Prenatal Development
and Infancy
Twins
• 1 egg, 1 sperm = 1 zygote. This divides into 2 and each forms
a baby: identical (monozygotic) twins
• 2 eggs, 2 sperm = 2 zygotes with diferent genetic material
forms fraternal (dizygotic) twins
Vid – prenatal dev from fertilization
http://www.youtube.com/watch?v=UgT5rUQ9EmQ
Human Dev Quiz
Name: ______________________
1. Human sperm and eggs each carry 46 chromosomes.
T or F?
2. Fraternal twins are dizygotic. T or F?
3. A virus is an example of a teratogen. T or F?
4. A hollow ball of cells is called a ___________
5. Implantation of the embryo in the uterus lining
occurs on day
12
10
30
Human Dev Quiz
Name: ______________________
1. Human sperm and egg each carry 23 chromosomes. T
or F?
2. Identical twins are dizygotic. T or F?
3. A teratogen is a toxic substance that negatively
affects a developing embryo.
T or F?
4. A hollow ball of cells is called a ___________
5. Implantation of the embryo in the uterus lining
occurs on day
12
10
30
1. FAS stands for ______________________
2. The structure where materials are exchanged
between the mother and fetus’ blood is the
_____________________
3. A girl and boy are born at the same time. They are
_______________ twins.
4. The human heart first develops around ____ after
fertilization
1 week 6 weeks
20 weeks
5. Cell division of a zygote is called _________, and as
cells divide they get smaller/bigger/ stay same size
1. FAS stands for ______________________
2. The structure where materials are exchanged
between the mother and fetus’ blood is the
_____________________
3. A girl and boy are born at the same time. They are
_______________ twins
4. The human heart first develops around ____ after
fertilization
1 week
6 weeks
20 weeks
5. Cell division of a zygote is called _________, and as
cells divide they get smaller/bigger/ stay same size
Prenatal Development –
• Conception: a human begins as a fertilized egg
(zygote). Combo of genes from mother and father.
• Prenatal weeks 0 – 8: Embryo. A bunch of cells with
some (but not much) definition.
• Prenatal weeks 8 – 38: Fetus. Organs and cell
specialization occurs. Growth.
• Birth: At 9 months.
Prenatal development animations –
LINKS NO LONGER WORK
• http://www.youtube.com/watch?v=NhoU4y0Jt04
• http://www.youtube.com/watch?v=JjkFL54Uado
• http://www.youtube.com/watch?v=kHybTthWwn0
What determines your personality?
• Combination of genetics (nature)
• And experience/environment (nurture)
• Genes from both parents give you your basic biological
structures (your body) and some aspects of your
personality, disposition and intelligence
• Sex chromosomes determine if you are male XY or
female XX
Things that influence prenatal development
• Teratogens are environmental agents (such as drugs or
viruses or chemicals),
• Diseases (such as German measles),
• Physical conditions (such as malnutrition)
may impair prenatal development and lead to birth
defects or even death
How We Develop During Infancy
Motor
Development
SensoryPerceptual
Development
Motor Development – infant reflexes
http://www.youtube.com/watch?v=8dI1UOziOgg
A reflex is an unlearned response to a specific
stimulus
The Babinski reflex occurs when an infant fans her
toes upward when her feet are touched
The grasping reflex occurs when an infant grasps
any object that touches their palms
The rooting reflex leads an infant to turn its mouth
toward anything that touches its cheeks and search
for something to suck
The sucking reflex leads an infant to suck anything
that touches its lips
The stepping reflex occurs when an infant is held
upright, used to learn to walk
Infant reflex modeling
• Pretend you’re a baby and perform the basic reflexes.
• How do these reflexes help a baby?
• Babies have basic survival needs – food, physical protection
• Babies can’t talk and ask for what they need
Sensory-Perceptual Development
VIDEO BELOW
• Preferential-looking technique is used to study
vision
• Two visual stimuli are displayed side by side, and the
researcher records how long the infant looks at each
stimulus
• If the infant looks at one stimulus longer, it is inferred he
can tell the difference between the two stimuli and has a
preference
• Video: http://www.youtube.com/watch?v=8J-JflThHks
Sensory-Perceptual Development
• Habituation: decrease in response to a stimulus once it
becomes familiar. Getting used to something.
• Infants look longer at novel (new) stimuli
• This tells us the baby can tell the difference between new and
old
• Infants also intensity their sucking of a pacifier in their
mouths when confronted with a novel stimulus
Sensory-Perceptual Development
• Vision is the least-developed sense at
birth
• Newborns’ visual acuity is 20/400 to
20/800
• Reaches 20/20 within the first year
• Color vision develops by 2 to 3 months
• Such stimulation is necessary for proper
development of the visual pathways and
cortex during infancy
• Newborns need to practice looking to form
good eyesight
Sensory-Perceptual Development
• Hearing in the newborn is more fully developed
than vision
• Can distinguish mother’s voice
• This develops in the womb before birth
• By 6 months, an infant’s hearing is comparable to that
of an adult
• Steadily declines from there. Never as good again
Sensory-Perceptual Development
• The senses of smell, taste, and touch are also fairly
well-developed at birth
• Infants can differentiate the smell of their mother
• Infants have innate understanding of objects and
movement – ex, solids cannot pass through each
other.
Sensory-Perceptual Development
• The brain contains about 100 billion brain cells
(neurons) at birth = stars in our galaxy!
• Infant’s brain is immature, connections between
neurons need to be formed
• Without visual experiences, the visual pathways do not
develop - vision permanently lost
• During infancy, networks of neurons used become
stronger. Those not used disappear.
Brain cell = Neuron