ESEB Natural Selection UnitVanderbilt University Inclusivity in the Biological Sciences

Introductory Lesson 1-2Learning objectives 2

Evidence of learning 3

Learning plan 3-4

Materials list 4

Step-by-step protocol 4-6

Guided Follow-Up Discussion 6-7

Troubleshooting 7

Modifications 8-9

Introductory Lesson1) What is natural selection in the context of evolution?

a) Lesson plan: Define natural selection for the students and ask for examples.b) Sample answers: Natural selection is the process where organisms that are best

suited to their environment survive and pass on their genetic traits in increasing numbers to the next generations. At the same time, organisms that are less adapted fail to survive or multiply at a lower rate. One famous example is Darwin’s study on finches in the Galapagos islands. He found that finches with different beaks were good at eating different foods. Finches with big beaks could break open and eat nuts, while finches with long beaks were good at catching insects. An example that students may be more familiar with is breeding dogs.

2) What is fitness and how does it relate to natural selection?a) Lesson plan: Ask students to define fitness and brainstorm factors that can

influence the advantage of a particular trait. Then ask them to describe how fitness and natural selection are related.

b) Sample answers: Are they a more attractive mate? Do they survive better than their peers? Do they have better access to food and nutrition? Natural selection works to select traits that allow for the most offspring to be produced for the next

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generation. So, natural selection is a way for nature to select the fittest individuals for survival.

3) What are the factors contribute to fitness of a population?a) Lesson plan: Ask them this question, think pair share, and then discuss with the

class.b) Sample answers: Genetic variation, inheritance of the trait, high rate of

population growth, and differential survival and reproduction4) What are some examples of natural selection?

a) Lesson plan: Provide a couple of case studies of natural selection. For example, Darwin’s finches would be a good case study to prepare the children for the game. Another example could be the peppered moth, which had a dark coloration selected for because of the industrial revolution darkening trees from pollution. Other examples are dog breeding and the development of antibiotic resistance in bacteria that are exposed to antibiotics.

Learning ObjectivesEstablished goals: Teach students the process of natural selection by mimicking the natural selection that may have occurred for Darwin’s finches.

Students will understand that…a. Variation in physical traits means that some individuals are selected over others in the

populationb. Evolution occurs through generations of natural selectionc. Environmental changes can influence natural selection

Students will know…a. How to define natural selection.b. Why genetic variation is important to natural selection.c. How to observe natural selection as a process by which evolution occurs.d. What happens to populations when natural selection changes due to environmental changes

Students will be able to…a. Explain how natural selection influences evolutionary change

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Evidence of LearningPerformance tasks: [What do we want the students to do to allow the teacher to assess if they understand the content?] Build data collection into the simulation and have students calculate mean, median, mode of the amount of food collected. They could use these calculations to graph the distribution of each “beak’s” ability to gather food. This could be followed up by discussion questions on the data, like questions about alternative scenarios and how they would affect the data.

Other evidence: Between rounds, ask the students to describe which “beaks” are better adapted for a given type of food and therefore more positively selected.

Pre- and post-assessment (ask students these questions before the lesson and afterwards): Correct answers in bold.

1) What is a generalist?a. A person in the militaryb. A living thing that can live anywherec. A living thing that can eat many kinds of foodsd. A person who studies many animals

2) What is a specialist?a. An animal that eats one specific kind of food onlyb. An animal that is picky about what food it eatsc. An animal that eats the same kind of food as other animalsd. An animal that can easily adapt to many foods

3) How could natural selection favor a “generalist” vs. a “specialist”?a. An animal that can eat many kinds of food gets better nutritionb. An animal that eats special foods will have less competitionc. Natural selection would not favor a generalist over a specialistd. A generalist can turn to alternative foods when one type disappears, while a specialist

cannot4) Natural selection acts on traits that affect an animal’s ability to survive. (True or False?)

Learning PlanHook their interest: Introduce, briefly, evolution and natural selection. It is recommended to follow the introductory lesson plan at the beginning of this document.Introduce essential question(s): How does natural selection work? What is required for natural selection to work?Equip students with ideas/vocabulary: Fitness, evolution, reproductive rate, genetic variation etc. For older groups include mutation as a vocab word and go over famous case studies like Darwin’s finches. Run simulation exercise: Protocol below

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Assessment: Use assessment questions above and guided discussion questions below.

Materials List1 1lb bag of black beans (included)

Scraps of paper (included)

30 Chopsticks (included)

30 Spoons (included)

30 Forks (included)

30 Binder clips (included)

30 Plastic cups (included)

Timer (not included)

Step-by-Step Protocol

Before you play:

1. Define the playing area: Create an open space on the floor or on a table where the “food” (represented by the beans or scraps of paper) can be laid out. Separate students into groups of ~10 and assign them to a “feeding area” of roughly 4’ by 4’. Each student will be given a nest box (cup) where they will need to put their food and they should be placed at the farthest

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corners/edges of the area. Food should be placed evenly in the middle. Each student should have to cover similar/same distances between food and the cup.

2. Prepare the playing area: Within the feeding area, place ~100 items of food (beans or scraps of paper) in the middle of the area. Be sure to spread out food items so that students will be able to have space to pick up food. Make the students place their nest boxes on the border of the feeding area.

3. Prepare the students: For each group, distribute the different utensils (forks, spoons, chopsticks, or binder clips), which represent “beaks,” evenly. If the number of students is not divisible by 4, give the more cumbersome “beaks” for the remainders (binder clips or chopsticks). For example, in a group of 10, 2 spoons, 2 forks, 3 binder clips, and 3 chopsticks. The students are to leave their “beak” in the nest until everyone is ready to start.

4. Explain the rules: a. Only the utensil can touch the foodb. Only one hand should be using the utensils to pick up food (see chopstick

troubleshooting)c. Only one piece of food can be picked up at a timed. The food only counts as collected if placed in your nest. If it is dropped before reaching

the nest, then leave it and go after another piece of foode. No dragging, sliding, or rollingf. If you mistakenly break a rule, put the food backg. Hands in the air with the “beaks” until the game begins and hands in the air when the

timer goes off at the end

Playing the game:

1. Set a timer for 45 seconds. 2. At the beginning of each round, tell the students to grab their utensil and raise their hands in

the air so they’re away from the food to start.3. When you yell “start”, the students will begin placing food into their nest boxes using their

assigned utensil.4. The round is over once the timer sounds. 5. Tell the students to count up how much food they were able to put into their box6. For each group, figure out the top two food collectors and the bottom two food collectors. 7. Explain that the bottom two collectors were outcompeted and therefore didn’t bring back

enough food to lay eggs and died off. Those two collectors will then be given the utensils of the top two collectors (if the top two are different utensils, randomly assign). This simulates the ability of the best food collectors to have offspring and spread in the population, while unsuccessful ones do not reproduce. Now can be a time for discussion on what happened (see below).

8. Reset the playing area by having the students reintroduce their food into the playing area.9. Repeat steps 1-8 one or two more times

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10. After the 2nd or 3rd round, discuss what the different populations look like. Have any “beaks” gone extinct? Which “beak” was most selected for and why?

11. If there is extra time, create a new scenario mimicking an environmental change. For example, say that there has been a dry season and only paper food has grown and no beans are left. Now, collect the beans and replace the food with scraps of paper.

12. Collect all the utensils and again distribute them evenly.13. Repeat steps 1-10 with the scraps of paper food.14. Repeat the game with two kinds of food at once. Assign students to one, the other, or both and

see how they survive over time (generalists vs specialists).

Guided Follow-Up Discussion

The following are some suggested questions to help the class understand the concepts from additional angles and so that they think more critically about the natural selection game they played. Teachers may elect to use any, all, or none of these or to add or modify them however they see fit. If you want to, you can ask them a question below and then simulate it by playing the game again with new rules that fit the scenario.

1. Can you come up with an environmental situation in which natural selection changes? Why? How could this change animal populations?

a. What would happen if a certain kind of food didn’t grow anymore?b. What if all of a certain food type was eaten and there was nothing left but another food

type?c. What if there were a new type of food introduced that wasn’t there before?d. What would you expect if there were multiple kinds of food around? What if only one

kind disappeared?2. Why is mutation such a fundamental part of natural selection? Can natural selection exist

without mutation or variation? Why?a. How do mutations and natural selection relate to each other?b. If all individuals were the exact same, with no variation, what would happen if they were

selected against?3. The X-Men are fictional characters with mutations that give them special abilities. For example,

Storm is a character who can manipulate weather and temperature. What is necessary for abilities (traits) like hers to be selected for and spread across the human population? Which mutations would be selected for? What kinds of traits would not?

a. What are some superpowers you can think of?b. Are they advantageous to the person or not?c. Based on your answer, do you expect their trait to be more or less likely than average to

be passed on in the population and spread?

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d. Are there any powers that would not be helpful to increase reproductive fitness?4. Darwin first observed natural selection in bird beaks. If you look up different bird beaks and food

types online, have students match the bird beak to the type of food they think it eats and ask them to explain why they think a kind of beak matches a type of food.

5. What would happen if there were more than one kind of food? For example, beans and paper? What would happen if some of the students specialized in one kind and other students could use both?

a. It may be good to ask them to make predictions and then run the exercise to see what happens.

b. Go over the terms generalist and specialist6. An old saying claims that "a jack of all trades is a master of none." Explain this concept with

reference to the bird beaks.7. The type of bird with the best rank in a particular environment will eventually outcompete all

others and drive them out of that environment. Why does natural selection in a stable environment favor specialists?

8. What is the advantage of being a generalist? How can generalists compete against specialists? (Hint: think about unstable or changing environments. Where are environments most stable? Compare the tropics and the poles.)

9. Where would you expect to find more species? In a complex environment with many food types, or in a simple environment with only a few food types? Why?

TroubleshootingProblem Solutions

Kids with chopsticks are not collecting anything. Allow them to use two hands so they can wedge the beans between the two sticks. You may also have them rubber band one end of the chopsticks for easier grip.

More than two kids tie for the lowest amount of food collected.

Have a “final showdown” with the tied kids having 15 seconds to pick up the most food

Kids are picking up too much food. Have the kids move their “nests” farther away so they have to carry their food a longer distance.

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Modifications

Modifications to add difficulty (for older students, such as high schoolers, or those who want a challenge)

Solutions

Add another color of bean (i.e. pinto beans) With two colors of beans, you can put down a white tablecloth with large black circles on it. When both sets of beans are poured onto the tablecloth, the black beans can blend well into the circles. This can add the aspect that the food or prey can also undergo selection. Over several rounds, you can show that the pinto bean will be picked up more than the black beans. This can be adapted to any kind of object that blends in with the table or floor surface that is being used. Alternatively, or additionally, randomly assign people to only one kind of “food” and put out more of one “food” than another, or put out only a limited amount of food to simulate competition and specialization vs. generalization.

Make the students design four different “beaks” to play the game.

Instead of using the spoon, fork, binder clip, or chopsticks, have the students make four other “beaks”. The students could also be split into 4 groups to design a beak. When the game is played, the class can see which beak is better designed for the food.

Modifications to simplify (for younger students, such as elementary schoolers, or students less familiar with the subject)

Solutions

Use only one type of food Students may feel lost if different foods are introduced. Just use the beans for a few rounds to show the concept.

Have the students play more than once. To reinforce the concepts, allow the students to play a second time with the other side of the plate, this time with another beans. Then, you

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can ask the students before each round what should happen and why.

Modifications for different class sizes Solutions

Groups of 1-10 Have only one group, though the game should be played with 5 or more people to be able to show the concept well. Modify the rules so only the bottom gatherer receives the top gatherers type of utensil

Groups of 10-20 Either one group or two will work for the game. If there is only one big group (over 15), then the bottom three gatherers will receive the top three gatherer’s utensils.

Groups of 20 or more I would suggest splitting these groups into size of roughly 9-12 people with the normal instructions.

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