Deadlines

John A - Natural Selection

NATURAL SELECTION OF POM POM AND UTENCIL TRAITS.

 

Materials:

200 ea. 10 mm Pom Poms  in three different colors.

Two bath towels or pieces of fabric that match two of the pom pom colors as close as possible.  Black is a good color choice for one as it is easy to find a color with black pom poms.

Plastic cups.

Plastic utensils. 10 ea. Knives, forks and spoons. 

Timer.

Calculator.

 

Prior Knowledge:

The students have an understanding of alleles and how different alleles of a gene can affect the phenotypes of an organism. 

 Students must understand that an organism must live long enough to reproduce  for its genetic information to be passed on to future generations.

The students must have a beginning understanding of artificial and natural selection.

 

 

Purpose:

 

The purpose of this lab is to show students how natural selection by a predator can affect the frequency of characteristics (alleles) found within a population of animals.  The lab will also show how natural selection acting on a prey species can affect the frequency of a characteristic found on a predator species.

 

Lab 1

 

1.  Start the lab with the presentation to the class of the prey species (pom poms) and, the environment

 (towel or fabric) that they live on.  Spread 30 ea. of the three different colors of pom poms on the black towel and have the students observe the “ecosystem”.

 

2.  Describe the predator (fork) and have the students make a hypothesis about how each of the three colors (adaptations) of the prey species might affect the ability of the pom poms to survive the predation and reproduce.  Their hypothesis must be written down in their lab note book.

 

3.  After the students have made their hypothesis, explain the rules of the lab.

-  First get two volunteers to help with data collection and supply them with calculators and data sheets.

 

-  Six predators will be chosen from the class and each will be assigned a fork as their feeding adaptation. 

-  The predators will be given a plastic cup to serve as their stomach.  The predators will be warned that the cup must remain upright and not come in contact with the towel to prevent scooping and shoveling. 

-  Predators will start with their back to the ecosystem and will be given thirty seconds to feed.

 -  Competition is encouraged but once a pom pom is captured by a predator it is off limits.

-   Students must stop feeding when the teacher calls out Stop.

 

 At the end of each “generation” count how many of each color of pom pom has been eaten, calculate the number of each pom poms remaining in the ecosystem, and have each surviving pom pom produce two off spring.  Record the results and continue with generations 2, 3, and 4 using the same rules.

 

Analysis:

 

1. Have the students use a line graph to plot the results of the population levels for each generation.

 

2. Ask the students if any of them had their hypothesis confirmed by the results.  Discuss how even negative results are useful.

 https://lh4.googleusercontent.com/_ioinZ7OgaII/TWqUFQ5sTII/AAAAAAAAMKc/D8GZtBxp1Gc/s800/P1000465.JPG

 

Lab 2

 

Tell the students that two new adaptations have appeared in a different but similar predator population in the form of a knife and a spoon.   Explain how we are only going to study the predator population this time and that the prey species will always start out with the same number of individuals at the beginning of each generation.

 

1.  Select 6 new students as predators and assign each student one of the three feeding adaptations.  2 w/ forks, 2 w/ knives and two with spoons.

 

2.  Explain to the students that the feeding rules are the same.

 

3.  Then, explain to the students that the two predators that eat the fewest amount of prey will die and not reproduce while the two predators that eat the most prey will survive and reproduce.  The two predators that come in second and third will survive to the next round but not produce any offspring.

 

4.  Have the students make a hypothesis as to which adaptation will be the most successful over four generations.

 

5. Perform the lab recording the number of each predator adaptation that is in each generation.

 

Analysis:

 

1. Have the students use a line graph to plot the results of the population levels for each generation.

 

2. Ask the students if any of them had their hypothesis confirmed by the results.  Discuss how even negative results are useful.

 

 

 References:
This is a great website for biology teachers.  Several good hands on ideas and they encourage you to use them.

 http://serendip.brynmawr.edu/sci_edu/waldron/

 


 Questions for the Students:

What are the observable adaptations/traits of the Pom Pom species?

 

 

 

Write your Pom Pom hypothesis here.  Do you think any of the fur color adaptations of the Pom Poms will result in natural selection?

 

 

 

 

 

What are some of of the adaptations/ traits found in the Utensil predator species?

 

 

 

Write your utensil predator hypothesis here.  Do you think any of the Utensil adaptations will result in natural selection?

 

 

 

 


Additional Questions:

1.  Did natural selection occur in the pom pom population?  In other words, did one pom pom adaptation/trait become more common over time while the other colors became less common?  What traits contributed to the survival of pom poms that survived to reproduce?

 

 

 

2   If we ran the simulation for 50 more generations, what would you predict the ratio of the colors in the pom pom population might be?

 

 

 

3.   What would you predict the ratio of the feeding adaptations might be after 50 more generations?

 

 

 

 

4.  Below is a series of pictures representing changes in a population of cacti.  Pictures 1 and 2 show what happened when a deer came to eat, picture 3 shows the cacti a few weeks later (notice the flowers on the right-hand cactus), and picture 4 shows the situation a few months later. 

See referenced website for pictures under evolution and diversity.  They would not copy over. 

 http://serendip.brynmawr.edu/sci_edu/waldron/

1

2

3

 

4

3

2

1

 

Recall that the three conditions listed below are necessary for natural selection to take place.

 

1.        Variation in characteristics within the population:  In picture 1, what is the main difference between the cactus on the left and the cactus on the right?

 

2.     Differences in survival and reproduction, fitness:  Why would a deer be more likely to eat the                          cactus on the left than the cactus on the right?

 

What effect does the deer's behavior have on the survival and reproduction of these two types of cactus?

 

3.    Heritability of characteristics from parent to offspring:  The difference between the cacti is a heritable characteristic (see picture 4). 

 

Do you think that evolution by natural selection is occurring in this cactus population?  Explain why or why not.

 

Pom Pom Survival Calculation Sheet

Habitat Type:

 

Pom pom Color

Black

Red

Green

# in generation 1

 

 

 

# eaten

 

 

 

# remaining (# generation 1 - # eaten)

 

 

 

# new (2 X # remaining)

 

 

 

# in generation 2 (# remaining + # new)

 

 

 

# eaten

 

 

 

# remaining (# generation 2 - # eaten)

 

 

 

# new (2 X # remaining)

 

 

 

# in generation 3 (# remaining + # new)

 

 

 

# eaten

 

 

 

# remaining (# generation 2 - # eaten)

 

 

 

# new (2 X # remaining)

 

 

 

# in generation 4  (# remaining + # new)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 Black Forest

 

Pom Poms

 

RED

BLACK

WHITE

TOTAL

Generation 1

Number

 

 

 

 

 

 

 

 

 

Generation 2

Number

 

 

 

 

 

 

 

 

 

Generation 3

Number

 

 

 

 

 

 

 

 

 

Generation 4

Number

 

 

 

 

 

 

 

 

 

 

 Red Forest

 

Utensils

 

KNIFE

FORK

SPOON

TOTAL

Generation 1

Number

 

 

 

 

 

 

 

 

 

Generation 2

Number

 

 

 

 

 

 

 

 

 

Generation 3

Number

 

 

 

 

 

 

 

 

 

Generation 4

Number

 

 

 

 

 

 

 

 

 

Data Collection Sheets

 

 

Comments