Introduction to Biology
Measurement
Conversion between units
Kilo (k)
103
1,000
Hecto (h)
102
100
Metric Prefixes
Deca (da) Base Unit
Deci (d)
1
10
Meter
10-1
10
Gram
0.1
Liter
Centi (c)
10-2
0.01
Milli (m)
10-3
0.001
When moving from one unit to the other, remember this:
- when you move to the right, the numbers get bigger because you multiply
- when you move to the left, the numbers get smaller because you divide
Example: How many centimeters is 3.5 hectometers?
Moving from hectometer to centimeters is to the right 4 times (104 = 10,000). So
multiply 3.5 x 104 or 3.5 x 10,000 = 35,000
Answer: 3.5 hm = 35,000 cm
Example: How many kilometers is 4.15 decimeters?
Moving from decimeters to kilometers is to the left 4 times (104 = 10,000). So divide
4.15 / 10,000 = .000415
Answer: 4.15 dm = .000415 km
Mean, Median, Mode
Mean = the average of a set of numbers
Median = the middle value when the values are ranked in numerical order
Mode = the value that occurs most often in a set of numbers
Example: An experiment has the following data collected: 5, 7, 3, 7, 7, 5, 9
Mean = 43 / 7 = 6.1428
Median = 7 (3, 5, 5, 7, 7, 7, 9)
Mode = 7 (the number 7 occurs the most often, 3 times)
Significant Figures
Addition and Subtraction
When measurements are added or subtracted, the number of decimal places in the
answer is equal to the number of decimal places in the measurement with the smallest
number of decimal places.
Example: If you add 1.23 and 4.567, you get an answer of 5.797. However, 1.23 and
4.567 have different number of decimal places.
Answer: Since there is no third decimal place in 1.23, the answer of 5.80 only has two
decimal places and thus three significant figures. (Rounding up or down rules apply)
Multiplying or Dividing
When multiplying or dividing measurements, the answer should have only as many
significant figures as the value with the fewest significant figures.
Example: A density calculation is made in which a mass of 5.31 g is divided by a
volume of 22 ml. The calculator output is 0.241363636 g/ml.
Answer: There are three significant figures in the mass but only two significant figures
in the volume measurement. Therefore, the density should have two significant figures
= 0.24 g/ml
Scientific Notation
= a shorthand way to write very large or very small numbers as a product of a number
times a power of 10
Example:
To convert from standard form to scientific notation
Standard Form
Scientific Notation
720, 000
7.2 X 105
5 decimals to the left
Exponent is 5
0.000291
4 decimals to the right
2.91 X - 4
Exponent is -4
To convert from scientific notation to standard form
Scientific Notation
Standard Form
7
4.63 X 10
46, 300, 000
Exponent is 7
7 decimals to the right
1.08 X 10 – 6
Exponent is – 6
0.00000108
6 decimal places left
Characteristics of Living Things
1) Cells
- all living things are composed of cells
2) Organization
- highly organized at molecular and cellular levels
3) Energy Use
- use energy in a process called metabolism
4) Homeostasis
- all living things maintain stable internal conditions
5) Response to Environment
- all organisms must respond to environment to survive
6) Growth
- all living things grow and develop
7) Reproduction
- essential for the continuation of a species
Steps to Scientific Thinking
Observing  Forming Hypothesis  Testing Hypothesis  Analyzing Data 
Evaluation Results
Independent Variable = a condition in a experiment that is changed or manipulated
Dependent Variable = observed or measured changes during an experiment
Qualitative Data = descriptions of the dependent variable
example: colors, sounds, yes or no
Quantitative Data = numerical measurements of the dependent variable
example: size, mass, frequency, temperature, rate