The Scientific Method and the Ecology of Ants

Andrew J. Penniman
2000

Objectives:

1.   Make and describe scientific observations.
2.   State a hypothesis based on one's own observations and/or information from the literature.
3.   Define and use the elements of a good experimental design: experimental variable,
      controls or constant variables, quantification.
4.   Design an experiment to test this hypothesis.
5.   Collect, interpret, present, and discuss data in writing.
 


INTRODUCTION

      In this laboratory exercise, we will discuss and practice using the scientific method.  This is, in fact, a process you have used all your life; it is simply a process of learning by trial and error (understanding that "error" is not necessarily a mistake).  The scientific method formalizes one way people learn throughout their lives.  Let's review the steps:

1. Observation:  This is simply being aware of, and curious about, what goes on in the world around us.  At one level, observation is a basic survival skill; we are taught from infancy to look both ways when we cross a street.  Scientists are no different, but they have been trained (or train themselves) to pay attention to phenomena others might overlook or think unimportant and to carefully record their observations.

      Thinking through what has been observed, a scientist tries to relate what has been seen (or heard, felt, smelled) to other observations, either his/her own or observations of others. A scientist will often consult books and articles in scientific journals (literature) in an effort to pull together all information that has a bearing on his/her observations.  Often, one tries to find cause-and-effect relationships between observations.
 

2. Proposing a hypothesis:  A hypothesis is a statement that explains what has been observed within the context of current knowledge.  (Some textbooks characterize a hypothesis as an "educated guess."  It is NOT; a scientist doesn't guess.) A person practicing science reasons that if the observations I know of are true, and connected as they seem to be, then [state a hypothesis here] should be true.  Most importantly, the hypothesis must be testable; that is, further observations, often by experiment, must be able to show the hypothesis to be true or false.   Scientists have no special claim to this step though they may formalize it by writing down the facts and reasoning they've used to arrive at this statement.
 

3. Test of the hypothesis:  Here the scientist tries to find those observations that will prove his/her hypothesis wrong.  This must seem paradoxical after expending so much mental energy making observations and coming up with a hypothesis.  But the hypothesis is drawn up "within the context of current knowledge."  Making more observations that confirm what we think we know may only reinforce our ignorance.  Science makes progress, we learn something new, when we prove what we thought we knew was wrong; then some other idea is closer to real truth.

      A hypothesis may be tested by simply continuing to observe, but with a sharpened idea of what to look for (astronomers can do little else).  Most often though, a scientist realizes that many factors in nature other than the one stated in the hypothesis may have influenced the observations. Then, one designs an experiment to limit the test to the one experimental variable.  In an experiment the experimental variable is allowed (or even caused) to vary and all other factors are held constant or controlled (controls).  Then, any resulting effect can be attributed to the experimental variable.

      A well-designed experiment specifies the materials and quantities used to do the experiment and allows or demands that results be quantified.  Then the scientist can state not only that an effect happened, but how much of an effect.  A small effect, or a minor difference between effects, may suggest the experimental variable does influence the original observations, but some other variable (one of the controlled variables) has a more significant effect.  In preparing to do an experiment, a scientist thinks carefully about how the results will be measured or quantified.
 

4. Result of the test:  Carrying out a test of the hypothesis and careful gathering of data* produces the results.  Ideally, the results verify or confirm the hypothesis or show the hypothesis to be incorrect.  In either case, the scientist is not done.  If the hypothesis was verified, one tries again (and again and again ) to test and falsify the hypothesis.  To do the same test again could only be expected to verify the hypothesis in the same way, so the scientist tries to devise a more rigorous test, or to find a way to measure the variables more precisely.  If the hypothesis was falsified, the scientist must try to understand how and why the hypothesis failed to predict the result and then state a new hypothesis (and then test that one again and again ).  Theoretically, one could get into an infinite loop with no logical exit.  As a practical matter, how far a scientist goes in testing hypotheses depends on his/her time and energy.

This word "data" is tricky.  It is actually a Latin plural.  It is thus wrong to say,  "This data is "
Instead, it is correct to say, "These data are "  That sounds funny to most people, and most journalists
and even some scientists get it wrong.  Now that you know, you will get it right.

      During this lab exercise, you will use observation, scientific curiosity, and investigational skills to learn something about the ecology of ants.  (Ecology refers to the branch of biology dealing with the interactions of organisms [ants] with their environment.)  You will have at your disposal many species of ants, several types of food (bait), meter sticks, and an outdoor laboratory (the school campus or your yard).  Using these materials and/or others you provide, each student or group of students is to design and carry out an experiment.  This will then be written up as a lab report to be turned in on the date assigned by your instructor.
 


METHODS & MATERIALS

      The class and the instructor should discuss what you (as a group) already know about ants.  Unless you have lived all your life in Antarctica or on the Arctic tundra, you must have seen ants.  Think about where and when you've seen some and what they were doing.  Some questions the class might discuss are:
  1.  What are ants?  What other animals are like ants?  In what way are they alike?
  2.  Ants live in groups called colonies or nests.  Who are the members of a colony and what
are their social/biological roles?  How does a colony grow?  How are new colonies
produced?
  3.  How do ants forage for food?  What have you and classmates seen ants eating?
What foods are nutritious for ants?
  4.  How do ant colonies interact with other colonies of the same or other species?

Notes:  Observations or background material.
 
 
 
 
 
 
 
 

      Based on these observations and/or background material from the instructor, each lab group should discuss and develop a hypothesis.  Remember that the hypothesis must be testable and you should discuss how you will test it.  Some questions that may lead you to a hypothesis are:

Do ants have food preferences or do they forage on any food available?  Do ants choose the most nutritious food or the tastiest?

Do different ants live in different habitats?  How many different kinds can be found in a habitat?  (Closely related species of ants may be similar in size and color, but if they look different they should be different species.)

How long does it take for a "scout" to recruit other members of the nest?  Does the time depend on distance to the nest, temperature, nature of the bait, or some other factors?

What species interactions can be observed?  If two or more species compete for food, what happens?

How far from the nest do workers forage?  Does the maximum distance depend on size of ant, temperature, or some other factors?
 

Suggested materials:

             meter sticks, 15 cm rulers, index cards, wooden splints, top loading balance,
 

Carbohydrates              Fats                Proteins                   Complex foods

sucrose (table sugar)      cooking oil       canned tuna               peanut butter
molasses                        lard                 canned chicken          cheese
cane syrup                     shortening       egg white                    mayonnaise
glucose                                                                                  ketchup
fructose
honey
corn starch
saltines
cereal

Other

aspartame (artificial sweetener)
saccharine (artificial sweetener)
Tabasco sauce
mustard
 

Hypothesis:
 

      Now it is time to use your ingenuity to develop a test for your hypothesis.  Remember, the most effective experiments are well controlled, in other words they are designed so that all factors are the same (constants), except for the one experimental variable.  For example, you may alter the food choice(s) available, or the distance that food is from the nest, but you would not want to alter both those variables in the same trial.  Plan your experiment and write out your procedure below.  This should be the exact procedure that you will use.  In good science, experiments are replicated (repeated) several times to confirm that the results were not simply a coincidence.  You should plan to repeat your experiment in at least two places, or with at least two species of ants, or on at least two dates.

What is your experimental variable?
 

What factors or variables will be kept constant?  (It is hard to think of everything, but consider how you will present baits to the ants.  For example, if you place baits on index cards, the index card becomes a variable--you should offer the ants an empty [control] card to see if it is the card itself that attracts ants.)
 

How will you gather data?  How often? (Will you watch the ants continuously, or will you check at regular intervals to see what they're doing?  What will the intervals be?)  How long will each experimental trial last?
 

How many times will you repeat this experiment?
 

Your procedure:
 
 
 
 
 

      Run your experiment and collect your data.  Do not discard, change, or "fudge" on any of your observations.  Use measurable quantifiable factors that can be presented in graph or table form.

      Depending on time available and the nature of your hypothesis you may or may not be able to test your hypothesis today. You might also try testing your hypothesis and find a need to change the hypothesis or the test methods.

      Different lab groups do different things.  Some groups meet on campus and carry out their test together.  Other groups are unable to meet together, so they agree on a procedure which each member carries out at home (or wherever), and they share data later.  This requires that all understand the details of the procedure.  Other groups find themselves unable to work together, so each individual decides on a hypothesis and tests it by him-/herself.  Any of these alternatives is OK as long as every student participates and can write his/her own paper.
 
 

Analyze your results and form some conclusions.  Do your data support your hypothesis?

Were there any variations (inconsistencies) in the observed behaviors?

Were there any surprises?
 
 

Explain.
 
 
 

If you were to do this experiment again, what new hypothesis might you make?  Where there any factors that might have inadvertently affected the outcome of your experiment?  What are the implications of your results?  How might this information prove useful?  When writing up this lab, follow the scientific paper format in the format preferred by your instructor.
 

Some Useful References:

Goetsch, Wilhelm.  1957.  The Ants.  University of Michigan Press, Ann Arbor.

Holldobler, Bert, and E.O. Wilson.  1990.  The Ants.  Belknap Press of Harvard University Press,
 Cambridge, MA.

Holldobler, Bert, and E.O. Wilson.  1994.  Journey to the Ants. A story of scientific exploration.
Belknap Press of Harvard University Press, Cambridge, MA.