Section 2 Chapter 3: Biological Beginnings
THE EVOLUTIONARY PERSPECTIVE
Natural Selection: is the evolutionary process that favors individuals of a
species that are best adapted to survive and reproduce.
Adaptive behavior: behavior that promotes an organism’ survival in the
Evolutionary Psychology: emphasizes the importance of adaptation,
reproduction, and “survival of the fittest” in shaping behavior.
“Fit” in this sense refers to the ability to bear offspring that survive long
enough to bear offspring of their own.
David Buss (1995, 2000, 2004), believes that just as evolution shapes our
physical features, such as body shape and height, it also pervasively
influences how we make decisions, how aggressive we are, our fears, and our
Every species has a mechanism for transmitting characteristics from one
generation to the next. This mechanism is explained by the principles of
genetics. Each of us carries a “genetic code” that we inherited from our
parents, and it is a distinctly human code. Because it carries this human code,
a fertilized human egg cannot grow into an egret, eagle, or elephant.
Chromosomes: threadlike structures that contain the remarkable substance
DNA; there are 23 pairs of chromosomes.
DNA: a complex molecule that contains genetic information. It has a double
helix shape, like a spiral staircase.
Genes: units of hereditary information composed of DNA. Genes direct cells
to reproduce themselves and to assemble proteins.
How do genes manage to get passed from generation to generation and end
up in all of the trillion cells in the body?
1. MITOSIS – cellular reproduction in which the cell’s nucleus
duplicates itself with two new cells being formed, each containing
the same DNA as the parent cell, arranged in the same 23 pairs of
2. MEIOSIS – a specialized form of cell division that produces cells
with only one copy of each chromosome. Meiosis forms eggs and
sperm (or gametes).
3. FERTILIZATION – a stage in the reproduction process whereby an
egg and a sperm fuse to create a single cell, called a zygote.
Zygote – a single cell formed through fertilization
Genotype – person’s genetic heritage; the actual genetic material.
Phenotype – the way an individual’s genotype is expressed in observed
and measurable characteristics.
Dominant-Recessive Genes Principle – if one gene of a pair is
dominant and one is recessive, the dominant gene exerts its
effect, overriding the potential influence of the other, recessive
Sex-Linked Genes – X-linked inheritance is the term used to
describe the inheritance of an altered (mutated) gene that is
carried on the X chromosome.
Genetic Imprinting – occurs when genes have differing effects
depending on whether they are inherited from the mother or the
Polygenic Inheritance – occurs when many genes interact to
influence a characteristic.
CHROMOSOME AND GENE-LINKED ABNORMALITIES:
o Down Syndrome – a chromosomally transmitted form
of mental retardation, caused by the presence of an
extra copy of chromosome 21.
o Sex-Linked Chromosome Abnormalities
Klinefelter syndrome – a chromosome
disorder in which males have an extra X
chromosome, making them XXY instead of
Fragile X syndrome – a chromosome
disorder involving an abnormality in the X
chromosome, which becomes constricted
and often breaks.
Turner syndrome – a chromosome disorder
in females in which either an X
chromosome is missing, making the person
XO instead of XX, or the second X
chromosome is partially deleted.
XYY syndrome – a chromosome disorder in
which males have an extra Y chromosome.
o Phenylketonuria (PKU) - genetic disorder in which an
individual cannot properly metabolize phenylalanine,
an amino acid. PKU is now easily detected but, if left
untreated, results in mental retardation and
Sickle-cell anemia – a genetic disorder that affects the
red blood cells and occurs most often in people of
African descent; blood disorder that limits the body’s
oxygen supply; it can cause joint swelling, as well as
heart and kidney failure.
NAME DESCRIPTION TREATMENT INCIDENCE
in a shortened life
Physical and oxygen
individuals live to
1 in 2,000
Diabetes Body does not
insulin, which causes
metabolism of sugar.
Early onset can be
fatal unless treated
1 in 2,500
Hemophilia Delayed blood
internal and external
can reduce or prevent
damage due to
1 in 10,000
Doesn’t usually appear
until age 35 or older;
death likely 10 to 20
years after symptoms
1 in 20,000
Neural tube disorder
that causes brain
Corrective surgery at
2 in 1,000
mental and physical
by an accumulation
of lipids in the
special diet are used,
but death is likely by 5
years of age.
One in 30
Jews is a
PRENATAL DIAGNOSTIC TESTS:
o Amniocentesis – a prenatal medical procedure in which a sample
of amniotic fluid is withdrawn by syringe and tested for any
chromosome or metabolic disorders; performed between the 12th
and 16th weeks of pregnancy.
o Ultrasound sonography – a prenatal medical procedure in which
high-frequency sound waves are directed into the pregnant
woman’s abdomen; can detect disorders such as microencephaly,
a form of mental retardation involving an abnormally small brain,
as well as giving clues to the baby’s sex.
o Chorionic villus sampling – a prenatal medical procedure in which
a small sample of the placenta (the vascular organ that links the
fetus to the mother’s uterus) is removed at some point between
the 8th and 11th weeks of pregnancy; allows a decision about
abortion to be made near the end of the first 12 weeks of
pregnancy, a point when an abortion is safer and less traumatic
than after amniocentesis, which is done between 12 and 16
weeks of pregnancy.
o Maternal blood screening / Triple screen – identifies pregnancies
that are at higher risk for birth defects such as spina bifida and
Down syndrome; it currently measures three substances in the
mother’s blood: alpha-fetoprotein, estriol, and human chorionic
INFERTILITY – defined as the inability to conceive a child after 12 months of
regular intercourse without contraception.
In vitro fertilization (IVF) – eggs and sperm are combined in a laboratory dish.
If any eggs are successfully fertilized, one or more of the resulting embryos is
transferred into the woman’s uterus or womb.
Gamete intrafallopian transfer (GIFT) – a doctor inserts eggs and sperm
directly into a woman’s fallopian tube.
Zygote intrafallopian transfer (ZIFT) – this a two-step procedure. First, eggs
are fertilized in the laboratory. Then, any resulting zygotes are transferred to
a fallopian tube.
PROBLEM POSSIBLE CAUSES TREATMENT
Low sperm count Hormone imbalance,
varicose vein in
Y chromosome gene
Immobile sperm Abnormal sperm shape
Problem in immune
PROBLEM POSSIBLE CAUSES TREATMENT
Ovulation problems Pituitary or ovarian
Antisperm secretions Unknown Acid or alkaline
Blocked fallopian tubes Infection caused by
IUD or abortion or by
removed from ovary
and placed in uterus
buildup in uterus)
until the thirties
removal of uterine
BEHAVIOR GENETICS – the field that seeks to discover the influence of
heredity and environment on individual differences in human traits and
TWIN STUDY – a study in which the behavioral similarity of identical twins is
compared with the behavioral similarity of fraternal twins.
Identical Twins (called monozygotic twins) – develop from a single
fertilized egg that splits into two genetically identical replicas,
each of which becomes a person.
Fraternal Twins (called dizygotic twins) – develop from separate
eggs and separate sperm.
ADOPTION STUDY – a study in which investigators seek to discover whether
the behavior and psychological characteristics of adopted children are more
like their adoptive parents, who have provided a home environment, or more
like their biological parents, who have contributed their heredity. Another
form of the adoption study is to compare adopted and biological siblings.
HEREDITY-ENVIRONMENT CORRELATIONS – which means that individuals’
genes influence the types of environments to which they are exposed.
Behavior geneticist Sandra Scarr (1993) described three ways that heredity
and environment are correlated:
Children inherit genetic
tendencies from their
parents and parents also
provide an environment
that matches their own
parents usually have
children and they are
likely to provide an
environment rich in
music for their
The child’s genetic
stimulation from the
environment that supports
a particular trait. Thus
genes evoke environmental
A happy outgoing child
elicits smiles and
Children actively seek out
“niches” in their
environment that reflect
their own interests and
talents and are thus in
accord with their genotype.
Libraries, sport fields,
and a store with
are examples of
children might seek out
if they have intellectual
interests in books,
talent in sports, or
SHARED ENVIRONMENTAL EXPERIENCES – siblings’ common environmental
experiences, such as their parents’ personalities and intellectual orientation,
the family’s socioeconomic status, and the neighborhood in which they live.
NONSHARED ENVIRONMENTAL EXPERIENCES – the child’s own unique
experiences, both within the family and outside the family, that are not
shared by another sibling. Thus, experiences occurring within the family can
be part of the “nonshared environment.”
EPIGENETIC VIEW – emphasizes that development is the result of an ongoing,
bidirectional interchange between heredity and environment.
1. Which is more persuasive to you: the views of evolutionary
psychologists or their critics? Why?
2. What are some possible ethical issues regarding genetics and
development that might arise in the future?
3. Someone tells you that they have analyzed their genetic
background and environmental experiences and reached the
conclusion that environment definitely have had little influence
on their intelligence. What would you say to this person about
their ability to make this self-diagnosis?
Santrock, J.W. (2006). Life-Span Perspective.10th Edition. McGraw-Hill. New York.
Mrs. Maria Angela L. Diopol