Transcript Lecture 02
Chapter 2
Evolution, Genetics, and
Experience
Thinking about the Biology
of Behavior
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From Dichotomies to Relations and
Interactions
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Is it physiological or psychological?
Descartes
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Is it inherited or is it learned?
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Is
the “naturenurture” debate
alive today?
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Problems with Traditional
Dichotomies – Mind-brain dualism
Brain
damage impacts
psychological functioning
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Problems with Traditional
Dichotomies – Nature-or-nurture
“
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A model of the biology of behavior
All
behavior is the product of
the interaction of three
factors:
Genes
Experience
Perception
of the current
situation
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Thinking about Human Evolution
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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Thinking about Human Evolution
Evolution
is a tinkerer, not an
architect – results are not perfect.
Not all existing behaviors or
structures are adaptive.
– incidental non-adaptive byproducts (such as the human belly
button)
Spandrels
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Thinking about Human Evolution
Not all existing adaptive characteristics
evolved to perform their current function.
– evolved to do one thing, but now
do something else (such as bird wings)
Exaptions
Similarities among species do not
necessarily mean that the species have
common origins.
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Thinking about Human Evolution
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
enivironmental 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.
More informative to look at relative
size of different brain regions.
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Evolution of the Human Brain
Brain
stem regulates reflex activities
that are critical for survival.
Cerebrum is involved in complex
adaptive processes such as learning,
perception, and motivation.
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Evolution of the Human Brain
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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Fundamental Genetics
Dichotomous
traits
True-breeding
lines
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
True-breeding
lines
White
(ww)
Brown (BB)
Brown
was the dominant trait,
appearing in all of the 1st generation
offspring (Bw)
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Mendel’s Experiments
–
Genotype –
Phenotype
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Mendel’s Experiments
gene
alleles
Homozygous
Heterozygous
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Chromosomes, Reproduction, and
Linkage
Genes
Chromosomes
Meiosis
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Chromosomes, Reproduction, and
Linkage
Gametes, eggs and sperm, 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
Linkage
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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Sex Chromosomes and SexLinked 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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The Interaction of Genetic Factors
and Experience
Ontogeny –
Phylogeny –
Ontogenetic development
is a product
of gene-experience
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