AP Biology
Graphing
Graphing is an important practice used by scientists to display the data that is collected during a controlled experiment. When a graph us put together incorrectly, it detracts the reader from understanding what you are trying to present. Most graphs contain 5 majorparts:
a.The Title – depicts what the graph is about. Reading the title gives the reader an understanding about the graph. A good title is closer to a sentence than a phrase and is usually found at the top of the graph.
b.Independent Variable – the variable that can be manipulated by the experimenter. Common independent variables include time, length / depth and temperature, to name a few. This variable is placed on thex-axis.
c.Dependent Variable – the variable that is affected directly by the independent variable. It is the result of what happened because of the independent variable. Example: How many oxygen bubbles are produced by a plant located at different depths below water. The number of oxygen bubbles will depend on the depth of the water. This variable is placed on theY-axis.
d.Scale – before you can plot your data points, you must figure out how much each box on your graph paper is worth. Scale doesn’t always have to start at zero, but it must be consistent. If you start off making each box worth 5 cm, each subsequent box must also be 5 cm. Always make sure your scale is labeled with the units of itsmeasurement.
e.Legend (or Key) – a short description about the graph’s data. Most often used to show what different patterns or colors represent on yourgraph.
A few rules and tips forgraphing:
1.Always use a pencil to draw your graph! (unless you useExcel)
2.Always draw lines with a ruler – do not freehand! Use the entire piece of graphpaper.
3.If you are graphing multiple subjects, use different colored or patterned lines, and explain what they are in yourlegend.
4.Choose an appropriate graph to present yourdata:
a.Line – when the independent variable is numerical and continuous. Example: measuring a change in something overtime.
b.Bar – when the independent variable is not continuous or when each comparison has only one data point. Use when you cannot show a gradualchange.
c.Pie – show percentages that add up to 100% (rarelyused).
Graphing Exercise1:
Two types of plants, A and B, were placed under water at various depths. The following table gives the number of oxygen bubbles that the plants released perminute.
Depth(meters) / Bubbles per minute Plant A / Bubbles per minute Plant B2 / 29 / 21
5 / 36 / 27
10 / 45 / 40
16 / 32 / 50
25 / 20 / 34
30 / 10 / 20
1.What are the independent and dependent variables? Why did you pick thesevariables?
2.Which type of graph would be best for this set of data?Why?
3.Which would be a good title for thisgraph?
4.What information would you include in the legend of yourgraph?
5.What will you label the X and Yaxes?
6.Draw the graph, following the providedguidelines.
7.Describe the graph in words: how did each plant change in thisexperiment?
8.Explain the results of this experiment, as best youcan.
Graphing Exercise2:
Background: Diabetes is a disease affecting insulin producing glands of the pancreas. If there is not enough insulin being produced by these cells, the amount of glucose in the blood will remain high. A blood glucose level above 140 mg/ml for an extended period of time is not normal. This disease, if not brought under control, can lead to severe complications and evendeath.
I.Use the following data to create an appropriate graph and answer the questions thatfollow.
Time after eating (inhours) / Blood Glucose (mg/ml) PersonA / Blood Glucose (mg/ml) PersonB0.0 / 140 / 140
0.5 / 180 / 230
1.0 / 195 / 220
1.5 / 190 / 205
2.0 / 185 / 190
2.5 / 182 / 180
3.0 / 180 / 160
4.0 / 175 / 150
II.Describe the changes in glucose levels after a meal for person A and personB.
III.Which individual would you potentially diagnose as a person with diabetes? What evidence do you have to support youranswer?
IV.If the time period was extended to 6 hours, what would be the expected blood glucose level for person A, and for person B? (assume they did not eat again during this timeperiod).
USE GRAPH PAPER ONLY (Available on a separatefile)
Graphing Exercise 3: Interpretinggraphs
In addition to being able to draw a graph based on collected data, you will also need to interpret data given to you in graph form. Answer the following questions, based on the presented graphs. Note: Most of these are not examples of great graphs, they are for interpretation practiceonly.
Identify the graph that matches each of the followingstories:
1.I had just left home when I realized I had forgotten my books, so I went back to pick themup.
2.Things went fine until I had a flattire.
3.I started out calmly, but sped up when I realized I was going to belate.
Graph v describes a typical day of a teenager.Answer:
4.What percent of the day is spent watchingTV?
5.How many hours in a day are spentsleeping?
6.Which activity takes the least amount oftime?
7.Which activity takes up a quarter of theday?
8.Which two activities together take up 50% oftheday?,
9.Which two activities together take up 25% oftheday?,
Answer, based on graphvi:
10.How many total miles did the cartravel?
11.Describe the motion of the car between 5 and12:
12.Which direction is represented by lineCD?
13.How many miles were traveled in the first two hours of thetrip?
Answer, based on graphvii:
14.What is the total freshman enrollment of thecollege?
15.What percent of the students are majoring inphysics?
16.How many students are majoring ineconomics?
17.How many more students major in PolySci thanPsych?
Graphing Exercise 4: Choosing the right graph Read the review about graphs (in a separatefile).
1.When is a circle graph more appropriate than a bargraph?
2.The population of 100 large African animals in a zoo are listed in the chart below. Construct a circle graph that indicates the percentage each animal is of the totalpopulation:
Line Graphs: Examine the graph of the population of the United States from 1880-1990 (Page 2 of the reviewreading).
3.Determine the approximate population of the USin:1935,1945,1985
4.Predict: what would be the population size of the United States in2010?
BarGraphs:
7.When do you need to use bar graphs, rather than a linegraph?
8.According to the precipitation graph in Hartford CT (page 3 of the review reading), how many centimeters of rain fell in Hartford on April11?
9.Can you see trends in the data set? If so – whichtrends?
10.Can a bar graph show a trend, even if the data are not continuous?Explain.
11.Can the bar graph be used to predict precipitation in Hartford on April 7th? Why or whynot?
Graphing Exercise 5: Choosing the right graph –cont.
12.In 1989, the US department of the interior reported that there were 360 endangered species of plants and animals in the United States. These endangered organisms included 32 species of mammals, 61 species of birds, 8 species of reptiles, 5 species of amphibians, 45 specie3s of fishes, 3 species of snails, 32 species of clams,8speciesofcrustaceans,10speciesofinsects,3speciesofspiders,and153speciesofplants.
Construct a graph that will compare total numbers of plants versus animals in1989.
13.Of the total number of endangered species (continued from question 12), 151 were vertebrates (mammals, birds, reptiles, amphibians, fishes). Construct a graph that will compare between the different types of vertebrates that areendangered.
14.After an outbreak of influenza, a student gathered data on the number of students who became ill,until she became sick on the 14th day of her study. The information she gathered is given in thetable.
Plot the data in agraph.
15.On which day were the most of thestudents ill?
16.during which period of time did the most of the studentsill?
17.What was the greatest number of students who were ill on any singleday?
18.Estimate the total number of students who were ill on the 15thday.