Population Interactions
A biologist obtained a sample of pond water from a pond and took the sample back to school. He took a sample of the pond water out
and discovered that there were only two unicellular organisms present in the sample:
1.
Euglena:
contains chloroplasts and produces its own food, therefore, it is a producer; and
2.
Amoeba:
contains no chloroplasts and has to eat other organisms, therefore, it is a consumer.
The biologist kept the sample of the pond water in a sealed jar and took a sample each day and counted the number of organisms
present. His results are recorded below.
POPULATIONS OF EUGLENA AND AMOEBA
DAY
Number of
Organisms
NUMBER
AMOEBA
EUGLENA
0
25
4
1
24
7
2
20
13
3
13
30
4
10
33
5
12
35
6
18
34
7
35
27
8
43
15
9
47
10
10
46
9
Plot a population curve on the graph paper given for both organisms from the above data. (PLOT BOTH CURVES ON THE SAME
GRAPH PAPER. USE A DIFFERENT COLOUR FOR EACH ORGANISM. Place the time on the x-axis, number of organisms on the
y-axis).
Using the graph you have constructed, what possible relationship(s) can you suggest exist between the Euglena and Amoeba
populations?
Answer the following questions:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
How many Euglena are in the jar at 2.5 days?
How many Amoeba are in the jar at 4.5 days?
What is happening to the number of Euglena on the sixth day?
What is happening to the number of Amoeba on the sixth day?
What is the maximum number of Euglena and when is this number achieved?
What is the maximum number of Amoeba and when is this number achieved?
If the student had counted the number of Euglena on the eleventh day, how many do you think would have been counted?
If the student had counted the number of Amoeba on the twelfth day, how mny do you think would have been counted?
Using these graphs, what possible relationship(s) can you suggest exist between the Euglena and Amoeba populations?
Based on these graphs, what would you estimate the Carrying Capacity would be for both the Euglena and Amoeba
populations?