Lifespan Lecture 3

Overview of Developmental Psychology

• Definition: Developmental Psychology studies systematic changes and continuities in individuals over time.

• Focus: Lifespan approach examines multi-directional lifelong gains and losses.

Previous Lectures Recap

• Theoretical Perspectives: Discussed main theories in developmental psychology, including Erik Erikson's contributions (born 1902-1994, theories published in 1963 and 1968).

• Research Methods: Addressed various methods and ethical considerations in developmental psychology.

Today's Lecture Objectives

1. Understand concepts of meiosis and mitosis.

2. Describe the behavioral genetic approach.

3. Define key terms related to heredity, such as heritability and environmentality (shared and non-shared).

4. Explore nature vs. nurture, emphasizing gene-environment interactions.

5. Investigate prenatal stages of development and factors affecting fetal health.

Genetic Foundations of Development

• Gregor Mendel's Contribution:

  • Conducted research on inheritance using sweet pea plants in 1865.

  • Established foundational ideas about traits linked to single genes, contrasting with polygenic traits.

• **Key Concepts from Mendel:

  • Genes:**

  • Basic units of heredity that come in pairs (alleles), one from each parent.

  • Concept of dominant vs recessive genes: Dominant traits expressed if at least one dominant allele is present, while recessive traits require two recessive alleles.

  • Genotype vs. Phenotype: Genotype refers to the genetic makeup; phenotype refers to the observable traits.

• Cell Division Processes:

  • Mitosis: Normal cell replication resulting in two identical daughter cells; crucial for growth and repair.

  • Meiosis: Specialized cell division producing gametes, which reduces chromosome number by half (to 23) to ensure genetic uniqueness post-fertilization.

Genetic Diversity and Inheritance Mechanisms

• Alleles and Genetic Diversity:

  • Monozygotic (identical) twins share 100% genetic similarity, while dizygotic (fraternal) twins share about 50%.

• Single Gene Pair Inheritance: Specific traits influenced by one pair of genes.

• Types of Genetic Inheritance:

  • Dominant: visible in heterozygotes.

  • Recessive: only visible when homozygous.

  • Incomplete Dominance: the phenotype is a blend of both alleles.

  • Co-dominance: both alleles are expressed fully, e.g., AB blood group.

Behavioral Genetics

• Focus: Examines how genetics and environment contribute to individual differences.

• **Heritability vs. Environmentality:

• Heritability (H^2):** Proportion of variance in a trait attributable to genetic differences; varies across populations and traits.

• Environmentality (E^2): Proportion of variance in a trait due to environmental factors.

• Uses twin studies to explore genetic vs. environmental influences, looking at shared vs. non-shared environments.

Gene-Environment Interactions

• Genetics influence sensitivity to environmental factors (e.g., exposure to teratogens).

• Passive Gene-Environment Correlation: Genetic propensities provided by the environment (e.g., musically inclined parents).

• Evocative Gene-Environment Correlation: Individuals evoke responses from their environment based on genetic traits (e.g., teachers recognizing artistic talent).

• Active Gene-Environment Correlation: Individuals actively seek experiences that align with their genetic propensities (e.g., risk-takers seek thrilling activities).

Prenatal Development Stages

• Germinal Stage (Weeks 1-2): Fertilization to implantation, development of zygote.

• Embryonic Stage (Weeks 3-8): Major organs develop; critical period for organogenesis.

• Fetal Stage (Week 9 to birth): Growth and refinement; development of body systems, brain, and sensory capacities.

  • Critical Period: Most sensitive time for developing organs (embryonic period).

• Influencing Factors: Teratogens (e.g., drugs, diseases) and their timing significantly impact prenatal outcomes.

Teratogenic Effects**

• Agents that can harm the fetus, most harmful during the embryonic period (e.g., alcohol leading to Fetal Alcohol Syndrome).

• Individual susceptibility depends on genetic factors and timing of exposure.

Birth and Postnatal Environment

• Perinatal Environment: Surrounding factors affecting the baby at birth; the APGAR test is used to assess newborn health immediately after birth.

• Longitudinal studies show resilience in at-risk children and highlight the importance of supportive postnatal environments.

Summary of Key Concepts

• Dominant vs. Recessive Traits: Understanding the basic principles of genetic expression.

• Meiosis and Mitosis: Distinguishing between types of cell division.

• Behavioral Genetic Approach: Insights into the sources of individual differences and the interactive effects of genes and environment.

• Prenatal Development: Critical insights into early stages of life and factors that can influence development.

Next Steps

• Complete readings on associated theories as noted for quiz preparation.

• Prepare for upcoming assessments based on lecture materials covered.