Name____________________________________
Date_________
Period____
Examining Survivorship Curves
Background:
Within a population, some individuals die very young while others live into old age. To a large extent, the pattern
of survivorship is species dependent. Three general patterns of survivorship have been identified. These three
have been summarized by survivorship curves, which are graphs that indicate the pattern of mortality (death)
in a population. A Type I curve shows high survivorship until old age, then high mortality. A Type II curve shows
near-constant, moderate survivorship of all different ages of a population. Type III curves show low survivorship
at the younger ages, with survivorship increasing as the population ages.
Procedure:
1. The population of three different organisms over time is represented in the data table below.
2. Year zero represents how many offspring were produced in a reproductive cycle.
3. For this exercise:
a. Assume each population of the three different organisms produce exactly 150 offspring.
b. Assume the maximum lifespan of the three different organisms is the same (20 years).
4. Calculate the percent surviving of all three populations for each year
(compared to the starting population)
5. On the axes provided, graph the percent surviving for each population over time,
each represented by a different line.
a.
Remember to title the graph, properly label and scale your axes, and provide a key
for the different lines (population 1,2 & 3)
Year
Total #
Surviving –
Population 1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
150
135
110
50
30
25
23
22
21
20
18
16
14
12
10
8
6
4
3
2
0
% SurvivingPopulation 1
Total #
Surviving –
Population 2
150
150
150
149
148
148
147
147
146
146
146
144
144
143
141
138
115
100
60
25
0
% SurvivingPopulation 2
Total #
Surviving –
Population 3
150
148
142
134
126
118
110
102
95
87
79
71
64
56
48
40
32
24
16
8
0
% SurvivingPopulation 3
Analysis Questions:
1. On your graph identify and label each curve as Type I, Type II or Type III.
2. Complete the descriptor for each survivorship type:
a. Type I: _________________
b. Type II: _________________
c. Type III: _________________
3. Identify each population as r-selected or K-selected. Also explain each of these strategies.
4. Population 1 was provided no parental care. Give three examples of species that use this strategy.
5. Population 2 was provided substantial parental care. Give three examples of species that use
this strategy
6. Would you expect a population in which most members survive for a long time to produce few or many
offspring at a single time? Which would be most advantageous to the population as a whole? Explain
7. Bubble population 3 received some level of parental care, but still demonstrated a roughly constant
mortality rate for the species through its entire life. This means that the individual's chance of dying is
independent of their age. Give three examples of species that use this strategy.
8. Suppose a human population in an impoverished, developing country exhibits a Type III survivorship curve.
What would you expect to happen to the curve over time if a dramatic improvement in medical
technology takes place? Explain.
9. What would you expect to happen to a population where the birth rate is about equal to the
death rate? Explain
10. How many humans presently occupy our planet? [look it up]
11. Is our population increasing, decreasing, or remaining stable? Explain with evidence