Dr. Mark A. McGinleyTexas Tech University

BIOL 5311Summer 2001

ActivityFrequency Distributions- Turtle

Ages

Frequency distribution histogramsYou have already had practice drawing a frequency distribution histogram graph

Now let’s try another example

Graptemys versa Texas Map Turtle

Graptemys versa (Texas Map Turtles) are common in ponds in Texas

Frequency Distributionssampling variation in traitsBiologists wanted to study the ages of turtles living in a pond near Lubbock

They caught all of the turtles in a pond and determines how old they were by looking at their shells.

Here is what the data looked likeLubbockAge in yearsAge in years Number of turtlesNumber of turtles

11 55

22 1010

33 1515

44 1010

55 55

Frequency DistributionLubbock

0

2

4

6

8

10

12

14

16

1 2 3 4 5

Age of the turtle in years

Number of individuals

Analyzing the GraphThere is a lot of interesting information in

this graph includingHow many turtles of each age live in the pond

Youngest age (minimum)Oldest age (maximum)Range

The maximum age – the minimum ageWhat age is the most common

mode

Look at the Graph and Answer These QuestionsHow many turtles are 1 year old?How many turtles are 2 years old?How many turtles are 3 years old?How many turtles are 4 years old?How many turtles are 5 years old?How many turtles lived in the

pond?

Look at the Graph and Answer These QuestionsHow old are the youngest turtles in

the pond?How old are the oldest turtles in

the pond?What is the range of ages of turtles

found in the pond?What is the most common age for

turtles?

Turning Graphs Into WordsIt is important to be able to turn information held in graphs into words.

Look at the graph you have just drawn and describe in a sentence or two what the graph tells us.

Turn the graph into wordsAll of the turtles in the pond were

between 1 and 5 years old. 5 turtles were 1 year old, 10 turtles were 2 years old, 15 turtles were 3 years old, 10 turtles were 4 years old, and 5 turtles were 5 years old.

Use Math To Answer Some Questions1. What percentage of turtles in the

pond are 2 years old?

2. What fraction of turtles in the pond are 4 years old?

3. Turtles of which age make up the largest fraction of the turtles in the pond?

New StudyNext the scientists were interested in comparing the ages of turtles living in a pond in Houston

They went to a pond in Houston, collected all of the turtles and determine their age

Here is what the data looked Here is what the data looked likelike

HoustonHoustonAge in yearsAge in years Number of turtlesNumber of turtles

11 2525

22 4040

33 2525

44 00

55 00

Frequency Distribution Time!!Draw the frequency distribution histogram for Houston.

Frequency DistributionFrequency DistributionHoustonHouston

0

5

10

15

20

25

30

35

40

1 2 3 4 5

Age of the turtle in years

Number of individuals

Look at the Graph and Answer These Look at the Graph and Answer These Questions About the Pond in HoustonQuestions About the Pond in Houston

►How many turtles are 1 year old?How many turtles are 1 year old?►How many turtles are 2 years old?How many turtles are 2 years old?►How many turtles are 3 years old?How many turtles are 3 years old?►How many turtles are 4 years old?How many turtles are 4 years old?►How many turtles are 5 years old?How many turtles are 5 years old?►How many turtles lived in the pond?How many turtles lived in the pond?

Look at the Graph and Answer These Look at the Graph and Answer These Questions About the Pond in HoustonQuestions About the Pond in Houston

►How old are the youngest turtles in How old are the youngest turtles in the pond?the pond?

►How old are the oldest turtles in the How old are the oldest turtles in the pond?pond?

►What is the range of ages of turtles What is the range of ages of turtles found in the pond?found in the pond?

►What is the most common age for What is the most common age for turtles in the pond?turtles in the pond?

Turn the graph into wordsTurn the graph into words

►All of the turtles in the pond were All of the turtles in the pond were between 1 and 3 years old. 25 between 1 and 3 years old. 25 turtles were 1 year old, 40 turtles turtles were 1 year old, 40 turtles were 2 years old, 25 turtles were 3 were 2 years old, 25 turtles were 3 years old.years old.

►There were more 2 year old turtles There were more 2 year old turtles than there were either younger or than there were either younger or older turtles.older turtles.

Comparing Ponds in Lubbock and HoustonThe easiest way for biologists to compare what is happening in the pond in Lubbock with the pond in Houston is to look at the two graphs side by side.

Comparing Two Graphs

0

2

4

6

8

10

12

14

16

1 2 3 4 50

5

10

15

20

25

30

35

40

1 2 3 4 5

Number ofindividuals

Age of turles in years

LubbockHouston

Discuss The Differences Between the Two Frequency DistributionsWhat questions can you ask about the differences between the Lubbock and Houston populations?