Representing and Applying Data

Interpreting Scientific Illustrations

As you read this textbook, you will see many drawings, diagrams, and photographs. Illustrations help you to understand what you read. Some illustrations are included to help you understand an idea that you can't see easily by yourself. For instance, we can't see atoms, but we can look at a diagram of an atom and that helps us to understand some things about atoms. Seeing something often helps you remember more easily. The text may describe the surface of Jupiter in detail, but seeing a photograph of Jupiter may help you to remember that it has cloud bands. Illustrations also provide examples that clarify difficult concepts or give additional information about the topic you are studying. Maps, for example, help you to locate places that may be described in the text.

Captions and Labels

Most illustrations have captions. A caption is a comment that identifies or explains the illustration. Diagrams, such as the one of the feather, often have labels that identify parts of the item shown or the order of steps in a process.

Learning with Illustrations

An illustration of an organism shows that organism from a particular view or orientation. In order to understand the illustration, you may need to identify the front (anterior) end, tail (posterior) end, the underside (ventral), and the back (dorsal) side of the organism shown.

You might also check for symmetry. Look at the illustration on the following page. A shark has bilateral symmetry. This means that drawing an imaginary line through the center of the animal from the anterior to posterior end forms two mirror images.

Radial symmetry is the arrangement of similar parts around a central point. An object or organism such as a hydra can be divided anywhere through the center into similar parts.

Some organisms and objects cannot be divided into two similar parts. If an organism or object cannot be divided, it is asymmetrical. Regardless of how you try to divide a natural sponge, you cannot divide it into two parts that look alike.

Some illustrations enable you to see the inside of an organism or object. These illustrations are called sections. Look at all illustrations carefully. Read captions and labels so that you understand exactly what the illustration is showing you.

Making Models

Have you ever worked on a model car or plane or rocket? These models look, and sometimes work, much like the real thing, but they are often on a different scale than the real thing. In science, models are used to help simplify large or small processes or structures that otherwise would be difficult to see and understand. Your understanding of a structure or process is enhanced when you work with materials to make a model that shows the basic features of the structure or process.

In order to make a model, you first have to get a basic idea about the structure or process involved. You decide to make a model to show the differences in size of arteries, veins, and capillaries. First, read about these structures. All three are hollow tubes. Arteries are round and thick. Veins are flat and have thinner walls than arteries. Capillaries are small.

Now, decide what you can use for your model. Common materials are often best and cheapest to work with when making models. Different kinds and sizes of pasta might work for these models. Different sizes of rubber tubing might do just as well. Cut and glue the different noodles or tubing onto thick paper so the openings can be seen. Then label each. Now you have a simple, easy-to-understand model showing the differences in size of arteries, veins, and capillaries.

What other scientific ideas might a model help you to understand? A model of a molecule can be made from gumdrops (using different colors for the different elements present) and toothpicks (to show different chemical bonds). A working model of a volcano can be made from clay, a small amount of baking soda, vinegar, and a bottle cap. Other models can be devised on a computer. Some models are mathematical and are represented by equations.

Predicting

When you apply a hypothesis, or general explanation, to a specific situation, you predict something about that situation. First, you must identify which hypothesis fits the situation you are considering. People use prediction to make everyday decisions. Based on previous observations and experiences, you may form a hypothesis that if it is wintertime, then temperatures will be lower. From past experience in your area, temperatures are lowest in February. You may then use this hypothesis to predict specific temperatures and weather for the month of February in advance. Someone could use these predictions to plan to set aside more money for heating bills during that month.

Sampling and Estimating

When working with large populations of organisms, scientists usually cannot observe or study every organism in the population. Instead, they use a sample or a portion of the populate for research. By making careful observations or manipulating variables with a portion of a group, information is discovered and conclusions are drawn that might then be applied to the whole population.

Scientific work also involves estimating. Estimating is making a judgement about the size of something or the number of something without actually measuring or counting every member of a population.

Suppose you are trying to determine the effect of a specific nutrient on the growth of black-eyed susans. It would be impossible to test the entire population of black-eyed Susans, so you would select part of the population for your experiment. Through careful experimentation and observation on a sample of the population, you could generalize the effect of the chemical on the entire population.

Here is a more familiar example. Have you ever tried to guess how many beans were in a sealed jar? If you did, you were estimating. What if you knew the jar of beans held one liter (1000 mL)? If you knew that 30 beans would fit in a 100-milliliter jar, how many beans would you estimate to be in the one-liter jar? If you said about 300 beans, your estimate would be close to the actual number of beans.

Scientists use a similar process to estimate populations of organisms from bacteria to buffalo. Scientists count the actual number of organisms in a small sample and then estimate the number of organisms in a larger area. For example, if a scientist wanted to count the number of microorganisms in a petri dish, a microscope could be used to count the number of organisms in a one square millimeter sample. To determine the total population of the culture, the number of organisms in the square millimeter sample is multiplied by the total number of millimeters in the culture.