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Chapter 2: Biological Beginnings ©2009 The McGraw-Hill Companies, Inc. All rights reserved. Life-Span Development Twelfth Edition
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Natural Selection: an evolutionary process by which those individuals of a species that are best adapted are the ones that survive and reproduce Based on Darwin’s theory 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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 David Buss is a very influential evolutionary psychologist ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 in each chromosome Genes direct cells to reproduce themselves and to assemble proteins Proteins: building blocks of cells and regulators that direct the body’s processes ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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Ultrasound Sonography: high-frequency sound waves 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 Maternal Blood Screening: identifies pregnancies with elevated risk for certain birth defects ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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Heredity – Environment Correlations: individuals’ genes may influence the types of environments to which they are exposed ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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Epigenetic view: development is an ongoing, bi-directional interchange between heredity and environment Heredity and environment operate together ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.
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