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Chapter 2
Biological Beginnings
Section 1: The Evolutionary Perspective
1. Natural Selection & Adaptive Behavior
A. Natural Selection is the evolutionary process by which those individuals of a species that are best adapted
are the ones that survive & reproduce
B. Charles Darwin wrote On the Origin of Species (1859); Only the strong survive
C. Adaptive Behavior is behavior that promotes an organism's survival in the natural habitat
2. Evolutionary Psychology
A. Evolutionary Psychology - Emphasizes the importance of adaptation, reproduction, & "survival of the fittest"
in shaping behavior
B. David Buss points out that just as evolution shapes our physical features, such as body shape & height, it also
pervasively influences how we make decisions, how aggressive we are, our fears, & our mating pattern
C. Evolutionary Developmental Psychology
1. An extended childhood period evolved because humans require time to develop a large brain & learn
the complexity of human society
D. Evaluating Evolutionary Psychology
1. Bidirectional View: in which environmental & biological conditions influence each other.
Section 2: Genetic Foundations of Development
1. The Collaborative Gene
A. Chromosomes - Threadlike structures that come in 23 pairs, one member of each pair coming from each
parent. Chromosomes contain the genetic substance DNA.
B. DNA - A complex molecule with a double helix shape that contains genetic information.
C. Genes - Units of hereditary information composed of short segments of DNA. Genes direct cells to reproduce
themselves & manufacture the proteins that maintain life.
D. Human Genome Project reported that humans only have about 30,000 genes (now said to be 20,500)
2. Genes & Chromosomes
A. Mitosis, Meiosis, & Fertilization
1. Mitosis - Cellular reproduction in which the cell's nucleus duplicates itself with 2 new cells being
formed, each containing the same DNA as the parent call, arranged in the same 23 pairs of
chromosomes
2. Meiosis - A specialized form of cell division that occurs to form eggs & sperm (or gametes), each of
which contains only 1/2 of the parent cell's genetic material.
3. Fertilization - A stage in reproduction whereby an egg & a sperm fuse to create a single cell, called a
zygote.
4. Zygote - A single cell formed through fertilization
B. Sources of Variability
1. Identical Twins (AKA monozygotic twins) develop from a single zygote that splits into 2 genetically
identical replicas.
2. Fraternal twins (called dizygotic twins) develop from separate eggs & separate sperms, making them
genetically no more similar than ordinary siblings
3. Genotype - A person's genetic heritage; the actual genetic material
4. Phenotype - The way an individual's genotype is expressed in observed & measurable characteristics
3. Genetic Principles
A. Dominant-Recessive Genes Principle
1. The dominant gene overrides the potential influence of the other gene, called the recessive gene. This
is the dominant-recessive genes principle.
B. Sex-Linked Genes
1. When a mutated gene is carried on the X chromosome, the result is called X-linked inheritance.
2. Females have a backup X, making males more likely to have the X-linked disease
C. Genetic Imprinting
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1. Genetic imprinting occurs when genes have differing effects depending on whether they are inherited
from the mother or the father
D. Polygenic Inheritance
1. Some Chromosomal Abnormalities: The treatments for these abnormalities do not necessarily erase
the problem but may improve the individual's adaptive behavior and quality of life.
4. Chromosomal & Gene Linked Abnormalities
Name
Description
Treatment
Down
syndrome
An extra chromosome causes mild to
severe retardation and physical
abnormalities
Surgery, early intervention,
infant stimulation, and
special learning programs
Incidence



1 in 1,900 births
at age 20
1 in 300 births at
age 35
1 in 30 births at
age 45
Klinefelter
syndrome
(XXY)
An extra X chromosome causes
physical abnormalities
Hormone therapy can be
effective
1 in 600 male births
Fragile X
syndrome
An abnormality in the X chromosome
can cause mental retardation, learning
disabilities, or short attention span
Special education, speech
and language therapy
More common in
males than in
females
Turner
Syndrome
(XO)
A missing X chromosome in females
can cause mental retardation and
sexual underdevelopment
Hormone therapy in
childhood and puberty
1 in 2,500 female
births
No special treatment
required
1 in 1,000 male
births
XYY Syndrome An extra Y chromosome can cause
above-average height
A. Chromosomal Abnormalities
1. Down Syndrome
a. Down Syndrome - A chromosomally transmitted form of mental retardation, caused by the
presence of an extra copy of chromosome 21.
b. Appears approximately once in every 700 live births
c. Women between the ages of 16 & 34 are less likely to give birth to a child with down syndrome.
2. Sex-Linked Chromosomal Abnormalities
a. Klinefelter Syndrome - A chromosomal disorder in which males have an extra X chromosome,
making them XXY instead of XY
b. Fragile X Syndrome - A chromosomal disorder involving an abnormality in the X chromosome,
which becomes constricted & often breaks
c. Turner Syndrome - A chromosomal disorder in females in which either an X chromosome is
missing, making the person XO instead of XX, or the 2nd X chromosome is partially deleted
1. Short in stature, webbed neck, may be infertile, may have difficulty in mathematics
d. XXY Syndrome - A chromosomal disorder in which males have an extra X chromosome
B. Gene-Linked Abnormalities
Name
Description
Treatment
Incidence
Cystic Fibrosis
Glandular dysfunction that
interferes with mucus production;
Physical and oxygen
1 in 2,000 births
therapy, synthetic enzymes,
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breathing and digestion are
and antibiotics; most
hampered, resulting in a shortened individuals live to middle
life span
age
Diabetes
Body does not produce enough
insulin, which causes abnormal
metabolism of sugar
Early onset can be fatal
unless treated with insulin
1 in 2,5000 births
Hemophilia
Delayed blood clotting causes
internal and external bleeding
Blood transfusion/injections 1 in 10,000 males
can reduce or prevent
damage due to internal
bleeding
Huntington
Disease
Central nervous system
deteriorates, producing problems
in muscle coordination and mental
deterioration
Does not usually appear
until age 35 or older; death
likely 10 to 20 years after
symptoms appear
1 in 20,000 births
Phenylketonuria Metabolic disorder that, left
(PKU)
untreated, causes mental
retardation
Special diet can result in
average intelligence and
normal life span
1 in 10,000 to 1 in
20,000 births
Sickle-Cell
Anemia
Blood disorder that limits the
body's oxygen supply, it can cause
joint swelling, as well as heart and
kidney failure.
Penicillin, medication for
pain, antibiotics, and blood
transfusions
1 in 400 African
American children
(lower among other
groups)
Spina bifida
Neural tube disorder that causes
brain and spine abnormalities
Corrective surgery at birth,
orthopedic devices, and
physical/medical therapy
2 in 1,000 births
Tay-Sachs
Disease
Deceleration of mental and
Medication and special diet
physical development caused by an are used, but death is likely
accumulation of lipids in the
by 5 years of age
nervous system
1 in 30 American
Jews is a carrier
1. Phenylketonuria (PKU) - A genetic disorder in which the individual cannot properly metabolize
phenylalanine, an amino acid. PKU is now easily detected- but if left untreated, results in mental
retardation & hyperactivity
2. Sickle-Cell Anemia - A genetic disorder that affects the red blood cells & occurs most often in African
Americans
C. Dealing with Genetic Abnormalities
Section 3: Reproductive Challenges & Choices
1. Prenatal Diagnostic Tests
A. Ultrasound Sonography
1. Ultrasound Sonography is a prenatal medical procedure in which high frequency sound waves are
directed into the pregnant woman's abdomen. The echo from the sounds is transformed into a visual
representation of the fetus' inner structure
B. Fetal MRI
1. Can provide more detailed images than ultrasound
C. Chronic Villus Sampling
1. A prenatal medical procedure in which a small sample of the placenta is tested
D. Amniocentesis
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1. A prenatal medical procedure in which a sample of amniotic fluid is withdrawn by syringe & tested for
chromosomal or metabolic disorders
E. Maternal Blood Screening
F. Noninvasive Prenatal Diagnosis (NIPD)
2. Infertility & Reproductive Technologies
A. Approximately 10-15% of couples in the US experience infertility
3. Adoption
A. Children who are adopted very early in their lives are more likely to have positive outcomes than children
adopted later in life.
B. Adopted children showed more behavioral problems than nonadoptees
C. Adopted children are more likely to have a learning disability than nonadopted children
D. Adopted children perform lower in school despite similar IQ & cognitive development to their nonadoptive
counterpart
Section 4: Heredity & Environment Interaction: The Nature-Nurture Debate
1. Behavior Genetics
A. Behavior Genetics - The field that seeks to discover the influence of heredity & environment on individual
differences in human traits & development
B. Twin Study - A study in which the behavioral similarity of identical twins is compared with the behavioral
similarity of fraternal twins
C. Adoption Study - A study in which investigators seek to discover whether the behavior & psychological
characteristics of adopted children are more like their adoptive parents, who provided a home environment,
or more like their biological parents, who contributed their heredity. Another form of the adoption study is
to compare adoptive & biological siblings
2. Heredity-Environment Correlations
A. Heredity-environment correlations means that individuals' genes may influence the types of environments
to which they are exposed
B. Passive Genotype-Environment Correlations - Correlations that exist when the biological parents, who are
genetically related to the child, provide a rearing environment for the child
C. Evocative Genotype-environment Correlations - Correlations that exist when the child's genotype elicits
certain types of physical & social environments
D. Active (Niche-Picking) Genotype-Environment Correlations - Correlations that exist when children seek out
environments they find compatible & stimulating
HeredityEnvironment
Correlation
Description
Examples
Passive
Children inherit genetic tendencies from
their parents, and parents also provide
an environment that matches their own
genetic tendencies
Musically inclined parents usually have
musically inclined children and they are
likely to provide an environment rich in
music for their children
Evocative
The child's genetic tendencies elicit
stimulation from the environment that
supports a particular trait. Thus genes
evoke environmental support
A happy, outgoing child elicits smiles and
friendly responses form others
Active (nichePicking)
Children actively seek out "niches" in
their environment that reflect their own
interests and talents and are thus in
accord with their genotype
Libraries, sports fields, and a store with
musical instruments are examples of
environmental niches children might seek
out if they have intellectual interests in
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books, talent in sports, or musical talents,
respectively
3. Shared & Nonshared Environmental Influences
A. Shared Environmental Experiences - Siblings' common environmental experiences, such as their parents'
personalities & intellectual orientation, the families socioeconomic status, & the neighborhood in which they
live
B. Nonshared Environmental Experiences - The child's own unique experiences, both within the family &
outside the family, that are not shared by another sibling. Thus, experiences occurring within the family can
be part of the "nonshared environment"
4. The Epigenetic View
A. Epigenetic View - Emphasizes that development is the result of an ongoing, bidirectional interchange
between heredity & environment.