Using the Scientific Method and the Metric System

How Do Biologists Study Living Things?
Scientific Method
•Observation: objective notation of a phenomenon
•Hypothesis: question that can be tested by experimentation
– Experiment
– Data Collection
– Conclusion
•Supported Hypothesis
•Theory: hypothesis supported by repeated testing
•Principle: theory supported over a long period of time

• Observation
– Behavior of snail
– Anatomical description using microscope
• Hypothesis
– Are large or small snails faster?
– Are warm or cold snails faster?

Use BOTH eyes
Set at 1X to start
Use to increase image size
Adjust to focus
Turn light on
Put your snail here
(clean off later!)
Observations with a Dissecting Microscope

A scientific measurement system where quantities differ by factors of 10.
Length
Meter (m)
Weight
Gram (g)
Volume
Liter (l)
Centimeter (cm)
100 cm = 1 m
Millimeter (mm)
1000 mm = 1 m
10 mm = 1 cm
Milligram
1000 mg = 1 g
Milliliter (ml)
1000 ml = 1 liter

Metric Measurements in Today’s Lab
Length
Ruler Scale
Weight Volume
Graduated cylinder using water displacement
Centimeter (cm) and tenths of cm
Ex. 5.3 cm
Grams and tenths of a gram
Ex. 8.6 grams
Milliliter (ml)
Ex. 11 ml

Length
Ruler
Centimeter (cm) and tenths of cm
Ex. 5.3 cm

Weight
Scale
Grams and tenths of a gram
Ex. 8.6 grams

Volume
Graduated cylinder using water displacement
Milliliter (ml)
Ex. 11 ml
Hint: Measure your snail’s volume after the races to keep him/her moving at optimal speed!

• Average = sum of distances number of measurements
• Significant figures
– Consistent with the smallest unit on the measuring device
– Eg. 2.43 cm, should be reported as 2.4 cm
– Round up if next number is 5 or above

3
2
1
0
6
5
4
Small Medium
Snail Size
Large
Warm
Cold

• Complete pages 7-13 from lab manual
• Be sure your instructor checks your completed worksheet before you leave the lab

Make sure your lab station and the surrounding benches look the same way they did when you arrived!

• Return your snail to the aquarium
• Empty and rinse graduated cylinders
• Rinse and dry watch glasses
• Leave glassware, rulers, string in a neat arrangement at your station
• Clean your work area
• Clean microscope stage, cover and return microscope to cabinet