1. Prepared by Jeffrey W. Grimm Western Washington University
PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel
Prepared by Jeffrey W. Grimm
Western Washington University
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2. Thinking about the Biology of Behavior
Chapter 2
Evolution, Genetics, and
Experience
Thinking about the Biology of Behavior
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From Dichotomies to
Relations and Interactions
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
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Is It Physiological or Psychological?
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
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5. Is It Inherited or Is It Learned?
The “nature-nurture” issue
Watson, a behaviorist, believed that all behavior was the product of learning (nurture)
Ethology, the study of animal behavior in the wild, focuses on instinctive (nature) behaviors
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Problems of Traditional
Dichotomies: Mind-Brain Dualism
Problem 1: Brain damage
has an impact on psycho-logical functioning. Example: Oliver Sacks’s case study of a man with asomatognosia
Deficiency in awareness
of parts of one’s own body
Due to damage to the
right parietal lobe
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FIGURE 2.1 Asomatognosia typically involves damage to the right parietal lobe.
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Problems of Traditional
Dichotomies: Mind-Brain Dualism
Problem 2: Chimps show psychological (i.e., “human”) abilities. For example: Gallup’s research on chimp self-awareness
Chimps spontaneously groom themselves in mirror
Chimps examine and touch red mark on their own face seen in mirror
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9. Problems of Traditional Dichotomies: Nature-or-Nurture
Many factors have an impact on behavior other than genetics (nature) or learning (nurture)
“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
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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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Human Evolution
While Darwin was not the first to propose that species evolve, he was the first to compile supporting evidence (and to suggest how evolution works)
Darwin presented 3 kinds of evidence
Darwin argued that evolution occurs through natural selection
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12. Human Evolution: Evidence for Evolution
Darwin’s evidence
Fossil evidence of evolution
Structural similarities among living species suggesting 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
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FIGURE 2.4 Four kinds of evidence supporting the theory that species evolve.
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14. Evolution and Behavior
Just as physical features can 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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15. 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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17. Course of Human Evolution Continued
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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18. Course of Human Evolution Continued
Emergence of humankind
Humans belong to family hominids, genus Homo
First homo species emerged from Australopethicus 2 million years ago
Homo sapiens emerged 200,000 years ago
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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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FIGURE 2.12 Vertebrate evolution.
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22. Thinking about Human Evolution Continued
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% of all known species are still in existence
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23. Thinking about Human Evolution Continued
Evolution does not necessarily result in perfect design
Not all existing behaviors or structures are adaptive
Spandrels—incidental nonadaptive by-products (such as the human belly button)
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24. Thinking about Human Evolution Continued
Not all existing adaptive characteristics evolved to perform their current function
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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25. Thinking about Human Evolution Continued
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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26. Evolution of the Human Brain
There is no relationship between brain size and intelligence
Brain size is generally correlated with body size
More informative to look at relative size of different brain regions
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FIGURE 2.13 The brains of animals of different evolutionary ages. Cerebrums are shown in yellow; brainstems are shown in purple.
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28. Evolution of the Human Brain Continued
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
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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
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 Continued
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 Continued
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 Continued
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
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 Continued
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: Structure and Replication
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
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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 – 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)
mRNA leaves nucleus and attaches to 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 Continued
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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Mitochondrial DNA
Mitochondrial DNA
Mitochondria are the energy-generating
structures found in the cytoplasm of all cells
Mitochondria have their own DNA
Mitochondria were once believed to come
from mother, but paternal mitochondrial DNA
has been found in one individual
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Mitochondrial DNA
Mitochondrial DNA
Research interest in mitochondrial DNA
Mitochondrial DNA may be responsible for some
disorders
Constant rate of mitochondrial DNA mutation has
been used as evolutionary clock to determine,
for instance, that hominids evolved in Africa and
spread around the world
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Modern Genetics
Modern genetics
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 Continued
Humans were found to have only about 25 thousand 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 Continued
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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FIGURE 2.21 Selective breeding of maze-bright and maze-dull strains of rats by Tryon (1934).
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FIGURE 2.22 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
Special diet during critical period of development lessens mental retardation
An example of interaction of genetics and environment
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Development of Birdsong
Young males must hear their species’ songs during 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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The Genetics of Human Psychological Differences
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 IQ s of identical twins whether raised together or apart is larger than that of fraternal twins raised together
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FIGURE 2.25 The correlations of the intelligence quotients (IQs) of identical and fraternal twins, reared together or apart (see Bouchard, 1998).
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Individual Differences Continued
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) – heritability of IQ was near 0 in impoverished twins and near 1 (maximum) in affluent twins
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