POWERPOINT PRESENTATION
FOR BIOPSYCHOLOGY,
9TH EDITION
BY JOHN P.J. PINEL
P R E P A R E D B Y J E F F R E Y W . G R I M M
W E S T E R N W A S H I N G T O N U N I V E R S I T Y
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Thinking about the Biology of Behavior
Chapter 2
Evolution, Genetics, and
Experience
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Learning Objectives
LO1: Thinking about the biology of behavior in terms of traditional physiological-
psychological and nature-nurture dichotomies is flawed: Explain and discuss.
LO2: Summarize the pathway of evolution from single-cell organisms to humans.
LO3: Describe 8 commonly misunderstood points about evolution.
LO4: Discuss the field of evolutionary psychology and the study of mate bonding.
LO5: Outline the mechanisms of gene expression.
LO6: Discuss several ways in which modern advances have changed our
understanding of genetic processes.
LO7: Discuss the rapid growth of the field of epigenetics.
LO8: Describe 3 classic examples of research on behavioral development, and how
each illustrates gene–experience interaction.
LO9: It is important to distinguish between the development of individuals and the
development of individual differences. Explain.
LO10: Explain heritability estimates and how they are commonly misinterpreted.
LO11: Describe 2 ways that twin studies can be used to study the interaction of
genes and experience (i.e., nature and nurture).
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There is a tendency to think in simple
dichotomies when explaining behavior.
Is it physiological or psychological?
Is it inherited or is it learned?
Both questions are common, yet misguided.
From Dichotomies to
Interactions
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Cartesian dualism: Descartes argued that the
universe consists of two elements.
Physical matter
Human mind (soul, self, or spirit)
Cartesian dualism viewed the mind and brain
as separate entities.
Is It Physiological or
Psychological?
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Problem 1: Brain damage has an impact on
psychological functioning.
Example: Oliver Sacks’s Case Study of a
Man with Asomatognosia Deficiency in awareness of parts of one’s
own body
Result of damage to the right parietal lobe
Problems of Traditional
Dichotomies: Mind–Brain Dualism
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FIGURE 2.1 Asomatognosia typically
involves damage to the right parietal
lobe.
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Is It Inherited or Is It Learned?
The “Nature–Nurture” Issue
Watson, a behaviorist, believed that all
behavior is the product of learning (nurture).
Ethology, the study of animal behavior in the
wild, focuses on instinctive (nature)
behaviors.
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Problem 2: Chimps show psychological (i.e.,
“human”) abilities—for an example, see
Gallup’s research on chimp self-awareness
Chimps spontaneously groom themselves in
mirror.
Chimps examine and touch the red marks on
their own faces after seeing their reflections in a
mirror.
Problems of Traditional
Dichotomies: Mind–Brain Dualism
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Many factors other than genetics (nature) or learning
(nurture) have an impact on behavior.
“Nurture” now encompasses learning and
environment.
While it is generally accepted that behavior is a
product of nature and nurture, many still ask how
much is determined by each—but genetic and
experiential factors do not merely combine in an
additive fashion. Interactionism
Problems of Traditional
Dichotomies: Nature or Nurture
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FIGURE 2.3 A schematic
illustration of the way in which
many biopsychologists think
about the biology of behavior.
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While Darwin was not the first to propose that species evolve, he was the first to compile supporting evidence (and to suggest ways in which evolution works).
Darwin presented 3 kinds of evidence.
Darwin argued that evolution occurs through natural selection.
Human Evolution
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Darwin’s Evidence
Fossil evidence of evolution
Structural similarities among living species suggest common ancestors.
Impact of selective breeding
Direct Observation of Evolution in Progress: Grant (1991)
Finches of the Galapagos islands changed dramatically after a single season of drought.
Human Evolution: Evidence
for Evolution
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FIGURE 2.4 Four kinds of evidence
supporting the theory that species
evolve.
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Evolution and Behavior
Just as physical features contribute to “fitness,” so do behaviors.
Some are obvious—the ability to find food, avoid predation, etc.
Some are less obvious—social dominance and courtship displays.
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Course of Human Evolution
Evolution of Vertebrates
Chordates have dorsal nerve cords.
Vertebrates are chordates with spinal bones.
Evolution of Amphibians
Bony fishes leave the water briefly.
Advantages include fresh water and new food sources.
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FIGURE 2.6 A recently discovered
fossil of a missing evolutionary
link is shown on the right, and a
reconstruction of the creature is
shown on the left. It had scales,
teeth, and gills like a fish and
primitive wrist and finger bones
similar to those of land animals.
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Course of Human Evolution
(Con’t) Evolution of Reptiles
Lay shell-covered eggs; covered by dry scales
Can live far from water
Evolution of Mammals
Develop mammary glands to nurture young
Eventually no longer lay eggs; raise young in mother’s body
Humans emerge from the order primates.
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Emergence of Humankind Humans belong to family hominids, genus Homo.
The first homo species emerged from Australopethicus2 million years ago.
Homo sapiens emerged 200,000 years ago.
Course of Human Evolution
(Con’t)
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FIGURE 2.9 A taxonomy of
the human species.
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FIGURE 2.10 The remarkably
complete skull of a 3-year-old
Australopithecus girl; the fossil is
3.3 million years old.
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Thinking about Human
Evolution (Con’t)
Evolution does not proceed in a single line.
Humans have only been around for a brief
period of time.
Rapid evolutionary changes do occur.
Fewer than 1 percent of all known species
are still in existence.
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Thinking about Human
Evolution (Con’t)
Evolution does not necessarily result in perfect design.
Not all existing behaviors or structures are adaptive.
Spandrels: incidental nonadaptive byproducts
(such as the human belly button)
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Thinking about Human
Evolution (Con’t)
Not all existing adaptive characteristics
evolved to perform their current functions.
Exaptations: evolved to do one thing, but now
do something else (such as bird wings)
Similarities among species do not
necessarily mean that the species have
common origins.
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Thinking about Human
Evolution (Con’t) Homologous structures: similar structures
due to a common evolutionary origin
Analogous structures: similar structures without a common origin
Convergent evolution: the evolution of similar solutions to the same environmental demands by unrelated species
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Evolution of the Human Brain
There is no relationship between brain size
and intelligence.
Brain size is generally correlated with body
size.
It is more informative to look at the relative
sizes of different brain regions.
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FIGURE 2.13 The brains of
animals of different evolutionary
ages—cerebrums are shown in
yellow; brain stems are shown in
purple.
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Evolution of the Human Brain
(Con’t) The human brain has increased in size
during evolution.
Most of the increase in size has occurred in the cerebrum.
Increased convolutions in the cerebrum have served to increase the volume of the cerebral cortex.
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Evolutionary Psychology:
Mate Bonding
Most species mate promiscuously.
Most mammals form polygynous mating
bonds.
Humans generally form monogamous bonds.
May be adaptive in allowing more attention to
survival of children
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Thinking about Evolutionary
Psychology Current aspects of mate bonding in humans
appear to be predicted by evolutionary
theory. Examples:
Men tend to value indications of fertility.
Women tend to value power and earning capacity.
Physical attractiveness predicts which women bond
with men of high status.
Mate attraction strategies: for women, physical
attraction; for men, displaying power and resources
Men are more likely than women to commit adultery. Copyright © 2014 Pearson Education, Inc.
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Fundamental Genetics
Dichotomous traits: occur in one form or the
other, never in combination
True-breeding lines: interbred members
always produce offspring with the same trait.
Mendel studied dichotomous traits in true-
breeding lines of pea plants.
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Mendel’s Experiments
Mendel crossed a line bred true for brown
seeds with one bred true for white.
First-generation offspring all had brown
seeds.
When the first generation were bred, the
result was ¾ brown and ¼ white seeds.
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Mendel’s Experiments (Con’t)
True-Breeding Lines
White (ww)
Brown (BB)
Brown was the dominant trait, appearing in all
of the first-generation offspring (Bw).
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Mendel’s Experiments (Con’t)
Phenotype: observable traits
Genotype: traits present in the genes
If the dominant trait is present in the
genotype (Bw), it will be observed in the
phenotype (brown seeds).
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FIGURE 2.15 How Mendel’s
theory accounts for the results of
his experiment on the inheritance
of seed color in pea plants.
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Mendel’s Experiments (Con’t)
• Each inherited factor is a gene.
• Two genes that control the same trait are called alleles.
• Homozygous: 2 identical alleles (BB, ww)
• Heterozygous: 2 different alleles (Bw)
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Chromosomes: Reproduction
and Recombination
• Genes are located on chromosomes in
the nucleus of each cell.
• Humans have 23 pairs of chromosomes,
with an allele on each chromosome.
• Meiosis: a process of cell division that
yields cells with just 23 chromosomes
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Chromosomes: Reproduction
and Recombination (Con’t)• Gametes, egg cells and sperm cells, are
produced by meiosis.
• When egg and sperm combine to form a fertilized egg (zygote), 23 pairs of chromosomes are again present.
• Mitosis: a form of cell division that yields daughter cells that have 23 pairs of chromosomes
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Chromosomes: Reproduction
and Recombination (Con’t)
• Meiosis leads to diversity as the 23 pairs of chromosomes are randomly sorted into the 2 gametes produced.
• Linkage: the tendency of traits encoded on the same chromosome to be inherited together
• Crossing over: increases diversity; “shuffles the genetic deck”
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Chromosomes are DNA molecules: double strands
of nucleotide bases wrapped around each other.
A nucleotide on strand 1 always pairs with a
particular nucleotide on strand 2.
To replicate, the strands unwind; each
nucleotide attracts its complementary base,
making two DNA molecules identical to the
original.
Chromosomes: Structure and
Replication
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FIGURE 2.18 DNA replication. As
the two strands of the original
DNA molecule unwind, the
nucleotide bases on each strand
attract free-floating
complementary bases. Once the
unwinding is complete, two DNA
molecules, each identical to the
first, will have been created.
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Sex Chromosomes and
Sex-Linked Traits
Sex chromosomes, X and Y, look different
and carry different genes. Female = XX
Male = XY
Sex-linked traits are influenced by genes on the sex chromosomes.
Dominant traits on the X chromosome will be seen more commonly in females—recessive ones in males.
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Genetic Code and Gene
Expression
Mechanism of Gene Expression
Strand of DNA unravels
Messenger RNA (mRNA) synthesized from DNA
(transcription)
The mRNA leaves the nucleus and attaches to a
ribosome in the cell’s cytoplasm.
Ribosome synthesizes protein according to 3-base
sequences (codons) of mRNA (translation).
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Genetic Code and Gene
Expression (Con’t) Regulation of Gene Expression
Enhancers: stretches of DNA that determine
whether particular structural genes initiate the
synthesis of proteins, and at what rate
Transcription factors: proteins that bind to DNA and
influence the extent to which genes are expressed
Epigenetics: the pattern of actual gene expression,
vs. the genes possessed, is most important.
Patterns of gene expression appear to be heritable.
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FIGURE 2.19 Gene
expression. Transcription of
a section of DNA into a
complementary strand of
messenger RNA is followed
by the translation of the
messenger RNA strand into
a protein.
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FIGURE 2.21 Two epigenetic
mechanisms.
Histone remodeling
involves modifications to a
histone protein (around
which DNA is coiled) and
can either decrease or
increase gene expression.
DNA methylation involves
the attachment of a
methyl group to DNA and
tends to reduce the
expression of adjacent
genes.
Mitochondrial DNA
Mitochondrial DNA
Mitochondria are the energy-generating
structures found in the cytoplasm of all cells.
Mitochondria have their own DNA.
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Mitochondrial DNA
Mitochondrial DNA
Research interest in mitochondrial DNA
• Mitochondrial DNA may be responsible for some
• disorders.
• The constant rate of mitochondrial DNA mutation has
• been used as an evolutionary clock to determine,
• for instance, that hominids evolved in Africa and
• spread around the world.
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Modern Genetics
Modern Genetics
The Human Genome Project mapped the 3 billion
base sequences of human DNA, as well as
those of some other species.
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Modern Genetics (Con’t)
Humans were found to have only about 25,000 genes,
leading to new discoveries.
• Only a small proportion of chromosome segments
contain protein-coding genes.
• Vast regions of DNA were once thought to be
inactive evolutionary remnants. However, they are
now thought to influence the structural genes.
• “Active nongene DNA”
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Modern Genetics (Con’t)
• MicroRNA appears to have an expanded role in
gene expression, beyond carrying information from
the nucleus.
• Some genes produce more than one protein.
• Alternative splicing of messenger RNA provides a
mechanism
• Evidence for expression of only one allele of a gene
(monoallelic expression) has accumulated in the
past few years.
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Behavioral Development: The
Interaction of Genetic Factors
and Experience
Three Influential Studies
Selective breeding of “maze-bright” and “maze-dull” rats
Phenylketonuria: a single-gene metabolic disorder
Development of birdsong
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of maze-bright and maze-dull
strains of rats by Tryon (1934).
(Data from Cooper, R.M., &
Zubek, J.P. (1958). Effects of
enriched and restricted early
environments on the learning
ability of bright and dull rats.
Canadian Journal of
Psychology, 12, 159-164.)
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FIGURE 2.23 Maze-dull rats
did not make significantly
more errors than maze-bright
rats when both groups were
reared in an enriched
environment. (Adapted from
Cooper & Zubek, 1958.)
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Phenylketonura: A Single-
Gene Metabolic Disorder
Due to Single Mutant Recessive Gene
A special diet during a critical period of
development lessens mental retardation.
An Example of Interaction between Genetics
and Environment
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Development of Birdsong
Young males must hear their species’ songs
during the critical period, or they develop
abnormal songs.
Young male canaries have left-side
neurological dominance for song, like human
left dominance for speech.
Adult male canaries grow new neurons each
spring: an early discovery of adult
neurogenesis.
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FIGURE 2.25 The neural
pathway responsible for the
production and learning of
song in the male canary.
The Genetics of Human
Psychological Differences The Minnesota study of twins reared apart
showed that identical twins are more similar
to each other than fraternal twins on all
psychological dimensions.
Example: Correlations of the IQs of identical twins
whether raised together or apart is larger than
that of fraternal twins raised together.
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Individual Differences (Con’t)
Heritability Estimates
Refer to populations, not to individuals
Cannot be generalized to populations from
dissimilar environments
Multiplier effect: genetically similar individuals seek
out similar environments
Turkheimer et al. (2003) found that the heritability of
IQ was near 0 in impoverished twins and near 1
(maximum) in affluent twins.
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