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Chapter 3&4

Chapter 3&4 Psychology.pdf

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University of Toronto Scarborough
Douglas Frayne

Chapter 3 The Development of Evolutionary Theroy - Darwin argued that, over time, organisms originate and become adapted to their environments by biological means. - Biological Evolution: changes that take place in the genetic and physical characteristics of a population or groups of organisms over time - Many behavioural differences among organisms, both within and across species, correspond to genetic and other biological differences. Understanding these differences and their evolutions allows psychologists to understand behaviour in terms of its possible origins and adaptive significance: the effectiveness of behaviour in aiding organisms to adapt to changing environmental conditions - Psychologists might research how past environmental conditions favoured a certain trait and over another and how immediate environment influences choices - They are interested in understanding both ultimate causes (evolutionary conditions that have slowly shaped the behaviour of a species over generations) of behaviour and proximate causes (immediate environmental events and conditions that affect behaviour) - By understanding how adaptive behaviour developed through the long-term process of evolution, psychologists are able to gain more thorough understanding of our ability to adjust to changes in our immediate environment - To understand the present, we must understand the past - Evolutionary psychology investigates how an organismʼs evolutionary history contributes to the development of behaviour patterns and cognitive strategies related to reproduction and survival during its lifetime - Culture: the sum of socially transmitter knowledge, customs, and behaviour patters common to a particular group of people. Psychologyʼs contribution to this understanding will be an explanation of how thinking and behaving shape cultural adaptations to changing environmental conditions The Origin of Species - Artificial Selection: a procedure in which particular animals are deliberately mated to produce offspring that posses especially desirable characteristics - Natural Selection: the consequence of the fact that, because there are physical and behavioural differences among organisms, they reproduce differentially. Within a given population, some animals - the survivors - will produce more offspring than will other animals Natural Selection - Mayr suggested that Darwinʼs theory can be traced to four insights: that species are not fixed, but rather change over time; that evolution is a branching process, implying that all species descended from a single common ancestor; that evolution is continuous, with gradual changes; and that evolution is based on natural selection - Natural Selection is based on two premises: 1. individuals within a population show variability in heritable behavioural and physical characteristics. 2. the capacity of the environment to sustain a population of any species is limited, producing competition - Darwin and Wallace realized that those individuals that compete better are more likely to survive and reproduce. To the extent that these characteristics are heritable, they would be likely to appear in the next generation - Darwinʼs careful study of natural history also convinced him that behavioural adaptations were essentially important to survival and therefore an important part of evolution - Reproductive Success: the number of viable offspring an individual produces relative to the number of viable offspring produced by other members of the same species - The two aspects of natural selection, variation and competition, are the critical factors that determine whether any particular animal and its offspring will enjoy reproductive success - Variation: - the differences found across individuals of any given species in terms of their genetic, biological (size, strength, physiology), and psychological (intelligence, sociability, behaviour) characteristics - An organismʼs genetic makeup, or its genotype, differs from that of all other individuals - As a result of these genetic differences, an individual organismʼs physical characteristics and behaviour, or its phenotype, also vary from every other individual - It is important to recognize that every individualʼs phenotype is produced by the interaction of its genotype with the environment - The genotype determines how much the environment can influence an organismʼs development and behaviour - The Grantsʼ study makes two important points: first, although evolution occurs over the long run, natural selection can produce important changes in the short run- in the space of only a few years. Second, phenotypic variation can produce important selective advantages that affect survival - Competition: - a striving or vying with others who share the same ecological niche or food, mates, and territory - Competition also occurs between species when members of difference species vie for similar ecological resources, such as food and territory - Natural selections works because the members of any species have different phenotypes. Because these phenotypes are cause by different genotypes, successful individuals will pass on their genes to their next generation - Over times, competition for food and other resources will allow only the best-adapted phenotypes (and their corresponding genotypes) to survive, thereby producing evolutionary change Heredity and Genetics - Genetics: the study of the genetic makeup of organisms and how it influences their physical and behavioural characteristics - Heredity: the sum of the traits and tendencies inherited from a personʼs parents and other biological ancestors - Gregor Mendel: demonstrated conclusively how height, flower colour, seed shape, and other traits of pea plants could be transmitted from one generation to the next. His inspired analysis explained the source of the variation of inherited traits - Genetics helps provide both proximal and ultimate explanations for psychological processes - The study of genetics tells us much about our society and the extent to which the differences among us are due either to the culture we grew up in or to the ancestors we have Basic Principles of Genetics - Heredity is determined by genetic material called DNA (deoxyribonucleic acid) - strands of sugar and phosphate that are connected by nucleotide molecules of adenine, guanine, thymine, and cytosine - As discovered by James Watson and Francis Crick, DNA is configured like a twisted ladder: the sugar and phosphate form the sides and the four nucleotides form the rungs - Gene: small units of DNA that direct synthesis of proteins and enzymes. Some genes contain a short sequence of nucleotides, whereas others many contain a sequence of millions - Genome: the total set of genetic material of an organism Genes as “Recipes” for Protein Synthesis - Genes influence our physical and behavioural development in the only way: through protein synthesis - Proteins are stings of amino acids, arranged in a chain whose order is specified by the way the nucleotides are linked together on the DNA molecules - A sequence of 3 nucleotides corresponds to an amino acid - The recipe is for combining the proteins necessary to create and develop physiological structures and for behaviour - how those structures might function in response to environmental stimulation - There are no genes for behaviour, only for the physical structures and physiological processes that are related to behaviour - Genes also direct the synthesis of enzymes: proteins that regulate the structure of bodily cells and the processes occurring within those cells - A faulty gene may contain instructions for a faulty enzyme, which produces serious physiological and behavioural problems - DNA molecules have large segments consisting of so-called “junks” - Junk DNA is not involved in the direct synthesis of proteins and for that reason is known as non-coding DNA - Non-coding DNA regulate the processes of other genes that synthesize proteins by genes. In this way, non-coding DNA can affect evolution including human evolution Chromosomes and Meiosis - Most genes are located on chromosomes: threadlike structures in the nuclei of living cells; contain genes - Genes are particular regions of chromosomes that contain the recipes for particular proteins - Each set of chromosome contains a different DNA molecule, and hence, a difference sequence of genes - We inherit 23 individual chromosomes from each of our parents, giving us 23 pairs, or 46 individual chromosomes - In 22 of these pairs of chromosomes, the two DNA molecules are of matching types. The remaining pair of chromosomes, the sex chromosome, contains the instructions for the development of male or female sex characteristics - In female, the two sex chromosomes are matching DNA molecules, labelled as X chromosomes, but in males the two chromosomes are of different types and labelled as X and Y chromosomes - Autosomes: the chromosomes that are not sex chromosomes - Sexual reproduction involves the union of a sperm, which carries genetic instructions from the male, and an ovum (egg) which carries genetic instructions from the female - First, sperm and ova contain only one member of each chromosome pair. Second, some of the genetic information on one member of a pair has been exchanged with the information from the other member - The reason that sperm and ova differ from ordinary body cells is that they are produced by a special reproductive process known as meiosis - Meiosis: the form of cell division by which new sperm and ova are formed. The chromosomes within the cell are randomly rearranged so that new sperm and ova contain 23 individuals chromosomes, or half of those found in other bodily cells - The assignment of the members of each pair of chromosomes to a particular group is a random process - Brothers and sisters may resemble each other but they are not exact copies - Identical twins are genetically identical, which occurs when when a fertilized ovum divides. Fraternal twins are not identical, occurs when a woman produces two ova, both of which are fertilized Dominant and Recessive Traits - Each pair of chromosomes contains pair of genes: one gene in each pair is contributed by each parent - Alleles: alternative forms of the same gene - Same allele = homozygous, different alleles = heterozygous - Dominant trait: the trait that is exhibited when an individual possesses heterozygous - Recessive trait: a trait that occurs only when it is expressed by homozygous alleles - Genetic contributions to our personal development and behaviour are extremely complex. One reason for this complexity is that protein synthesis is often under polygenic control - that is, influenced by many pairs of genes, not just a single pair - The inheritance of behaviour is even more complicated, because different environments influence the expression of polygenic traits The Importance of Genetic Diversity - Sexual reproduction increases a speciesʼ ability to adapt to environmental changes - Sexual reproduction leads to genetic diversity because there are two different copies of the DNA molecule in the childʼs genome - Genetically diverse species have a better chance of adapting to a changing environment. When the environment changes, some members are genetically diverse species may have genes that enable them to survive in the new environment - Natural selection can favour species that reproduce sexually because of the adaptive value of genetic diversity Influences of Gender on Heredity - Sex-linked genes resides only on the sex chromosome - Sex-influenced genes are genes that appear more frequently in one sex than in the other Mutations and Chromosomal Aberrations - Changes in genetic material are cause by mutations or chromosomal aberrations - Mutations: accidental alterations in the DNA code within a single gene. Mutations can be either spontaneous, occurring naturally, or the result of environmental factors such as exposure to high-energy radiation - Chromosomal aberration: the rearrangement of genes within chromosomes or change in the total number of chromosomes Genetic Disorders - Many genes decrease an organismʼs viability - its ability to survive - Down syndrome: a genetic disorder caused by a chromosomal aberration resulting in an extra twenty-first chromosome. People having down syndrome show impairments in physical, psychomotor, and cognitive development - Huntingtonʼs disease: a genetic disorder caused by a dominant lethal gene in which a person experiences slow but progressive mental and physical deterioration - Phenylketonuria (PKU): a genetic disorder caused by a particular pair of homozygous recessive genes and characterized by the inability to break down phenylalanine, an amino acid found in many high-protein foods. The resulting high blood levels of phenylalanine cause mental retardation Heredity and Behaviour Genetics - Heritability: the amount of variability in a given trait in a given population at a given time due to genetic factors - Heritability pertains only to the variation of a trait in a specific population, does not apply to individuals - Behaviour genetics: the study of genetic influence on behaviour Studying Genetic Influences - Mendelian trait: a trait showing a classical dominant, recessive, or sex-linked pattern of inheritance. Mendelian traits are usually dichotomous and are controlled by a single locus - Francis Golton: attempted to apply concepts of heredity to psychology. His studies showed that intelligence tends to run in families - Non-mendelian trait: a trait that does not show the inheritance pattern described by Mendel. Non-mendelian traits are usually polygenic and how continuous variation in phenotype - The primary tools for behaviour genetics are artificial selection, segregation analysis, and allelic association Artificial Selection in Animals - Any selected trait can be selected in a breeding
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