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Chapter 2
Biological Beginnings
PowerPoints developed by Nicholas Greco IV,
College of Lake County, Grayslake, IL
(c) 2012 The McGraw-Hill Companies, Inc.
The Evolutionary Perspective
 Natural Selection and Adaptive Behavior
natural selection -- the evolutionary process
by which those individuals of a species that
are best adapted are the ones that survive
and reproduce
survivors are better adapted to their world
than are the non-survivors
(Darwin, 1859; Johnson & Losos, 2008)
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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
the ability to pass your genes to the next
generation
(Promislow, Fedorka, & Burger, 2006)
(c) 2012 The McGraw-Hill Companies, Inc.
Evolutionary Developmental
Psychology
 Humans take longer to become
reproductively mature
 Humans require time to develop a large brain
and learn the complexity of human societies
 Thus, length of childhood period is extended
 Evolved mechanisms are not always
adaptive in contemporary society
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Evaluating Evolutionary
Psychology
 Bandura (1998) rejects what he calls “onesided evolutionism”
 An alternative is a bidirectional view, in
which environmental and biological
conditions influence each other
 Evolution gave us bodily structures and
biological potentialities
 People have used their biological capacities
to produce diverse cultures -- aggressive and
pacific, egalitarian and autocratic
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Genetic Foundations of
Development
 Each of us carries a “genetic code” that we
inherited from our parents
 A fertilized human egg carries this human
code
 Fertilized human egg cannot grow into any
other species
 Each of us began life as a single cell which
contained our entire genetic code
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Chromosomes
 Nucleus of each human cell contains
chromosomes
 Chromosomes -- thread-like structures made
up of deoxyribonucleic acid, or DNA
 DNA is a complex molecule that has a double
helix shape, like a spiral staircase, and
contains genetic information
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Genes
 Genes -- units of hereditary information
short segments of DNA
 Genes direct cells to reproduce themselves
and to assemble proteins
 Proteins
the building blocks of cells
the regulators that direct the body’s processes
(Mader, 2008)
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Human Genome Project
 Preliminary map of the human genome -- the
complete set of developmental instructions
for creating proteins that initiate the making
of a human organism
 Each human has approximately 20,500 genes
 Human genome consists of many genes that
collaborate both with each other and with
non-genetic factors inside and outside the
body
 Genetic expression is affected by their
environment
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Mitosis
 All body cells, except the sperm and egg,
have 46 chromosomes arranged in 23 pairs
 Body cells reproduce by a process called
mitosis
 During mitosis, the cell’s nucleus—including
the chromosomes—duplicates itself and the
cell divides
 Two new cells are formed, each containing
the same DNA as the original cell
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Meiosis
 Sex cell division is different type of cell
division
 Eggs and sperm (or gametes) are formed in
meiosis
 A cell of the testes (in men) or ovaries (in
women) duplicates its chromosomes but
then divides twice, thus forming four cells
 Each of these has only half of the genetic
material of the parent cell
 By the end of meiosis, each egg or sperm
has 23 unpaired chromosomes
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Fertilization
 Zygote -- an egg and a sperm fuse to
create a single cell
 In the zygote, the 23 unpaired
chromosomes from the egg and sperm
combine to form one set of 23 paired
chromosomes
One chromosome of each pair is from
the mother’s egg and the other from the
father’s sperm
Each parent contributes half of the
offspring’s genetic material
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The 23rd Pair of Chromosomes
 Slight difference in the 23rd pair
 In females, the 23rd pair consists of
two chromosomes called X
chromosomes
 In males, the 23rd pair consists of an X
and a Y chromosome
 The presence of a Y chromosome is
what makes an individual male
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Sources of Variability
 Combining genes of two parents
increases genetic variability in the
population
 Chromosomes in the zygote are not
exact copies of the parents
 Another source of variability comes
from DNA
mutated gene -- a permanently altered
segment of DNA
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Genotype and Phenotype
 Genotype -- all of a person’s genetic material
 Phenotype -- observable characteristics
 Phenotypes include
physical characteristics (such as height,
weight, and hair color)
psychological characteristics (such as
personality and intelligence)
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Dominant-Recessive Genes
Principle
 Dominant -- one gene of a pair always exerts
its effects
 Recessive gene -- exerts its influence only if
the two genes of a pair are both recessive
may be overridden by a dominant gene
may be carried from generation to generation
but not expressed in phenotype
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Sex-Linked Genes
 X-linked inheritance -- mutated gene is
carried on the X chromosome
males have no “backup” copy to counter the
harmful gene
females have a second X chromosome, which
is likely to be unchanged
Females who have one changed copy of
the X gene are known as “carriers”
(Turner, 2006)
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Polygenic Inheritance
 Genetic transmission is usually quite
complex
few characteristics reflect the influence of only
a single gene or pair of genes
 Polygenically determined characteristics -determined by the interaction of many
different genes
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Chromosome- and Gene-Linked
Abnormalities
 Down syndrome -- caused by the presence of
an extra copy of chromosome 21
once in every 700 live births
women aged 16 - 34 are less likely to give
birth to a child with Down syndrome
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Sex-Linked Chromosome
Abnormalities
 Klinefelter syndrome -- extra X chromosome
 Fragile X syndrome -- results from an
abnormality in the X chromosome
X chromosome becomes constricted and
often breaks
 Turner syndrome -- females have either an X
chromosome missing or part of one X
chromosome is deleted
 XYY syndrome -- male has extra Y
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Gene-Linked Abnormalities
 Phenylketonuria (PKU) -- individual cannot
properly metabolize phenylalanine, an amino
acid
left untreated, phenylalanine builds up in the
child, producing mental retardation and
hyperactivity
 Sickle-cell anemia -- genetic disorder that
impairs the body’s red blood cells
most often in African Americans
red blood cell becomes a hook-shaped
“sickle” that cannot carry oxygen properly
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Other diseases that result from
genetic abnormalities
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Cystic fibrosis
Diabetes
Hemophilia
Huntington disease
Spina bifida
Tay-Sachs disease
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Behavior Genetics
 Behavior genetics seeks to discover the
influence of heredity and environment on
individual differences in human traits and
development
 Behavior geneticists often study either twins
or adoption situations
(Plomin, DeFries, & Fulker, 2007; Vogler, 2006)
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Behavior Genetics
 In a twin study, the behavioral similarities
between identical twins is compared with the
behavioral similarities between fraternal
twins
 In an adoption study, investigators seek to
discover whether the behavior and
psychological characteristics of adopted
children are more like those of their adopted
parents
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Heredity-Environment
Correlations
 Passive genotype-environment correlations
occur because biological parents, who are
genetically related to the child, provide a
rearing environment for the child
 Evocative genotype-environment
correlations occur because a child’s
characteristics elicit certain types of
environments
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Heredity-Environment
Correlations
 Active (niche-picking) genotype-environment
correlations occur when children seek out
environments that they find compatible and
stimulating
 Niche-picking refers to finding a setting that
is suited to one’s abilities
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The Epigenetic View
 Development is the result of an ongoing,
bidirectional interchange between heredity
and the environment
 Heredity and environment operate together—
or collaborate—to produce a person’s
intelligence, temperament, height, weight,
ability to pitch a baseball, ability to read, etc.
(Gottlieb, Wahlsten, & Lickliter, 2006)
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Gene X Environment (G x E)
Interaction
 The interaction of a specific measured
variation in DNA and a specific measured
aspect of the environment
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The Course of Prenatal
Development
 Fertilization to birth
 Prenatal development lasts approximately
266 days
 Three periods
Germinal
Embryonic
Fetal
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The Germinal Period
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First two weeks after conception
Creation of the fertilized egg (the zygote)
Cell division
Attachment of the zygote to the uterine
wall
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The Germinal Period
 Blastocyst -- consists of an inner mass of
cells that will eventually develop into the
embryo
 Trophoblast -- outer layer of cells that later
provides nutrition and support for the
embryo
 Implantation -- the attachment of the
zygote to the uterine wall
 takes place about 10 to 14 days after
conception
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The Embryonic Period
 Occurs from two to eight weeks after
conception
 Rate of cell differentiation intensifies
 Begins as the blastocyst attaches to
the uterine wall
 Every body part eventually develops
from these three layers
endoderm
ectoderm
mesoderm
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The Embryonic Period
 The mass of cells is an embryo
 Organogenesis -- the process of organ
formation during the first two months of
prenatal development
organs are especially vulnerable to
environmental influences
 Life-support systems for the embryo
develop rapidly
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Life-Support Systems for the
Embryo
 Amnion -- bag containing a clear fluid in
which the developing embryo floats
 Umbilical cord contains two arteries and
one vein and connects the baby to the
placenta
 Placenta consists of a disk-shaped group
of tissues in which small blood vessels
from the mother and the offspring
intertwine but do not join
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The Fetal Period
 Fetal period begins two months after conception
and lasts for seven months
 Three months after conception -- fetus is about 3
inches long; weighs about 3 ounces
 By the end of the fifth month, the fetus is about
12 inches long and weighs close to a pound
 At birth, the average American baby weighs 7½
pounds and is about 20 inches long
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The Fetal Period
 See Figure 2.8 on page 48
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Three Trimesters
 The germinal and embryonic periods occur
in the first trimester
 The fetal period begins toward the end of
the first trimester and continues through
the second and third trimesters
 Viability (the chances of surviving outside
the womb) occurs at the beginning of the
third trimester
About 24-25 weeks after conception
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The Brain
 By the time babies are born, they have
approximately 100 billion neurons
 The basic architecture of the brain is
assembled during the first two trimesters
 The third trimester and the first two years
of postnatal life are characterized by
connectivity and functioning of neurons
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The Brain
 The neural tube develops out of the
ectoderm and forms at about 18 to 24
days after conception
 Two birth defects related to the failure of
the neural tube to close are:
Anencephaly
Spina bifida
 Folic acid may prevent neural tube defects
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The Brain
 The generation of new neurons is called
neurogenesis
 Neuronal migration occurs at 6-24 weeks
after conception
 At about the 23rd prenatal week,
connections between neurons begin to
form
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Prenatal Tests
 Ultrasound sonography
 non-invasive
 high-frequency sound waves
 Fetal MRI
 Used to obtain more detailed images than ultrasound
 Chorionic villus sampling (CVS)
 tiny tissue sample from the placenta is removed and
analyzed
 Amniocentesis
 sample of amniotic fluid is withdrawn and tested for
chromosome or metabolic disorders
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Prenatal Tests
 Maternal blood screening
 Identifies pregnancies that have an elevated risk for
birth defects such as spina bifida and Down
syndrome
 Triple Screen
 Measures three substances in the mother’s blood
 If abnormal, ultrasound is performed, then
amniocentesis
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Infertility and Reproductive
Technology
 Approximately 10-15 couples in the
United States experience infertility
Defined as the inability to conceive a
child after 12 months of regular
intercourse without conception
 In vitro fertilization (IVF)
25 to 30 percent of pregnancies achieved by
fertility treatments result in multiple births
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Hazards to Prenatal
Development
 A teratogen is any agent that can
potentially cause a birth defect or
negatively alter cognitive and
behavioral outcomes
Drugs
Incompatible blood types
Environmental pollutants
Infectious diseases
Maternal stress, advanced maternal and
paternal age
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Hazards to Prenatal
Development
 The dose, genetic susceptibility, and
the time of exposure influence both
the severity of damage to an embryo
or fetus and the type of defect
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Hazards to Prenatal
Development
 Prescription drugs
 Antibiotics
 Antidepressants
 Hormones
 Accutane
 Psychoactive drugs
 Caffeine
 Alcohol (Fetal alcohol spectrum disorders, FASD)
 Nicotine
 Cocaine
 Methamphetamine
 Marijuana
 Heroin
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Hazards to Prenatal
Development
 Incompatible blood types
 Difference in blood groups -- A, B, O, and AB
 Rh factor
 Environmental hazards
 Toxic wastes
 X-ray radiation
 Maternal diseases
 Rubella
 Syphilis, genital herpes, HIV/AIDS
 Diabetes
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Hazards to Prenatal
Development
 Other Parental Factors
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Maternal diet and nutrition
Overweight before and during pregnancy
Folic acid is important for normal prenatal development
Eating fish -- mercury levels
Maternal age -- 35 years or older at risk
Emotional states and stress
 Anxiety
 Depression
 Paternal factors
 Smoking
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Prenatal Care
 Involves a defined schedule of visits for medical care
 Provides screening for manageable conditions and
treatable diseases
 Includes comprehensive educational, social, and
nutritional services
 Centering Pregnancy is a new program that is
relationship-centered and provides complete prenatal
care in a group setting.
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The Birth Process
 The Birth Process
first stage -- contractions cause the woman’s
cervix to stretch and open
second stage begins when the baby’s head
starts to move through the cervix
third stage is afterbirth
placenta, umbilical cord, and other
membranes are detached and expelled
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Childbirth Setting and
Attendants
 In the United States, 99 percent of births take
place in hospitals
 Midwives
 Practiced throughout the world
 95 percent of the midwives who delivered babies in
the United States were certified nurse-midwives
 Doulas
 A caregiver who provides continuous physical,
emotional, and educational support for the mother
before, during, and after childbirth
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Methods of Childbirth
 Medications
Three basic kinds of drugs
Analgesia
Anesthesia
Oxytocics
 Natural and Prepared Childbirth
Natural childbirth -- reduce pain with breathing
techniques and relaxation
Prepared childbirth -- a.k.a. Lamaze
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Methods of Childbirth
 Other Non-Medicated Techniques to
Reduce Pain
Waterbirth -- giving birth in a tub of warm
water
likely to be less stressful for the baby and
the mother
Massage -- reduce pain and anxiety
Acupuncture -- insertion of strategically
located needles
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Breech or Cesarean Delivery
 Breech position -- buttocks rather than
head emerge first
Can prevent the baby from breathing normally
 Cesarean delivery -- the baby is removed
from the mother’s uterus through an
incision made in her abdomen
May be lifesaving but carries the risks of
major surgery
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Apgar Scale
 Used to assess the health of
newborns at one and five minutes
after birth
 A score, or reading, of 0, 1, or 2 on
each of these five health signs
heart rate, respiratory effort, muscle tone,
body color, and reflex irritability
 Anoxia -- an insufficient supply of oxygen
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Low Birth Weight and Preterm
Infants
 Low birth weight -- less than 5½ pounds at
birth
Very low birth weight -- under 3 pounds
Extremely low birth weight -- under 2
pounds.
 Preterm -- born three weeks or more
before full term
 Small-for-date -- birth weight is below
normal when the length of the pregnancy
is considered
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Incidence and Causes of Low
Birth Weight
 Incidence of low birth weight varies
considerably from country to country
Related to poverty, maternal health status,
maternal nutrition
 More health and developmental problems
than normal-weight infants
At school age, more likely to have a learning
disability, attention deficit hyperactivity
disorder, or breathing problems such as
asthma
(Moss, 2006; Wocadlo, & Rieger, 2006)
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Nurturing Low Birth Weight and
Preterm Infants
 Kangaroo care -- a way of holding an infant so
that there is skin-to-skin contact for two to three
hours per day over an extended time in early
infancy
 Massage therapy -- firm stroking with the palms
of the hands three times per day for 15-minute
periods
 Bonding -- formation of a connection, especially
a physical bond, between parents and the
newborn in the period shortly after birth
(Feldman & others, 2003; Field & others, 1986)
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The Postpartum Period
 Postpartum period -- lasts for about six
weeks after childbirth or delivery or until
the mother’s body has completed its
adjustment and has returned to a nearly
pre-pregnant state
 Physical and psychological adjustments
 Involution -- process by which the uterus
returns to its pre-pregnant size
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Emotional and Psychological
Adjustments
 Baby blues -- two to three days after birth,
many women begin to feel depressed,
anxious, and upset
 Postpartum depression -- a major
depressive episode about four weeks after
delivery
 Fathers also undergo considerable
adjustment in the postpartum period, even
when they work away from home all day
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Postpartum Blues and Postpartum
Depression Among U.S. Women
 See Figure 2.11 on page 64
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