A meter is the standard for length in the metric system. Akilogramis the stan-
dard for mass in the metric system. Agramuses the same prefixes as a meter to
specify the number of grams that are represented by a value. For example, a kilo-
meter is 1,000 meters and a kilogram is 1,000 grams. This makes it a lot easier
to learn the metric system since the number of grams and meters are indicated
by the same set of prefixes.
Table 3-2 contains a list of various ways to express a gram. You’ll notice that
this table contains two prefixes that were not used in Table 3-1. These are deka-
and hecto-. The prefix deka- means 10 and the prefix hecto- means 100. That’s
10 grams and 100 grams.SIZING UP MICROORGANISMS
How small is a microorganism? You are probably asking yourself this question
after learning the metric system of measurement. The answer depends on the
kind of microorganism that you are measuring. As you’ll remember from
Chapter 1, there are two general categories of microorganisms. These are pro-
karyotes and eukaryotes. Fig. 3-1 illustrates the relative size of a microorganism
when compared to other things.(^50) CHAPTER 3 Observing Microorganisms
Prefix Value in Grams
Kilo (kg) 1,000 g
Hecto (hg) 100 g
Deka (dag) 10 g
Gram (g) 1 g
Deci (dg) 0.1 g
Centi (cg) 0.01 g
Milli (mg) 0.001 g
Micro (μg) 0.000001 g
Nano (ng) 0.000000001 g
Pico (pg) 0.000000000001 g
Table 3-2. Units of Mass in the Metric System