Copyright © 2006 by Allyn and Bacon Chapter 2 Evolution, Genetics, and Experience Thinking about the Biology of Behavior This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program.
Copyright © 2006 by Allyn and Bacon From Dichotomies to Relations and Interactions
Copyright © 2006 by Allyn and Bacon Is it physiological or psychological? Descartes
Copyright © 2006 by Allyn and Bacon Is it inherited or is it learned?
Copyright © 2006 by Allyn and Bacon Is the “nature- nurture” debate alive today?
Copyright © 2006 by Allyn and Bacon Problems with Traditional Dichotomies – Mind-brain dualism Brain damage impacts psychological functioning
Copyright © 2006 by Allyn and Bacon Problems with Traditional Dichotomies – Nature-or-nurture “
Copyright © 2006 by Allyn and Bacon A model of the biology of behavior All behavior is the product of the interaction of three factors: Genes Experience Perception of the current situation
Copyright © 2006 by Allyn and Bacon Thinking about Human Evolution Evolution does not proceed in a single line. Humans have only been around for a brief period of time. Rapid evolutionary changes do occur. Fewer than 1% of all known species are still in existence.
Copyright © 2006 by Allyn and Bacon Thinking about Human Evolution Evolution is a tinkerer, not an architect – results are not perfect. Not all existing behaviors or structures are adaptive. Spandrels – incidental non-adaptive by- products (such as the human belly button)
Copyright © 2006 by Allyn and Bacon Thinking about Human Evolution Not all existing adaptive characteristics evolved to perform their current function. Exaptions – evolved to do one thing, but now do something else (such as bird wings) Similarities among species do not necessarily mean that the species have common origins.
Copyright © 2006 by Allyn and Bacon Thinking about Human Evolution Homologous structures – similar structures due to a common evolutionary origin Analogous structures – similar structures without a common origin Convergent evolution – the evolution of similar solutions to the same enivironmental demands by unrelated species
Copyright © 2006 by Allyn and Bacon Evolution of the Human Brain There is no relationship between brain size and intelligence. Brain size is generally correlated with body size. More informative to look at relative size of different brain regions.
Copyright © 2006 by Allyn and Bacon Evolution of the Human Brain Brain stem regulates reflex activities that are critical for survival. Cerebrum is involved in complex adaptive processes such as learning, perception, and motivation.
Copyright © 2006 by Allyn and Bacon Evolution of the Human Brain The human brain has increased in size during evolution. Most of the increase in size has occurred in the cerebrum. Increased convolutions in the cerebrum have served to increase the volume of the cerebral cortex.
Copyright © 2006 by Allyn and Bacon Fundamental Genetics Dichotomous traits True-breeding lines Mendel studied dichotomous traits in true-breeding lines of pea plants
Copyright © 2006 by Allyn and Bacon Mendel’s Experiments Crossed a line bred true for brown seeds with one bred true for white First generation offspring all had brown seeds When the first generation were bred, the result was ¾ brown and ¼ white seeds.
Copyright © 2006 by Allyn and Bacon Mendel’s Experiments True-breeding lines White (ww) Brown (BB) Brown was the dominant trait, appearing in all of the 1 st generation offspring (Bw)
Copyright © 2006 by Allyn and Bacon Mendel’s Experiments Phenotype – Genotype –
Copyright © 2006 by Allyn and Bacon Mendel’s Experiments gene alleles Homozygous Heterozygous
Copyright © 2006 by Allyn and Bacon Chromosomes, Reproduction, and Linkage Genes Chromosomes Meiosis
Copyright © 2006 by Allyn and Bacon Chromosomes, Reproduction, and Linkage Gametes, eggs and sperm, are produced by meiosis When egg and sperm combine to form a fertilized egg (zygote), 23 pairs of chromosomes are again present Mitosis – a form of cell division that yields daughter cells that have 23 pairs of chromosomes
Copyright © 2006 by Allyn and Bacon Chromosomes, Reproduction, and Linkage Meiosis leads to diversity as the 23 pairs of chromosomes are randomly sorted into the 2 gametes produced Linkage – the tendency of traits encoded on the same chromosome to be inherited together Crossing over – increases diversity, “shuffles the genetic deck”
Copyright © 2006 by Allyn and Bacon Sex Chromosomes and Sex- Linked Traits Sex chromosomes, X and Y, look different and carry different genes Female = XX Male = XY Sex-linked traits - influenced by genes on the sex chromosomes Dominant traits on the X chromosome will be seen more commonly in females, recessive ones in males
Copyright © 2006 by Allyn and Bacon The Interaction of Genetic Factors and Experience Ontogeny – Phylogeny – Ontogenetic development is a product of gene-experience