SC.912.L.15.13 - Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success.

Teacher Demo: Natural Selection Sim

-Teacher could set up a very vague example of their own and show the class the experimental procedure, making note of each individual job the group members will have to be responsible for (timing, recording, fishing, etc.)

Goldfish Lab

Objective: Using inquiry skills, students will design hypotheses, experimental tests, and conduct behavioral observations to test if/how goldfish make adaptive decisions about forming schools.

Subject: Biology/Life Science

Audience: High School or Middle School

Time Required: 4 (or 5) full periods (40-50 minute periods)

Brief Overview

            Students will work in groups to investigate adaptive schooling behavior of goldfish. One goldfish will be placed in the middle of a Tupperware tank. On each side of the tank, there will be a jar, and within the jars the students will place one of five things, depending on which hypothesis they decide to test: a small school of goldfish, a large school of goldfish, no fish, white paper, or orange paper. Students will then monitor how much time the goldfish that was placed in the middle of the tank spends near each of the jars. By doing this, the students will determine if goldfish prefer to associate with other fish, with larger schools, or with colored paper that resembles the color of the fish.

The study of animal behavior provides a wonderful tool to teach about adaptation and natural selection, and this experiment teaches students how to design and implement an experiment.

Learning Objectives

1)      To understand how the forces of natural selection give rise to adaptive traits.

2)      To understand that there is a great amount of individual variation in nature, upon which natural selection acts.

3)      To understand that behavior is just like any other trait that natural selection can act upon, and that natural selection gives rise to adaptive behaviors.

4)      Gain experience with the scientific method by actively deciding upon a research question, and by formulating a prediction or hypothesis.

5)      Gain experience designing experimental tests by learning about variables-of-interest, controls, repetition, and sample size.

6)      Gain experience analyzing data; learn statistical significance, and how to create a visual representation of their data (bar graph).

Background

Natural selection and behavior

Natural selection is easy to teach and easy to comprehend when we discuss the basics, for example, frogs with webbed feet can swim better, and thus webbed feet is selected for because it allows frogs to catch more food or to avoid predators. Or long necks in giraffes are selected for because the necks allow them to reach the leaves unavailable to other animals. These examples of the process of evolution by natural selection are very clear: there is individual variation, some individuals do better than others at survival and reproduction, and the traits are heritable.  Easy. 

Unfortunately, because it is so easy to grasp, I think it becomes a bit boring if nothing else is added.  The neat thing about teaching about animal behavior is that it allows you to take the lesson on natural selection to a much deeper level.  Behavior is selected upon just like the neck of the giraffe.  If some individuals behave in ways that increase their survival and reproduction, and that behavior has a heritable component, then the behavior will be selected for.  Interestingly, animals are not stuck with a set behavior; unlike the giraffe, which is stuck with a 7.5 foot neck, most animals are able to switch between many different behaviors depending on the environmental conditions.  Think of a fish, which is able to ‘decide’ the best behavior based on the social environment (do I maintain constant vigilance, or do I snooze for a bit).  Such ‘decision rules’ are what natural selection acts upon.  Any variation in how likely an individual is to switch from behavior A to B is subject to selection, and when you think about the variety of reactions an animal has to the diversity of environments it may encounter, the power behind natural becomes strikingly apparent.

Schooling

Animals gain many adaptive benefits by living in a group or school; one of these benefits is that animals in a school can more easily avoid predation.  For example, predation risks can be reduced if all animals in a school work together to scan for predators.  Imagine a school of 10 fish looking every which way for approaching predators; with their 20 eyes, they are going to have a much better chance than a lone animal would at seeing a predator who might be lurking nearby.  This is just one of the ways that being in a school can be much safer than being alone.

General Procedure from the Student’s Perspective

Working in groups of 2-4, students will decide on one of three hypotheses they wish to test.

These are their options:

1. Fish prefer to join a large school of fish, rather than a small school of fish.

2. Fish prefer to spend time near orange objects, rather than white objects.

3. Fish prefer to join a school, rather than be by themselves.

They will be encouraged to design their own experiment, however it is helpful to give them an example of how they could set it up, and then let them creatively alter your suggestion.

Everyone will have:

Aquarium divided into an X-side and Y-side (teacher will have to draw on aquarium with grease pencil)

A black garbage bag to wrap around the aquarium (Make sure to leave the side with the dividing line on it open so you can watch the fish!)

Test fish (labeled T on drawing below)

2 Jars

They will have a choice of what they want to put into the jars.  Depending on their hypothesis, they can put in the jars:

Orange or white paper

10 fish

5 fish

2 fish

1 fish

0 fish

	T

 

Here is the best way to perform the experiment (but you should encourage them to change it around if they need to in order to test additional hypotheses or it they think of improvements): As a fist step, they will place a jar with fish or paper on each side of the tank, then they will introduce a test fish (labeled T above) to the middle of the tank, and then they will count the amount of time their test fish spends in either the X or Y side of the tank.  Each trial will last 120 seconds (2minutes).  They will repeat the trials 6-10times. They will use a new test fish for each trial.  After all trials are completed, they will calculate the average amount of time their test fish spent on each side of the tank.

Each teammate will be assigned a different responsibility.  One person will count the amount of time the test fish spends on the X-side (will count seconds), the other person will count time spent on the Y-side, and the third will act as the data recorder.  The data recorder will listen to the other two teammates, and will write down the seconds the test fish spends on each side of the tank.  The data recorder will write these values on the Raw Data Table (see handout).

General Procedure from the Teacher’s Perspective

The teacher should be in charge of giving the students the appropriate numbers of fish for each jar.  The same fish will stay in the jars throughout all the trials during each class period.

The teacher should also be in charge of giving the students new test fish between each experimental trial.   Put the test fish in a Dixie cup with water, and give one fish at a time to each group. 

The teacher will be in charge of timing the two-minute trials.  It works best if the teacher has everyone in the class start recording the data at the same moment.  Tell the students to start, and at this moment, they should pour their test fish into the middle of the aquarium, and then after 2 minutes have elapsed, you can tell them to stop.

Students can be in charge of adding and removing the test fish from their aquaria.  Give each team a net to allow them to do this.  After each trial is over, the students can return the test fish to a resting tank.  Students should keep the test-fish that were previously used out of the main tank from where new test fish will be taken.  This is important so the same fish is not tested twice, and it is also nice to only use fish once so as to not stress them unduly.

Setup and equipment

Obtaining Rosy Red Goldfish

Pet stores sell Rosy Red Goldfish for <0.20 cents each.  150 goldfish are required for a classroom of approximately 25 students.  The total cost ~ $30.00.  The same fish can be used for many back-to-back periods without hurting the fish.  They are very resilient critters.

Maintaining the fish

Goldfish are quite easy to maintain in the classroom. Place them in a medium sized aquarium, or a large Tupperware bin. Make sure to aerate the water with a pump and air stone.  Water should be changed weekly.  Before you add new water to the aquarium, be sure to let the water stand for at least 24 hours to let the chlorine burn off; chlorine is the number one killer of aquarium fish.  Feed them once daily.

Additional equipment to purchase

You will need ~10 clear Tupperware bins to serve as aquaria (approx. 15”x10”x6”), 20 large mouth ball jars, grease pencil, ~10 small nets, Orange and white paper, Dixie cups.

Preparing the students

To assist students in developing their experimental methods, you should review the general rules of experimental design. Specifically, you should make sure the students know the variable-of-interest (number of fish in the jars, or color of paper in the jars), what data are to be collected (time spent on either side of tank). Also make sure to walk them through thinking about other factors that may affect the experiment. For example, they might want to try rotating the aquarium between each experimental trial. That way, if the fish has a side-preference (say it likes to hang out on the brighter side, near the window), you will be able to disentangle this preference from a preference for what is in the jars.)

Emphasize the importance of creating humane and ethical experiments that cause as little harm to these organisms as possible.

Data Analysis

Students will plot (bar-graph) the average amount of time the fish spent on each side of the tank on their worksheet. After each student has done this, have each student group plot their data on the whiteboard so results from different hypotheses can be compared and discussed. This is an appropriate time to discuss significance of the findings. You do not need to use statistical equations for this. Instead, you can simply discuss how much variability appears in the students’ results and how this affects how certain they can be about their findings. For example, if all of the student groups found that their fish spent more time on the same side of the tank, that finding is more certain than if the results varied considerably from one group to the next.

Schedule for Curriculum Implementation

Day1:  Discuss natural selection and adaptive behavior, and then design the experiment on

paper by drawing the experimental setup, and by writing a sequential list of experimental steps

Day2:  Set up experiment; begin to collect data (perform 2-4 trials)

Day3:  Re-set up experiment; collect data (perform 4-8 additional trials).  Note: you may

need one additional period in order to collect enough data.

Day4:  Graph data; present results; discuss different hypotheses

Assessment Strategy

Students will have to design an appropriate test of the hypothesis they choose, and the experimental test must have two important components: only the variable-of-interest should be changed between the experimental trials, and the students should implement an appropriate control.  Students will also be assessed on their ability to work in a group to collect data, to share data, and to collaborate and come up with a conclusion about the behavior of the fish.   Students will also have to design an appropriate bar-graph, and to generate and interpret their results.  All of these can be assessed via the worksheets.