Laboratory Exercise 3 Balancing Chemical Equations Pillbug Behavior - PDF - PDF

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```					Name: General Biology Laboratory Exercise

Laboratory Exercise 3: Balancing Chemical Equations & Pillbug Behavior
1. Balancing chemical equations helps scientists understand changes in molecules that occur in organisms. Researchers determine the reactants and the products of a chemical reaction. The reactants are the starting molecules. The products are the ending molecules. The number of each type of atom (carbon, nitrogen, etc.) should be the same on each side of the equation. When the reactant molecules and the product molecules are known, all one has to do to balance the chemical equation is change the number of each molecule (the number in front of each molecule) to make the atoms of the reaction equal on both sides of the equation. Example: The process of aerobic respiration done by mitochondria in your cells starts with glucose (C6H12O6) and oxygen (O2) and ends up with carbon dioxide (CO2) and water (H2O). The small numbers after each letter indicate the number of each type of atom that make up the molecule. First, we will set up our reactants and products into the form of a chemical equation: C6H12O6 + O2 CO2 + H2O Our equation is currently unbalanced, with 6 carbon atoms, 12 hydrogen atoms, and 8 oxygen atoms on one side and 1 carbon atoms, 3 oxygen atoms, and 2 hydrogen atoms on the other side. To balance the equation we increase the number of each molecule. (DO NOT change the number of atoms within each molecule as that will change the reaction completely!) 6 CO2 + 6 H2O C6H12O6 + 6 O2 Now we have 6 carbon atoms, 12 hydrogen atoms, and 18 oxygen atoms in our reactants and the same number in our products. We have balanced the chemical equation! Now you try. Balance the following unbalanced equations. a. b. c. d. e. f. g. H2 O2 Zn + + Cl2 O3 HCl KCl F2 O2 + O2 SF6 Fe2O3 CO2 + 1 H2O + ZnCl2 O2 + H2 HCl

KClO3 S8 Fe C2H6 + +

Pillbug Behavior adapted from experiments developed by Harry Dilner Review the activity at following link before coming to lab (we will not be observing fruit fly mating behavior, but the remainder of the activity is appropriate): http://www.phschool.com/science/biology_place/labbench/lab11/intro.html I. Background Information 1. Ethology is the study of animal behavior. 2. Behavior is an animal's response to sensory input, and falls into two basic categories: learned and innate (inherited). 3. Orientation behaviors place the animal in its most favorable environment. If an organism responds to bright light by moving away, that is a taxis. If an animal responds to bright light by random movements in all directions, that is referred to as kinesis. 4. In taxis, the animal moves toward or away from a stimulus. Taxis is often exhibited when the stimulus is light, heat, moisture, sound, or chemicals. 5. Kinesis is a movement that is random and does not result in orientation with respect to a stimulus. 6. Biotic and abiotic factors are limiting factors that control the maximum size of a given population, thus an animal must search for an appropriate environment. This process is called habitat selection. II. Pillbug Facts 1. Many people mistakenly think that pillbugs are insects but these organisms are crustaceans (as are lobsters, shrimp, and crabs). Both insects and crustaceans are classified in a larger group known as the arthropods. Arthropods are animals with exoskeletons and jointed appendages. 2. Pillbugs are classified in a group of crustaceans known as isopods. About 4000 species of isopods have been identified. Most isopods live in marine habitats, some live in fresh water, and a few, including pillbugs, live on land in moist environments. 3. Some land isopods roll up in a ball or pill when disturbed, hence the term pillbug. Other names for pillbugs are sow bugs, wood lice, potato bugs, and roly-polies. We will use the terms roller to describe a pillbug that rolls up in a ball and hiker to describe a pillbug that runs when disturbed. 4. Because pillbugs breathe through gill-like structures, they must live in moist places. They prefer dimly lighted or dark habitats and live underneath rocks, logs, boards, leaves, etc. They eat decaying wood, leaves, and other vegetation. 5. Pillbugs are 5 to 15 mm long and have three body regions; head, thorax, and abdomen. Most of the exoskeleton consists of shield-like plates. The body is flattened laterally. Each of the seven pairs of legs is identical. There is one obvious pair of antennae, another inconspicuous pair of antennae, and one pair of compound eyes. 6. The young hatch from eggs that are carried in a brood pouch under the thorax of the female. The young are self-sufficient after hatching.

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7. Pillbugs grow by molting. They shed their exoskeleton and grow a new one. During molting pillbugs crawl out of the back half of the old exoskeleton first, and a few days later crawl out of the front half. 8. Pill bugs are safe to handle. They do not bite, sting, or transmit diseases to humans. They do not harm other plants or animals. They are not economically important, but they play an important role in decomposing dead plant material. III. Introduction to Pillbugs In this activity, you will learn some important aspects of pillbug anatomy and behavior. The knowledge and skills you acquire in this activity will be of help to you when you design and conduct your pillbug investigation. Materials Petri dishes Filter paper Spoon for collecting pillbugs Dissecting microscope for observations 50-mL beaker for water Procedure: Collect 40 pillbugs of fairly large size as directed by your instructor. Using the spoon and brush, place six pillbugs in the Petri dish. Work with these 6 pillbugs in answering the following questions. 1. Are your pillbugs hikers or rollers: How many hikers do you have? How many rollers? 2. What is the length in millimeters of your shortest pillbug? How long is your longest pillbug? 3. How many pairs of legs does a pillbug have? Do all of your pillbugs have the same number of legs? 4. How many antennae does a pillbug have? What do you think are the functions of the antennae? 5. How many eyes does a pillbug have? Are the eyes compound (many facets, like a fly’s eye) or simple? 6. Does a pillbug have an endoskeleton or an exoskeleton? How can you tell?

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7. Place a pillbug upside down on a piece of paper. Describe how it turns over.

8. What does a pillbug do when it comes to an edge where there is a drop off?

9. Can pillbugs climb up steep smooth surfaces like the edges of the Petri dish? Can pillbugs climb up rough surfaces like your arm? 10. Put a pillbug in a beaker of water for a few seconds. Take it out of the water and place it on the piece of paper. Observe it carefully and describe its behavior.

11. How fast can a pillbug run? Make an X in the center of the copy paper. Place the pillbug on the center of the X. Let it go and record the time in seconds that it takes the pillbug to run off the paper. Place another X where it left the paper. Measure the distance between the 2 Xs in centimeters. Calculate the speed of the pillbug in cm/sec. IV. Designing and Reporting an Investigation using Pillbugs 1. Brainstorm with your lab group about possible pillbug behavior you would like to investigate with regard to habitat selection. List 3 investigations, manipulating only one variable per test. All students will do a control group and the first two experimental tests. The control and all experimental tests will start with 10 pillbugs on each side, and see how many are on each side after 10 minutes. o Wet vs. Dry filter paper
o o

Light vs. Dark Petri dish Choose one more experimental test:

2. As you design and conduct each of your experiments, address each of the following questions. o How will the variables be controlled? o How will variables be measured? o How will variables be manipulated? o What equipment and supplies do I need? o Does my experimental design really do what it is supposed to do? o Will my experiment answer my question? o Have I identified all of the variables? o How many pillbugs will I use in the investigation? o How many times will I repeat the investigation? o Have I accounted for possible sources of error? o How might the pillbug behavior I am investigating affect the ability of pillbugs to survive in their natural environment?

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3. Pillbug Experiment 1:
o

Wet vs. Dry filter paper

Observations:

o

Hypothesis:

o

Prediction:

o

Test:

1. Controlled variables:

2. Control group:

Wet vs. Wet filter paper

3. Experimental group: Wet vs. Dry filter paper 4. Number of repetitions of this experiment:
o

Raw data: Control Data (class data) Experimental Data (class data)

o

Data analysis: 1. Control group (% on each side of control group):

2. Experimental group (% wet & % dry):

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o

Conclusions (Compare experimental group with control group):

4. Pillbug Experiment 2:
o

Light vs. Dark Petri dishes

Observations:

o

Hypothesis:

o

Prediction:

o

Test:

1. Controlled variables:

2. Control group: 3. Experimental group:

Dark vs. Dark Petri dishes Light vs. Dark Petri dishes

4. Number of repetitions of this experiment:
o

Raw data: Control Data (same as Experiment 1) Experimental Data (class data)

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o

Data analysis: 1. Control group (% on each side of control group):

2. Experimental group (% light & % dark):

o

Conclusions (Compare experimental group with control group):

5. Pillbug Experiment 3 (test only one variable):
o

Observations:

o

Hypothesis:

o

Prediction:

o

Test:

1. Controlled variables:

2. Control group: 3. Experimental group: 4. Number of repetitions of this experiment:

7

o

Raw data: Control Data (same as Experiment 1) Experimental Data (your data)

o

Data analysis: 1. Control group (% on each side of control group)::

2. Experimental group:

o

Conclusions (Compare experimental group with control group):

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