Topic 3.2 Notes – Physical Development Across the Lifespan

How Physical Development Changes Across the Lifespan

Physical development means changes in the body and nervous system that affect what you can do, how you respond, and even how you think and learn.

The core pattern is simple:

• Before birth, prenatal influences can shape later physical and psychological outcomes.
• Infancy and childhood, reflexes and motor skills grow, which increases independence.
• Adolescence, a growth spurt and puberty lead to reproductive maturity.
• Adulthood, many abilities level off and then decline gradually, but not all at the same speed.

One AP idea to keep in mind the whole time is this: development follows the same basic sequence for most people, but timing differs because maturation interacts with health, nutrition, experience, and environment.

Prenatal Influences on Later Development

Before birth, the body and brain are developing fast, so outside influences can matter a lot. AP does not test the named prenatal stages here. It cares about what can affect development and the later results.

What can affect prenatal development

Major influences include:

• Teratogens
  Environmental agents that interfere with prenatal development.
• Maternal illness
  Infections and health conditions can affect the fetus.
• Genetic mutations and chromosomal differences
  Some are inherited, some happen spontaneously.
• Hormonal factors
  Hormones guide growth and tissue differentiation.
• Broader environment
  Nutrition, pollution, stress, and prenatal care all matter.

Teratogens

The placenta helps, but it is not a complete barrier.

• Common teratogens include alcohol, nicotine, drugs, some medications, chemicals, and radiation.
• Alcohol is the classic AP example.
  • Prenatal alcohol exposure can cause fetal alcohol spectrum disorders.
  • Effects can include growth restriction, central nervous system damage, and later problems with attention, memory, impulse control, learning, and judgment.
• Nicotine is linked to low birth weight, premature birth, and restricted growth.

Maternal illness and health

• Rubella during pregnancy can cause hearing, vision, and heart problems.
• Zika virus is linked to microcephaly and impaired brain development.
• Diabetes, malnutrition, fever, low oxygen, and stress can also affect development.

Genetic and hormonal factors

• Mutations may be inherited or spontaneous.
• Down syndrome involves an extra chromosome 21.
• Hormones regulate growth, so endocrine disruption can alter typical development.

Broader prenatal environment

• Good nutrition supports body and brain growth.
• Folic acid helps reduce neural tube defect risk.
• Pollution and heavy metals can harm neurological development.
• Prenatal health care lowers risk by catching and managing problems.

What AP questions usually want is the link. Example: prenatal alcohol exposure can later affect attention because it can disrupt nervous system development. Also remember that prenatal research often shows association, and association alone does not always prove causation.

Physical Development in Infancy and Childhood

This period is all about growing control over the body. As children gain movement, they also gain new ways to explore, learn, and act independently.

Maturation and motor development

Maturation is a biologically guided growth process. Development tends to happen in a predictable order, even if children reach milestones at different ages.

Two patterns show that order:

• Cephalocaudal = development from head to toe
• Proximodistal = development from the center outward

Cephalocaudal and proximodistal patterns

Gross and fine motor skills

Motor development matters because it increases independence. A child who can crawl, grasp, and walk can explore more, which changes learning opportunities.

Infant reflexes

A reflex is an automatic, unlearned response.

• Rooting reflex
  Touch the cheek and the infant turns toward it and opens the mouth.
• Sucking reflex
  Touch the mouth and sucking begins.
• Moro reflex
  Startle response.
• Palmar grasp reflex
  The hand closes around an object.

These reflexes show early neurological functioning. If a reflex is absent, uneven, or lasts too long, that can signal a concern.

Visual cliff and depth perception

Eleanor Gibson and Richard Walk used the visual cliff to study depth perception in infants.

Visual cliff experiment

In the photo, the caregiver is encouraging the infant from across the apparent drop. If infants avoid that side, it suggests early depth perception. One subtle AP point here: avoidance supports depth sensitivity, but if an infant does not avoid it, that does not automatically prove no depth perception.

Critical and sensitive periods

• Critical period
  A narrow window when an experience must happen for typical development.
• Sensitive period
  A broader window when experience is especially effective.

For humans, language exposure is the main example. Early exposure supports more typical language development.

In animals, Konrad Lorenz studied imprinting in goslings. They followed the first moving object they saw early in life. That is a classic timing effect, but it is a non-human animal example, not human attachment.

Physical Development in Adolescence

Adolescence brings fast physical change, and those visible changes affect how teens see themselves and how others treat them.

The adolescent growth spurt

This is a rapid increase in height, weight, and body size. It usually begins earlier in females than in males. Because growth can be uneven, coordination may look awkward for a while.

Puberty and sex characteristics

Puberty is sexual maturation and the development of reproductive capability.

• Primary sex characteristics
  Structures directly involved in reproduction
• Secondary sex characteristics
  Visible traits linked to maturation but not directly required for reproduction

Important milestones:

• Menarche = first menstrual period
• Spermarche = first ejaculation

These physical changes can affect self-image, social treatment, and behavior, which is why puberty matters psychologically too.

Physical Development in Adulthood

Adulthood covers most of life. Physical abilities often level off and then gradually decline, but there is huge variation from person to person.

• Menopause is the end of menstrual cycles and natural reproductive capacity.
• Male reproductive decline is usually more gradual.
• Mobility and flexibility often decrease with age.
• Reaction time slows, especially on rapid-response tasks.
• Visual acuity declines.
  • Presbyopia means trouble focusing on nearby objects.
• Auditory acuity declines.
  • Presbycusis is age-related hearing loss, often affecting high frequencies first.

A common test mistake is assuming physical decline means loss of intelligence. It doesn’t. A person may perform worse because of slower reaction time or reduced hearing or vision, even when cognitive ability is still strong.