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Chapter 3

Chapter 3. Biological Beginnings. Natural Selection. Natural selection is the evolutionary process that favors individuals of a species that are more adapted to survive and reproduce . Charles Darwin.

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Chapter 3

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  1. Chapter 3 Biological Beginnings

  2. Black Hawk College

  3. Black Hawk College

  4. Natural Selection • Natural selection is the evolutionary process that favors individuals of a species that are more adapted to survive and reproduce. Black Hawk College

  5. Charles Darwin • Observed that most organisms reproduce at tremendous rates, yet populations remain nearly constant. • Reasoned that an intense, constant struggle for food, water, and resources must occur among the numerous young born. • Those that survive pass on their genes to the next generation. • Believed that those who survive are superior to those who do not. Black Hawk College

  6. Adaptive Behavior • Adaptive behavior is behavior that promotes an organism’s survival in the natural habitat. • It involves the organism’s modification of its behavior to include its likelihood of survival. • All organisms must adapt to particular places, climates, food sources, and ways of life. • Natural selection designs adaptation to perform a certain function. • Attachment is a system designed by natural selection to ensure a human infant’s closeness to the caregiver for feeding and protection from danger. Black Hawk College

  7. Evolutionary Psychology • This branch of psychology emphasizes the importance of adaptation, reproduction, and “survival of the fittest” in explaining behavior. • It focuses on conditions that allow individuals to survive or to fail. • It believes natural selection favors behaviors that increase organisms’ reproductive success and their ability to pass their genes on the next generation. • David Buss believes that evolution shapes both our physical features and pervasively influences how we make decisions, how aggressive we are, our fears, and our mating patterns. Black Hawk College

  8. Evolution and Life-SpanDevelopment • Developmentalist Paul Baltes believes that the benefits of evolutionary selection decrease with age. • He also believes that the need for culture increases with age. Black Hawk College

  9. The Benefits of Evolutionary Selection Decrease with Age • Selection operates mainly during the first half of life during the period of reproductive fitness. • Given the much shorter life span in early human evolution, selection pressure could not function often in the later years of life. • This results in older adults having a higher number of deleterious genes and dysfunctional gene expressions, such as Alzheimer’s. Black Hawk College

  10. The Need for Culture Increases with Age • As older adults weaken biologically, they need culture-based resources, such as cognitive skills, motivation, socialization, literacy, and medical technology. • Baltes stresses that a life span shift in the allocation of resources takes place away from growth and toward maintenance and the regulation of loss. Black Hawk College

  11. Evaluating Evolutionary Psychology • Albert Bandura • Steven Jay Gould • Theodore Dobzhansky • The Bidirectional View Black Hawk College

  12. Albert Bandura • Acknowledges the important influence of evolution on human adaptation and change • Rejects “one-sided evolutionism”—defining social behavior as the product of evolved biology • Believes the pace of social change gives testimony that biology permits a range of possibilities Black Hawk College

  13. Steven Jay Gould • Concluded that in most domains of human functioning, biology allows a broad range of cultural possibilities Black Hawk College

  14. Theodore Dobzhansky • Points out that the human species has been selected for learnability and plasticity, allowing us to adapt to diverse contexts rather than have our behavior be biologically fixed Black Hawk College

  15. The Bidirectional View • States that evolutionary pressures created changes in biological structures for the use of tools. • This enables organisms to manipulate, alter, and construct new environmental conditions. • Environmental innovations of increasing complexity, in turn, produced new selection pressures for the evolution of specialized biological systems for consciousness, thought, and language. Black Hawk College

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  17. Genetic Foundations • Each of us carries a genetic code that we inherited from our parents. • This code is located within every cell in our bodies. • The code is the mechanism for transmitting characteristics from one generation to the next. Black Hawk College

  18. Genetic Building Blocks • DNA • Genes • Chromosomes Black Hawk College

  19. Definition of DNA • Deoxyribonucleic acid is a complex molecule, shaped like a double helix, that contains genetic information. Black Hawk College

  20. What Are Genes? • The units of hereditary information—short segments composed of DNA—that act as a blueprint for cells to reproduce themselves and manufacture the proteins that maintain life. Black Hawk College

  21. Definition of Chromosomes • Threadlike structures comprised of thousands of genes, that come in 23 pairs, one member of each pair coming from each parent Black Hawk College

  22. Mitosis and Meiosis • Mitosis is the process by which each chromosome in the cell’s nucleus duplicates itself. • Meiosis is the process by which cells divide into gametes (testes/sperm in males, ovaries/eggs in females), which have half the genetic material of the parent cell. Black Hawk College

  23. Mitosis Focus is on cell growth and repair The number of chromosomes present remains the same (the chromosomes copy themselves) Two daughter cells are formed Meiosis Involves sexual reproduction The chromosomes are halved Four daughter cells are produced The Difference Between Mitosis and Meiosis Black Hawk College

  24. The Process of Human Reproduction • Reproduction begins when a female gamete (ovum) is fertilized by a male gamete (sperm). • This produces a zygote—a single cell formed through fertilization. • In the zygote, two sets of unpaired chromosomes combine to form one set of paired chromosomes. Black Hawk College

  25. Genetic Principles • Dominant-recessive genes principle • Sex-linked genes • Polygenically inherited characteristics • Reaction range • Canalization Black Hawk College

  26. Dominant-Recessive Genes Principle • If one gene of a pair is dominant and one is recessive, the dominant gene exerts its effect, overriding the potential influence of the other, recessive gene. • A recessive gene exerts its influence only if the two genes of a pair are both recessive. Black Hawk College

  27. Sex-Linked Genes • Two of the 46 chromosomes human beings normally carry are sex chromosomes. Ordinarily females have two X chromosomes and males have an X and a Y. Black Hawk College

  28. Polygenic Inheritance • The genetic principle that many genes can interact to produce a particular characteristic. • There are more than 50,000 genes, imagine the possible combinations! Black Hawk College

  29. Genotypes and Phenotypes • Genotype - an individual’s genetic heritage, the actual genetic material. • Phenotype - the way an individual’s genotype is expressed in observed and measurable characteristics. • Physical traits: height, weight, eye color • Psychological characteristics: intelligence, creativity, personality • For each genotype, a range of phenotypes can be expressed. Black Hawk College

  30. Reaction Range • Reaction range is the range of possible phenotypes for each genotype, suggesting the importance of an environment’s restrictiveness or richness. Black Hawk College

  31. Canalization • Canalization is the term chosen to describe the narrow path, or developmental course, that certain characteristics take. • Preservative forces help protect or buffer a person from environmental extremes. Black Hawk College

  32. Behavior Genetics • This is the study of the degree and nature of behavior’s hereditary basis. • It assumes that behaviors are jointly determined by the interaction of heredity and environment. • Behavior genetics often uses twins or adoption situations to study the influence of heredity on behavior. Black Hawk College

  33. Twin Studies • The behavioral similarity of identical twins is compared with the behavioral similarity of fraternal twins. • Identical twins (monozygotic twins) develop from a single fertilized egg that splits into two genetically identical replicas, each of which becomes a person. • Fraternal twins (dizygotic twins) develop from separate eggs and separate sperm, making them genetically no more similar than ordinary siblings. Black Hawk College

  34. Issues with Twin Studies • By comparing groups of identical and fraternal twins, behavior geneticists capitalize on the basic knowledge that identical twins are more similar genetically than are fraternal twins. • However, adults might stress the similarities of identical twins more than those of fraternal twins. • Identical twins might perceive themselves as a “set” and play together more than fraternal twins. Black Hawk College

  35. Adoption Studies • Investigators seek to discover whether, in behavior and psychological characteristics, adopted children are more like their adoptive parents, who provided a home environment, or more like their biological parents, who contributed their heredity. • Another method is to compare adoptive and biological siblings. Black Hawk College

  36. Molecular Genetics • There is now a great deal of enthusiasm about the use of molecular genetics to discover the specific locations on genes that determine an individual’s susceptibility to many diseases and other aspects of health and well-being. Black Hawk College

  37. Genome • The term used to describe the complete set of instructions for making an organism • Contains the master blueprint for all cellular structures and activities for the life span of the organism • The human genome consists of tightly coiled threads of DNA Black Hawk College

  38. The Human Genome Project • Began in the 1970s • In the process of mapping the human genome • Has located the genes for Huntington disease, some forms of cancer, and many others • May possibly be used to transplant healthy copies of missing/defective genes into affected cells • May lead to the development of drugs that will alter the genetic makeup of the affected cells Black Hawk College

  39. Chromosome Abnormalities Down Syndrome Klinefelter Syndrome Fragile X Syndrome Turner Syndrome XYY Syndrome Gene-Linked Abnormalities Phenylketonuria Sickle-Cell Anemia Chromosome and Gene-Linked Abnormalities Black Hawk College

  40. Down Syndrome • Caused by the presence of an extra chromosome • Characterized by: • round face • flattened skull • extra fold of skin over the eyelids • protruding tongue • short limbs • retardation of motor and mental abilities • Women younger than 18 and older than 38 are more likely to have Down syndrome babies. Black Hawk College

  41. Klinefelter Syndrome • Sex-linked chromosome abnormality • Males have an extra X chromosome, making them XXY instead of XY • Characterized by: • undeveloped testes • enlarged breasts • become quite tall Black Hawk College

  42. Fragile X Syndrome • Sex-linked chromosome abnormality • The X chromosome becomes constricted and often breaks • Characterized by: • mental deficiency (varied in form from mental retardation to short attention span) • Occurs more frequently in males Black Hawk College

  43. Turner Syndrome • Sex-linked chromosome abnormality • Females are missing an X chromosome, making them XO instead of XX • Characterized by: • shortness of stature • webbed neck • possible mental retardation • possible sexual underdevelopment Black Hawk College

  44. XYY Syndrome • Sex-chromosome linked abnormality • The male has an extra Y chromosome • Early belief surrounding the syndrome was that the extra Y chromosome contributed to male aggression and violence. • Researchers have since found that XYY males are no more likely to commit crimes than are XY males. Black Hawk College

  45. Phenylketonuria • Gene-linked abnormality • The individual cannot properly metabolize an amino acid • Currently easily detected • Treated by diet to prevent an excess accumulation of phenylalanine. • If left untreated it can result in mental retardation and hyperactivity. Black Hawk College

  46. Sickle-Cell Anemia • Gene-linked abnormality • Occurs most often in African Americans • Affects the shape of red blood cells, hindering their ability to carry oxygen to the body’s cells • Results in anemia and early death of the individual Black Hawk College

  47. Other Genetic Abnormalities • Cystic Fibrosis • Diabetes • Hemophilia • Huntington Disease • Spina Bifida • Tay-Sachs Disease Black Hawk College

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  49. Prenatal Diagnostic Tests • Amniocentesis • Ultrasound Sonography • Chorionic Villi Sampling • Maternal Blood Test Black Hawk College

  50. Amniocentesis • A prenatal medical procedure in which a sample of amniotic fluid is withdrawn by syringe and tested to discover if the fetus is suffering from any chromosomal or metabolic disorders • Performed between the 12th and 16th weeks of pregnancy • There exists a small risk of miscarriage (one in every 200-300) Black Hawk College

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