Biology Reference
In-Depth Information
Population E
800
400
0
10
20
30
40
800
400
0
50
60
70
80
Generation
FIGURE 2-16.
Fluctuations in the levels of the azuki been weevil, Callosobruchus chinensis, (solid line) and wasp,
Heterospilus prosopidis, (dashed line) populations. (From Utida, S. [1957]. Cyclic fluctuations of
population density intrinsic to the host-parasite system. Ecology, 38, 442-449. Used by permission.)
160
140
Hare
Lynx
120
100
80
60
40
20
1845
1855
1865
1875
1885
1895
1905
1915
1925
1935
Time in years
FIGURE 2-17.
Fur catch records for Canadian lynx and snowshoe hare from the Hudson Bay Company. (From
Fundamentals of ecology, 3rd ed., by ODUM. [1971]. Reprinted with permission of Brooks/Cole,
a division of Thomson Learning: www.thomsonrights.com. Fax: (800) 730-2215.)
The cyclic behavior of the predator-prey population levels requires that
a delicate balance be maintained between the dynamic rates of change of
the interacting populations. Notice, for example, how close the
population levels in Figures 2-15, 2-16, and 2-17 come to the horizontal
axis at times. If the predator population were driven to extinction, the
prey would develop undisturbed. Alternatively, if the prey population
were destroyed, the predators would also die off. Although
numerous ecological and biological factors need to be simultaneously
present to maintain balance, the system should also be robust enough to
maintain its dynamics in the presence of common environmental noise.
In what follows, we shall consider some mathematical models capable of
generating oscillatory behavior and examine conditions under which the
system is able to preserve this behavior in the long run.
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