4.67

4.04

3.25

2.67

2.16

1.43

3528211470

-Time <days)^Maiit height (cm}^

Table 1 Experimental Datafor Plant Growth versus Time

USING GRAPHING SKILLS

INTRODUCTION:Recorded data can be plotted on a graph. A graph is a pictorial representation of information recorded in adata table. It is used to show a relationship between two or more different factors. Two common types ofgraphs are line graphs and bar graphs. In this investigation, you will interpret and construct a line graph

and a bar graph.

LINE GRAPHS:In laboratory experiments, you will usually be controlling one variable and seeing how it affects anothervariable. Line graphs can show these relations clearly. For example, you_mighl.perform an experiment inwhich you measure the growth of a plant over time to determine the rate of the plant's growth. In thisexperiment, you are controlling the time intervals at which the plant height is measured. Therefore, time iscalled the independent variable. The height of the plant is the dependent variable. Table 1 gives some

sample data for an experiment to measure the rate of plant growth.

The independent variable is plotted on the x-axis. This axis will be labeled Time (days), and will havea range from 0 days to 35 days. Be sure to properly label your axis including the units on the values.

The dependent variable is plotted on the >>-axis. This axis will be labeled Plant Height (cm) and willhave a range from 0 cm to 5 cm. Think of your graph as a grid with lines running horizontally from the y-axis, and vertically from the x-axis. To plot a point, find the x (in this example time) value on the x axis.Follow the vertical line from the x axis until it intersects the horizontal line from the^-axis at thecorresponding >> (in this case height) value. At the intersection of these two lines, place your point.

Figure 1 shows what a line graph of the data in Table 1 might look like.

Date: _

Class:BIOLOGY:

Name:

i

m

10Time Spent on Production Work

Figure 6

The data are represented accurately, but it is not easy to draw conclusions quickly. Remember that whenyou are creating a graph, you want the graph to be as clear as possible. If we graph the exact same data ona graph with slightly different axes, as shown in Figure 6, it may be much easier to draw conclusions.

31

Time Spent on Production Work

Figure 5Radii of the Planets

Figure 4

BAR GRAPHS:Bar graphs make it easy to compare data quickly. We can see from Figure 4 that Jupiter has the largestradius, and that Pluto has the smallest radius. We can also quickly arrange the planets in order of size.

Bar graphs can also be used to identify trends, especially trends among differing quantities. ExamineFigure 5 below.

figure 1

Numerical scale

//s/

Line Graph

PROCEDURE:

Part A. Interpreting Graphs:

1. The type of graph that best shows the relationship betweentwo variables is the line graph. A line graph has one or morelines connecting a series of points. See Figure 1. Along thehorizontal axis, or x-axis, you will find the manipulatedvariable in the experiment. Along the vertical axis or^-axis,you will find the responding variable.

5. Why is it important to have all parts of a graph clearly labeled and drawn?(l)

Explain the reason for your answer.(l)

4. Which type of graph would you use to show comparisons?(l)

3. Where do you place the manipulated variable on a line graph?(l)

2. How could you plot more than one responding variable on a line graph?( 1)

Explain why?(1)

ATM:To correctly interpret and construct a line graph and a bar graph.

PRE-LAB DISCUSSION:Read the entire investigation. Then answer the following questions.

1. Would a line graph or a bar graph be better for showing the number of birds of each color in a

population?(l)

Figaro 3

Figure 23. A bar graph is another way of showing relationships between variables. A bar graph also contains an x-axis

and a ^-axis.

But instead of points, a bar graph uses a series of columns to display„ , .data. See Figure 3. On some bar graphs, the ^-axis has labels rather thana numerical scale.

This type of bar graph is used only to show comparisons.

Plant 1Plant 2Plant 3

201015Time (Days)

its

-"' ^

SrowdiofPla

•' ^^' .•'

<

7/•''//.' J

/.>

0<

•s

| 4

na

1

10

12

2. Use the line graph in Figure 2 below to answer questions a through f below. (6)

f.How long did it take for plant 1 to grow 6 cm?

Part B. Constructing Graphs:

1. When plotting data on a graph, you must decide which variable to place along the jc-axis andwhich variable to place along the v-axis. Label the axes of your graph accordingly. Then youmust decide on the scale of each axis; that is, how much each unit along the axis represents. Scalesshould be chosen to make the graph as large as possible within the limits of the paper and still includethe largest item of data. If the scale unit is too large, your graph will be cramped into a small area andwill be hard to read and interpret. If the scale unit is too small, the graph will run off the paper. Scaleunits should also be selected for ease of locating points on the graph. Multiples of 1. 2. 5. or 10 are

easiest to work with.

Figure 44. Use the bar graph in Figure 4 (above) to answer questions a through e below. (5)

a.At birth, what is the average number of red blood cells per mm3 of blood?

b.What appears to happen to the number of red blood cells between birth and 2 months?

c What happens to the number of red blood cells between the ages of 6 and 8 years?

d.Between what ages is a human likely to have 4.6 million red blood cells?

e.After 14 years of age, do males or females have a higher red blood cell count?

Tlma

YearsMonths

(M)(4+

•

14+-it"

14;

128•>o.

4?

-cp;

1?to8*b4?Birth

!• ^

-*!

isIt^s?Si^^lif

i?

i?

5.0

4.9

4.6

4.7

464.5

0

Red Blood Cell Count During Human Growth

L _ _c

| i

ii

it z .i

_ ~ it _: _ _ _in _ii

t

i

I i iI 1 !" " X it 1

it

__ _ _ __L[__ l_ _

; _ : i : : z

I I

III I" ^ ~ it" I I" I

25

57

60

38

30

25

15

Breathing rate (per minute)

27

25

23

20

18

15

10

Temperature (C)

DATA TABLE 1: Breathing rate of freshwater Sunfish.2. Use the information recorded in DataTable 1 to construct a line graph on thegrid provided below. You should label eachaxis, mark an appropriate scale on each axis,plot the data, connect the points, and give your

graph a title. (10)Use 2 small squares = 1CUse 1 small square = 1 breath per minute.

1 1 1

1I

l

J

| !1! 1 1 j1 1

^_ X^ _ 4: ' _

; j

i

I iix _,_

__ r:_ it^_ it! 1 1\ \

i i i '

_^ ^j_ ^ _

i

j i

i

_: ::: :x__

[ 1_I_ ^

I

X - -

Z ~ - ~X" _ ~

i1 i i

z i it _ ^ x; 1

Average Rainfall in Willamette Valley

ID

Dec.

5

Nw.

3

Oct

2

Sept.

1

Aug.

2

July

8

June

16

May

24

April

28

Mar

21

Fell.

15

Jan.

Rainfall |mL|

Month

3. Use the information recorded in Data Table 2 to construct a bar graph on the grid provided below. Youshould label each axis, mark an appropriate scale on each axis, plot the data, darken/color the columnsof the graph, and give your graph a title. (10) (Use 5 small squares = lmonth: 2 small squares = lmL.)

Data Table 2

5. Using Graphs: What is an advantage of using multiple lines in a line graph? (See Figure 2.) (1)

Explain your answer. (4)

.y-axis

4. Using Graphs: You are conducting an experiment to measure the gain in mass of a young mouseover a ten-week period. In constructing a graph to represent your data, which variable should you

place along the ^-axis and which variable should you place along the^-axis? (2)

3. Using Graphs: Does a steep curve on a line graph indicate a rapid or slow rate of change?(l)

2. Comparing and Contrasting: How is a line graph different from a bar graph?(2)

ANALYSIS AND CONCLUSIONS:1. Comparing and Contrasting: How is a graph similar to a data table?(2)