Adaptation and Variation Notes PDF

EVOLUTION     scientific  theory  =  explains  observations  in  our  natural  world  using  a  wealth  of  evidence  and  allows   us  to  make  testable  predictions  (it  is  more  than  an  educated  guess)     some  exam...

EVOLUTION     scientific  theory  =  explains  observations  in  our  natural  world  using  a  wealth  of  evidence  and  allows   us  to  make  testable  predictions  (it  is  more  than  an  educated  guess)     some  examples  of  scientific  theories  are  the  theory  of  evolution,  atomic  theory,  cell  theory,   theory  of  gravity     Adaptation  and  Variation     Organisms  will  have  to  face  some  environmental  challenges  such  as:       famine   competition  for     severe  weather   resources     Organisms  that  have  genetic   information  that  enable  them  to     survive,  WILL  survive,    and  they   ORGANISMS   can  then  reproduce  and  pass  this     genetic  information  on  to  their     offspring!   loss  of  habitat   climate  change       urbanization           ORGANISMS      IF  ORGANISMS  LACK  DIVERSITY     IF  ORGANISMS  SHOW  DIVERSITY;     PLENTY  OF  INTERACTIONS   THEY  CAN’T  ADAPT  TO   WITHIN  THE  ENVIRONMENT;  CAN   CHANGES  IN  THE  ENVIRONMENT     ADAPT!  CHANGES  ARE  SEEN  IN     ORGANISMS  OVER  TIME  AND  THEY     EVOLVE         EXTINCTION   SURVIVE         Adaptations  Lead  to  Survival     adaptation  =  a  structure,  behaviour  or  physiological  (internal  body  function)  that  helps  an  organism   survive  and  reproduce  in  a  particular  environment     Example:    Stick  insects  can  camoflage  themselves  from  their  predators.  Camoflage  is  an  adaptation!   Their  colour  matches  their  environment  and  they  have  a  stick-­‐like  appearance  that  allows  them  to   blend  in  with  the  vegetation.  These  adaptations  make  the  stick  insect  well  suited  to  its  habitat.   Because  the  predators  can’t  see  the  stick  insects,  this:   increases  their  chances  of  survival   increases  their  chances  of  reproducing        Structural   Behavioural   Physiological   camoflage   migration   hibernation   sharp  talons  or  beaks   “freezing”  behaviour  (remain   ability  to  conserve  fat  and   excellent  vision   motionless)   water   padded  feet   hunt  in  packs   concentrated  urine   webbed  feet   groups  of  aminals  form   play  dead   layer  of  fat/fur   outward  facing  circle  to   metamorphosis   mimicry  =  a  harmless  species   check  for  predators   plants  have  scents  to  attract   resembles  a  harmful  species  in   living  in  groups   flies/bees   colouration  or  structure  (ex.   nest  parasitism  (cowbirds,   monarch  and  viceroy)   cuckoo  birds)   wings  (leading  to  flight)   spray  foul-­‐smelling  scent   try  to  appear  larger  to  ward   off  predators   hair  for  warmth,  protection   whiskers   sharp  teeth   large  beaks   hooves   striped  or  spotted  fur   brightly  coloured  feathers   scales     How  do  adaptations  arise?   over  generations  –  very  slowly   organisms  accumulate  changes  that  help  them  survive  and  reproduce     Where  do  these  changes  in  organisms  come  from?  From  MUTATIONS  in  their  DNA.     Mutations  are  random,  heritable  changes  in  the  DNA  of  organisms.  As  these  mutations  build-­‐up  over   the  generations,  we  see  changes  in  the  characteristics  of  organisms.     Mutations           Variations         Adaptations     Mutations  result  in  variations  which  ultimately  lead  to  adaptations.    Variations  are  structural,   functional  or  physiological  differences  between  individuals  in  a  population.  (Not  all  varitions  lead  to   adaptations!)  Environmental  conditions  will  determine  whether  a  variation  in  an  individual  has  a   positive  or  negative  effect  on  their  survival  and  ability  to  reproduce.  Adaptations  are  the  result  of  a   gradual  build-­‐up  of  changes  that  help  an  organism  survive  and  reproduce.         ENVIRONMENTAL   The  organism  with  the  variation     ORGANISM  WITH  VARIATION  "A  "  IS  UNAFFECTED  -­‐   ORGANISM    IS  NOT  AFFECTED  AT  ALL  IN  ITS  ABILITY  TO   SURVIVE  AND  REPRODUCE   that  increases  chances  of  surviving     also  has  a  higher  chance  of  passing   STRESS   this  variation  on  to  their  offspring.   ORGANISM  WITH  VARIATION  "B"  EXPERIENCES  A     POSITIVE  EFFECT  -­‐  IT  HAS  AN  INCREASED  CHANCE  OF   SURVIVAL  AND  REPRODUCTION     This  variation  is  seen  more   frequently  in  the  population  and  it   ORGANISM  WITH  VARIATION  "C"  EXPERIENCES  A   will  be  considered  a  characteristic   NEGATIVE  EFFECT  -­‐  IT  HAS  A  DECREASED  CHANCE  OF   SURVIVAL  AND  REPRODUCTION   of  that  population.           NOTE:   Environments  change  over  time  …..  so  …..  a  particular  characteristic  that  does  not  give  an   advantage  now  ….  may  be  essential  for  survival  later.     Let’s  take  a  look  at  the  example  of  the  English  peppered  moth  (Biston  betularia)  in  Manchester,   England.  This  is  an  excellent  example  of  how  a  mutation  led  to  a  variation  which  in  turn  led  to  an   adaptation  in  the  entire  population.     Up  to  the  1840’s:   trees  were  covered  with  light-­‐coloured  lichen  (algae  and  moss)   98%  of  the  moths  were  of  the  grey-­‐flecked  variety  and  2%  were  dark   the  dark  ones  stood  out  against  the  lichen  and  were  easily  seen  by  their  predators  (birds)   and  eaten     Then  the  Industrial  Revolution  happened  and  air  pollution  increased  causing  the  lichen  to  die  and  there   was  a  lot  of  soot  on  the  trees.           In  the  1890’s:   the  population  of  peppered  moths  had  changed  quite  dramatically   5%  were  of  the  grey-­‐flecked  variety  and  95%  were  dark   the  grey-­‐flecked  were  easily  seen  by  the  birds  on  the  darker  trees   more  of  the  dark  ones  survived,  reproduced  and  passed  on  their  genes  to  their  offspring     The  difference  between  the  moths  of  the  1840’s  and  1890’s  is  GENETIC.         We  will  be  able  to  re-­‐inforce  the  key  concepts  of  adaptations  and  how  they  relate  to  evolution  by   referring  to  the  folowing  videos  with  links  on  the  LMS:     “The  Rock  Pocket  Mouse”   “Malaria  and  Sickle-­‐Cell  Anemia”   “How  Animals  Adapt”   25  Animals  and  Insane  Survival  Adaptations”     Within  a  population,  there  is  a  lot  of  genetic  varition  due  to  the  different  alleles  carried  by   individuals.  In  the  human  population,  sexual  reproduction  leads  to  tremendous  genetic  diversity   (different  combinations  of  alleles)  as  a  result  of  the  random  assortment  of  chromosomes  during   metaphase  I  and  crossing  over  during  prophase  I  of  meiosis.     mutations  in  a  gene  for  a  particular  trait  can  give  rise  to  new  alleles  for  a  trait   mutations  are  the  only  source  of  new  variations   mutations  can  be  harmful  or  beneficial  or  have  no  effect  at  all   mutations  need  to  occur  in  gametes  to  remain  within  a  population   mutations  that  occur  in  somatic  cells  are  lost  when  the  organism  dies.     Mutations  can  give  a  selective  advantage  to  an  organism.    A  selective  advantage  is  a  genetic   advantage  of  one  organism  over  its  competitors.    Selective  advantage  helps  an  organism  survive  the   changing  environmental  conditions  and  reproduce.     To  appreciate  selective  advantage,  let’s  look  at  antibiotic  resistance.     Antibiotic  Resistance     bacteria  reproduce  quickly   if  a  random  mutation  leads  to  a  new  allele  that  increases  the  chance  of  survival,  the   bacterium  that  has  this  allele  will  survive,  reproduce  and  pass  this  genetic  information  to  its   offspring   since  the  bacteria  reproduce  so  quickly,  in  very  short  time,  the  allele  that  gives  the  selective   advantage  is  more  common  in  the  overall  population  –  this  increases  the  chance  of  the   population  surviving!     Bacteria  ex.  Staphylococcus  aureus         lts  i n     ta t i o n  resu ic   u t om  m ntibio   Rand allele  for  a e   new   a n c resist Antibiotic  resistant  strain   Original  strain  of  S.  aureus   of    S.  aureus   Exposure  to  antibiotic   Population  with  the  new   allele  survives  and   All  die!   reproduces.   ANTIBIOTIC  RESISTANT   STRAIN  IS  PREDOMINANT!