Snail lab prep notes William and Tell broadcast system Table on chalkboard: Name Wt (g) warm spd (cm/m) cold spd (cm/m) Hand out by size-class, then designate limits of size classes based on actual weight data, e.g., <3.5g, 3.6-6.5 g, >6.5g).

Snail races lab Read pages 1-3 in lab manual Soundtrack for William and Tell Overture

Part 1: Background: The Metric System and the Scientific Process

The Realm of Science By its nature, science deals with detectable things in nature Undetectable or supernatural phenomena fall within the realms of philosophy and religion

Experimental or Hypothetical-deductive (H-D) Science Used for most modern research Follows the Scientific Method Procedures that ensure reliable conclusions Sometimes abbreviated as O.H.E.C. Number of steps can vary

Scientist observes some phenomenon Step 1: OBSERVATION (O.) Scientist observes some phenomenon Considers it unique or worthy of investigation Give example

Step 2: HYPOTHESIS (H.) A TENTATIVE EXPLANATION for the phenomenon; a “scientific guess”

- Hypothesis is accepted or rejected Step 3: EXPERIMENTAL TESTS (E.) EXPERIMENTS: re-creation of the phenomenon under controlled conditions Methods recorded, therefore replicable - Certain FACTORS or INFLUENCES are manipulated - E.g., set to high, medium, and low - Tests are conducted - Analysis Usually involves statistics because data are normally samples - Hypothesis is accepted or rejected Need 2 examples, with different designs

Interpretation of results Step 4: Conclusions (C.) Interpretation of results What do the results mean? The step most subject to bias Scientific peers might interpret results differently

WIDELY-RECOGNIZED explanations SCIENTIFIC THEORIES WIDELY-RECOGNIZED explanations Based on lots of evidence, scientific tests Many individual studies E.g., gravity, evolution Example of theory vs hypothesis

Objectives of today’s lab: 1) Practice taking measurements in the metric system 2) Test the influence of body size and temperature on snail speed

Procedures: Lab procedures in general: Bring a small calculator – or mobile phone Work in 4-person groups Most of today’s lab will be individual work Each person will hand in a worksheet

The Metric System Why is the metric system considered more convenient? Based on multiples of 10 10 millimeters = 1 what? centimeter 10 centimeters = 1 what? decimeter 10 decimeters = 1 what? meter

Linear measures What does linear refer to? a straight line What increment is numbered on the metric scale of your plastic ruler? A centimeters is about the width of a fingernail What is the smallest metric increment on your plastic ruler? What is the total length of your ruler in cm? In mm? What increment is numbered on the English scale of your plastic ruler?

This? This? This? This? This? This? What is this?

What is half of a 16th? Half of a 32nd? Fractions of an inch also have decimal equivalents: 1/4 = 1 ÷ 4 = 0.25

Weight measures Also multiples of 10 in the metric system: 1 kilogram = 1,000 grams 1 gram = 1,000 milligrams English system: __ oz = 1 lb 16 2,000 ____ lbs = 1 ton

Volume measures How would you define the volume of something? The 3-D space it occupies Volumes of cubes are straightforward E.g., 1 cm3 = 1 cm x 1 cm x 1 cm How would you determine the volume of a snail? By Displacement of Water Start with any amount of water Submerge the snail Record the increase in total volume

The top is curved up on the sides Read the meniscus from the bottom The top is curved up on the sides Water adheres to the plastic Read here Meniscus Adhesion

Final point on the metric system Universality: Conversions can easily be made between lengths, volumes, and weight: 1 ml of water (at “STP”) = 1 cm3 of water = 1 g of water

Accuracy: degree of agreement between a measured value and the accepted value.  Precision: extent to which a set of measurements agree with their mean

Take a snail of the size provided by the instructor To lift snails, drag them sideways Small snails have thin shells – don’t squeeze Determine range of sm, md, and lg categories (e.g., <3, 3-6, >6) Name your snail

Measure your snail’s width and length Measure first using centimeter scale of your ruler Then use inch scale, recording in fractions What is a numerator?, denominator? Actually measured Calculated from left to right For calculation, 1-1/16 = 17/16 (for example) No “naked decimals”: e.g., .02 -> 0.02, 5 -> 5.0

Weigh your snail Must “tare” the scale so weight of “weigh-boat” will be ignored i.e., do not include weight of weigh-boat 1) Place empty boat on scale 2) Press tare button 3) Place snail on boat 4) Record weight

Measure your snail’s volume by displacement of water Choose an appropriate sized cylinder larger diameter than your snail Start with enough water to fully immerse the snail Increments on cylinders are in milliliters

Part 2 The races (experimental tests): Propose your hypotheses: 1) the influence of size on speed 2) the influence of temperature on speed 5 warm races, 60 seconds each 5 cold races, 60 seconds each Return to ice after each race

Part 3, observation (respiratory pore) (smell) (touch)