Download Heredity and Behavior

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We contain messages from our parents on
our chromosomes
Chromosome- Threadlike strands of DNA
molecules that carry genetic information
◦ Each cell contains 23 pairs of chromosomes
◦ One chromosome comes from each parent
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Parents can produce an outrageous variety of
combinations of chromosomes
Overlap of chromosomes explains similarities to
parents
◦ Class examples
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1.) Family Studies
2.) Twin Studies
3.) Adoption Studies
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Examine blood relatives
◦ Look for resemblance on specific traits
◦ Expect greater similarity if heredity effects traits
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Schizophrenia studies are an example of this
◦ 9% of siblings of schizophrenic patients show symptoms
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What is a major problem with these studies?
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These studies compare both identical and fraternal
twins on trait similarity
Identical Twins- Emerge when a single egg splits
◦ Exact same genetic blueprint
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Fraternal Twins- 2 separate eggs are fertilized
simultaneous
◦ Average of 50% gene overlap
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What do results suggest?
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These studies examine the resemblance between
adopted children and both their biological and
adoptive parents
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More similarity to biological parents= heredity
More similarity to adoptive parents = environment
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What do results show?
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Heredity and Experience have a joint
influence
Interactive Effects- Both heredity and
environment seem to play off one another
◦ Schizophrenia example
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To review, what does evolutionary psychology say
about behavior?
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Natural Selection- Heritable characteristics
that provide a survival or reproductive
advantage are more likely to be passed to
subsequent generations
◦ These genes are thus selected over time
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Include adaptations:
Adaptation- An inherited characteristic that
increased in a population (through natural
selection) because it helped solve problem of
survival or reproduction during time it emerged
◦ Ex.) Human preference for fatty food
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Organisms are born with behavioral adaptations for
both survival and reproduction
Examples of natural behaviors organisms do to
survive:
◦ Human fear of heights, snakes…etc
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Examples of behavioral adaptations designed
to improve organisms chance of reproductive
survival:
◦ In many species, females demand material goods
and service from males in return for copulation
opportunities
◦ Black-tipped hangingflies insist on gift of food
before they mate
 They even tie the length of copulation to the size of the
gift.
Anyone notice any parallels to modern society?