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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
g s
cale
)
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
Av
era
ge
nu
mb
er
of
se
ed
sp
er
rep
rod
uc
ing
in
div
idu
al
(lo
g s
ca
le)
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
ge
clu
tch
siz
e
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
er o
f P
aram
eciu
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
e fo
llo
win
g w
inte
r (%
)
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
er o
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
rin
t (h
a p
er p
erso
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
man
po
pu
lati
on
(b
illi
on
s)
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
th o
r d
eath
rat
e p
er 1
,000
peo
ple
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
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