Populations are unable to sustain exponential growth for very long because environments are not unlimited. Eventually growth rates are reduced by a shortage of food, space or some other factor. These factors constitute what is known as ‘environmental resistance’ and their effect upon growth may produce a logistic growth curve. The data shown in the Table below illustrate this pattern of growth for three species’ populations, each beginning with a population of 10 individuals. Table 1: Temporal changes in the numbers of individuals of three different species’ populations, observed in the wild. Time (units) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Population 1 10 15 20 28 39 48 57 66 81 88 93 107 108 108 108 108 119 Population 2 10 11 12 14 17 19 21 25 29 33 37 41 40 43 46 49 46 Population 3 10 17 27 39 52 64 67 69 70 78 83 86 88 80 84 78 75 Draw a graph showing the growth of the species’ populations with time: put all species’ populations on a single figure. Extend the y-axis to 180. Label the axes and provide a suitable legend. 2. The carrying capacity of the environment with respect to any population is the maximum number of individuals that can be supported. What do you think are the carrying capacities for these species’ populations? Draw horizontal lines on the graph indicating this for each species’ population. Adjust your figure legend. 3. Assuming the original 10 organisms grew exponentially, doubling in size with every unit of time, calculate the population size from t0 to t4 and draw the position of this curve on your graph. Adjust your figure legend.
Populations are unable to sustain exponential growth for very long because environments are not unlimited. Eventually growth rates are reduced by a shortage of food, space or some other factor. These factors constitute what is known as ‘environmental resistance’ and their effect upon growth may produce a
Table 1: Temporal changes in the numbers of individuals of three different species’ populations, observed in the wild.
|
Time (units) |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
|
Population 1 |
10 |
15 |
20 |
28 |
39 |
48 |
57 |
66 |
81 |
88 |
93 |
107 |
108 |
108 |
108 |
108 |
119 |
|
Population 2 |
10 |
11 |
12 |
14 |
17 |
19 |
21 |
25 |
29 |
33 |
37 |
41 |
40 |
43 |
46 |
49 |
46 |
|
Population 3 |
10 |
17 |
27 |
39 |
52 |
64 |
67 |
69 |
70 |
78 |
83 |
86 |
88 |
80 |
84 |
78 |
75 |
- Draw a graph showing the growth of the species’ populations with time: put all species’ populations on a single figure. Extend the y-axis to 180. Label the axes and provide a suitable legend.
2. The carrying capacity of the environment with respect to any population is the maximum number of individuals that can be supported. What do you think are the carrying capacities for these species’ populations? Draw horizontal lines on the graph indicating this for each species’ population. Adjust your figure legend.
3. Assuming the original 10 organisms grew exponentially, doubling in size with every unit of time, calculate the population size from t0 to t4 and draw the position of this curve on your graph. Adjust your figure legend.
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