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Chapter 3 Evolution, Heredity, and Behavior

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Steve Joordens

Chapter 3 Evolution, Heredity, and Behavior -------The Development of Evolutionary Theory Darwin said, organisms originate and become adapted to their environments by biological means over time. Biological evolution: changes that take place in the genetic and physical characteristics of a population or group of organisms over time Adaptive significance: the effectiveness of behavior in aiding organisms to adapt to changing environmental conditions Ultimate causes: evolutionary conditions that have slowly shaped the behavior of a species over generations Proximate causes: immediate environmental events and conditions that affect behavior (Psychologists are interested in both causes) Sexual behaviors of gerbils—Clard and Galef have trace this difference between males to the presence or absence of testosterone during the gestation period. (Males who are better sexual performers and males who are better parents. The selective value of both strategies over the long history of gerbil evolution maintains this difference) We are members of the human species-an ultimate cause And we have learned to act in special ways-a proximate cause Both biology and environment contribute to our personal development Evolutionary psychology: how an organism’s evolutionary history contributes to the development of behavior patterns and cognitive strategies related to reproduction and survival during its lifetime Culture: the sum of socially transmitted knowledge, customs, and behavior patterns common to a particular group of people No theory of behavior can be complete without considering the role of evolution ***the voyage of the beagle (Darwin) ***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 behavioral differences among organisms, they reproduce differentially. Within a given population, some animals—the survivors—will produce more offspring than will other animals. Wallace: recognize the natural selection first ***natural selection Mayr’s comments on evolution: the species are not fixed but changing over time; evolution is a branching process and implying that all species descend from a single common ancestor; evolution is continuous, with gradual changes; evolution is based on natural selection 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 Variation and competition are the critical factors that determine whether any particular animal and its offspring will enjoy reproductive success. (May not be physical strength for sure) Variation: the differences found across individuals of any given species in terms of their genetic, biological (size, strength, physiology), and psychological (intelligence, sociability, behavior) characteristics. Genotype: an organism’s genetic makeup Phenotype: the outward expression of an organism’s genotype, an organism’s physical characteristics and behavior The genotype determines how much the environment can influence an organism’s development and behavior Rosemary Grant’s study on Finches: although evolution occurs over the long run, natural selection can produce important changes in the short run; phenotypic variation can produce important selective advantages that affect survival Competition: a striving or vying with others who share the same ecological niche for food, mates, and territory Also occurs between different species ----- Heredity and Genetics Genetics: the study of the genetic makeup of organisms and how it influences their physical and behavioral characteristics Heredity: the sum of the traits and tendencies inherited from a person’s parents and other biological ancestors (Gregor Mendel uncovered the basic principle of heredity) ***Basic principles of genetics DNA (deoxyribonucleic acid): the DNA structure resembles that of a twisted ladder,. Strands of sugar and phosphates are connected by rungs made from nucleotide molecules of adenine, thymine, guanine, and cytosine (James Watson&Francis Crick) Genes: small units of DNA that direct the synthesis of proteins and enzymes Genome: the total set of genetic material of an organism Human has 24, 25 DNA molecules and 30000 or 40000 genes *genes as “recipes” for protein synthesis No genes for behavior, only for the physical structures and physiological processes that are related to behavior “learning gene”: dopamine Enzymes: proteins that regulate the structure of bodily cells and the processes occurring within those cells (genes also direct the synthesis of enzymes) *chromosomes and meiosis Chromosomes: threadlike structures in the nuclei of living cells; contains genes (most genes are located here) Human has 23 pairs of chromosomes Sex chromosomes: the chromosomes that contain the instructional code for the development of male or female sex characteristics Autosomes: the chromosomes that are not sex chromosomes 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 12 individual chromosomes, or half of those found in other bodily cells *dominant and recessive traits Alleles: alternative forms of the same gene Dominant trait: the trait that is exhibited when an individual possesses heterozygous alleles Recessive trait: a trait that occurs only when it is expressed by homozygous alleles Parents each contribute the same allele, the gene combination is called homozygous, if different, heterozygous Recessive trait is not present when an individual is heterozygous Protein synthesis is often under polygenic control ***the importance of genetic diversity Sexual reproduction increases a species’ ability to adapt to environmental changes ***influences of gender on heredity Sex-influenced genes: in one sex only or in both sexes ***mutations and chromosomal
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