1. Life-Span Development
Twelfth Edition
Chapter 2:
Biological Beginnings

2.  Natural Selection: an evolutionary process by which
those individuals of a species that are best adapted are
the ones that survive and reproduce
• $$ The study of human evolution was put forth by Charles
Darwin
• Survival characteristics are passed on in genes
 Can produce a gradual modification of the population over many
generations
• Survival characteristics may change based on environmental
conditions
 Adaptive Behavior: behavior that promotes an
organism’s survival in the natural habitat

3.  Evolutionary Psychology: emphasizes the
importance of adaptation, reproduction, and
“survival of the fittest” in shaping behavior
• Fit: the ability to bear offspring that survive long
enough to bear offspring of their own
 Natural selection favors behaviors that increase
reproductive success
• $$ Evolutionary developmental psychology
suggests that the way in which people develop is
adaptive

4.  Extended childhood period allows time to
develop a large brain and learn complexity of
human society
 Many evolved psychological mechanisms are
domain-specific
• Information processing
 Evolved mechanisms are not always adaptive
in contemporary society

6.  Why do humans live so long after
reproduction?
• Perhaps older people improve the survival rate of
babies
 Paul Baltes: benefits of evolutionary selection
decrease with age
• Natural selection is tied to reproductive fitness
• Does not weed out harmful conditions that appear
among older adults
 Increases our need for culture

7.  Evolutionary psychology approach is just one
theory of many
• It has its limitations and weaknesses, and its critics
 Bidirectional view: environmental and
biological conditions influence each other
• Evolution gives us bodily structures and biological
potentialities, but it does not dictate behavior
• People create behavior in the context of culture

8.  Human life begins as a single cell
 Nucleus of each cell contains chromosomes
• Chromosomes: thread-like structures made up of DNA
• DNA: a complex double-helix molecule that contains
genetic information
 $$ Genes: units of hereditary information that are
comprised of short segments of DNA
• Genes direct cells to reproduce themselves and to
assemble proteins
 Proteins: building blocks of cells and regulators
that direct the body’s processes

9.  Each gene has its own unique location on a
particular chromosome
• Results indicated that humans have
about 20,000 to 22,000 genes
 Genes collaborate with each
other and with non-genetic factors
inside and outside the body
 Genetic expression is affected
by the environment

10.  All cells in the human body (except sperm and
egg) have 46 chromosomes arranged in 23
pairs
 Mitosis: reproduction of cells
• Nucleus (including chromosomes) duplicate, and
the cell divides
 Meiosis: cell division that forms sperm and
eggs (gametes)
• Each cell divides twice, forming four cells with 23
unpaired chromosomes

11.  Fertilization: fusing of sperm and egg to create a zygote
• Creates one set of paired chromosomes (23 from each
parent)
 Child’s sex determined by 23rd pair of chromosomes
• XY = male XX = female
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12.  Combining genes of both parents increases
genetic variability
• Chromosomes in zygote are not exact copies
 Identical (monozygotic) twins develop from a
single zygote that splits into two
 Fraternal (dizygotic) twins develop from
separate eggs and sperm
 Gene mutations can permanently alter
segments of DNA

13.  Genotype: a person’s genetic material
 Phenotype: observable characteristics
• A range of phenotypes can be expressed for each
genotype
 Dominant-Recessive Genes Principle: a
dominant gene always exerts its effects,
overriding the potential influence of the
recessive gene
• A recessive gene only exerts influence if both genes
in a pair are recessive

14.  $$ Genetic Imprinting: when genes have
differing effects depending on whether they are
inherited from the mother or the father
 Polygenetic Inheritance: characteristics that are
determined by the interaction of many different
genes
• Most characteristics are determined in this manner

15.  Chromosome abnormalities usually involve the sperm
and ovum lacking a normal set of 23 chromosomes
• Down syndrome: caused by the presence of an extra copy
of chromosome 21
 Sex-linked abnormalities involve the presence of an
extra X or Y chromosome (or the absence of one)
• Klinefelter syndrome: males born with XXY instead of
XY
• Turner syndrome: females born with XO rather than XX,
sometimes causing infertility
• XYY syndrome: males with extra Y chromosome

16. Fragile X syndrome
• $$ is usually characterized by some sort of mental
deficiency. This deficiency could include having:
a. mental retardation.
b. a short attention span &
c. a learning disability.
•occurs more often in males than females; X
chromosome constricted or breaks off

18.  Every individual carries DNA variations, but
most do not display a disorder
 Today, many genetic diseases can be detected
prior to and immediately after birth
• However, knowledge of genetic flaws leads to
difficult choices about how to manage such
information
 Genetic counselors help people make
reproductive decisions

19.  $$ Ultrasound Sonography: high-frequency sound
waves are directed into the woman's abdomen
1. used to create a visual representation of fetus’s inner
structures
 Fetal MRI: magnetic resonance imaging designed to
diagnose fetal malformations
 Chorionic Villus Sampling: small sample of placenta
is removed to detect genetic and chromosomal
abnormalities
 Amniocentesis: samples amniotic fluid to test for
chromosomal or metabolic disorders

20.  $$ Maternal Blood Screening: identifies pregnancies
with elevated risk for certain birth defects; such as both
Down syndrome and spina bifida
 Down Syndrome: genetic disorder that causes lifelong
mental retardation, developmental delays and other
problems. The cause of Down syndrome is one of
three types of abnormal cell division involving
chromosome 21.
 Spina Bifida: a portion of the neural tube fails to
develop or close properly, causing defects in the
spinal cord and in the bones of the backbone.

21.  Infertility: the inability to conceive a child after 12 months of
attempting
 In Vitro Fertilization (IVF): egg and sperm are combined in a
laboratory dish; fertilized egg is transferred to woman’s uterus
• Success depends on woman’s age
• Increases risk of multiple births
 Higher risk of life-threatening
problems
 Health risks to mother
 Possible psychological
effects on children

22.  Adoption: an alternative to infertility treatment
• Children adopted early in life fare better than
children adopted later
• Somewhat more likely to experience psychological
and school-related problems than non-adopted
children
• No differences in antisocial behavior or self-esteem
• Vast majority of adopted children adjust effectively,
and most parents are satisfied with their decision to
adopt

23.  Behavior Genetics: seeks to discover the
influence of heredity and environment on
individual differences in human traits and
development
• Twin studies: compare identical (monozygotic)
twins with fraternal (dizygotic) twins
• Adoption studies: compare the characteristics of
adopted children with their adoptive parents and
their biological parents
 May also compare adopted and biological siblings

24.  Heredity – Environment Correlations:
individuals’ genes may influence the types of
environments to which they are exposed

25.  Shared environmental experiences: siblings’
common experiences
 Non-shared environmental experiences: a
child’s unique experiences, both within and
outside the family
• Shared environment accounts for little of the
variation in children’s personality or interest
• Heredity influences the non-shared environments
through heredity–environment correlations

26.  Epigenetic view: development is an ongoing,
bi-directional interchange between heredity
and environment
• Heredity and environment operate together

27.  The relative contributions of heredity and
environment are not additive
 Complex behaviors have some genetic loading
that gives people a propensity for a particular
developmental path
 Our environment is complex, and the interaction
of heredity and environment is extensive
 Much needs to be learned about specific ways in
which environment and genetics interact to
influence development