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