In  this  unit  we  discussed  the  role  of  DNA  in  cells.  We  have  talked  a  good  deal  about  how  proteins  are  made,  and   their  many  functions  within  an  organism.  Our  next  evolution  connection  will  look  at  the  theory  of  evolution  by   natural  selection;  we  will  learn  how  species  can  change  over  time,  and  how  new  species  can  come  to  be.    As  you  go
through  this  evolution  connection,  keep  in  mind  that  mutations  in  DNA  and  their  resulting  changes  in  protein   structure  are  responsible  for  all  the  variation  we  see  in  the  organisms  of  Earth!
Anthro.palomar.edu
Part  I:  Evidence  for  Evolution
Look  for  the  following  sections,  each  of  which  examines  a  different  type  of  evidence  for  evolution:
•
Structural  Homologies
•
Fossil  Evidence
•
Observational  Evidence  (we  can  observe  changing  populations)
•
Molecular  Evidence
Go  to   http://evolution.berkeley.edu/evolibrary/article/evo_01
Start  with  “Patterns”.    Explore  the  following  pages  in  this  module:
à  Homologies  and  Analogies.
1.
What  are  homologies?  What  are  analogies?  Which  one  comes  from  a  common  ancestor?
2.
Bird  and  bat  wings  are  analogous.    Why  did  similar  structures  evolve  separately  in  these  two  groups?
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Video:  “Who  Was  Charles  Darwin?”
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
3.
What  characteristics  made  Darwin  especially  well  suited  for  science?
4.
What  did  Darwin  see  and  do  on  his  5-­‐year  voyage  aboard  the   Beagle ?
5.
What  new  idea  did  Charles  Darwin  introduce  to  science?  How  did  it  challenge  the  current  understanding  of   biodiversity?
Video:  “How  Do  We  Know  Evolution  Happens?”   http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
6.
How  do  fossils  give  us  a  picture  of  change  over  time?
7.
What  distinguishing  feature  of  the  fossil  Pakicetus  skull  identified  it  as  related  to  a  whale?  Why  was  this   surprising?
8.
Why  do  scientists  seek  fossils  that  are  intermediate  in  form  and  time  between  modern  forms  and  their   probable  earliest  ancestors?
Interactive:  Transitional  Fossils
http://www.pbs.org/wgbh/nova/evolution/fossil-­‐evidence.html
9.
This  resource  describes  5  important  transitional  fossils  that  have  helped  our  understanding  of  evolutionary
Fossils   history.    Fill  in  the  table  below  with  information  about  each  one.
Represents  a  link  between   what  two  modern  groups?
What  physical  structure(s)  were  modified   from  earlier  ancestors?
Tiktaalik  rosae
How  long  ago?
Thrinaxodon
Archaeopteryx
Ambulocetus   natans
Australopithecus   afarensis
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Video:  How  Does  Evolution  Really  Work?     http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
10.
What  are  the  four  components  of  natural  selection?
A.
B.
C.
D.
11.
What  determines  an  individual  hummingbird’s  beak  length?
12.
What  factors  in  the  environment  might  select  for  beak  length  and  shape  within  hummingbird  populations?
13.
How  can  hummingbird  DNA  help  Dr.  Schneider  determine  the  evolutionary  history  of  hummingbirds?
In-­‐class  activity:  The  Grant
Finch  Study  Data
Interactive:  Darwin’s  Predictions   http://www.pbs.org/wgbh/nova/evolution/darwins-­‐predictions.html
Many  scientific  discoveries  have  supported  Charles  Darwin’s  original  theory  of  evolution  by  natural  selection.    This   interactive  examines  12  predictions  Darwin  made,  and  discusses  supporting  discoveries  that  have  been  made  since
Darwin’s  publication  of  his  book.
14.
For  each  prediction,  briefly  describe  the  supporting  evidence.
Evolution  happens
Evolution  happens   through  natural   selection
Evolution  by  natural   selection  must  have   a  mechanism
The  mechanism  is   natural,  not   supernatural.
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Embryology  is  "the   strongest  single   class  of  facts  in  favor   of  change  of  forms."
Sexual  selection  also   drives  evolution.
All  animals,   including  humans,   descend  from  a   common  ancestor.
Humans  evolved   from  an  ape-­‐like   ancestor.
Modern  humans   arose  in  Africa.
The  Earth  is  at  least   several  hundred   million  years  old.
Gaps  in  the  fossil   record  will  be  filled   in  with  key   transitional  fossils.
An  insect  with  a
foot-­‐long  tongue   must  exist  to   pollinate  this  orchid.
In-­‐class  activity:  Birds,  beaks,
and  natural  selection.
Go  to   http://evolution.berkeley.edu/evolibrary/article/evo_01
Click  on  “Mechanisms”.  You  will  progress  through  all  pages  of  this  module.
15.
Briefly  describe  each  of  the  following  mechanisms  of  evolution:
A.    Mutation:
B.  Migration:
C.  Genetic  Drift:
D.  Natural  Selection:
16.
What  are  the  three  sources  of  genetic  variation  in  sexually  reproducing  populations?
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17.
List  three  examples  of  behaviors  that  have  evolved  by  natural  selection.
18.
Why  do  organisms  do  things  that  don’t  necessarily  increase  their  chance  for  survival:  peacocks  grow  giant   tails,  penguins  care  for  their  young,  and  lobsters  produce  thousands  of  offspring.
19.
Define  sexual  selection.
20.
How  does  artificial  selection  support  Darwin’s  theory?
21.
List  three  examples  of  adaptations  that  have  arisen  by  natural  selection.
22.
What  are  vestigial  structures?  Give  an  example  of  a  vestigial  structure.
Flashy  Fish
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act2.html
23.
Fill  in  the  chart  below.
Pros   Cons
Drab  colors
Flashy  colors
24.
In  which  pool  does  each  survive  best?  Why?
25.
Why  does  it  make  sense  for  females  to  choose  the  brightest  males?  (Hint:  after  running  your  simulation  you   will  be  looking  at  the  results  page.  Click  on  “read  summary”  under  the  results  window.)
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In-­‐Class  Activity  1:  Grant  Finch  Study  Data
Natural  Selection  in  Real  Time
"When  we  made  the  comparison  between  the  size  of  the  offspring  generation  and  the  population  before  selection,  we   found  a  measured,  evolutionary  response  had  taken  place  and  it  was  almost  identical  to  what  we  had  predicted."   -­‐
Peter  Grant
Darwin  thought  that  evolution  took  place  over  hundreds  or  thousands  of  years  and  was  impossible  to  witness  in  a   human  lifetime.  Peter  and  Rosemary  Grant  have  seen  evolution  happen  over  the  course  of  just  two  years.
The  Grants  study  the  evolution  of  Darwin's  finches  on  the  Galapagos  Islands.  The  birds  have  been  named  for
Darwin,  in  part,  because  he  later  theorized  that  the  13  distinct  species  were  all  descendants  of  a  common  ancestor.
Each  species  eats  a  different  type  of  food  and  has  unique  characteristics  developed  through  evolution.  For  example,   the  cactus  finch  has  a  long  beak  that  reaches  into  blossoms,  the  ground  finch  has  a  short  beak  adapted  for  eating   seeds  buried  under  the  soil,  and  the  tree  finch  has  a  parrot-­‐shaped  beak  suited  for  stripping  bark  to  find  insects.
The  Grants  have  focused  their  research  on  the  medium  ground  finch,   Geospiza  fortis,   on  the  small  island  of  Daphne
Major.  Daphne  Major  serves  as  an  ideal  site  for  research  because  the  finches  have  few  predators  or  competitors.
(The  only  other  finch  on  the  island  is  the  cactus  finch.)  The  major  factor  influencing  survival  of  the  medium  ground   finch  is  the  weather,  and  thus  the  availability  of  food.  The  medium  ground  finch  has  a  stubby  beak  and  eats  mostly   seeds.  Medium  ground  finches  are  variable  in  size  and  shape,  which  makes  them  a  good  subject  for  a  study  of   evolution.
The  first  event  that  the  Grants  saw  affect  the  food  supply  was  a  drought  that  occurred  in  1977.  For  551  days  the   islands  received  no  rain.  Plants  withered  and  finches  grew  hungry.  The  tiny  seeds  the  medium  ground  finches  were   accustomed  to  eating  grew  scarce.  Medium  ground  finches  with  larger  beaks  could  take  advantage  of  alternate  food   sources  because  they  could  crack  open  larger  seeds.  The  smaller-­‐beaked  birds  couldn't  do  this,  so  they  died  of   starvation.
In  1978  the  Grants  returned  to  Daphne  Major  to  document  the  effect  of  the  drought  on  the  next  generation  of   medium  ground  finches.  They  measured  the  offspring  and  compared  their  beak  size  to  that  of  the  previous  (pre-­‐ drought)  generations.  They  found  the  offsprings'  beaks  to  be  3  to  4%  larger  than  their  grandparents'.  The  Grants   had  documented  natural  selection  in  action.
While  beak  size  is  clearly  related  to  feeding  strategies,  it  is  also  related  to  reproduction.  Female  finches  tend  to   mate  with  males  that  have  the  same  size  beaks.  These  factors  together  can  add  to  the  development  of  new  species.
The  Grants  return  each  year  to  Daphne  Major  to  observe  and  measure  finches.  They  have  been  collecting  data  on   the  finches  for  over  25  years  and  have  witnessed  natural  selection  operating  in  different  ways  under  different   circumstances.
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Grants’ Finch Study Data
Figure 1 1976 All Daphne Birds
N = 751
1978 Survivors
N = 90
Beak Depth (mm)
Figure 1: Histogram of distribution of beak depth of medium ground finches ( Geospiza fortis ) on
Daphne Major, before and after the drought of 1977 (Grant 1986). Reprinted by permission of
Princeton University Press.
Figure 2
Midparent Bill Depth (mm)
=1976 population and
=1978 population
Figure 2: Relationship between beak depth of offspring and their parents in the medium ground finch ( Geospiza fortis ) population on Daphne Major. The slope of the relationship is the heritability
(Boag 1983).
1
©2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
7

Figure 3 A
Estimates ± 95%
Confidence Limits
B
Daphne. All Edible Species x ± s.e.
Figure 3: Changes in Geospiza fortis population and seed abundance on Daphne major, before and after the drought of 1977 (Grant 1986).
2
©2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
8

In-­‐class  Activity  2:  Modeling  Natural  Selection
Birds, Beaks, and Natural Selection—A Simulation
In this simulation, students gather data to see how beak mutations can influence natural selection.
Objective
Students learn about the role of mutations in natural selection and evolution.
Procedures
1.
The three to four students in your group represent individual wading birds within a population of 100 birds. This population of wading birds has a wild-type beak that will be made of tongue depressors.
2.
Look at the wild-type beak model and construct a similar beak by wedging the screw
2 cm from the tips of the tongue depressors and using the rubber band to wrap the ends of the tongue depressors, making the beak like tongs.
3.
You will simulate the wading birds feeding.
• Add to your aquarium four of each type of food for each person in your group.
• Take turns feeding for 15 seconds to see how many of each type of food you get, using the feeding rules.
–Pick up only one piece of food at a time.
–Don't use the edge of the aquarium to hold food.
–Don't put your hand below water.
• Replace food before the next feeding trial.
–Wipe up any water on floor between trials.
• Each member of the group should do three trials of feeding; after each trial, record the results in the “Bird Beak Data Sheet.”
4.
Calculate and compare the average number of food pieces and types of food captured by your team members.
1
© 2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
Adapted with permission from “Genetics and the Evolution of Bird Beaks” by Bonnie Chen.
9

5.
Now assume that three to four birds (your team members) in your population will undergo mutations in the genes that code for beak length. Each student will pick a mutation handout that will explain the kind of mutation and how it will affect the beak size of your offspring.
6.
Follow the instructions on your mutation sheet. If you received a beak mutation that requires a change, you will need to create the new beak for your offspring. For long beak mutations, use the extra-long glued tongue depressors, a screw, and the rubber band to make the beak tong-like. For short beak mutations, cut the wild-type beaks exactly in half using the scissors. Some mutations do not affect your offspring's beak; you will use the same wild-type beak. Answer these questions with your group:
• What was the significance of having only four individuals within a population of 100 wading birds have a mutation?
• Why did some mutations lead to a change in beak length and some not?
7.
You will now feed as your offspring, Generation 1. Because this time all members of a group will feed at once , two teams will work together during the feeding of the offspring. While one group feeds, the other group will time and monitor the feeding.
Then teams will switch roles. There will be three feeding trials of 15 seconds each, following the feeding rules, and food will be replaced between trials. Record your feeding data on the “Bird Beak Data Sheet” after each trial.
8.
Determine the survival rate of your offspring by following the directions below and record results in the “Bird Beak Data Sheet” in the Generation Results column.
Guidelines for determining offspring survival:
• If offspring consumed less than half of the parent's average number/amount of food minus 2, they will die. For example, if offspring consumed 4 pieces of food and parent's average number/amount of food was 14, then they will die. (4 is less than 5x14-2=5)
• If offspring consumed between half parent's average minus 2 to half of the parent's average, they will survive and reproduce 1 offspring.
• If offspring consumed more than half the parent's average, they will survive and reproduce 4 offspring.
9.
Compare your data and discuss the following questions in your group and record responses below.
• What happened when the offspring with changed beaks and the offspring with wild-type beaks fed together?
• For each type of beak, which food types were consumed? Which types were consumed the most?
2
© 2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
10

• Based on the number of food items consumed, which birds survived? Which birds survived and produced the most offspring?
• Why might some surviving birds produce different numbers of offspring?
• What other factors besides beak length affected feeding in your population?
• What would you expect to happen to the population if the second generation were allowed to feed and reproduce under the same conditions?
• How did this simulation demonstrate natural selection?
• What is the role of mutations in natural selection?
• What is the role of sexual reproduction in natural selection?
• Which does natural selection act upon: the genotype or phenotype of traits?
• Explain the significance of the following statement: Natural selection operates on individuals, but evolution occurs at the level of the population.
• How is this simulation like the real world and how is it different in relation to feeding, mutations, beak lengths, and reproduction?
3
© 2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
11

12

Mutation Handout: Birds, Beaks, and Natural Selection Activity
------------------------------------------------------------------------------------------------------------
No change in beak length:
Mutation does not change beak length. Protein codes for a beak length the same size as the wild-type beak.
Same as parent generation: two tongue depressors connected together (15 cm)
------------------------------------------------------------------------------------------------------------
Long beak:
Mutation changes beak length. Protein codes for a beak longer than the wild-type beak.
Construct the long beak by using the long tongue depressors made of two tongue depressors glued together. Use a screw and rubber bands to secure the top of the beak like tongs. Wrap the rubber bands very tightly. Make sure that the beak will fully close!
------------------------------------------------------------------------------------------------------------
Short beak:
Mutation changes beak length. Protein codes for a beak shorter than the wild-type beak.
Mark the halfway point of the tongue depressors in the wild-type beak. (7.5 cm) Using scissors, cut the wild-type beak in half along the 7.5 cm line.
------------------------------------------------------------------------------------------------------------
No change in beak length:
Mutation does not change beak length. Protein codes for a beak length the same size as the wild-type beak.
Same as parent generation: two tongue depressors connected together (15 cm)
------------------------------------------------------------------------------------------------------------
© 2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.
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