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Lab #2: Scientific Method & Pond Water - Introduction

Part 1. Listen to the radio story at the link below: https://www.npr.org/sections/deceptivecadence/2012/01/02/144482863/double-blind-violin-test-can-you-pick-the-strad

Part 2. Read the article below.

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Part 3. Take a look at the following organisms and then write a sentence describing how you can distinguish each organism from others on the page.

Cyanobacteria – blue green bacteria

Merismopedia

http://cfb.unh.edu/phycokey/Choices/Cyanobacteria/cyano_colonies/MERISMOPEDI

A/Merismopedia_Image_page.html

Nostoc (Anabaena looks very similar)

https://en.wikipedia.org/wiki/Nostoc

http://fmp.conncoll.edu/Silicasecchidisk/LucidKeys3.5/Keys_v3.5/Carolina35_Key/M

edia/Html/Nostoc_Main.html

Oscillatoria

http://fmp.conncoll.edu/Silicasecchidisk/LucidKeys3.5/Keys_v3.5/Carolina35_Key/M

edia/Html/Oscillatoria_Main.html

https://botit.botany.wisc.edu/botany_130/diversity/bacteria/Oscillatoria.html

Green algae

Volvox

https://en.wikipedia.org/wiki/Volvox

Chlamydomonas

http://cfb.unh.edu/phycokey/Choices/Chlorophyceae/unicells/flagellated/CHLAMYDOMONAS/Chlamydomonas_Image_page.html

Spirogyra

https://www.dreamstime.com/stock-photo-freshwater-algae-spirogyra-sp-ready-

used-to-make-food-image71349708

http://protist.i.hosei.ac.jp/PDB/Images/Chlorophyta/Spirogyra/group_C/sp_07.html

Oedogonium

http://protist.i.hosei.ac.jp/PDB/Images/Chlorophyta/Oedogonium/sp_1d.html

Gonium

https://en.wikipedia.org/wiki/Gonium

protists

Euglenoids – [protist] uniclelluar flexible cells with red eyespot and flagella Diatoms – [protist]

Euglena

http://protist.i.hosei.ac.jp/pdb/images/mastigophora/euglena/gracilis/gracilis_1b.html

Phacus

http://fmp.conncoll.edu/Silicasecchidisk/LucidKeys3.5/Keys_v3.5/Carolina35_Key/Me

dia/Html/Phacus_Main.html

Assorted species

https://en.wikipedia.org/wiki/Diatom

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Team

Members:

Lab #2: Scientific Method & Pond Water

Scientific experiments often try to determine the effect of one thing (the independent variable) on something else (the dependent variable) by conducting a controlled experiment. In a controlled experiment, only one thing is changed between two groups. The experimental group is the same as the control group except that the experimental group also receives the one independent variable being tested by the experiment.

1. Match the terms on the left with the definition on the right. Use any resource you like.

Dependent variable

Independent variable

Confounding variable

Controlled variable

Experimental group

Control group

a. the data that is observed and measured.

b. the only variable that is intentionally changed between two groups; the variable that is being tested.

c. factors other than the one that is deliberately varied that might also affect the outcome of the experiment.

d. factors that might alter the outcome of the experiment but that are eliminated from consideration because they are deliberately kept constant across all groups.

e. the group that receives the independent variable.

f. the group that does not receive the independent variable.

2. Read the “knuckle cracking experiment” from the course website (under “cool science” tab).

What was the independent variable in this experiment?

What was the experimental group in this experiment?

What was the dependent variable in this experiment?

What was the control group in this experiment?

Describe a confounding variable that was controlled?

Describe a confounding variable that was not controlled?

Do you believe the conclusions of this study – do you feel confident that you could crack your own knuckles and without increasing your risk of arthritis? Explain your answer.

Imagine that instead of the experiment described, the researcher had (1) cracked the knuckles on both hands for 50 years, and then (2) observed developed arthritis in both hands. Would this experiment demonstrate a connection between knuckle cracking and arthritis? Explain your answer

3. Listen to the “Double-blind violin test” from the course website (under “cool science” tab).

What is meant by a “double-blind” study? Why is it important that this study be double-blind?

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Practicing the Scientific Method

Observation: Water quality affects the type of organisms that grow within it. Complete the table below.

Ecosystem type Example of this ecosystem

Sample #

Write down the genus of some of the organisms you saw, then estimate the number

of each organism within the field of view

How many different types of creatures did you see?

natural,

unpolluted lake

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Diatoms: Unknown genus #1 (~10) Green algae: Volvox (~5) Chlamydomonas (~5) Spirogyra (~20) Oedogonium (~10)

Group 1: Group 3: Group 5:

Group 2: Group 4: Group 6:

Average: ______

Water contaminated by

nitrogen-rich fertilizer

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Group 1: Group 3: Group 5:

Group 2: Group 4: Group 6:

Average: ______

Water contaminated by toxic chemicals

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Group 1: Group 3: Group 5:

Group 2: Group 4: Group 6:

Average: ______

Water contaminated by organic pollution

(e.g. sewage)

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Group 1: Group 3: Group 5:

Group 2: Group 4: Group 6:

Average: ______

How do natural, unpolluted ecosystems differ from contaminated ecosystems? Question: Now, what about the water retention ponds on the SFC campus…are they healthy ecosystems?

Hypothesis:

Prediction: Write down a testable prediction based on your hypothesis. If [hypothesis], then [ X ].

Test: 1. Collect water sample from a SFC retention pond. 2. Prepare a wet mount of water sample from the SFC retention pond. 3. Observe multiple replicates of water samples with a compound microscope. Results:

How many different types of creatures did each person see in the SFC retention pond sample?

Write down the genus (and number) of the organisms seen in the retention pond sample.

Team Member A: Team Member C:

Team Member B: Team Member D:

Team Average: _____

Conclusion: Compare the results from the SFC water sample with observations from other ecosystems:

Your results support / reject (circle one) your hypothesis.

Critical Thinking: Do you believe enough data was collected for your conclusion to be reliable? Explain briefly.

What are indicator organisms?