
and Tay-Sachs disease
Reproductive
Challenges and Choices
• Prenatal diagnostic tests:
– Amniocentesis: samples amniotic fluid
– Ultrasound sonography: high frequency
sound waves used
– Chorionic villus sampling: small sample of
placenta is removed during 8th–11th week
– Maternal blood test
• Infertility and reproduction technology:
– In vitro fertilization: egg and sperm united
in laboratory dish
– Gamete intrafallopian transfer: egg and
sperm deposited directly into fallopian tube
– Zygote intrafallopian transfer: eggs
fertilized in lab then zygote deposited into
fallopian tube
• Consequences of multiple births:
– Higher risks of life-threatening problems
– Health risks to mother
– Psychological effects on children
• Another alternative: adoption
0
10
20
30
40
29.2% 31%
24.5%
ZIFT IVF GIFT
Type of Assisted Reproduction
Success Rates of Three Different Assisted Reproduction Techniques
Figure 3.10
There was little variation
in success rates based on
couples’ ages, so results
are combined.
• Childrearing challenges after adoption:
– Infancy: attachment?
– Early childhood: integration into family
– Middle and late childhood: curiosity about
real/biological parents
– Adolescence: child’s reflection on adoptive
status
Heredity,
Environment,
and Individual Differences
0
10
20
30
40 Natural conception
In vitro fertilization
Figure 3.11
Self- esteem
School functioning
Peer relations
Socioemotional Functioning of Children Conceived Through In Vitro Fertilization or Naturally Conceived
• Heredity and environment interact to produce development; each person’s development varies
• Behavior genetics:
– Most research based on twin and adoption studies
– Twin studies compare identical (monozygotic) twins with fraternal (dizygotic) twins
– Adoption studies compare child’s traits with those of adoptive and biological parents
– All studies conducted in developed countries only
• Genotype–environment correlations:
– Intelligent biological parents who like to read
provide books and encouragement for child to
read – likely outcome is skilled reader
– Active, smiling, cooperative, and attentive child
gets more pleasant, encouraging responses from
adults than passive, quiet child
– Some children actively seek out aspects of their
environment that enhance their ability to excel
• Siblings’ shared and nonshared environmental experiences analyzed 2 ways
– Shared examined as common experiences like family SES, parental personalities, and neighborhood
– Nonshared examined as child’s unique experiences inside & outside family not shared by siblings
• Personal relationship with each parent
• Friends and classmates
• Teachers and other influential adults
• “Niches” sought out due to unique personality traits (musical/artistic abilities)
Figure 3.14
Heredity–environment correlation view
Environment Heredity
Epigenetic view
Environment Heredity
Comparison of the Heredity–Environment
Correlation and Epigenetic Views
• Epigenetic view: development is an ongoing,
bidirectional interchange between
heredity/genetics and environment
– Example: baby has inherited genes but is
exposed to toxins during prenatal development
– Outcome can change genetic development
during the prenatal or infancy period
– Such an example can impact on the nature vs
nurture debate
The End