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  1. 1. Life-Span Development Twelfth Edition Chapter 2: Biological Beginnings
  2. 2.  Natural Selection: an evolutionary process by which those individuals of a species that are best adapted are the ones that survive and reproduce • $$ The study of human evolution was put forth by Charles Darwin • Survival characteristics are passed on in genes  Can produce a gradual modification of the population over many generations • Survival characteristics may change based on environmental conditions Adaptive Behavior: behavior that promotes an organism’s survival in the natural habitat
  3. 3.  Evolutionary Psychology: emphasizes the importance of adaptation, reproduction, and “survival of the fittest” in shaping behavior • Fit: the ability to bear offspring that survive long enough to bear offspring of their own  Natural selection favors behaviors that increase reproductive success • $$ Evolutionary developmental psychology suggests that the way in which people develop is adaptive
  4. 4.  Extended childhood period allows time to develop a large brain and learn complexity of human society Many evolved psychological mechanisms are domain-specific • Information processing Evolved mechanisms are not always adaptive in contemporary society
  5. 5.  Why do humans live so long after reproduction? • Perhaps older people improve the survival rate of babies Paul Baltes: benefits of evolutionary selection decrease with age • Natural selection is tied to reproductive fitness • Does not weed out harmful conditions that appear among older adults  Increases our need for culture
  6. 6.  Evolutionary psychology approach is just one theory of many • It has its limitations and weaknesses, and its critics Bidirectional view: environmental and biological conditions influence each other • Evolution gives us bodily structures and biological potentialities, but it does not dictate behavior • People create behavior in the context of culture
  7. 7.  Human life begins as a single cell Nucleus of each cell contains chromosomes • Chromosomes: thread-like structures made up of DNA • DNA: a complex double-helix molecule that contains genetic information $$ Genes: units of hereditary information that are comprised of short segments of DNA • Genes direct cells to reproduce themselves and to assemble proteins Proteins: building blocks of cells and regulators that direct the body’s processes
  8. 8.  Each gene has its own unique location on a particular chromosome • Results indicated that humans have about 20,000 to 22,000 genes Genes collaborate with eachother and with non-genetic factorsinside and outside the body Genetic expression is affected by the environment
  9. 9.  All cells in the human body (except sperm and egg) have 46 chromosomes arranged in 23 pairs Mitosis: reproduction of cells • Nucleus (including chromosomes) duplicate, and the cell divides Meiosis: cell division that forms sperm and eggs (gametes) • Each cell divides twice, forming four cells with 23 unpaired chromosomes
  10. 10.  Fertilization: fusing of sperm and egg to create a zygote • Creates one set of paired chromosomes (23 from each parent) Child’s sex determined by 23rd pair of chromosomes • XY = male XX = female 11
  11. 11.  Combining genes of both parents increases genetic variability • Chromosomes in zygote are not exact copies Identical (monozygotic) twins develop from a single zygote that splits into two Fraternal (dizygotic) twins develop from separate eggs and sperm Gene mutations can permanently alter segments of DNA
  12. 12.  Genotype: a person’s genetic material Phenotype: observable characteristics • A range of phenotypes can be expressed for each genotype Dominant-Recessive Genes Principle: a dominant gene always exerts its effects, overriding the potential influence of the recessive gene • A recessive gene only exerts influence if both genes in a pair are recessive
  13. 13.  $$ Genetic Imprinting: when genes have differing effects depending on whether they are inherited from the mother or the father Polygenetic Inheritance: characteristics that are determined by the interaction of many different genes • Most characteristics are determined in this manner
  14. 14.  Chromosome abnormalities usually involve the sperm and ovum lacking a normal set of 23 chromosomes • Down syndrome: caused by the presence of an extra copy of chromosome 21 Sex-linked abnormalities involve the presence of an extra X or Y chromosome (or the absence of one) • Klinefelter syndrome: males born with XXY instead of XY • Turner syndrome: females born with XO rather than XX, sometimes causing infertility • XYY syndrome: males with extra Y chromosome
  15. 15. Fragile X syndrome• $$ is usually characterized by some sort of mentaldeficiency. This deficiency could include having:a. mental retardation.b. a short attention span &c. a learning disability.•occurs more often in males than females; Xchromosome constricted or breaks off
  16. 16.  Every individual carries DNA variations, but most do not display a disorder Today, many genetic diseases can be detected prior to and immediately after birth • However, knowledge of genetic flaws leads to difficult choices about how to manage such information Genetic counselors help people make reproductive decisions
  17. 17.  $$ Ultrasound Sonography: high-frequency sound waves are directed into the womans abdomen1. used to create a visual representation of fetus’s inner structures Fetal MRI: magnetic resonance imaging designed to diagnose fetal malformations Chorionic Villus Sampling: small sample of placenta is removed to detect genetic and chromosomal abnormalities Amniocentesis: samples amniotic fluid to test for chromosomal or metabolic disorders
  18. 18.  $$ Maternal Blood Screening: identifies pregnancies with elevated risk for certain birth defects; such as both Down syndrome and spina bifida Down Syndrome: genetic disorder that causes lifelong mental retardation, developmental delays and other problems. The cause of Down syndrome is one of three types of abnormal cell division involving chromosome 21. Spina Bifida: a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones of the backbone.
  19. 19.  Infertility: the inability to conceive a child after 12 months of attempting In Vitro Fertilization (IVF): egg and sperm are combined in a laboratory dish; fertilized egg is transferred to woman’s uterus • Success depends on woman’s age • Increases risk of multiple births  Higher risk of life-threatening problems  Health risks to mother  Possible psychological effects on children
  20. 20.  Adoption: an alternative to infertility treatment • Children adopted early in life fare better than children adopted later • Somewhat more likely to experience psychological and school-related problems than non-adopted children • No differences in antisocial behavior or self-esteem • Vast majority of adopted children adjust effectively, and most parents are satisfied with their decision to adopt
  21. 21.  Behavior Genetics: seeks to discover the influence of heredity and environment on individual differences in human traits and development • Twin studies: compare identical (monozygotic) twins with fraternal (dizygotic) twins • Adoption studies: compare the characteristics of adopted children with their adoptive parents and their biological parents  May also compare adopted and biological siblings
  22. 22.  Heredity – Environment Correlations: individuals’ genes may influence the types of environments to which they are exposed
  23. 23.  Shared environmental experiences: siblings’ common experiences Non-shared environmental experiences: a child’s unique experiences, both within and outside the family • Shared environment accounts for little of the variation in children’s personality or interest • Heredity influences the non-shared environments through heredity–environment correlations
  24. 24.  Epigenetic view: development is an ongoing, bi-directional interchange between heredity and environment • Heredity and environment operate together
  25. 25.  The relative contributions of heredity and environment are not additive Complex behaviors have some genetic loading that gives people a propensity for a particular developmental path Our environment is complex, and the interaction of heredity and environment is extensive Much needs to be learned about specific ways in which environment and genetics interact to influence development