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Lecture 8

Unit 1 - Lecture 8 - Evolution & Behavior.docx

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Dalhousie University
PSYO 1011

PSYO 1011 Evolution & Behavior 1 Lecture 8: Evolution & Behavior October 6, 2009 Definitions: • Evolution o Process of change in the inherited traits of a population from one generation to the next o Change over time in the frequency with which particular genes & characteristics occur o Genetic variations arise through mutations • Natural Selection o Heritable traits helpful for survival & reproduction  Become more common in a population  Harmful traits become rarer • Adaptation o Products of natural selection o Change, via natural selection, that allows organism to meet survival challenges o Domain Specific Adaptations  Designed to solve specific problems Human Evolution: • Application of above concepts to human evolution • Prominent Theory o Scarce vegetation favored bipedal locomotion  Because it freed hands to use weapons  Fostered tool use o Group hunting more successful  Encourage social organization & development of specialized roles in group  i.e.) hunter/protector (males); nurturer of young (females) o Tool use, bipedal locomotion & social organizations place new selection pressures on body & brain  Human brain evolves over period of several million years • Greatest growth occurs in areas concerned with higher mental processes o i.e.) attention, memory, thought & language Comparing Species: • Comparative Method o Determine the function & phylogeny (relatedness) of behavior o Useful in tracing evolutionary pathway • Homology o Similarity between species based on a common ancestor • Analogy o Similarity based on convergent evolution rather than ancestry Possible Homologues to the Human Smile: • Chimps & Macaques o Silent teeth-bearing display PSYO 1011 Evolution & Behavior 2  Submissive behavior (macaques)  Greeting smile (chimps) o Relaxed open-mouthed display  During playful fighting  Accompanied by vocalizations • Humans o 2 Kinds of smiles  Greeting smile – homologous to teeth-bearing display in chimps  Happy smile – homologous to open-mouthed display in chimps Deprivation Experiments: • Determine whether behavior is dependent upon experience • Raise animal in isolation of others • Results: o Smiling in humans- no o Fighting in rats- no o Singing in songbirds- yes Vestigial Characteristics: • Traits which have lost their original function in a species through evolution • May be: o Anatomical structures (appendix) o Biochemical pathways (L-gulonlactone oxidase) o Behaviors  Grasping reflex (primate babies cling to their mother’s fur)  Sugar preference (only in recent times readily available) Sociobiology: • Study of social systems in animals o Mating o Aggression o Helping Parental Investment: • Time, energy & risk for survival involved in caring of offspring • If parental investment unequal, parent who invests more in offspring will be o More vigorously competed for o More discriminating • Polygyny o One male mates with many females • Polyandry o One female mates with many males • Monogamy o Equal inve
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