Name: _________________________________________________ Period: _________ Date: ___________

General Biology

Lab: Natural Selection in Bird Beaks

 

Background:

The theory of natural selection, proposed simultaneously by Charles Darwin and Alfred Wallace, states that individuals that are better suited to their surroundings have a greater chance of surviving and reproducing than do individuals that are less well suited.  In other words, the environment naturally selects better-adapted individuals.  Because better-equipped individuals win the “struggle for survival,” natural selection is sometimes referred to as “survival of the fittest.”

In this lab, you and your lab table group members will demonstrate the interaction between a bird’s beak and the bird’s ability to pick up certain types of seeds.  Each member in your group will have a different “bird beak”.  You will compare the survival possibilities of each type of bird.  The higher the survival rate, the greater the chance that a bird will live to produce offspring with similar beak shapes.  Those birds with beaks that make it difficult or impossible to survive are selected against, and consequently will not pass on their genes to future offspring.

 

Materials:

4 Petri dishes

2 types of seeds

4 different beaks

 

Procedure:

  1. Each student in the group is assigned a “beak” and is allowed a few minutes of practice picking up seeds and moving them into their Petri dish.  Remember, you can’t argue with inheritance.  You’re stuck with the beak you were born with, so make the most of it!
  2. Each group of students will use their beaks to “prey” off of the same population of seed in their environment (the lab table).
  3. When the signal is given to begin, each bird will begin to feed in his or her environment.  Each beak is to handle ONE SEED AT A TIME (No scooping or using fingers!!)  A seed counts ONLY if it stays in the Petri dish when dropped.  The time interval for each feeding session is 30 seconds.
  4. After 30 seconds are up, you will hear “STOP”.  Count the seeds that you have collected with your bird beak and record the total in Data Table 1.  Then average the seed collection for your beak.
  5. Repeat steps 3 and 4 and record your data in Data Table 1.  Then average the seed collection for your beak.
  6. Now, run the experiment again, using the same beak but with a different seed.  Repeat the experiment, and don’t forget to fill in your data sheet: Data Table 2. 
  7. Record your groups’ AVERAGES for each beak type on the board.  Then record the class averages data for each beak type in your data table.
  8. Calculate the average amount of prey captured by each beak type, and the average amount captured by the individuals in the class.
  9. Make a BAR GRAPH  of the class average for each beak type and for each seed type.  Use the graph paper provided.

 

 

 

 

 

 

 

 

 

Data:

Data Table 1:  Bean seed

Title: ___________________________________________________________________________

 

Type of Beak

No. of seeds collected, trial 1

No. of seeds collected, trial 2

Average of trials 1 and 2

Class Data from Board for each lab station

Class Average for Beak Type

1

2

3

4

5

6

Clothes Pin

 

 

 

 

 

 

 

 

 

 

 

Test Tube Clamp

 

 

 

 

 

 

 

 

 

 

 

Forceps

 

 

 

 

 

 

 

 

 

 

 

Alligator Clip

 

 

 

 

 

 

 

 

 

 

 

                                          Class Average, Total Prey Captured All Beak Types: ____________

Data Table 2: Rice seed

Title: _________________________________________________________________________

 

Type of Beak

No. of seeds collected, trial 1

No. of seeds collected, trial 2

Average of trials 1 and 2

Class Data from Board for each lab station

Class Average for Beak Type

1

2

3

4

5

6

Clothes Pin

 

 

 

 

 

 

 

 

 

 

 

Test Tube Clamp

 

 

 

 

 

 

 

 

 

 

 

Forceps

 

 

 

 

 

 

 

 

 

 

 

Alligator Clip

 

 

 

 

 

 

 

 

 

 

 

                                          Class Average, Total Prey Captured All Beak Types: ____________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Analysis:

  1. What is the definition of natural selection?

 

 

 

  1. Which beak shape did you have?

 

  1. Compare the amount of prey you PERSONALLY captured to the average amount of prey captured by all the individuals of your beak type.  Did you capture more than the average, or less?  What do you think that means in terms of your own personal survival?

 

 

 

  1. Now compare the amount of prey you personally captured to the average amount of prey captured by the entire class.  Did you capture more than the average or less?  What about the other individuals of your beak type?

 

 

  1. Let’s say that anyone who captured more than the total class average of prey was able to survive and pass on their genes (including their beak type) to the next generation.  How many individuals (use the class data from the board for each lab station) of each beak type survived and reproduced?

 

 

 

Type of Beak

Type of Seed

Clothes pin

Test tube clamp

Forceps

Alligator clamp

Beans

 

 

 

 

Rice

 

 

 

 

 

 

 

 

  1. Based on the class average for amount of prey captured, which bird beak type(s) would be selected against?  What do you think may happen to this variation of bird?

 

 

 

  1. Which bird beak type will be naturally selected to pass on their genes to future generations?

 

 

 

  1. Why would the beak type in question #7 be an example of a “good” or well adapted variation?

 

 

 

  1. List and briefly explain three other characteristics (other than beak shape) that could help a bird survive if this were a “natural” environment.

 

a.

 

 

b.

 

 

c.

 

 

Graph

 

Title: ____________________________________________________________________________________