Chapter 2: Measurements in Biology (The Metric System and Data Analysis)

International System of Units (SI)

Metric System

Metric System

Devised in 1700’s during French Revolution to replace chaotic collection of units. Goal to produce single measurement system bases on the decimal/base 10 system as opposed to franactions

Measured observations

More powerful than simple descriptive ones. need to measure or cut

US Metric

1 mi = 1750 yd = 5280 ft = 63,360 in

Metric values

1 km = 1,000 m = 100,000 cm = 1,000,000

meter m

length

liter L

volume

kilgram kg

weight

Celcius

Temperature

water freezes

0

20-24

room temp

37

human body

100

boiled water

Units of time are NOT decimal

sec, min, hr, day

G,M,k,h,da,u,d,c,m,micro,n

9,6,3,2,1,0,-1,-2,-3,6,9

Density

M/V (in g/mL)

Liquid containers

Hold liquid, can help approximate volume but not precisely

Large volumes (50-1000 mL)

bottles, beakers, Erlenmeyer flasks

Smaller

conical and glass tubes

Tiny

Microcentrifuge/eppendorf tubes

Accurate measurements Large

graduated cylinder

Smaller

Pippettors with glass pipets

Tiny

Micropippetors

Statisitics

Measure a small sample instead of everything

n

sample number, how many measurements you have

statistical measure of average values

mean and median

Statistical measure of how data varies

range, variance, and standard deviation

mean

average of values

median

value in middle of data set

range

difference between high and low

variance

sum of squared deviations from mean divided by n-1

standard deviation

square root of variance