Question

Pre-lab Activities

1. Practice the Scientific Method

Step 1. Observation. Write down something surprising that you noticed this week and you don’t understand. NOTE: if you can’t think of anything interesting that happened this week, you may use an example from any part of your life.

EXAMPLE: This morning I woke up and there was a dead raccoon on my front doorstep!

Observation(s):

This morning I woke up and the tree in me from the yard had fallen over.

Step 2 Question. Write down a question that you have about the observation from step one (what more would you like to know about what was observed?).

HINTS: As a rule, you want to think like a reporter and ask factual cause and effect questions – questions that begin with what, when, where, why or how. More subjective questions (e.g. concerning morality) may be better addressed by the application of philosophical or ethical principles and may be difficult (or impractical) to address using science alone. Aim for a question that is likely to have a definitive answer (even though you don’t know what the answer is). The more specific you make your question, the easier it may be to test.

EXAMPLE: What caused the raccoon to die?

Question(s):

What caused the tree to fall over?

When did the tree fall over?

Why did the tree fall over?

Step 3 Hypothesis. Propose an explanation for the observation. A hypothesis must be something that can be tested. IMPORTANT: you do not know ahead of time if this explanation is correct – the beauty of science is that even if your hypothesis is wrong that is OK!! It is often wise to initially create as many reasonable hypotheses (i.e. possible explanations) as you can and to start by testing the one you think is most likely to be true.

EXAMPLE: The raccoon had rabies.

Hypothesis:

The roots of the tree were damaged/weak causing the tree to fall.

Heavy winds last night caused the tree to fall.

Step 4 Investigation. Next design a way to test if your hypothesis is correct or incorrect. One way is to think about the implications of your hypothesis and use it to make predictions that can be tested. NOTE: you do not need to have the expertise to do the test you propose if it is possible. This is just a hypothetical scenario.

EXAMPLE: IF the raccoon died of rabies, THEN it should still have antibodies against the rabies virus in its bloodstream. TO TEST THIS, WE COULD test the raccoon’s blood.

Predictions of a hypothesis (IF… THEN…), and ways to test it (TO TEST THIS WE COULD…):

Step 5 Analysis

Normally you would conduct the experiment in step 4 and collect data. Discuss what data you might collect from your test(s) and how you would interpret it – remember you are trying to collect information that allows you to answer a question; try to think of all the possible results you might get from your test.

EXAMPLE: The raccoon’s blood test could come back positive indicating that it did have rabies, or it could be negative indicating that it died of other causes.

Analysis (POSSIBLE RESULT “X” WOULD MEAN…; POSSIBLE RESULT “Y” WOULD MEAN…):

Step 6 Conclusion

This is where you decide if, based on your data, your hypothesis is accepted or rejected. If accepted, we may want to run the test again or make new predictions and design new tests to verify that our hypothesis is supported. If rejected, may want to modify it or generate a different hypothesis. We don’t have real data yet so now let’s pretend the hypothesis is rejected. Come up with an alternative hypothesis.

EXAMPLE: If we find the rabies test was negative, this would mean our hypothesis is rejected. Another hypothesis that we could test is whether the raccoon was killed by an animal and dragged onto the porch.

Conclusion:       

2. Experimental Design

In order to make scientific investigations meaningful and to minimize bias, scientists must use well-designed experiments. It is vital to be aware of variables that could impact the results, use standards (i.e. controls) in order to validate results and keep an open mind to the possibility that a hypothesis may be supported or rejected.

The following scenario will be used to illustrate how variables, controls, and experimental design can be properly implemented in an experimental setting. Refer to this scenario to answer the questions below.

A team of doctors wants to find out if the daily consumption of olive oil affects breast cancer rates in women. Rationale: Olive oil contains oleic acid, a monounsaturated fat that lowers the levels of a protein produced by a breast cancer gene in women (Her-2/neu). The doctors hypothesize that increased consumption of olive oil will reduce the incidence of breast cancer in women.

Independent variable: a factor that is expected to cause an effect; manipulated by the experimenter.

1. What is the independent variable for the above scenario?

Dependent variable: a factor that changes as a result of the independent variable; a factor that you will measure.

2. What is the dependent variable for the above scenario?

Controlled variables: things that could interfere with experimental results; must stay the same for all groups in your experiment! There are often many controlled variables for an experiment.

3. What are the two controlled variables for the above scenario?

In addition to determining the independent, dependent and controlled variables for an experiment, the scientist must also determine exactly how to set up the experiment. This is called experimental design.

Experimental groups: individuals/subjects that experience the manipulated independent variable. An experiment might have just one experimental group or it could have multiple experimental groups.

4. For the scenario above, describe an appropriate experimental group.

Control group: Don’t confuse this with controlled variables! The control group consists of individuals/subjects that do not experience the manipulated independent variable. The control group allows for a conclusion that changes in the experimental group(s) caused by independent variables.

5. For the scenario above, describe an appropriate control group.

Lab Activity: Isopod food and smell preferences?

You will now proceed to apply the concepts you have learned to design your own scientific investigation. The subjects you will study are isopods (also known as pill bugs, potato bugs and sow bugs). You will work as a group to test the smell or food preferences of isopods. Be gentle while handling these animals since these are your experimental subjects and you do not want them to die. We also have a limited supply of pill bugs.

Figure 1: Isopods are a type of arthropod. Arthropods are animals that have jointed legs and an exoskeleton. Other arthropods include insects, spiders, and crabs. Isopods typically feed on decaying matter and sometimes live plants. Their bodies are dark gray to white and divided into a head, thorax, and abdomen. The abdomen is subdivided into seven segments, and they have seven pairs of walking legs. Isopods are often found in dark, moist places because they hide from predators and because they breathe through gills, which must be kept moist in order to exchange gasses with the surrounding air.

This is one question, for experiment Overview.
Working as a group, design an experiment to determine the food or smell preferences for the isopods. You will have several possibilities to choose from including food choice (crackers, cat food, apple) and smell preferences (various essential oils and spices).

The experiments will be carried out in an apparatus made of multiple experimental chambers connected by openings that allow the isopods to move from one to the next. You should give the isopods 2 options, placing one in each experimental chamber as shown below. In this investigation, you will be using a control chamber rather than a control group. The control chamber will not have any options placed in it and will serve as a reference to compare the preferences of the isopods. Designate the small middle chamber as the control chamber.

Using 10 isopods, you will give the isopods free access to all chambers for 10 minutes. Every minute, you will count how many isopods are in each chamber.

Experimental chamber 1 with Option 1 control Experimental chamber 2 with Option 2

1.   Design your experiment; complete the chart below for your experiment:

What question are you trying to answer with your experiment?

State your hypothesis.

If your hypothesis is correct, what do you predict will happen?

Independent variables (what you are testing)

Dependent variable (what you are measuring)

Controlled factors (things that are the same for all chambers)
Graph. Vertical horizontal

What is the control for this experiment?

2.   Set up your experiment. Obtain one chamber apparatus with 2 experimental chambers and a middle section. Place the options you are testing in separate chambers of the apparatus and place nothing into the small middle chamber.

When placing the options in the experimental chambers, follow these guidelines:
a.   Use small amounts of material placed throughout the experimental chamber rather than in one pile in the middle.
b.   Chop or grind food options so that the food is accessible to the small isopods.
c.   Control for the amount of material used. Use the scales to weigh out equal amounts of each option to place in each experimental chamber.

3.   Obtain ten (10) isopods from the instructor and place them in the control (middle) chamber. Use the supplied gates to block access to the experimental chambers. Cover the control chamber with the supplied lid for 5 minutes to allow the isopods to acclimate to their new environment. Be sure to place the lids on the experimental chambers before starting your experiment.

4.   After the acclimation period, track the isopods movement every minute for a total duration of 10 minutes. Record the number of isopods in each chamber at each time point in the table provided below.

Table of # isopods in each experimental chamber:
Time (min) 0, 1, 2 , 3 ,4 ,5, 6, 7, 8, 9, 10
Control
Option 1:
Option 2:

5.   After the 10-minute experimental period is over, carefully remove the isopods from the experimental apparatus and return them (gently!) to their terrarium.

6.   Clean up your experiment including cleaning out, drying and putting away the experimental apparatus. Throw away ground-up or chopped up food options as well as used filter paper.

7.   On the following page, make a bar graph of your results.

a.   Graph the number of isopods on the vertical (y) axis and the time (minutes) on the horizontal (x) axis.
b.   Your graph should include a title, labeled axes, and a legend.
Graph. Vertical horizontal
1to 10 vertical # of isopods chamber.
1to 10 horizontal minutes.

Post Lab questions:

1.   Based on your data, do you accept or reject your hypothesis? State your findings and refer to your actual data. If your hypothesis was rejected or if your data was inconclusive, that’s ok! It happens all the time in science and is part of the process (although not discussed much).

2. If you were to do this experiment again, what would you change about your experimental design? What would you keep the same?

Answer 1

PRE-LAB ACTIVITIES:

A)

STEP - 1: OBSERVATION

The milk got curdled up all of a sudden when i added it to my coffee.

STEP - 2: QUESTION

What makes the milk curdled up suddenly?

STEP - 3: HYPOTHESIS

The milk got curdled up because it is already at the verge of spoilage.

STEP - 4: INVESTIGATION

If the milk is already at the verge of spoilage then it's acidity level will be higher than the normal milk. To test this we can use pH meter to find the pH of the milk.

STEP - 5: ANALYSIS

The pH value of the milk after testing came back as 5.5 which is much lower than normal pH value 6.5. This possible result of low pH means the milk i added to coffee had more acidity than the normal milk.

STEP - 6: CONCLUSION

Based on the hypothesis and the analysis we can conclude that when the milk was just on the verge of spoilage and bacteria have produced some–but not enough–acid to curdle the cold milk, a little bit of extra acid from the coffee along with the heat caused the milk to curdle.