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Extinction and Evolution(1/20 and 1/22)

by: Maddibrooks

Extinction and Evolution(1/20 and 1/22) GEOL105

Marketplace > College of Charleston > Geology > GEOL105 > Extinction and Evolution 1 20 and 1 22
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GPA 3.8

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These notes cover the information from Week 3 Lecture 1 and Lecture 2--extinction and evolution.
Earth History
Class Notes
Earth History, Geology, History of life on earth, Science
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This 11 page Class Notes was uploaded by Maddibrooks on Friday January 22, 2016. The Class Notes belongs to GEOL105 at College of Charleston taught by Egerton in Spring 2016. Since its upload, it has received 53 views. For similar materials see Earth History in Geology at College of Charleston.


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Date Created: 01/22/16
Notes  1/20     I. Extinction   a. The  ultimate  death  of  a  species   b. Over  the  past  500  million  years,  there  have  been  5  mass  extinction   events   c. Many  scientists  think  we  are  in  the  6  mass  extinction  event  and   humans  are  the  cause  of  it   i. Because  more  species  are  going  extinct  faster  than  any  other   time  in  Earth’s  history   d. Extinction  is  an  inevitable  consequence  of  evolution   e. A  species  is  extinct  when  all  interbreeding  populations  have  been   eliminated   f. Average  lifespan  of  a  species  is  about  2-­‐11  million  years   g. 99.9%  of  all  species  that  have  ever  lived  are  now  extinct   II. Background  Extinctions   a. Background  extinction  rate  averages  2.0-­‐4.6  families  per  million  years   b. Species  with  wider  geographic  distributions  better  resist  extinctions   i. They  adapt  better  to  changes  in  environment   c. Causes  of  background  extinctions   i. Disease   ii. Habitat  disruption   1. Volcano   iii. Climate  change   iv. Introduction  of  new  predators   1. Humans  made  the  Dodo  bird  go  extinct   v. Introduction  of  new  parasites   1. Can  kill  the  host   vi. Niche  competition   1. New,  sharper  beak  can  allow  another  bird  to  get  more   grubs  from  the  ground  than  a  bird  with  a  more  blunt   beak—causing  competition  for  food   vii. Ocean  current  changes   III. Mass  Extinctions   a. Identified  by  the  pattern,  duration,  breadth,  and  magnitude   i. Short  geological  time  (a  few  million  years)   1. <10  million  years;  most  <5  million  years   ii. Wide  spectrum  of  habitats   1. Talking  about  marine  and  land  species   IV. Extinction   a. Prevent  biases  in  patterns  and  magnitude  of  extinction:  high  sampling   worldwide   b. Lazarus  Taxa   i. Appear  to  be  extinct,  but  may  occur  later  in  time  (pseudo-­‐ extinction)   ii. During  an  extinction  event,  a  species  finds  a  very  small  habitat   to  survive  through  the  extinction  and  then  reappear  later  in   time   iii. Ex:  Coelacanths:  no  fossil  record  after  66  million  years,  but   found  living  today   1. Occupy  a  very  rare  environment  that  typically  doesn’t   get  preserved   c. Mass  extinction  =  global  change  of  the  physical  environment   i. Affects  widespread  species   ii. Environmental  stress  must  generally  be  abnormally  severe   1. Stretch  across  ecological  lines   2. Too  rapid  for  species  to  adapt  or  migrate  from  changing   environment   a. Ex:  deforestation,  global  temperature  change   (some  species  are  migrating  to  higher  latitudes,   because  it’s  getting  too  hot  for  them  where  they   are)   d. The  Big  Five  Extinctions   i. Ordovician-­‐Silurian  Extinction   1. 450-­‐440  million  years  ago   2. 60-­‐70%  of  species  became  extinct   ii. Late  Devonian  Extinction   1. 375-­‐359  million  years  ago   2. 70-­‐80%  of  species  became  extinction   iii. Permian-­‐Triassic  (Biggest!)   1. 251  million  years  ago   2. Marine=90-­‐97%  of  species  extinct   3. Terrestrial  (land)=75%  extinct   4. The  biggest  mass  extinction   iv. Triassic-­‐Jurassic  Extinction   1. 200  million  years  ago   2. 70-­‐75%  species  became  extinct   v. Cretaceous-­‐Paleocene  (Most  famous)   1. Extinction  of  the  dinosaurs   2. 66  million  years  ago   3. 75-­‐80%  species  extinct   4. Only  one  attributed  to  an  asteroid  hitting  Earth     e. Common  Proposed  Causes   i. Sea-­‐level  change   1. Associated  in  one  way  or  another  with  all  of  the  major   mass  extinctions   2. Changes  can  affect  most  environments   3. Issue:  sea  level  changes  may  pre-­‐  or  post-­‐date  the   extinction  event;  no  evidence  that  this  causes  mass   extinction   4. Raising  sea  level  can  cause  reef  environments  to   become  submerged  too  deep  in  the  sea,  so  then  they   won’t  be  getting  enough  sunlight,  thus  becoming  extinct   ii. Climatic  Change   1. Associated  with  all  of  the  major  mass  extinctions   2. Temperature  is  the  main  force   a. Caused  by  all  factors  mentioned  in  Climate   Change  lecture  (1/15)   3. Issue:  climatic  changes  may  pre-­‐  or  post-­‐date  the   extinction  event   iii. Bolide  Impact   1. Proposed  for  all  major  mass  extinctions   2. Giant  asteroid  hits  Earth   3. First  proposed  for  the  Cretaceous-­‐Paleocene  extinction   4. Evidence:  Iridium,  microtektites,  shock  quartz,  impact   crater   a. Spike  in  Iridium  in  fossil  samples   b. Microtektites=  tiny  molten  pieces  of  glass,   thrown  up  into  the  atmosphere  from  impact,  and   rains  back  down   5. Issue:  may  pre-­‐  or  post-­‐date  the  extinction  event   iv. Volcanic  Activity   1. Proposed  for  most  major  mass  extinctions   2. Alternative  to  bolide  impact   3. Flood  basalts   a. Sulfuric-­‐acid  aerosols  into  atmosphere   i. Thick  blanket  around  the  Earth,  that   prevents  sunlight  from  coming  in   ii. Causes  a  freezing  cold  climate  that   animals  can’t  adapt  to   b. Increased  Iridium   c. Shock  Quartz   4. Both,  volcanic  activity  and  Bolide  impact  have  similar   evidence,  that’s  why  people  go  back  and  forth  between   which  one  is  the  more  accurate  one   V. Recovery   a. Survival  interval  after  extinction   i. Initial  period:  only  rare  appearances  of  taxa,  low  diversity   ii. Dominant  taxa  appear  to  be  those  that  can  flourish  in  stressful   conditions  (disaster  species)   iii. Rebound  phase:  new  species  start  to  appear  and  other   reappear  as  Lazarus  taxa   iv. Recovery  interval:  sustained  rapid  diversification     VI. Diversification   a. Origins  of  diversity   i. Diversification  can  occur  when  evolutionary  innovations  allow   biota  to  invade  empty  ecospace   1. Cambrian  explosion   2. Ordovician=  proliferation  and  expansion  of  suspension   feeding  communities         Notes  1/22     I. Evolution   a. Decent  with  modification  from  a  common  ancestor   i. Passed  on  via  genes   1. Genes  that  allow  a  species  to  survive  favorably  over   another  type   ii. Populations  evolve,  not  individuals   b. Constrained  by  the  history  of  the  evolving  organisms   i. Had  a  beak  to  start  with,  so  the  beak  is  what  changed  (didn’t   grow  a  whole  new  beak)   II. Fitness     a. The  ability  to  survive  and  pass  on  genes  to  the  next  generation   i. Not  necessarily  the  strongest,  fastest,  or  biggest,  but  the   organisms  that  survive  better  than  others   ii. Must  reproduce  and  the  offspring  with  the  new  characteristic   also  must  reproduce   III. Adaptation   a. Goodness  of  fit  of  an  organism  to  its  environment,  modified  by  natural   selection   i. How  well  does  that  organism  fit  in  with  that  environment?   ii. Ex:  dolphins  vs.  sharks   iii. The  organism  that  has  the  characteristic  to  survive   better=adaptation   1. It’s  a  random  mutation   2. A  bird  can’t  decide  to  grow  a  bigger  beak   iv. Must  be  heritable,  functional  to  the  current  organism,  and   increase  the  fitness  of  the  organisms  that  have  it   IV. Adaptations  and  Exaptations   a. Exaptations:  functionally  useful  structures  that  were  not  shaped  by   natural  selection  for  current  use   i. Biological  structures  that  may  have  multiple  functions   ii. Example:  Feathers  didn’t  evolve  for  flying,  initially  evolved  to   keep  an  animal  warm  (downy),  but  over  time,  they  developed   other  useful  functions  (flight)   V. Natural  Selection   a. Ability  of  organisms  of  one  generation  to  obtain  representation  in  the   next  generation   b. Offspring  survive  preferentially  over  other  varieties   c. NOT  survival  of  the  fittest,  it’s  what  survives  better!   d. Examples   i. Variation  in  traits…some  beetles  are  green  and  some  are   brown   ii. Differential  reproduction…green  beetles  tend  to  get  eaten  by   birds  and  survive  to  reproduce  less  often  than  brown  beetles   do   1. More  brown  beetles   iii. There  is  heredity.  The  surviving  brown  beetles  have  brown   baby  beetles  because  this  trait  has  a  genetic  basis   1. Random!  The  beetles  didn’t  decide  brown  is  better,   birds  just  happened  to  like  the  green  beetles  better   iv. End  result:  brown  coloration=more  offspring=more  common   in  population   e. Pesticide  Resistance   i. Non-­‐random  survival=what  survives  is  not  random,  the   characteristic  that  allows  a  species  to  survive  is  random     VI. Natural  Selection  (again)   a. Ability  of  organisms  of  one  generation  to  obtain  representation  in  the   next  generation   b. Mutations  that  allow  the  organism  to  favorably  survive,  such  as   characteristics  that  allow  organisms  to:   i. Obtaining  food   1. Different  beaks  for  different  types  of  food  (picture  of   finches)   ii. Avoiding  being  food  (camouflage)   1. Good  example  of  not  being  the  strongest  or  the  biggest,   the  ability  to  hide  well  is  what  allows  it  to  survive   iii. Successful  reproduction:  helps  explain  unusual  structures  and   behaviors   1. Acts  on  behaviors  as  well  as  physical  structures   2. Male  birds  with  flashy,  bright  feathers  to  attract  the   attention  of  a  female   3. The  best  features  that  allow  males  to  attract  females   4. Ex:  Peacocks   a. Male  peacocks  have  an  average  of  150  eyes   i. Usually  the  ones  that  mate   b. Males  with  fewer  than  130  eyes  rarely  mate   c. Illustrates  female  choice   d. The  big  feathers  of  peacocks  have  no  use  other   than  to  attract  female   c. Descent  with  modification:  descendants  from  a  common  parent   i. Explains  the  grouping  of  all  organic  beings   ii. Evolution  is  the  descent  with  modification  from  a  common   ancestor,  but  exactly  what  has  been  modified?     iii. Evolution  only  occurs  when  there  is  a  change  in  gene   frequency  within  a  population  over  time.     iv. These  genetic  differences  are  heritable  and  can  be  passed  on  to   the  next  generation  —  which  is  what  really  matters  in   evolution:  long  term  change.     • “The  difference  in  weight  in  example  1  came  about  because  of   environmental  influences  —  the  low  food  supply  —  not  because  of  a   change  in  the  frequency  of  genes.  Therefore,  example  1  is  not   evolution.  The  changing  color  in  example  2  is  definitely  evolution:   these  two  generations  of  the  same  population  are  genetically   different”   d. Descent  with  modification:  Alteration  of  Pre-­‐existing  structures   i. Evolution  is  constrained  by  the  history  of  the  evolving   organism   1. Builds  upon  what  is  already  present  genetically   2. Pre-­‐existing  structures  modified  to  perform  functions   different  from  the  original  function   3. Ex:  arms     a. Variety  of  organisms  that  have  the  same   structure,  but  it’s  slightly  modified  (can  be  seen   below)   VII. Homologous   a. Reveals  ancestry   b. Traits  inherited  by  two  different  organisms  from  a  common  ancestor   c. Evolutionary  relationship  but  may  have  different  function.  Feature   evolved  once.   d. Example:  The  arm  of  a  human,  the  wing  of  a  bird  or  a  bat,  the  leg  of  a   dog  and  the  flipper  of  a  dolphin  or  whale  are  homologous  structures     i. They  have  different  purposes,  but  share  common  traits.     ii. They  are  considered  homologous  structures  because  they  have   a  similar  underlying  anatomy.       VIII. Analogous   a. Evolutionary  convergence  in  function  between  unrelated  groups.   Feature  appears  multiple  times  in  unrelated  lineages   b. Similarity  due  to  convergent  evolution,  not  common  ancestry   i. Convergent  evolution:  “Process  in  which  two   distinct  lineages  evolve  a  similar  characteristic  independently   of  one  another.”   ii. Often  occurs  because  both  lineages  face  similar  environmental   challenges  and  selective  pressures.   c. Examples:  There  are  many  kinds  of  flying  animals—bats,  birds,   insects,  etc.  All  of  these  organisms  have  wings.  Comparing  the  wing  of   these  animals  reveals  more  differences  than  similarities.     i. Insects  have  two  pairs  of  wings,  while  bats  and  birds  have  one   pair   ii. Insect  wings  lack  bones,  but  bird  and  bat  wings  have  them.   iii. Butterfly  wings  are  covered  in  scales,  bird  wings  in  feathers,   and  bat  wings  with  bare  skin.   d. All  of  these  organisms  have  adapted  to  life  in  the  air  by  evolving  wings   i. These  wings  evolved  independently  in  each  of  these  groups   and  don’t  indicate  that  they  are  closely  related,  so  the   possession  of  wings  is  an  analogous  trait       IX. Panda’s  Thumb   a. A  modified  wrist  bone  that  acts  like  a  thumb  (but  is  not  a  thumb)   b. Allows  it  to  hold  bamboo  better  and  eat  more  bamboo  successfully   c. Was  passed  down  to  offspring  and  now  all  pandas  have  it   d. The  panda  thumb  and  the  human  thumb  don't  grow  from  the  same   bones.     i. This  is  more  evidence  that  they  are  analogous  structures.     ii. However,  the  panda  thumb  is  homologous  to  a  wrist  bone  in   humans,  and  the  human  thumb  is  homologous  to  the  first   finger  in  pandas!      


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