Transcript Mr. Duez - Atascocita High School Psychology

Objective: 10/20/15
Provided notes, SWBAT evaluate how evolved
tendencies influence behavior, and describe the
interactive effects of heredity & the environment.
Agenda:
1. Do Now
2. Notes-genetics
3. Project
Biological Behavior, Heredity, &
Evolutionary Psychology
“We have found the most interesting
universe, & it is us.” - David Eagleman
Heredity & Behavior: Is It All in the Genes?
Do Now: In your groups discuss and answer the
following question.
Do genetic or environmental factors have a greater
influence on your behavior? Do inherited traits or life
experiences play a greater role in shaping your
personality?
Heredity & Behavior: Is It All in the Genes?
Physical characteristics such as height, hair
color, blood type, & eye color are largely
shaped by heredity.
What about psychological characteristics, such as
intelligence, moodiness, impulsiveness, & shyness?
To what extent are people’s behavioral qualities molded by
their genes?
Behavioral Genetics: An
interdisciplinary field that studies the
influence of genetic factors on
behavioral traits.
Field has grown by leaps & bounds since the
1970s, & this research has shed new light on the
age-old nature versus nurture debate.
Basic Principles of Genetics
Every cell in your body contains enduring messages
from your mother & father. These messages are
found on the chromosomes that lie within the
nucleus of each cell.
Chromosomes: Strands of DNA (deoxyribonucleic
acid) molecules that carry genetic information
Zygote: A single cell formed by the union of a
sperm & an egg.
A single pair of parents can produce an extraordinary
variety of combinations of chromosomes.
Each parent’s 23 chromosome pairs can be scrambled in
over 8 million different ways, yielding roughly 70 trillion
possible configurations when sperm & egg unite.
Everything is a matter of probability. Except for identical
twins, each person ends up with a unique genetic blueprint.
Sex Characteristics - Primary/Secondary
Primary & secondary sexual characteristics refer to
specific physical traits that differentiate males &
females in sexually dimorphic species; that is,
species in which males & females look different.
Primary sexual characteristics are there from birth
Secondary sexual characteristics emerge at
puberty (such as low voices & beards in men, & high
voices & no facial hair in women)
Which parent decides whether a baby will be a boy or a girl?
In humans & many other species of animals, the father
determines the sex of the child.
Neither parent gets to decide. Almost everyone has around a 50%
chance of having a boy & a 50% chance of having a girl.
What we can say is that dad's sperm determines whether a
baby will be a boy or a girl. About 1/2 of his sperm will make a
boy & half a girl. The sex of the baby depends on which sperm
gets to the egg first.
In the XY sex-determination system, the female-provided ovum
contributes an X chromosome & the male-provided sperm
contributes either an X chromosome or a Y chromosome,
resulting in female (XX) or male (XY) offspring, respectively.
Hormone levels in the male parent affect the sex ratio of sperm in
humans. Maternal influences also impact which sperm are more
likely to achieve conception.
Homozygous & Heterozygous
genotypes.
Like chromosomes, genes operate in
pairs, with one gene in each pair
coming from each parent.
Whether people have attached or
detached earlobes is determined by
a single pair of genes.
In the heterozygous condition, genes
for detached earlobes are dominant
over genes for attached earlobes.
HOMOZYGOUS
HETEROZYGOUS
Basic Principles of Genetics
Like chromosomes, genes operate in pairs, with
one gene of each pair coming from each parent.
Homozygous condition: The two genes in a specific pair
are the same.
Heterozygous condition: The two genes in a specific pair
are different.
When the parents contribute genes for different types of
earlobes (the heterozygous condition), one gene in the
pair—called the dominant gene—overrides or masks the
other, called the recessive gene.
Dominant Gene: One that is expressed when paired genes
are different.
Recessive Gene: One that is masked when paired genes
are different.
Dominant & Recessive Genes
A dominant gene is expressed no matter what.
A recessive gene can only be displayed if BOTH the genes received from the
parents are the same recessive gene.
Think of it this way: A dominant gene is like the sun & recessive genes are like the stars.
If the sun is in the sky the stars cannot be seen even though they are there. Likewise, when a dominant gene is
present the recessive genes are all hidden. But if there are no dominant genes around we can see
recessive genes. In humans, the gene for brown eyes is dominant & the gene for blue eyes is recessive.
So if we received one brown gene from dad & one blue gene from mom only the brown gene would be
expressed. Our eyes would be brown (Image 1).
Basic Principles of Genetics
Because genes operate in pairs, a child has a 50%
probability of inheriting a specific gene in a particular gene
pair from each parent.
Ranges from 100% for identical twins down to 6.25% for
second cousins
Genotype: A person’s genetic makeup.
Phenotype: Refers to the ways in which a person’s genotype is
manifested in observable characteristics.
Genotype is determined at conception & is fixed forever.
In contrast, phenotypic characteristics (hair color, for
instance) may change over time. They may also be modified
by environmental factors. Most human characteristics appear to
be polygenic traits, or characteristics that are influenced by
more than one pair of genes.
3 to 5 gene pairs are thought to determine skin color.
Identical vs. Fraternal
Identical (monozygotic) twins emerge
from one zygote that splits, so their
genetic relatedness is 100%.
Identical vs. Fraternal
Fraternal (dizygotic) twins emerge from
two separate zygotes, so their genetic
relatedness is only 50%.
Higher correlations found for identical twins
indicate that they tend to be more similar to each
other than fraternal twins on measures of general
intelligence & measures of specific personality
traits, such as extraversion.
However, the fact that identical twins are far from
identical in intelligence & personality also shows
that environment influences these
characteristics.
Identical twins tend to be more similar than fraternal twins (as reflected in higher
correlations) with regard to intelligence & specific personality traits, such as
extraversion. Fndings suggest that intelligence & personality are influenced by
heredity.
Basic Principles of Genetics
Epigenetics: Study of
heritable changes in gene
expression that do not
involve modifications to the
DNA sequence.
Specific genes’ effects can
be dampened or silenced
by chemical events at the
cellular level, leading to
phenotypic alterations in
traits, health, & behavior.
David Eagleman: Brain Over Mind
Evolutionary Psychology
Evolutionary Psychology: The study of how evolutionary
principles help explain the origin & function of the human
mind, traits, & behaviors.
★ Natural selection & adaptation
★ Evolutionary success may help explain similarities
★ An evolutionary explanation of human sexuality
Why do people so easily acquire a phobia of snakes?
An evolutionary psychologist would note that snakes
are often poisonous… so those who more readily
learned to fear them were more likely to survive &
reproduce.
Can we apply the same logic to phobias about heights?
Enclosed spaces?
Clowns?
“Can we doubt (remembering that many
more individuals are born than can
possibly survive) that individuals having
any advantage, however slight, over
others, would have the best chance of
surviving and procreating their kind? . .
This preservation of favourable
variations and the rejection of injurious
variations, I call Natural Selection.”
- Charles Darwin
Principle of Natural Selection:
Heritable characteristics that provide a
survival or reproductive advantage are
more likely than alternative characteristics to
be passed on to subsequent generations and
thus come to be “selected” over time.
Please note: The process of natural selection works on
populations rather than individual organisms.
Evolution occurs when the gene pool in a
population changes gradually as a result
of selection pressures.
This process tends to be extremely gradual. It generally
takes thousands to millions of generations for one trait
to be selected over another.
Khan Academy: Intro to Evolution & Natural Selection