Bill Size Matters

Now that we have covered prey adaptations, let us discuss predator adaptations. If prey adapt to avoid being captured, then the predator must adapt as well in order to gain energy through food. As discussed in the previous blog, adaptations must be heritable and increase the organism’s fitness. In the following experiment, we will be discussing the adaptation of beak lengths of birds.

In a fictional land called “Clipland,” there are three different beak lengths demonstrated by binder clips, a large, medium, and small. Beaks are randomly assigned to students and each student is given a cup as a stomach. The group will be split in two to represent “West Clipland” and “East Clipland.” Prearranged food bags will be given out to the two sides in rounds as shown in the table below:

	2nd Season	3rd  Season	4th Season
East Clipland	4 handfuls popcorn seeds ½ lb lima beans 50 marbles	1 handful popcorn 20 lima beans 50 marbles	100 marbles
West Clipland	4 handfuls popcorn ½ lb lima beans 50 marbles	6 handfuls popcorn 20 lima beans 5 marbles	8 handful popcorn

Each group starts at season two at separate areas. They are given 15 seconds to pick up as many items as they can only with the binder clips and place them in their stomach. Each item is given a different point worth and each beak size is assigned a goal of points in order to survive. Double the assigned points to survive for a reproduction point goal. At the end of the round, all those who reached their survival goal will move on to the next round and any who failed to reach the goal will become a spectator. If any of the survivors obtained enough point to reproduce, a spectator may rejoin as its offspring with the same beak length as its parent. After the survivors and offspring have been tallied, they will empty their stomachs in the original bag to clean up the “feeding” space and spread out season two’s feed bag. Repeat this process for season three and four. After season four, clean up all the materials and tally the results of “East Clipland” and “West Clipland.” The first season is the original population of each beak length before the beginning of season two. My personal demonstration resulted as follows:

West Clipland

	1st Season	2nd Season	3rd Season	4th Season
Bigbill	2	0	0	0
Mediumbill	3	3	1	1
Smallbill	2	2	1	0

East Clipland

	1st Season	2nd Season	3rd Season	4th Season
Bigbill	4	2	2	3
Mediumbill	3	0	0	0
Smallbill	3	2	2	0

As shown in the table above, the fitness of the organisms fluctuates with the size of food available. When marbles were most prominent, bigbill binder clips were favored. When popcorn was the prominent food source, the smallbill binder clips were favored. These results show the short term natural selection. Intraspecies competition is apparent as the different sized beaks as some beak lengths were ultimately eliminated. For this purpose, Clipland is an excellent example of predator adaptations in contrast to prey adaptation.

Credit to Al Janulaw and Judy Scotchmoor

Can you see me know? Cryptic Coloration

Today is about adaptations but before we can talk about adaptations we need to know what constitutes as an adaptation. An adaptation is a trait that has been naturally selected through mutations that are heritable and must increase the organism’s fitness. An organism’s fitness is determined by its survival and reproduction rates. In this natural selection lab, all of these components will be visually displayed in a fun, interactive manner.

 

You will need three identical, large bins; three colors of shredded paper; 3 colors of pipe cleaners cut into small segments that match the shredded paper; 3 cups; and a magnetic wand. Each bin will be designated with one primary color, A, B, or C. Bin number 1 will consist of half of A’s shredded paper supply and a quarter of B’s and C’s color supply. Bin number 2 will consist of half of B’s shredded paper supply and a quarter of A’s and C’s color supply. Lastly, bin number 3 will consist of half of C’s color supply and a quarter of A’s and B’s color supply. Overall, the bins should have a color ratio of 2:1:1 with a different predominant color in each bin. If the primary color is not predominant, then adjust the color ration of shredded paper. These bins are now the habitats for the experiment. The pipe cleaners should be cut into 1.5-2 inch lengths and separated into nine bags total with three bags of each color. One bag of each color should be placed at each of the habitats so that all three bins have all three different colors. These pipe cleaners are now the prey of the paper habitats.

The class will be separated in three different groups so one group will be at each habitat. They will need to designate a timer, a predator, a math wizard, and a habitat manager. The predator will be given a cup to be its stomach for its captured prey. The habitat manager is in charge of making sure the habitat starts with the right number of prey and the correct amount of prey are added after each round. The math wizard has the duty of figuring out how many prey should be added after each round. The timer simply keeps track of time so that the predator does not take more prey then it should. These roles should be switched at each new habitat for fairness and fun. Once the roles have been decided amongst the group, the predator must turn away from the habitat as the habitat manager slightly hides 8 pipe cleaners of each color in the bin. Once the habitat manager is satisfied with hiding the prey, the predator can turn back towards the bin. The timer will tell the predator when to start and allow the predator 20 seconds to hunt for prey. The predator must grab as many pipe cleaners as they can, one at a time, and place it in their stomach (cup) before time runs out. When 20 seconds is over, the predator must count how many prey of each color they have in their stomach and inform the math wizard. The math wizard will then fill out the worksheet for the first generation and compute how many prey of each color need to be added to the habitat to signify reproduction. The habitat manager will then add the number of prey to the bin without the predator watching. Once the prey has been added and hidden, the predator may turn around and begin hunting on the timer’s cue. This process will be repeated so there are three rounds total to signify three generations. After three generations at one habitat has been completed, the current group must use the magnetic wand to fish out the rest of the remaining pipe cleaners so there are no pipe cleaners left in the bin. Groups will then change habitats and switch roles. They will repeat the process they performed at the first habitat and record the results. If the class is well-behaved and focused, you can try to have them complete all three habitats. My groups’ example experiment is below and is a similar format to the worksheet that should be provided to each group.

Generation 1:

Primary Habitat Color: A	Prey Color: A	Prey Color: B	Prey Color: B
Number in habitat to start	8	8	8
Number prey caught in hunt	2	1	0
Number of prey still in habitat	8-2 = 6	8-1 = 7	8-0 = 8
New offspring to be added to habitat (number from previous row)	6	7	8
Total number prey in habitat to begin next generation (surviving prey+offspring)	6+6 = 12	7+7 = 14	8+8 = 16

Generation 2:

Primary Habitat Color: A	Prey Color: A	Prey Color: B	Prey Color: B
Number in habitat to start	12	14	16
Number prey caught in hunt	1	7	4
Number of prey still in habitat	12-1 = 11	14-7 = 7	16-4 = 12
New offspring to be added to habitat (number from previous row)	11	7	12
Total number prey in habitat to begin next generation (surviving prey+offspring)	11+11 = 22	7+7 = 14	12+12 = 24

Generation 3:

Primary Habitat Color: A	Prey Color: A	Prey Color: B	Prey Color: B
Number in habitat to start	22	14	24
Number prey caught in hunt	4	5	8
Number of prey still in habitat	22-4 = 18	14-5 = 9	24-8 = 16
New offspring to be added to habitat (number from previous row)	18	9	16
Total number prey in habitat to begin next generation (surviving prey+offspring)	18+18 = 36	9+9 = 18	16+16 = 32

            As shown above, the prey color A in its matching colored habitat was the hardest for the predator to find so its reproduction rate was the highest. That means prey color A had the highest fitness in this particular habitat due to its increased survival and reproduction rate. The color of the prey is heritable as shown by color A prey only reproducing color A offspring, color B prey only reproducing color B offspring, and color C prey only reproducing color C offspring. If this experiment is done with the other habitats it is apparent that the color of the prey compared to its habitat is important to survival. The adaption of color is called cryptic coloration. The ability to camouflage, or blend in to its habitat, is a great asset for survival. This visual representation demonstrates the advantage of adaptations as well as the qualifications to be considered an adaptation.





Credit to Dr. Alec Lindsay for the lab