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• According to the competitive exclusion principle,
what outcome is expected when two species with
identical niches compete for a resource?
• Based on your answer above. If a new species is
introduced to an area that have the same niche as
an other native species that already is living in the
area, who would have an advantage and why?
• Consider a grassland with five trophic levels:
grasses, mice, snakes, raccoons, bobcats. How
would plant biomass change if the bottom-up
model applied? If the top-down model applied?
Explain.
• Most prairies experience regular fires, typically
every few years. These disturbances tend to be
relatively modest. How would the species
diversity of a prairie likely be affected if no burning
occurred for 100 years. Explain.
• An important species in the Chesapeake Bay is the
blue crab. It is an omnivore, eating eelgrass and
other primary producers as well as clams. It is also
a cannibal. Humans and sea turtles eat blue crabs.
– Draw a food web that includes the information above.
– Assuming the top-down model for this system,
describe what would happen to the abundance of
eelgrass if humans stopped eating blue crab.
Understanding problems in community ecology often requires the
integration of a number of ecological principles. Explain the
following by using as many learned principles as you can.
• A small clan of hyenas killed an antelope. While they
were feeding on the carcass, two female lions
approached and chased them away from the carcass.
• The Hawaiian woodpecker has a distinctive beak that
is used as a tool. Males have larger beaks and they
peck on tree trunks, while females peck on branches
and twigs. They have the lowest reproduction rate
among all small birds (1 chick/year). But they care for
their young. The decline of their numbers
corresponds with the introduction of rats, cats and
logging in the island.