Psy Beh 101D - Lecture 2 - Biological Beginnings.rtf

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Psychology and Social Behavior
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Kara Thorsen

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Lecture 2: Biological Beginnings Lifespan Developmental Psychology January 18 , 2012 Lecture 2: Biological Beginnings  Evolutionary Psychology  Genetics of reproduction  Behavior Genetics and the Epigenetic View  Prenatal Development  Birth Evolutionary Developmental Psychology  Emphasizes the importance of adaptation, reproduction, and “survival of the fittest” in shaping behavior and development  Evolutionary Psychology explains… o Extended childhood period o Development of specialized cognitive modules o Craving for high-calorie foods and overeating when food is available o Why humans live long after reproducing  Natural selection applies to characteristics during child-bearing years, so diseases of old age have not been eliminated Genetics of Reproduction  The nucleus of each human cell contains chromosomes, which are threadlike structures made of deoxyribonucleic acid, or DNA  DNA is a complex molecule, is shaped like a spiral staircase, and contains genes, the units of hereditary information o Human Genome: approx. 22,000 genes  Mitosis: process of cell duplication for non-sex cells o 46 chromosomes in 23 pairs 46 chromosomes in 23 pairs  Includes 1 pair of sex chromosomes: XX for Females, XY for Males o Duplicates, then divides once 2 cells  Meiosis: process of cell duplication for gametes (sex cells) o Gametes: ovum (female sex cell) and sperm (male sex cell) o 46 chromosomes in 23 pairs 23 unpaired chromosomes  Includes one, unpaired sex chromosome (X or Y) o Duplicates, recombines genes, then divides twice 4 unique cells  Fertilization: fusion of sperm and ovum o 23 unpaired (ovum) + 23 unpaired (sperm) = 46 chromosomes, 23 pairs o Fertilized egg = zygote o DNA is comprised of 50% father’s and 50% mother’s genetic information  Genetic Principles o Dominant-Recessive Genes  Dimples, freckles are dominant  Attached earlobes are recessive o Sex-linked Genes  Hemophilia, Fragile X syndrome o Polygenetic Inheritance  Height, hair color Behavior Genetics  Goal: Determine the relative influence of heredity and environment on individual differences in traits and development  General Method: Investigate similarities and differences between biological and adoptive siblings  Twin studies o Behavioral similarity of…  Identical twins (100% shared genes) vs.  Fraternal twins (50% shared genes) o If a characteristic/behavior (e.g, conduct problems) is more common in identical twins than fraternal twins, then there is a genetic influence  Adoption studies o Similarities between adopted children and their…  Biological parents (contribute genes, not environment) vs.  Adopted parents (contribute environment, not genes) o Similarities between adopted children and their…  Biological siblings raised apart (share genetics, not environment)  Adoptive siblings (share environment, not genetics)  Characteristics showing genetic influence on inter-individual variability - General intelligence -Vocational interest -School achievement - Big 5 personality - Depression - Schizophrenia - Autism - Reading disability - Alzheimer’s disease Heredity-Environment Correlations  Genes influence the type of environments, making it more difficult to interpret the results of twin and adoption studies  Passive genotype-environment correlations: occur because biological parents (genetically related) provide the rearing environment  Genes for intelligence + an intelligence-enhancing environment  Evocative genotype-environment correlations: child’s characteristics (genetics) elicit certain types of environments  Easy temperament, smiling children evoke more pleasant responses  Active (niche-picking) genotype-environment correlations: children seek out environments they find compatible and stimulating  Outgoing children seek out social contexts Shared and Non-shared Environmental Influences  Shared environmental experiences: siblings’ common experiences, such as parents’ personalities or socioeconomic status  Non-shared environmental experiences: a child’s unique experience within and outside of the family, such as differential parenting, peer groups, and teachers  Growing up in one family makes siblings dissimilar o Contrasting roles for different siblings o Contrasting parental behavior towards children Gottlieb’s Epigenetic View  Development is the result of an ongoing, bi-directional interchange between heredity and the environment  The environment is influenced by an individual’s heredity o E.g., Selection of suitable contexts and activities  Genes and gene expression are influenced by non-genetic factors inside and outside the body o Environmental conditions hormone changes turn genes “on” or “off” o Stress increase in cortisol fivefold increase in DNA damage Conception and Prenatal Development  One egg released from an ovary once per month o All eggs present at birth More complications at older ages  In men, sperm are generated over time  Fertilization normally occurs in a fallopian tube, and the fertilized egg travels to the uterus, where implantation occurs Stages of Prenatal Development  Period of the Zygote (Germinal Period)  Period of the Embryo  Period of the Fetus Period of the Zygote (Germinal Period)  Begins with fertilization  Ends with implantation in the uterus o Start of pregnancy (approx. 2 weeks after fertilization)  Cell division  Travels down the fallopian tubes as cell division occurs o Zygote: first few cell divisions (~ 4 days)
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