Physical Development

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Chapter 2

• Physical Development

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The prenatal development period is the time
from conception to birth.
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The human zygote is the cell that is formed by
the union of the sperm and ovum.
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The human zygote contains one set of 23
chromosomes from the mother and another set of 23
chromosomes from the father.
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Polygenetic Traits

• Human characteristics that result from the
  interplay of multiple genes.
• skin color
• height

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A trait not expressed reflects a recessive
gene.
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A DNA Molecule (Figure 2.2)
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Males have an X and a Y chromosome.Females have
two X chromosomes.
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Approximately 160 males are conceived for every
100 females.
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Sex-linked Characteristics

• Traits from recessive genes
• that are carried on the sex chromosome.

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Monozygotic twins come from the same fertilized
egg and contain the same genetic instructions.
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Dizygotic twins develop from two different eggs.
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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.

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• http//www.youtube.com/watch?vAZSfAJEpElc downs
  slide show

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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

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Genotype

• The genes a person inherits
• from both parents for any particular trait.

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Phenotype

• The actual expression of inherited traits.

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The average period of human gestation is 38 weeks.
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Prenatal Development is divided into three major
stages

• germinal period
• embryonic period
• fetal period

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Stages of Prenatal Development
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Teratogen

• Any environmental substance or disease that
  causes abnormal development of the fetus.

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The most common and direct cause of low birth
weight is poor nutrition.
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The human brain is the largest among land mammals
relative to body size.
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The human brain is not fully mature until early
adulthood.
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The Central Nervous System

• consists of the brain, spinal cord, and nerve
  cells
• controls almost every aspect of human
  functioning

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Left Side of the Brain (Figure 2.6)
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Half of the neurons produced during prenatal
development die.
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Myelination

• process whereby the neurons and dendrites
  become coated with a fatty substance called
  myelin
• enables neural impulses to travel faster

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The idea that there is a critical period for
brain development is an issue of debate.
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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.(Hisc
ock Kinbourne, 1987)
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Both cerebral hemispheres influence more aspects
of cognitive functioning than was previously
thought.
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Perceptual development involves the processing
of sensory information by the brain.
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Habituation is the decrease in an infants
response to a stimulus after repeated exposure to
it.
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Fetuses can react to sound.
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Babies prefer sweet fluids to other tastes, and
they dislike sour and bitter tastes.
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The sense of smell is present at birth.
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Newborns are responsive to touch.
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Attachment is the process by which infants form
strong, affectional ties with their caregivers.
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Intermodal perception means that events or
objects can be simultaneously perceived by
multiple senses.
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Why does knowledge of childrens perceptual
development have important implications for
educators?
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Learning Disabilities

• are not due to a lack of motivation or effort
  on the childs part
• is not due to poor teaching
• is not due to a lack of intelligence
• is not due to any temporary causes

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Possible Causes for Learning Disabilities

• Heredity
• Problems during pregnancy and birth
• Incidents after birth

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Children with specific learning disabilities
exhibit a wide range of academic learning
problems.
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Potential Signs of Learning Disabilities,
continued.
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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

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Many physical disabilities result from damage to
the central nervous system.
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Children with low vision cannot read
newsprint-size letters, even with corrective
lenses.
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Children who are blind have either 20/200 vision
or a limited field of vision.
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Traumatic Brain Injury

• an acquired injury to the brain
• either open or closed head injury
• has significant impact on learning

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Children with deaf-blindness have dual sensory
impairments.
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The degree of integration into the general
classroom depends on a childs level of
cognitive development and communication ability.
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Autism

• a neurological disorder
• affects the functioning of the brain
• more common in boys than girls

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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

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Girls tend to walk earlier than boys.
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By the early childhood years, boys outperform
girls on most gross motor tasks.
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Children or adolescents with poor motor skills
may avoid physical activities and become
sedentary.
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Childhood obesity has been on the rise.
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As motor skills develop and children begin to
spend more time away from the careful supervision
of parents, the incidence of accidental injuries
rises.
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Too may children are pushed into competitive
sports before their motor skills have
significantly matured.
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The average infant weighs approximately 7.5
pounds at birth.
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During the first year, an infants weight will
triple.
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Cephalocaudal Development

• Growth starts at the head and proceeds downward
• The infants brain, neck, and trunk develop
  before the legs

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Proximal-distal Development

• Development begins in the center and proceeds
  outward.
• Organs develop before the arms or hands

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Physical growth slows down during the preschool
and elementary years.
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The average American is growing taller today.
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Heredity plays an important role in determining
a childs shape and size.
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Nutrition is a core element of well-being
throughout life.
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Sleep is a vital component of health and
well-being.
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Puberty refers to the period in which a young
person becomes capable of sexual reproduction.
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Ethnic differences in the onset of puberty are
not well understood.
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Puberty is a dramatic period of physical
development, second only to infancy.
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Puberty often leads to changes in adolescents
self-image, self-confidence, family relations,
moods, relations with the opposite sex, and
many other behaviors.
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There is considerable individual variability in
the onset of puberty.
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Early physical maturity in girls can have some
positive consequences, but it also poses some
risks.
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Young people today face a number of risks and
challenges, including drug use, early sexual
experimentation, and AIDS.
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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 1217 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, 8085
  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.

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The percentage of young people who are overweight
has more than doubled in the last 30 years.
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Childhood obesity has increased rapidly in the
last 30 years.
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The eating disorder anorexia nervosa mainly
affectsadolescent girls between the ages of 14
and 18.
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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.
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It is commonly believed that drug problems
among young people are at an epidemic level in
the United Stated.
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As a consequence of popular culture and
societys relaxed attitudes about sexuality,
many researchers believe that young people are
dealing with sexual issues at a younger age than
ever before.
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Compared with adults, adolescents are at a higher
risk for acquiring sexually transmitted diseases
(STDs), including HIV.
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The problem that has received the most
attention is adolescent pregnancy.
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Schools, like other ecological contexts, support
healthy development of children and adolescents
and prevent risky behavior.