Biological Beginnings: Evolution and Genetics

Biological Beginnings

• Evolutionary perspective: Emphasizes natural selection, where best adapted individuals survive and reproduce, and explains why we behave in certain ways and how we develop over time.

Genetic Foundations

• Chromosomes: 46 chromosomes (23 pairs) in every human cell, with XX indicating a female and XY indicating a male.
• DNA: A complex molecule with a double helix shape, containing genetic information, and located in the nucleus of cells.
• Genes: Units of hereditary information composed of DNA, which help cells reproduce and assemble proteins that direct body processes.
• Meiosis: A specialized form of cell division that occurs to form eggs and sperm (gametes).
• Fertilization: The stage in reproduction when an egg and a sperm fuse to create a single cell, called a zygote.
• Zygote: A single cell formed through fertilization.
• Twins:
  • Monozygotic (identical): 100% identical, developed from the same fertilized egg.
  • Dizygotic (fraternal): 50% identical, developed from separate eggs.
• Genotype and phenotype:
  • Genotype: The actual genetic material.
  • Phenotype: The observable expression of genes, influenced by stress, sleep, and other environmental factors.

Chromosomal Abnormalities

• Down syndrome: A strong predictor of the likelihood of having an infant with Down syndrome is the mother's age.

Behavior Genetics

• Twin and adoption studies:
  • Adoption study: Compares adopted children to their adoptive parents (environment) and biological parents (heredity).
  • Twin study: Compares behavioral differences between identical and fraternal twins, considering environmental factors.
• These studies help understand the role of environment and genes in development.

Hereditary and Environmental Interactions

• Heredity-environment correlations:
  • Passive: Biological parents provide a rearing environment.
  • Evocative: Genetically-influenced characteristics elicit certain environments.
  • Active: Individuals seek and choose environments based on their gene tendencies.
• Gene by environment interactions:
  • Epigenetic view: The result of ongoing bidirectional interchange between heredity and environment.
  • G x E interaction: The interaction between specific measured variations in DNA and specific measured aspects of the environment.

Prenatal Development

• Three periods of prenatal development:
  • Germinal: 2 weeks.
  • Embryonic: 6 weeks, with 3-layer cell formation.
  • Fetal: 28-30 weeks, from week 8 to birth.
• Organogenesis: Organ development occurs during the embryonic period.
• Age of viability: 22-26 weeks, when the fetus can survive outside the womb.
• Fetal learning: The fetus can distinguish its mother's voice from others.
• Teratogens: Environmental agents that cause damage during the prenatal period, including:
  • Prescription and non-prescription drugs.
  • Environmental hazards.
  • Infections and diseases.
• Extent of harm: Caused by dose, heredity, age of exposure, and sensitive periods.
• Hazards to development:
  • Environmental hazards.
  • Maternal diseases.
  • Maternal diet and nutrition.
  • Maternal age: Relates to developmental outcomes, such as infertility, miscarriage, and chromosome abnormalities.
  • Emotional states and stress: Deprives the fetus of oxygen and nutrients.
  • Paternal factors: Abnormalities of sperm can lead to miscarriage or cancer.

The Birth Process

• 98% of births occur in hospitals, with midwives and doulas as components.
• Analgesia, anesthesia, and oxytocin/pitocin are used to manage pain and induce labor.

Assessing the Newborn

• Apgar scale: Evaluates the newborn's condition, with a score of 7+ indicating good condition, 4-6 indicating some assistance needed, and 3 or below indicating serious danger.

Preterm and Low Birth Weight Infants

• Preterm infant: Born 3+ weeks before full term (37 or fewer weeks).
• Low birth weight: Weighing less than 5 pounds, 5 ounces.
• Normal weight: 5.5 pounds to 8 pounds.
• Consequences of preterm and low birth weight: Problems in physical growth, learning, movement, social skills, and emotional well-being, which may continue into adulthood.
• Nurturing low birth weight infants:
  • Kangaroo care: Skin-skin contact on the bare chest, which stabilizes heart rate, temperature, and breathing.

Postpartum Period

• Bonding: The connection between the mother and infant after birth.
• Postpartum depression: Experienced by 10% of mothers, 4 weeks after birth.
• Blues: A mild, short-term depression experienced by 70% of mothers, lasting 2-3 days.

Down Syndrome

• Mother's age is the strongest predictor of having an infant with Down syndrome.

Behavior Genetics

• Twin and adoption studies:
  • Adoption study: compares adopted children to adoptive and biological parents to determine the role of environment and heredity.
  • Twin study: compares behavioral differences between identical and fraternal twins to determine the role of genes and environment.

Hereditary and Environmental Interactions

• Heredity-environment correlations:
  • Passive genotype-environment correlation: biological parents provide rearing environment.
  • Evocative genotype-environment correlation: genetically-influenced characteristics elicit certain environments.
  • Active genotype-environment correlation: seeking and choosing environments based on gene tendencies.

Shared and Non-Shared Environmental Experiences

• Shared environmental experiences: common experiences among family members, such as parenting style, socioeconomic status, and household environment.
• Non-shared environmental experiences: unique experiences to each individual within a family.

Evolutionary Perspective

• Evolutionary perspective: emphasizes natural selection, where best adapted individuals survive and reproduce.
• Charles Darwin's theory: changes occur gradually over time through many generations.

Genetic Foundations

• Chromosomes:

  • 46 chromosomes (23 pairs) in humans.
  • XX = female, XY = male.

• DNA:

  • A complex molecule with a double helix shape.
  • Contains genetic information.

• Genes:

  • Units of hereditary information composed of DNA.
  • Help cells reproduce and assemble proteins.

• Meiosis:

  • A specialized form of cell division that occurs to form eggs and sperm.

• Fertilization:

  • A stage in reproduction when an egg and sperm fuse to create a single cell, called a zygote.

• Zygote:

  • A single cell formed through fertilization.

• Twins:

  • Monozygotic (identical) twins: 100% identical.
  • Dizygotic (fraternal) twins: 50% identical.

• Genotype and phenotype:

  • Genotype: actual genetic material.
  • Phenotype: observable expression of genes, influenced by stress, sleep, etc.

Gene by Environment Interactions

• Epigenetic view: ongoing bidirectional interchange between heredity and environment.
• G x E interaction: interaction of specific measured variation in DNA and specific measured aspect of environment.

Prenatal Development

• Three periods of prenatal development:

  • Germinal period: 2 weeks.
  • Embryonic period: 6 weeks, 3-layer cells.
  • Fetal period: 28-30 weeks.

• Organogenesis: organ development during embryonic period.

• Age of viability:

  • Ability to survive outside of womb.
  • Can determine sex.

Teratogens and Fetal Learning

• Teratogens: environmental agents that cause damage during prenatal period.

• Fetal learning: ability to distinguish mother's voice from others.

• Extent of harm:

  • Caused by dose, heredity, age of exposure.
  • Includes low birth weight and high birth weight.

• Teratogen types:

  • Prescription and nonprescription drugs.
  • Environmental hazards.
  • Infections/disease.

• Hazards to development:

  • Environmental hazards.
  • Maternal diseases.
  • Maternal diet and nutrition.