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Chapter 1

PSY 220 Chapter Notes - Chapter 1: Evolutionary Psychology, Epigenetics, Chest Hair

Course Code
PSY 220
Hurwitz Barry

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PSY220- Psychobiology
1.1- The Biological Approach to Behavior
Mind-body problem- what is the relationship between mental experience and brain
Biological psychology- the study of physiological, evolutionary, and developmental
mechanisms of behavior and experience
Hard problem-given this universe composed of matter and energy, why is there such a
thing as consciousness?
Biological Explanations of Behavior
Physiological explanation- relates behavior to the activity of the brain and other
organisms; deals with the machinery of the body; how does it relate to the physiology of
the brain and other organs?
Ontogenetic explanation- describes how a structure of behavior develops, including the
influence of genes, nutrition, experiences, and their interactions; how does it develop
within the individual?
Evolutionary explanation- reconstructs the evolutionary history of a structure or
behavior; what evolved from what/ how did the capacity for the behavior evolve?
Functional explanation- describes why a structure of behavior evolved as it did; states
why something was advantageous and therefore evolutionarily selected; why did the
capacity for this behavior evolve?
Genetic drift- when a gene spreads by accident within a small, isolated population
Biological explanations of behavior do not necessarily assume that the individual
understands the purpose or function of the behavior.
1.2 Genetics and Behavior **not on Exam I
Genes- units of heredity that maintain their structural identity from one generation to
Chromosomes- strands of genes
DNA bases:
Adenine, guanine, cytosine, thymine
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RNA bases:
Adenine, guanine, cytosine, uracil
Proteins consist of 20 amino acids, and the order of those amino acids depends on the
order of DNA and RNA bases.
Enzymes- biological catalysts that regulate chemical reactions in the body
Homozygous gene- identical pair of genes in the two chromosomes
Heterozygous gene- unmatched pair of genes on the two chromosomes
Dominant gene- shows a strong effect in either the homozygous or heterozygous
Recessive gene- shows its effects only in the homozygous condition
The genes on the sex chromosomes (designated X and Y) are known as sex-linked genes.
All other chromosomes are autosomal chromosomes and their genes are known as
autosomal genes.
XX= female
Sex-limited genes- present in both sexes, generally on autosomal chromosomes, but
active mainly in one sex (ex. Chest hair on men, breasts on women)
Mutation- a heritable change in a DNA molecule
Epigenetics- deals with changes in gene expression without modification of the DNA
Heredity and Environment
To determine the contributions of heredity and environment on a certain characteristic,
researchers rely mainly on two kinds of evidence. First, they compare monozygotic twins
and dizygotic twins.
Monozygotic- “from one egg”; the twins have the same genes
Dizygotic- “from two eggs”; the twins do not have the same genes
A stronger resemblance between monozygotic than dizygotic twins suggests a genetic
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