Graphs Each point represents one row in a table. A graph is a line plot of a data set. Each point represents one row in a table.

Table and Graph Sam's Weight Month Weight in kg January 49 February 54 March 61 April 69 May 73

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

DATA Data 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 axis Independent variable: X axis

REMEMBER!!!! IndeX Independent in the X (axis)

How to determine the variables? The DEPENDENT depends on the INDEPENDENT The _________ depends on the ________.

Title The title must include both variables and the scientific name of the organism: Example: “ The effect of Miracle Grow on the growth of Phaseolus vulgaris”

Number of survivors (log scale) Title? 1,000 100 Number of survivors (log scale) Females 10 Males 1 2 4 6 8 10 Age (years)

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

LINE GRAPHS REMEMBER!!! IN BIOLOGY, YOU WILL USE MOST OF THE TIME. (No bar graphs unless instructed to.)

Identify the elements in this graph Value of Sarah's Car Year Value 2001 $24,000 2002 $22,500 2003 $19,700 2004 $17,500 2005 $14,500 2006 $10,000 2007 $ 5,800

1.IMPROVE the title of this line graph.    2.What is the range of values on the horizontal scale? 3.What is the range of values on the vertical scale? 4.How many points are in the graph?  5.What was the highest value recorded? 6.What was the lowest value recorded? 7.Did the value of the car increase or decrease over 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 distribution Does feeding by sea urchins and limpets affect seaweed distribution? Experiment by WJ Fletcher near Sydney, Australia Sea urchin 80 Both limpets and urchins removed 60 Seaweed cover (%) Only urchins removed Limpet 40 Only limpets removed 20 Control (both urchins and limpets present) August 1982 February 1983 August 1983 February 1984

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.

Average number of seeds per reproducing individual 4.0 10,000 3.8 3.6 Average number of seeds per reproducing individual (log scale) 1,000 Average clutch size 3.4 3.2 3.0 100 2.8 1 10 100 10 20 30 40 50 60 70 80 Plants per m2 (log scale) Females per unit area 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.

Number of Paramecium/mL 1,000 800 600 Number of Paramecium/mL 400 200 5 10 15 Time (days) 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.

Parents surviving the following winter (%) 100 Male Female 80 60 Parents surviving the following winter (%) 40 20 Reduced brood size Normal brood size Enlarged brood size

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 graph?

180 150 120 Number of Daphnia/50 mL 90 60 30 20 40 60 80 100 120 140 160 Time (days) A Daphnia population in the lab

Number of females 1975 1980 1985 1990 1995 2000 Time (years) 60 Number of females 40 20 1975 1980 1985 1990 1995 2000 Time (years) A song sparrow population in its natural habitat

Infant mortality (deaths per 1,000 births) Life expectancy (years) 60 80 50 60 40 Infant mortality (deaths per 1,000 births) Life expectancy (years) 30 40 20 20 10 Developed countries Developing countries Developed countries Developing countries

Ecological footprint (ha per person) Available ecological capacity 16 14 12 New Zealand 10 USA Germany Ecological footprint (ha per person) 8 Australia Netherlands Japan Canada Norway 6 Sweden UK 4 Spain World 2 China India 2 4 6 8 10 12 14 16 Available ecological capacity (ha per person)

They can illuminate social conditions and help us plan for the future Age structure diagrams can predict a population’s growth trends Rapid growth Afghanistan Slow growth United States Decrease Italy Male Female Age Male Female Age Male Female 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 8 6 4 2 2 4 6 8 8 6 4 2 2 4 6 8 8 6 4 2 2 4 6 8 Percent of population Percent of population Percent of population They can illuminate social conditions and help us plan for the future

Human population (billions) The human population increased relatively slowly until about 1650 and then began to grow exponentially 6 5 4 Human population (billions) 3 2 The Plague 1 8000 B.C. 4000 B.C. 3000 B.C. 2000 B.C. 1000 B.C. 1000 A.D. 2000 A.D.

Birth or death rate per 1,000 people The demographic transition is associated with various factors in developed and developing countries 40 30 20 Birth or death rate per 1,000 people 10 Sweden Mexico Birth rate Birth rate Death rate Death rate 2050 1750 1800 1850 1900 1950 2000 Year