APA3121 lec 2 Biological foundations of development

Nature (development)

Biology and genetics driving sequenced growth.

Nurture (development)

Environment, culture, and experiences after birth.

Nature vs. Nurture debate

How genetics and environment shape personalities and traits.

Behavioural genetics

The science of how genes and environments influence behaviour.

Adoption studies

Comparing adopted children to genetic and adoptive parents.

Twin studies

Research methods used to study traits like temperament.

Non-shared environment

Different experiences causing developmental differences in siblings.

Biological development

Physiological changes transforming a zygote into an adult.

Genes

DNA sequences determining appearance, survival, and behavior.

Chromosomes

Nucleus structures containing genes that instruct protein synthesis.

Sex chromosomes (Allosomes)

XX = Female, XY = Male.

Dizygotic twins

Fraternal twins resulting from two ova fertilized by two separate sperm, forming two zygotes.

Monozygotic twins

Identical twins resulting from one zygote that splits into two cell clusters.

Genotype

An individual's unique genetic code.

Phenotype

Directly observable physical and behavioural characteristics.

Allele

Genes located on the same place on the corresponding pairs of chromosomes.

Down syndrome (Trisomy 21)

A chromosomal abnormality caused by an extra chromosome, with risks increasing by maternal age.

Germinal stage

The prenatal period spanning weeks 1-2 where the zygote divides and implants into the uterine lining.

Embryonic stage

The prenatal period spanning weeks 3-8 focused on the growth of organs, tissues, and cell differentiation.

Fetal stage

The prenatal period spanning weeks 9-40 involving rapid growth and refinement of bodily systems.

Cephalocaudal development

Growth that occurs from the head to the tail.

Proximodistal development

Growth that occurs from the midline outward.

Hypertrophy

An increase in the relative size of an individual cell.

Hyperplasia

An increase in the absolute number of cells.

Fetal brain development at 8 weeks

Nerves are making connections with each other, muscles, organs, and other tissues.

Fetal brain development at 12 weeks

Nerves send out simple signals that stimulate reflexes.

Fetal brain development at 20 weeks

Myelin starts growing around nerves.

Fetal brain development at 28 weeks

Nerves connect with designated organs such as the senses.

Third trimester brain development

Brain development ramps up and the brain triples in weight.

Neuron proliferation rate prenatally

Neurons proliferate at a rate of 250,000 per minute.

Congenital defects

Anomalies present at birth, regardless of whether causes are genetic or extrinsic.

Dominant vs. recessive disorders

Dominant results from one defective gene; recessive requires a defective gene from each parent.

Teratogen

Any agent or drug that causes abnormal prenatal development upon exposure.

Fetal alcohol syndrome effects

Heart defects, facial, joint, and limb deformities, and small brain size.

Fetal nourishment mechanism

Diffusion of oxygen and nutrients between fetal and maternal blood in the placenta.

Primary ossification centers

Areas in the midportion of long bone shafts where bone ossification begins.

Secondary ossification centers

Areas near the end of bone shafts that support bone growth in length.

Appositional bone growth

The addition of new layers on previously formed bone layers.

Periosteum

A very thin outer covering of the bone.

Prenatal muscle growth

Occurs via hyperplasia and hypertrophy.

Postnatal muscle growth

Hyperplasia continues briefly after birth, then growth occurs predominantly by hypertrophy.

Muscle fiber types

Includes slow-twitch (type I) and fast-twitch (type IIa).

Undifferentiated muscle fibers at birth

Approximately 15% of muscle fibers have yet to differentiate.

Childhood muscle fiber distribution

By year 1, muscle fiber distribution is similar to adults.

Sex differences in muscle mass

Minimal during childhood, differing greatly after adolescence due to hormones.

Adolescent muscle mass accumulation

Boys add muscle mass until 17 (54% body weight); girls until 13 (45%).

Prenatal adipose tissue development

Appears at 3.5 months, increases in last 2 months, weighing 0.5 kg at birth.

Childhood adipose tissue growth

Grows by hyperplasia and hypertrophy; cell size doesn't increase significantly until puberty.

Postnatal fat increase timeline

Rapid increase in first 6 months; gradual increase until age 8.

Internal vs subcutaneous fat

Internal fat increases faster than subcutaneous until ages 6-7.

Subcutaneous fat distribution differences

Boys add more to trunks; girls add more to limbs and legs.

Critical periods of fat increase

Occurs during the first 4 postnatal months and during puberty.

Height percentiles in childhood

Children tend to maintain relative percentiles after 2 or 3 years.

Growth velocity

The speed at which a person grows taller over a specific period.

Growth rate stages

Infancy is fastest, early childhood slows, middle childhood is steady.

Pubertal growth spurt differences

Girls' spurt occurs around 10.5 years; boys' around 12.5 years.

Weight susceptibility

Body weight is very susceptible to extrinsic factors.

Relative growth

Differential rates of growth in body parts cause notable appearance changes.

Physiological maturation

The developmental process leading to a state of full function.

Secondary sex characteristics

Forms or structures used to assess physiological maturation in adolescents.

Catch-up growth

Rapid physical growth recovering potential growth lost to negative extrinsic influences.

Newell's model of constraints

Shows how physical growth changes individual interactions and movement.