TEDDY GRAHAM NATURAL SELECTION



Teddy Graham Lab:

Read all INFORMATION below as you complete the Lab:

Natural selection is the process in which organisms that are best adapted to a set of environmental conditions will survive long enough to reproduce. By reproducing, these organisms will pass the successful genetic information to the next generation. Those organisms that are not as well adapted are more likely to die before they have a chance to pass on their genes. The overall composition of the population will change as the survivors with the more beneficial genes or adaptations produce more offspring.

As you read through the Lab you will be given a series of assignments that must be done on your paper to ensure you are reading as you are told to do so. I have learned that throughout the year my students are not reading, so those of you who do read and complete the required assignments will receive a higher grade. Do not tell anyone in your group what is going on, just do all the assignments correctly and you will get full credit for the lab.

Natural selection is sometimes referred to as “survival of the fittest”. (Write the phrase “survival of the fittest” above your name on the student date sheet) The organisms that are best adapted will be the parents of the next generation. It is important to note that the organisms do not adapt to their environment. (Draw a flower on the back bottom right hand corner of your student data sheet, in the square provided) For example, in a desert setting, narrow leafed plants survive at a higher rate than broad leafed plants. The narrow leafed plant is better adapted to the dry environment because it does not lose as much water through its leaves. The broad leafed plant would lose too much water and die before reproducing. The broad leafed plant can’t adapt to the desert environment. The narrow leafed plants DO NOT “become adapted”, rather they possess adaptations that make them better suited for survival. (Draw a cactus on the back bottom left hand corner of your student data sheet, in the square provided) An adaptation is an inherited trait that gives an organism possessing that trait a reproductive advantage. When natural selection is occurring, those organisms that possess the adaptation survive at a higher rate than those that do not possess the adaptation.

PURPOSE

In this activity, you will simulate the events of natural selection. The population experiencing natural selection in this simulation is a population of bears. There are two kinds of bears – happy and sad bears. 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 impossible to catch.

MATERIALS

Teddy Grahams

Paper towels or napkins

Calculators

PROCEDURE

1. Read the follow directions carefully:

You are a bear-eating monster. You like happy-bears because they taste sweet and are easy to catch. Sad bears are not part of your diet because they are bitter, sneaky, and impossible to catch. For this reason, 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 last year.

2. Form a hypothesis about what you expect to happen to the number of Happy and

Sad bears over time. Write your hypothesis in the space provided on the student data sheet.

3. Establish your generation 1 population of bears by having one partner reach in the box, without looking, and randomly select 20 bears.

4. Place the 20 bears on a clean paper towel. Count how many happy and sad bears are present. Record your numbers for generation 1 on the student data sheet (Table 1)

5. Simulate predation by choosing 5 happy bears from the population and eating them. If you only have 3 or 4 happy bears, eat them first and then consume enough sad bears to meet your quota. For example, if you have only 3 happy bears, eat them and 2 sad bears. Remember – you prefer the happy bears.

6. To simulate reproduction in the population, close your eyes, reach into the bag, and choose 5 bears to add to your paper towel. This should bring the total number of bears to 20

7. Record the number of happy and sad bears that are now present in generation 2 in your table.

8. The other partners should now take a turn at being the predator. The predator should eat 5 happy bears from the population. If there are not 5 happy bears, follow the procedure in step 5.

9. Simulate reproduction in the population by repeating step 6. Count the numbers of each type of bear in the replenished population and record the data for generation three in your table.

10. Repeat steps 8 and 9 one more time for a total of 4 generations of data.

11. Determine the percentage of happy and sad bears for each generation and record the percentages in Table 2. To determine the percentage take the number of happy or sad bears and divide by the total number of bears for that generation and multiply the answer by 100. For example, if there were 12 sad bears and 8 happy bears in a generation, then there were 20 bears total. To obtain the percentage of sad bears you would divide 12 by 20 and then multiply the answer by 100. To obtain the percentage of happy bears you would divide 8 by 20 and then multiply the answer by 100.

12. Create a line graph on what happens to the bear population. Graph the number of bears for each generation for both the happy and sad bears on the same graph using a different color for each type of bear. Put the number of bears as the dependent variable on the y-axis (every line represent a bear) and the generations as the independent variable on the x-axis (Every 6th line a generation). (Starting with 0) (Make sure to include a key and label your graph).

13. Create a pie graph using the percent data for both the happy and sad bears for each generation. In the graph put the % of each bear population and use the same two colors you used to represent the happy and sad bears in the line graph.

14. Answer the questions after completing the graphs.

STUDENT DATA SHEET NAME________________________

NATURAL SELECTION PERIOD: ____ DATE_________

WITH TEDDY GRAHAMS

HYPOTHESIS

_____________________________________________________________________________________

DATA

Table 1. The number of bears for each generation

|Generation |Number of |Number of |Total Population |

| |Happy bears |Sad bears |of Bears |

|1 | | | |

|2 | | | |

|3 | | | |

|4 | | | |

Table 2. The percentage of bears for each generation

|Generation |Percentage of Happy bears |Percentage of Sad bears |

|1 | | |

|2 | | |

|3 | | |

|4 | | |

Line Graph of Generation vs Number of Bears

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

For each generation create a pie graph below: (Put in the % of each bear then color the happy and sad bears the same color used in the line graphs).

QUESTIONS

1. What was the adaptation of the variation that gave the individual an advantage over the other in the population?

2. Explain why this adaptation was an advantage.

3. What was the selective pressure (i.e. types of selection) (disruptive, stabilizing or directional) that created the advantage of one version of the trait compared to the other version of the trait and why?

4. What happened to the percentage of each type of bear over time?

a) Happy?

b) Sad?

5. How does this compare with your hypothesis?

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Key

Key

Generation 1

Generation 4

Generation 3

Generation 2

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