1. From 1968 to 1990, the population of snow geese nesting grew near Churchill, Manitoba, increased from about 2 000 pairs (4 000 individuals) to about 22 500 pairs (45 000 individuals) with a nesting density of around 1 000 nests per square mile. Snow geese winter along the coasts of Texas and Louisiana. Prior to 1960, marshes along these coasts provided the main food sources (reeds, roots, and tubers) for the geese. Destruction of these marshes and increased crop production of rice, corn, and soybeans has occurred since that time. The stubble from these crops and spilled grains are easily obtained food sources for the snow geese. Reduction in hunting and greatly increased food supplies from cultivation near their wintering ground has cut mortality rates of snow geese in half over this period.
The high nesting density of the snow geese has left little foraging or nesting space for other species of birds, and a decline in several duck species and shore birds has been observed. Simultaneously, intensive foraging by the snow geese erodes and dries out patches of Arctic soil, reduces regrowth of grasses and sedges, and greatly increases soil salinity.
—from Brodie, 1997
Question 2 (1 point)
The goose population is probably in
a)
in the exponential growth phase of an S curve
b)
at carrying capacity
c)
in the lag phase of the growth curve
d)
exponential growth forming a J curve
Perch are a smaller fish that feed mostly on small invertebrates and tiny “shiner” minnows. Perch in turn are hunted by larger game fish like Northern Pike and Walleye. Larger birds such as the scoop-billed pelican also feed on perch, particularly the young minnows that swim in large schools. Recently, the cormorant, a diving bird that preys on perch, have increased dramatically in number. Because perch are prized by anglers for their excellent meat, they have been fished hard for many years. In Moose Lake, like many northern Alberta lakes, perch populations have fallen dramatically. Which row accurately describes the relationships occurring in the lake?
Interspecific competition Intraspecific competition predator prey
A
Pelican-pelican
perch-human
perch
cormorant
B
Cormorant-pelican
human-human
northern pike
perch
C
Northern Pike - Walleye
cormorant-pelican
perch
shiner minnow
D
Perch-perch
shiner minnow - walleye
cormorant
perch
A
B
C
D
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