There are many different units that can be used for measurements. This may not only lead to incorrect data measurements, but also to confusion about which units are most appropriate. Therefore, a standard set of units is used for each type of measurement in the biology lab.

## Using Standard Units

Take a look around you – you are surrounded by a variety of objects that come in all shapes and sizes.

There are likely just as many ways that you can measure each of these objects. You can measure their lengths, the area they take up, their volumes, masses, weights, even their densities.Each of these measurements also has many possible units. For example, you can measure length in feet, yards, inches, meters, miles, and kilometers. Volume can be measured in units such as liters, ounces, and cubic centimeters. Can you see how this gets very confusing very quickly? If you didn’t have a standard unit for each of these, you’d end up doing a lot of converting between them.

And each time you convert, you lose some accuracy in your measurement because you probably round the numbers a little as well.So what’s a scientist to do? Well, we certainly can’t NOT measure things; that’s a key component of working in the biology lab. Collecting and analyzing data requires accurate and understandable measurements, so in order to ensure the best data collection possible, we use a standard set of units called the **metric system**. Most other countries in the world use the metric system for their measurements, and any good biological data should be measured using these units, regardless of the types of measurement you are taking.

## Types of Measurement Units

You may or may not already be familiar with the metric system, but the good news is that, even if you have never seen it before, it’s quite simple to use.

There are specific units to use for each type of measurement, so you never have to guess at which one will be best. Let’s take a look at which units in the metric system are standard for the different types of measurements you’ll encounter in the biology laboratory.First let’s start with length. In biology, the standard unit of this type of measurement is the **meter**, represented by a lower-case ‘m.

‘ In general, a meter is about the same as 3 feet, but not exactly. It’s more like 3.28 feet, but even that is a rounded number. Think that 0.28 feet isn’t important? It may not be for one meter, but if you have 10 meters and you round off that 0.

28 feet each time, you end up rounding a total of 2.8 feet away – and that’s almost an entire meter!Area is also measured in meters because area is squared length. So if you have an area that is 3 meters by 5 meters, your area is 3m x 5m, or 15 m^2.

Interestingly, though the definition of the meter has since been changed, the length of a meter was originally intended to represent one ten-millionth of the distance on Earth from the equator to the North Pole!The standard unit for volume is the **liter**, represented by an upper-case ‘L’. One liter is about the same as 33 ounces, but again, not quite. A more accurate conversion is 33.81 ounces in each liter, or about 4 cups.

See how quickly this gets messy? This is exactly why we stick with one unit for each type of measurement, in this case, the liter.For mass (which is NOT an object’s weight!) we use the standard unit of **kilogram**, represented by the letters ‘kg.’ Think of a quart of milk and that’s the amount of mass you’re looking at here. We don’t use pounds because this represents **weight**, which is actually the force due to gravity. Mass is the amount of matter an object has, weight is how much force that object is being pulled to the earth with. This is an important distinction, because if you went to the moon, you’d weigh less because there is less gravity there.

However, you’d still have the same mass because no matter where you go, you’re still made of the same amount of ‘stuff’ known as matter.Finally, we measure temperature using **degrees Celsius** in the biology lab, represented by the degrees symbol and a capital letter ‘C’ (;C). Converting between Celsius and Fahrenheit is not as simple as we have seen with the other units of measurement, and we need an equation to help us understand this one. To convert from Fahrenheit to Celsius, we use the equation ;C = (;F – 32) x 5/9. If you want to have the temperature in ;F, you convert from ;C through this equation: ;C x 9/5 + 32.The other important thing to keep in mind is that Celsius is a capital C because it is named after Swedish scientist Anders Celsius, who proposed the original Centigrade scale.

This scale was named as such because it has 0 being the freezing point of water and 100 being its boiling point, and the prefix ‘centi’ means ‘100.’

## Lesson Summary

It’s easy to see why having a standard set of units is important in the biology lab. If one person measures length in meters, and one person measures it in feet, you could end up having measurements that don’t quite match. Rounding units is a dangerous game because every time you round, your measurements become less accurate, and, after enough small rounding, this can add up to a big difference!Having standard units like the **meter**, **liter**, **kilogram**, and **degrees Celsius** allows scientists to communicate effectively and efficiently.

When standard units are used, there’s no need for tricky conversions, and this greatly reduces miscommunications and errors, making scientific measurements as accurate and clear as possible.

## Learning Outcomes

Upon completing this lesson, you should be able to:

- Explain why it is important to have a standard set of units for scientific measurement
- Identify the standard measurement units for length, volume, mass, and temperature
- Discuss the potential for error when having to convert between units of measurement