Download Power Point Chapter 2

Chapter 2
Physical Development
The prenatal development period
is the time
from conception to birth.
The human zygote is the cell
that is formed by the union
of the sperm and ovum.
The human zygote contains one
set of 23 chromosomes from the
mother and another set of 23
chromosomes from the father.
Polygenetic Traits
Human characteristics that result
from the interplay of multiple genes.
skin color
height
A trait not expressed
reflects
a recessive gene.
A DNA Molecule (Figure 2.2)
Males have an X and a Y
chromosome.
Females have two X
chromosomes.
Approximately 160 males are
conceived for every 100 females.
Sex-linked Characteristics
Traits from recessive genes
that are carried on the sex chromosome.
Monozygotic twins come from
the same fertilized egg and
contain the same genetic
instructions.
Dizygotic twins develop from two
different eggs.
Down Syndrome
• There is an extra twenty-first chromosome or
a piece of one.
• The disorder occurs 1 out of 1,000 live
births.
• Incidence has been linked to the age of the
mother.
• Children have a very characteristic
appearance.
Fragile-X Syndrome
• One of the leading causes of mental retardation
and developmental disabilities
• Caused by a single gene
• More common in males than females
• Can be detected through genetic screening
and DNA analysis
Genotype
The genes a person inherits
from both parents for any particular trait.
Phenotype
The actual expression of inherited traits.
The average period of human
gestation is 38 weeks.
Prenatal Development is divided
into three major stages:
• germinal period
• embryonic period
• fetal period
Stages of Prenatal Development
Teratogen
Any environmental substance or disease that
causes abnormal development of the fetus.
The most common
and direct cause
of low birth weight
is poor nutrition.
The human brain is the largest
among land mammals relative to
body size.
The human brain is not fully
mature until early adulthood.
The Central Nervous System
• consists of the brain, spinal cord,
and nerve cells
• controls almost every aspect of
human functioning
Left Side of the Brain (Figure 2.6)
Half of the neurons produced
during prenatal development die.
Myelination
• process whereby the neurons and
dendrites become coated with a fatty
substance called myelin
• enables neural impulses to travel
faster
The idea that
there is a “critical period”
for brain development
is an issue of debate.
Though often thought true,
there is no strong
scientific evidence
to categorize individual
differences in learning styles
according to left- and right-brain
hemispheric specialization.
(Hiscock & Kinbourne, 1987)
Both cerebral hemispheres
influence more aspects of
cognitive functioning than was
previously thought.
Perceptual development
involves the processing of
sensory information
by the brain.
Habituation is the decrease in an
infant’s response to a stimulus
after repeated exposure to it.
Fetuses can react to sound.
Babies prefer sweet fluids to
other tastes, and they dislike sour
and bitter tastes.
The sense of smell
is present at birth.
Newborns
are responsive to touch.
Attachment is the process by
which infants form strong,
affectional ties with their
caregivers.
Intermodal perception
means that events or objects
can be simultaneously perceived
by multiple senses.
Why does
knowledge of children’s
perceptual development
have important implications
for educators?
Learning Disabilities
• are not due to a lack of motivation
or effort on the child’s part
• is not due to poor teaching
• is not due to a lack of intelligence
• is not due to any temporary causes
Possible Causes for Learning Disabilities
• Heredity
• Problems during pregnancy and birth
• Incidents after birth
Children with specific learning
disabilities exhibit a wide range
of academic learning problems.
Potential Signs of Learning Disabilities, continued.
Attention Deficit Hyperactivity Disorder
(ADHD)
• a commonly diagnosed behavior disorder
• characterized by developmentally
inappropriate levels of activity,
concentration, distractibility and
impulsivity.
• more frequent in boys than in girls
Many physical disabilities result
from damage to the central
nervous system.
Children with low vision cannot
read newsprint-size letters, even
with corrective lenses.
Children who are blind
have either 20/200 vision
or a limited field of vision.
Traumatic Brain Injury
• an acquired injury to the brain
• either open or closed head injury
• has significant impact on learning
Children with deaf-blindness
have dual sensory impairments.
The degree of integration
into the general classroom
depends on a child’s level
of cognitive development
and communication ability.
Autism
• a neurological disorder
• affects the functioning of the brain
• more common in boys than girls
By age 5 or 6, most children:
• can copy simple geometric shapes
• can manipulate buttons and zippers
• may be able to tie their own shoes
• can print the alphabet, letters in
their name, and numbers 1 - 10
• may write large and not well
organized on paper
Girls
tend to walk
earlier than boys.
By the early childhood years,
boys outperform girls on most
gross motor tasks.
Children or adolescents with poor
motor skills may avoid physical
activities and become sedentary.
Childhood obesity
has been on the rise.
As motor skills develop and
children begin to spend more
time away from the careful
supervision of parents, the
incidence of accidental injuries
rises.
Too may children are pushed into
competitive sports before their
motor skills have significantly
matured.
The average infant
weighs approximately
7.5 pounds at birth.
During the first year, an infant’s
weight will triple.
Cephalocaudal Development
• Growth starts at the head and proceeds
downward
• The infant’s brain, neck, and trunk develop
before the legs
Proximal-distal Development
• Development begins in the center and
proceeds outward.
• Organs develop before the arms or hands
Physical growth slows down
during the preschool and
elementary years.
The average American
is growing taller today.
Heredity plays an important role
in determining
a child’s shape and size.
Nutrition is a core element
of well-being throughout life.
Sleep is a vital component of
health and well-being.
Puberty refers to the period in
which a young person becomes
capable of sexual reproduction.
Ethnic differences in the onset of
puberty are not well understood.
Puberty
is a dramatic period
of physical development,
second only to infancy.
Puberty
often leads to changes
in adolescents’ self-image,
self-confidence,
family relations,
moods,
relations with the opposite sex,
and many other behaviors.
There is considerable
individual variability
in the onset of puberty.
Early physical maturity in girls
can have some
positive consequences,
but it also poses some risks.
Young people today face a
number of risks and challenges,
including drug use, early sexual
experimentation, and AIDS.
FIGURE 2.13 Concerns of Children and Adolescents Today
Source: Child Welfare League of America, 2005.
• In 2001, almost half of the total number of enrollees in Medicaid were
children under age 19.
• In 2002, 425,493 babies were born to girls ages 15 to19, a birthrate of 43 per
1,000 girls.
• In 2002, an estimated 2,209,000 children ages 12–17 were dependent on or
abusing illicit drugs or alcohol.
• Co-occurring mental health and substance abuse disorders are increasingly
prevalent in youth; of youth treated for substance abuse disorders,
80–85% also have a mental health disorder.
• In 2003, 1,687,814 children under age 18 were arrested; of these arrests,
25,531 were for violent crimes and 11,501 were for possession of a
weapon.
• A 2001 census showed that 104,413 children are housed in
juvenile correction facilities in the United States.
• In 2001, 1,890 children under age 20 committed suicide in the United States,
a rate of 2.6 per 100,000 children.
The percentage of young people
who are overweight has more
than doubled in the last 30 years.
Childhood obesity has increased
rapidly in the last 30 years.
The eating disorder
anorexia nervosa
mainly affects
adolescent girls
between the ages
of 14 and 18.
Bulimia nervosa is an eating
disorder in which one goes on an
eating binge and then vomits or
uses laxatives as a way of
purging the body.
It is commonly believed
that drug problems
among young people
are at an epidemic level
in the United Stated.
As a consequence
of popular culture
and society’s relaxed attitudes
about sexuality,
many researchers believe
that young people
are dealing with sexual issues
at a younger age than ever before.
Compared with adults,
adolescents are at a higher risk
for acquiring sexually transmitted
diseases (STDs), including HIV.
The problem
that has received
the most attention
is adolescent pregnancy.
Schools,
like other ecological contexts,
support healthy development
of children and adolescents
and prevent risky behavior.