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Lecture 5

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Department
Psychology
Course
PSYCH 2TT3
Professor
Reuven Dukas
Semester
Fall

Description
PNB  2XC3   Week  5   Oct.  8,  2013   Hamilton’s  Rule   • An  action  should  ↑  in  frequency  if  the  benefit  (b)  received  by  the  donor’s  relatives,  weighted  by  their  relatedness  ( r)   to  the  donor,  exceeds  the  direct  fitness  cost  ( c)  to  the  donor:  rb>c     Naked  Mole  Rat   • Spend  almost  all  their  time  underground   • The  only  known  mammals  that  show   eusociality.  WHY?   o Reproductive  division  of  labor ,  communal  care  of  young,  &  overlapping  generations   • Test  of  relatedness  using  DNA  fingerprinting  –  analysis  of  polymorphic  regions  of  DNA  by  specific  cutting   &   separation  using  gel  electrophoresis  (differential  migration  of  particles  based  on  electric  charge) .   • Unusually  high  relatedness  in  the  naked  mole  rat  as  a  result  of  inbreeding .   • Is  the  high  relatedness  a  sufficient  explanation?   o No.  Why  not?  rb>c  We  need  to  evaluate  the  benefit  of  helping  vs.  the  cost  of  reproducing  alone .   • Conclusion   o The  simple  fitness  measure  of  lifetime  reproductive  success  may  no t  be  sufficient.   o Evolution  implies  a  change  in  gene   frequency,  so  we  must  also  think  at  the  levels  of  genes .     Should  one  kill  its  sibling?   • Only  if  the  benefit  outweighs  the  cost.   • R  to  oneself  =  1   • R  to  sibling  =  0.5  (assuming  same  father)   • If  one’s  survival  is  at  risk,  it  should  fight  w/  its  sibling   • Again,  rb>c     Should  a  parent  sacrifice  her  life  for  her  offspring?   • How  much  should  a  parent  invest  in  an  offspring?   The  investment  per  offspring  should  depend  on  the   lifetime  cost   &  benefit  to  the  parent   • Conflict:  Offspring  may  seek  more  than  parents  should  provide.     Phylogeny   • All  living  species  are  the  product  of  descent  w/  modifications  from  common  ancestors.   • We  can  reconstruct  the  phylogenetic  history  of  species.   • Relatedness  is  determined  by  common  ancestry.   • Understanding  the  evolution  of  certain  behaviours,  their  timing   &  #  of  independent  origins.     The  Evolution  of  Agriculture   • Agriculture  means…   o Planting  of  certain  cultivars  in  particular  substrates   o Cultivation  aimed  at  improving  crop  growth  (fertilizing,  pro tection  from  weeds  &  pests…)   o Harvesting  food   o Nutritional  dependence   • Agriculture  evolved  in  ants,  termites   &  beetles  over  50  mil  yrs  ago   &  in  humans  10000  yrs  ago.   • Insect  agriculture  involves  growing  fungi  on  gardening  substrate  (i.e.  plant  material)   &  protecting  their  crop  from   undesired  species  (weeds  &  pests).  Use  of  pesticide  is  common.   • The  evolution  of  agriculture  in  insects   o 9  independent  origins  of  insect  agriculture   o No  reversal  to  non-­‐agriculture  life     Sizes  in  biology   • 1mm  =  10^-­‐3m   • 1µm  =  10^-­‐3mm  =  10^-­‐6m   • 1nm  =  10^-­‐3µm  =  10^-­‐9m   • Bacteria  &  cells:  1-­‐30µm   • Viruses:  20-­‐100nm     PNB  2XC3   Week  5   Oct.  8,  2013   Chemotaxis   • The  ability  of  organisms  &  cells  to  move  up  or  down  chemical  gradients .   • Successive  comparison,  which  requires  a  minimum  of  one -­‐step  ‘memory’   • Bacteria  can  only  keep  the   same  direction  or  tumble  to  change  direction .   • Simultaneous  comparison  is  impossible  b/c  the   change  chemical  gradient  across  the  body  is  too  small .   • Do  humans  use  simultaneous  comparison?  Yes  (i.e.  hearing  from  both  ears).   • Chemotaxis  in  E.  coli   o Detection  by  receptors   o Conduction  by  messenger   o Processing  based  on  messenger  concentration  (‘polling’)   o Transmission  of  decision   o Response   • Chemotaxis  in  C.  elegans   o A  small  soil  worm  (1mm)  that  feeds  on  bacteria,  w/  ~959  cells  &  302  neurons,  w/  all  synapses  mapped  &   entirely  sequenced  genome.   o Researchers  can  turn  off  individual  neurons  by  laser  ablation   &  record  from  individual  neurons.   • Is  chemotaxis  learning?   o Learning  is  the  ability  to  acquire  an  internal  representation  of  new  info .   o But  there’s  no  true  representation  of  new  info   –  it  is  more  like  a  set  of  decisions  affected  by  new  info .   o The  convention  is  that  chemotaxis   is  not  learning.     Innate  Behaviour   • A  behavioural  pattern  that  appears  in   its  fully  functional  from  the  1  time  it’s  performed.  That  is,  the  animal  may   have  not  had  prior  experience  w/  the  cues  that  elicit  the  behaviour  (i.e.  Birds  follow  innate,  species -­‐specific  nest   building  instructions  including:  what  material  to  use,  where  to  find  it,  where  to  build  it,  how  to  build  it ).   • Village  weaverbird:  Male  chooses  a  forked  branch   &  weaves  it  around  himself.  Then  he  stands  out  of  the  circle   &   weaves  until  completing  the  roof   &  nest  cup  (C).  Then  he  weaves  backwards  to  create  a  doorway  (E) .  After  obtaining   a  mate,  he  weaves  an  entrance   tube.     Egg  Rolling  Instinct  in  Geese   • Rolls  egg  back  to  nest.   • If  it’s  smooth  &  near  the  nest,  it  must  be  an  egg.  Will  roll  this  object  to  nest  too.   • Ensures  that
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