By Beth Merrill – AMGEN Summer Science Institute 2005
Porter Middle School - 7 th grade Science
Learning Goals:
-
To help students understand the concept of Natural Selection
-
To help students understand the concept of sexual selection
-
To explain to students the interplay between selection factors
-
To understand that DNA underlies evolution
Standards:
Genetics – a typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences.
Evolution- Biological evolution accounts for the diversity of species developed through gradual processes over many generations.
Investigation and experimentation – scientific progress is made by asking meaningful questions and conducting careful investigations.
Discussion:
Darwin, when he proposed the theory of Natural Selection, felt that evolution was such a slow process that it would never be seen in a person’s lifetime. Scientists have found evidence that in some cases Natural Selection in a much quicker way. The book
The Beak of the Finch points out that Finches evolve differences in beak size seasonally as climate alters from wet to dry. These differences are so small that they could only be picked up with a computer comparison of the data, but it has been proven that beak size of the population varies with the amount of water on the island. The same kind of data has been collected from guppies in
South America and a fish in Lake Victoria Africa called the cichlid.

Key Vocabulary:
Evolution Natural Selection adaptation habitat environment population.
Prior Knowledge:
Genetics, ecological principals
The Scientific Method, and Lab Reports
Teacher Directed Instruction:
Estimated time 1 to 2 class periods
1.
Show Power Point on Natural Selection Whole class http://travelin-tigers.com/msdocs/01b.ppt
2.
Show video clip about Charles Darwin: Reluctant Rebel http://www.pbs.org/wgbh/evolution/library/02/2/1_022_04.html
3.
Have students read the selected reading from Beak of the
Finch by Jonathan Weiner. Note: The method of reading is up to the teacher depending on student reading abilities . www.clunet.edu/BioDev/marcey/assi/evoess_05.htm
Go to selected readings and choose The Beak of the Finch
The password is Darwin (all lower case letters)
Adaptation link: http://evolution.berkeley.edu/evosite/evo101/IIIE5Adaptation,Shtml
Natural Selection link: http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.Shtml

Guided Practice:
After students finish the reading then the teacher will guide them through listing the conditions described in the reading that were observed in the stream where the guppy populations lived. These will be the basis for setting up the classroom river experiment.
Examples:
Color patterns of male and female guppies, habitat conditions for each population observed, number and type of enemy species, when they hunt and how many guppies they eat per hour.
Independent Practice:
Before starting the classroom river experiment the students will use their laptops to go through the on line lesson called Flashy Fish http://www.pbs.org/wgbh/evolution/educators/lessons/lessons4/act
2.html
Assessment:
On line
After completing the on line lesson Flashy Fish the students will then prepare the first experiment ”the guppy river population study” using the examples they have picked from the reading “The
Beak of the Finch” to build the “river” and its population of guppies and their enemies.

Estimated time: 2 class periods
Materials Needed:
List of habitat population of guppies + enemies
Scissors
Colored pencils
A variety of colored paper (to become the river bottom and guppy habitat)
Unlined white paper for guppies and enemies
Procedure:
1.
Each student will draw, color and cut out 12 guppies of each type found in the populations. These will become the initial population and future population of the river.
2.
Set up the ”river” winding through the room. (You will probably need to move tables/chairs out of the way).
3.
Choose four students to represent the two types of enemy fish and one to represent the enemy prawn.
4.
Before placing the guppy populations send the “enemy” fish and prawn outside the room.
5.
Set up the fish populations following the observed placement in their individual habitats.
6.
Allow the enemy fish and prawn to reenter the “river” and allow them to hunt for 2 minutes. At the end of two minutes count the eaten fish and the surviving fish.
7.
Students are to enter the numbers on their data charts.
8.
Send the enemy fish and prawn out again and “repopulate the river (spawning time) as per the findings in the Beak of the
Finch reading.

9.
Allow two more hunting and spawning times, and then graph the findings from the data charts.
Guppy images – http://centralpets.com/animals/fish/freshwater-fish/fwf4660.html
Crenicichla alta, a cichlid fish: http://aquavisie.vetry.org/Database/Vissen/Crenicichla-html
Rivulus hartii , a cichlid fish: http://www25.brinkster.com/aquavisie/Fotos_vissen/Rivulus_hartii
.html
Analysis Questions:
1.
What happened to the number of guppies in the population that was in the protective coloration area?
2.
What did you notice about the guppies in the unprotected areas? Did their numbers increase or decrease or stay the same?
3.
Did you see any changes in coloration in the guppy populations? Why or Why not?
4.
What conclusions can you draw from this study?
Assessment examples – see assessment tools:
Lab Report Rubric
General assignment rubric

Materials:
-Variety of Teddy bear grahams
(honey, cinnamon, chocolate chip, and chocolate.)
-plastic sandwich bags for Teddy Bear graham populations
-Laptops (if available)
-Graph paper and lined paper
-Pen/pencil
-Hand lens
Teacher Preparation :
Fill each bag with an initial population of Teddy Bear Grahams.
Pass out one bag to each group of students (between 3 to 6 students per group works nicely)
Directions:
A. Read the following story about the teddy bears.
You are a bear-eating monster. There are two kinds of bears: happy bears and sad bears. You can tell the difference between them by the way they hold their hands. Happy bears hold their hands high in the air, and sad bears hold their hands down low.
Happy bears taste sweet and are easy to catch. Sad bears taste bitter, are sneaky, and hard to catch. Because of this, you eat only happy bears. New bears are born every “year” (during hibernation) and the birth rate is one new bear for every old bear left from the last year.

B.
After reading the story students are to write a prediction about the outcome of each population of bears.
C. After writing their prediction:
1.
Obtain a population of bears.
2.
Record the number of happy bears, sad bears, and the total population for each generation in your data table.
3.
Eat three happy bears.
4.
Obtain a new generation from the teacher, and repeat the steps (2 &3) for two generations. You should complete 3 generations total.
5.
Be sure to record your data in you data table for each generation!
6.
Graph your data
7.
Write a paragraph explaining what happened to each population of bears and why. Contrast your conclusions with your original predictions.
:
Presentation Rubric
Lab Report Rubric
General assessment rubric

Estimated time: two weeks
Discussion:
Dandelions must grow and flower if they are to reproduce. If a lawn or school playing field is regularly mower, the longstemmed dandelions are not selected, and only the short-stemmed ones have enough time between mowing to reproduce their kind.
If a field is allowed to grow without mowing, the short-stemmed dandelions are not selected because they cannot get the flower head up high enough to disperse the seeds.
Dandelions Article – The American Biology Teacher “A Simple
Demonstration of Natural Selection in the Wild Using the
Common Dandelion” May 1994
Materials:
PVC pipe grids measuring 1 meter by 1 meter square ( two per site)
Observation journals (one per student) or Laptops for data
Lens/optic scope if available
Measuring tools
Graphing paper or computer program to graph data

Protocol:
Student groups will be expected to follow the established
Lab Report format. Therefore before locating study site each group will develop a Hypothesis.
Procedure:
1.
Student groups will locate and place PVC grid on two separate areas of grass in the school quad where dandelions are found. One area will be mowed and the other area will not be mowed.
2.
Students will count and note the location of each dandelion found within their grids. They will also measure the length of the stems.
3.
After the mowed area is mowed students will count and measure the dandelions stem length in each of the grids.
4.
Students will continue to monitor their areas and collect data for 2 weeks
5.
At the end of two weeks the students will graph their data and complete their Lab Reports.
6.
Each student group will present their findings to the class.
Assessment examples – see assessment tools section :
Lab Report Rubric:
Group Presentation Rubric:
Journal rubric

4
Full accomplishment!
_demonstrates a full understanding and use of the central concepts and ideas
- recorded work communicates thinking clearly, using some combination of written, symbolic and visual means
3
Substantial accomplishment!
-demonstrates essential understanding of the central ideas and concepts
-recorded work communicates thinking clearly, but some pieces may be missing
2
Partial accomplishment!
-demonstrates partial but limited understanding of the central ideas and concepts
-recorded work may be incomplete, misdirected, or not clearly presented
1
Little accomplishment!
-demonstrates little or no understanding of the central ideas and concepts
-recorded work is difficult to comprehend

Daily entries
Use of scientific language
Concept understanding
Regular daily entries
Entries 90% of the time
Entries 80% of the time
Entries less than 80% of the time
Consistent, accurate usage of scientific terms
Adequate usage of scientific terms
Occasional use with few errors
No terms or frequent errors in usage
Shows understanding of key concepts
Usually demonstrates understanding
Inadequately demonstrates understanding
Poor understanding of concepts
4
3
2
1
2
1
4
3
Rating
4
3
2
1

Frequent and proper use of scientific terminology appropriate for the Lab used
Strongly disagree 1
Disagree 2
Agree 3
Strongly agree 4
Data collection was within expected norms, explanations were given where they deviated
Conclusion is appropriate for the data collected and shows a strong grasp of the scientific concepts
Writing style shows neatness, grammatical correctness, good spelling
Strongly disagree 1
Disagree 2
Agree 3
Strongly agree 4
Strongly disagree 1
Disagree 2
Agree 3
Strongly agree 4
Strongly disagree 1
Disagree 2
Agree 3
Strongly agree 4
The lab write up was complete with graphs and charts where appropriate. Check the parts present. Purpose___ Materials list___ Procedures___ Data and
Strongly disagree 1
Disagree 2
Agree 3
Strongly agree 4 observations___ Graph or graphs___ Questions___ , and
Conclusion____
The response to the questions Strongly disagree 1

were carefully thought out and well reasoned
1
Organization Audience cannot understand presentation because there is no sequence of information
Subject knowledge
Students do not have a grasp of information; students cannot answer questions about subject
2
Audience has difficulty following presentation because students jump around
Students are uncomfortable with information and are able to answer only rudimentary questions
Graphics Students use superfluous graphics or
Disagree 2
Agree 3
Strongly agree 4
Students occasionally use graphics that rarely
3
Students presents information in logical sequence which audience can follow
Students are at ease with expected answers to all questions, but fail to elaborate
4
Students present information in logical, interesting sequence which audience can follow
Students graphics relate to text and
Students demonstrate full knowledge (more than required) by answering all class questions with explanations and elaboration
Students graphics explain and reinforce screen text and

Mechanics
Eye contact and elocution no graphics support text and presentation
Students presentation has four or more spelling errors and/or grammatical errors
Student reads all of report with no eye contact
Student mumbles, incorrectly pronounces terms, and speaks too quietly for students in the back of class to hear
Presentation has three misspellings and/or grammatical errors
Student occasionally uses eye contact, but still reads most of the report.
Student’s voices are low. Students incorrectly pronounce terms audience members have difficulty hearing presentation presentation presentation
Presentation has no more than two misspellings and/or grammatical errors
Student’s voices are clear.
Students pronounce most words correctly.
Most audience members can hear presentation
Presentation has no misspellings or grammatical errors
Students use clear voices and correct, precise pronunciation of terms so that all audience members can hear presentation
______