PSYC 001 Chapter 2 Notes PDF

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PSYC 001 Chapter 2 Notes Chapter 2: The genetic and evolutionary roots of behavior Genetics and Data  Chromosomes: Structures in the nucleus of each cell that contain the genes, the units of hereditary transmission. A human cell has 46 chromosomes arranged in 23 pairs  DNA (deoxyribonucleic acid): The complex molecule that is the constituent of genes Genes  Rungs of DNA: A (adenine), T (thymine), C (cytosine), and G (guanine). Each rung consists of a pair of these subunits: A always pairs with T, and C always pairs with G.  Gene: A section of a DNA molecule that contains instructions for how and when to assemble a protein. Genes are located on chromosomes.  The DNA in each chromosome encodes instructions for building hundreds of different proteins  Chromosomes: Human cells have 23 pairs, for a total of 46 chromosomes per cell Gene Expression  Virtually every cell in a person’s body contains a copy of the same 46 chromosomes, collectively called the person’s genome  Within each cell, the genes are not all active all the time. Instead, some genes in each cell are expressed and some are notfactors work by modifying the biochemical environment inside the cell, and it’s this intracellular environment that turns specific genes “on” or “off”  How (or whether) genes will be expressed depends on both the environment and experience o Ex) timing, temperature, cells nearby, outside world/environmental setting  Genotype: The complete set of an organism’s genes.  Phenotype: The overt characteristics and behaviors of an organism Gene Transmission  In humans, each egg and each sperm contains 23 chromosomes rather than the normal complement of 46 (i.e., 23 pairs)  Every sperm and egg are different Interactions among Genes  Gregor Mendel and pea plantsgenetic inheritance  If the paired genes are identical, we say that the individual is homozygous for that gene; if the two are different, the individual is heterozygous for the gene.  Allele: An alternative form of a specific gene  Dominant: A term for a gene that directs the development of a particular characteristic even when the corresponding gene on the other chromosome is different—i.e., some other allele.  Recessive: A term for a gene that directs the development of a particular characteristic only if the corresponding gene on the other chromosome matches it—i.e., is the same allele.  Codominant: a relationship in which both genes in the pair affect the phenotype.  Incomplete dominance: a person with two different alleles will have a phenotype that’s intermediate between the types favored by each allele on its own Polygenic inheritance  Polygenic inheritance: A pattern in which many genes all influence a single trait o Ex) bipolar disorder and schizophrenia o Same logic: The genes that are part of the polygenic pattern come in pairs, and the genes within each pair may have the same alleles or different ones. If the genes are different, then one allele may be dominant or (more likely) incompletely dominant or codominant. And, above all, the way that the genotype is reflected in the person’s phenotype will depend on an interaction between the genetic pattern and numerous factors in the person’s environment and experience Evolution by natural selection

Proximate cause: The influences within an organism’s lifetime that led to its particular traits or behaviors  Ultimate cause: The reasons why, over many years of evolution, a particular trait or behavior helped members of a population to survive and reproduce The principles of natural selection  Charles Darwin: On the Origin of Species o All life on Earth had a shared origin, so that all creatures had descended from an ancient common ancestormodern species had emerged—through some process of modification o Notion of evolution through natural selection  Natural selection: The mechanism that drives biological evolution. It refers to the greater likelihood of successful reproduction for organisms whose attributes are advantageous in a given environment.  Naturalistic fallacy: The (mistaken) idea that anything “natural” must be “good.”  Natural selection depends only on whether an organism is well suited to its current environmentThe mechanisms of evolution certainly have no way to peer into the future, to know which traits will serve the organism well in environments to come Genes and evolution  Three principles o There must be variation among the individuals within a population o Certain of the variants must survive and reproduce at higher rates than others o The traits associated with this superior survival and reproduction must be passed from parents to offspring  All the individuals in a species actually have enormously similar genomes But against this backdrop of uniformity, individuals do vary in their genotype o Random variation in sexual reproduction o Process of reproducing chromosomes—usually accurate but mutations can occur  Mutations: Errors in the replication of DNA  Either have no effect or harm the organism; Some mutations do confer an advantage for survival and reproduction—and, in all cases, mutations contribute to the genetic diversity within a species  Evolution is often described as “survival of the fittest,” but this phrase is actually misleading because survival itself is not all that evolution is about. o Personal survival does matter, of course, but only insofar as it enables the organism to reproduce and pass along its genes to the next generation. o Ex) piping plover, Belding’s ground squirrel Evidence for evolution by natural selection  Selective Breeding  Fossils  Mutations and transmission of genes  Anatomical leftovers in modern species that reveal the evolutionary past of the species  Molecular structure of the genome in various organisms The unity of life  Darwin: all modern organisms descended, with modifications over time, from a common ancestor  The unity of life is essential to psychologyBecause of our shared ancestors, we have much in common with other species; and this is why we can learn a great deal about us by studying them The Genetics and Evolution of Behavior 

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For behaviors just as for physical traits, evolution requires the same three conditions: variation among individuals; a higher rate of reproductive success for individuals with some of the variations; and some means of passing the successful variation from one generation to the next  Psychological traits are part of an animal’s phenotype  Evolution has in many cases guided an organism toward relatively well-defined behaviors, like a particular courtship dance or a specific style of nest building BUT even in these cases, evolution has favored mechanisms that produce flexibility in how an animal acts. o Changing climates natural selection would favor individuals that could shift their behavior in response to new circumstances and that could rapidly deploy new skills appropriate for an altered setting.  Niche construction: The process in which organisms, through their own behaviors, alter the environment and create their own circumstances. o Niche refers to all of the factors in an organism’s environment that have the potential to affect its life  Evolution favors flexibility and learning—in part because environments inevitably vary, and in part because organisms end up changing their environment and need to cope with those changes The Biological Roots of Smiling  Species specific: Pertaining to just one species The origins of smiling  Smiling occurs w/o a history of observational learning  Species general: Pertaining to all organisms in a species Smiles in other species  We find similar emotional expressions in animals with genomes similar to ourssmiling is species general (found in the entire species), but it is not species specific (found only in one species).  Types of smiles o Expressive of your inner state, produced when you feel happy, eye muscles move o Polite in nature, it’s rarely produced without an audience, pulls the corners of one’s lips upward but with little movement of the eyes  The fact that smiles emerge with no history of learning tells us that this behavior is strongly shaped by inborn (genetic) factorsuniversality of smiling (across cultures and across species)ancient origin for this behavior, shaped by natural selection The Genetics of Intelligence  Intelligence refers to the capacity that allows people to acquire new knowledge and use it to draw conclusions, solve problems, and adapt to new circumstance Comparison among relatives  Humans: a 50% overlap between each child’s genetic pattern and the pattern of each parent; 50% overlap, on average, between each child’s pattern and the pattern of his or her biological siblings  Dizygotic (DZ): Twins that develop from two different eggs that are simultaneously fertilized by two sperm. Like ordinary siblings, they share 50% of their genes; show less resemblance in intelligence, although they resemble each other more than do randomly selected individuals  Monozygotic (MZ): Twins that develop from a single fertilized egg that then splits in half. These twins are genetically identical; resemble each other closely in their intelligence levels Heritability  Environmental factors and genotypes influence intelligence  Heritability ratio (H): A measure that describes, for a given population in a given environment, what proportion of the variance of a trait is due to genetic differences. o Heritability = Genetic variance/Total phenotypic variance

o Can take a value between 0 and 1, where 0 indicates that none of the phenotypic variability is attributable to the genome, and 1 indicates that all of the phenotypic variability is attributable to the genome. o **tells us only about the causes of variation within the population studied, and it applies only to the particular environment in which the population was studied o **tell us nothing about the genetic influence on an individual’s traits The evolution of intelligence  Environment of evolutionary adaptiveness (EEA): The environment that was in place when a trait was evolving.  Natural selection has no way to peer into the future. The process depends only on whether an organism’s traits help it to survive and reproduce in its current environment. The Evolution of Mating Patterns Mating systems  Monogamy: A mating pattern in which one male and one female form an enduring reproductive partnership.  Polygamy: Any mating system in which a member of one sex mates with several members of the opposite sex.  Males vs females o The more offspring a creature has that survive to maturity and reproduce, the better represented its genes will be in the next generationBy this logic, “success” in an evolutionary context often means having as many surviving off- spring as possiblemales=many mates o Females maximize their reproductive success by mating just a few times during their lives—but ensuring the health and well-being of each of their youngfewer partners o Cultural expectations? Which mate does the choosing?  Females: reproduction=costlyhas to be selective  Males: reproduction≠costly wants to maximize partners, can’t be too selective  In many species it’s the female who chooses whether to mate or not  Courtship o If it’s the females who do the choosing, then the burden falls on the males to attract and persuade their potential partners. Human mate choice  Both males and females are selective in choosing their sexual partners, and mating happens only when both partners consent  Different values between men and women: attractiveness, age, status; both value kindness and intelligence Jealousy  Basis for jealousy in romantic relationships may be different in the two sexes o Men care more about sexual loyalty than emotional loyalty and women care more about emotional loyalty Paternity  From an evolutionary perspective, males should take care of their own young (and so protect their genetic legacy) but should not take care of other men’s young Some Final Thoughts: The Strengths and The Limits of Evolutionary Theorizing  Human behavior, thoughts, and feelings are shaped by human biology; and human biology, in turn, includes the genetic blueprint that each of us inherits  A genetic pattern does not establish someone’s destiny; a genotype does not in any way guarantee a particular phenotype.

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Natural selection works simply by favoring traits if those traits help the organism survive and reproduce in its current environment...