GraphsA graph is a

line plot of a data set.

Each point represents one row in a table.

Table and GraphTable and Graph

Sam's WeightSam's Weight

MonthMonth Weight in kgWeight in kg

JanuaryJanuary 4949

FebruaryFebruary 5454

MarchMarch 6161

AprilApril 6969

MayMay 7373

A graph must include: Title with both variables Even scale Labeled axes with units Correctly plotted data Correctly placed variables on

axes Key, if applicable Must be neat, easy to visualize

trend

DATAData is the core of scientific

investigation. Scientists look for trends in data and then try to explain the trend.

Scientists use graphs to see the trend in the data.

TREND The connecting lines

allow us to visualize the TREND in the data.

You should be able to look at a graph and summarize the trend shown by the graph.

Placement of variables

Dependent variable:

Y axisIndependent variable:

X axis

REMEMBER!!!!

IndeXIndependent in the X (axis)

How to determine the variables?

The DEPENDENT depends on the

INDEPENDENT

The _________ depends on the

________.

TitleThe title must include both

variables and the scientific name of the organism:

Example: “ The effect of Miracle Grow on the growth of Phaseolus vulgaris”

Title?Title?

Males

Females

10

Age (years)

Nu

mb

er o

f su

rviv

ors

(lo

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cale

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4 6 80 2

1,000

100

10

1

Line Graph It is used when there is a

sequence though time from one point to another, or when you are measuring a variable that changes with distance from a fixed point.

It allows you to see increasing or decreasing trends

REMEMBER!!! IN BIOLOGY, YOU WILL USE

LINE GRAPHSMOST OF THE TIME.

(No bar graphs unless instructed to.)

Value of Sarah's CarValue of Sarah's Car

YearYear ValueValue

20012001 $24,000$24,000

20022002 $22,500$22,500

20032003 $19,700$19,700

20042004 $17,500$17,500

20052005 $14,500$14,500

20062006 $10,000$10,000

20072007 $ 5,800$ 5,800

Identify the elements in this graphIdentify the elements in this graph

1.IMPROVE the title of 1.IMPROVE the title of this line graph. this line graph.     

2.What is the range of 2.What is the range of values on the values on the horizontal scale?horizontal scale?

3.What is the range of 3.What is the range of values on the values on the vertical scale?vertical scale?

4.How many points 4.How many points are in the graph? are in the graph? 

5.What was the 5.What was the highest value highest value recorded?recorded?

6.What was the lowest 6.What was the lowest value recorded?value recorded?

7.Did the value of the 7.Did the value of the car increase or car increase or decrease over decrease over time? (trend)time? (trend)

QUESTION ANSWER

1. Improve the title of this line graph?   

Value of Sarah's Car from ‘01 to ‘07

2.What is the range of values on the horizontal

scale?2001 to 2007

3.What is the range of values on the vertical

scale?0 to 25,000

4. How many points are in the graph?    7

5. What was the highest value recorded? $24,000

6. What was the lowest value recorded? $5,800

7.Did the value of the car increase or decrease

over time?decrease

Does feeding by sea urchins and limpets affect seaweed Does feeding by sea urchins and limpets affect seaweed distribution? Experiment by WJ Fletcher near Sydney, Australiadistribution? Experiment by WJ Fletcher near Sydney, Australia

August1982

Seaurchin

August1983

February1983

February1984

Both limpetsand urchinsremoved

Limpet

80

60

40

20

0

Onlyurchinsremoved

Only limpets removed

Control (bothurchins andlimpets present)

Sea

wee

d c

ove

r (%

)

SCATTER POINT GRAPH

It is used when there is no reason to assume any sequence between points. It has no line connecting the points – each point represents an independent, random event.

It allows you to see broad increasing or decreasing trends in the data.

10,000

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nu

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rep

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uc

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in

div

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1,000

100

100101Plants per m2 (log scale)

Plantain. The number of seeds produced by plantain (Plantago major) decreases as density increases.

Song sparrow. Clutch size in the song sparrow on Mandarte Island, British Columbia, decreases as density increases and food is in short supply.

Av

era

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clu

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siz

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2.880

Females per unit area

3.0

3.8

4.0

3.4

3.6

3.2

60 705030 40200 10

Time (days)

Nu

mb

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f P

aram

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m/m

L

1,000

0

400

5

200

100

15

800

600

A Paramecium population in the lab

Bar Graph It is used when the

independent variable represents a category rather than a numerical value. Only the height of the bar has any numerical meaning.

It allows you to see differences between the categories or groups of categories.

010

2030

4050

6070

8090

1stQtr

3rdQtr

East

West

North

Female

Par

ents

su

rviv

ing

th

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win

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Normalbrood size

100

80

60

0Reduced

brood sizeEnlarged

brood size

Male

40

20

Pie Graph

A pie chart (or a circle graph) is a circular chart divided into sectors, illustrating relative

magnitudes or frequencies or percents. In a pie chart, the arc length of each sector, is proportional to the quantity it represents. Together, the sectors create a full disk. It is named for its resemblance

to a pie which has been sliced.While the pie chart is perhaps the most ubiquitous

statistical chart in the business world and the mass media, it is rarely used in scientific or

technical publications

How to establish a relationship from a graph

The relationship is linear if you can draw a straight line through

the data points Inverse if the graph of the relationship

appears to be a curve. Inversely proportional to x. As x

increases, y decreases there might be no relationship at all. In this

case, you may see data points scattered in an irregular cloud so that you cannot draw a straight line or a smooth curve through them.

What can you tell about this What can you tell about this graph?graph?

Time (days)

Nu

mb

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f D

aph

nia

/50

mL

180

0

90

20

60

400

60

150

120

A Daphnia population in the lab

30

80 100 120 140 160

Time (years)

Nu

mb

er o

f fe

mal

es

1975 1980

40

19850

1990

60

A song sparrow population in its natural habitat

20

1995 2000

Infa

nt

mo

rtal

ity

(dea

ths

per

1,0

00 b

irth

s)

50

40

30

20

10

0Developedcountries

60

Developingcountries

Lif

e ex

pec

tan

cy (

year

s)

80

40

20

0Developedcountries

60

Developingcountries

Eco

log

ical

fo

otp

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t (h

a p

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n)

14

12

10

8

6

4

16

0

2

02 4 6 8 10 12 14 16

Available ecological capacity(ha per person)

New Zealand

AustraliaCanada

Sweden

WorldChina

India

SpainUK

Japan

Germany

Norway

USA

Netherlands

Rapid growthAfghanistan

AgeMale

Percent of population

Female

8 6 4 2 2 4 6 80

45–4940–4435–3930–3425–2920–2415–1910–14

5–90–4

85+80–8475–7970–7465–6960–6455–5950–54

Slow growthUnited States

AgeMale

Percent of population

Female

6 4 2 2 4 6 80

45–4940–4435–3930–3425–2920–2415–1910–14

5–90–4

85+80–8475–7970–7465–6960–6455–5950–54

8

Decrease Italy

Male

Percent of population

Female

6 4 2 2 4 6 808

•Age structure diagrams can predict a population’s growth trends

•They can illuminate social conditions and help us plan for the future

8000B.C.

Hu

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(b

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6

5

4

3

2

1

0

4000B.C.

3000B.C.

2000B.C.

1000B.C.

The Plague

0 1000A.D.

2000A.D.

•The human population increased relatively slowly until about 1650 and then began to grow exponentially

Bir

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peo

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40

30

20

10

Sweden

2050

Year20001900 19501850

0

18001750

Birth rateDeath rate

MexicoBirth rateDeath rate

•The demographic transition is associated with various factors in developed and developing countries