2. why is it useful for an ecologist to identify the keystone species in an ecosystem?

the keystone species is only important in early stages of succession, and so the ecologist can

safely ignore changes in its population at later stages.

the keystone species is the most susceptible to pollution, and so its numbers give an

indication of the levels of pollutants in an area.

the keystone species is critical to maintaining the stability of an ecosystem, and changes in its

population indicate changes in ecosystem health.

the keystone species is important for the cycling of matter and must be maintained or the

biogeochemical cycles will be affected.

3. competition over resources occurs between organisms

participating in an herbivorous relationship.

forming a symbiotic relationship.

attempting to occupy the same niche.

initiating primary succession after a disturbance.

4. the lowest trophic level in an ecosystem

has the lowest quantity of stored energy.

has the greatest biomass.

is made up of heterotrophs

contains detritovores.

5. what is true of the energy that is passed from one trophic level to the next in a food chain?

about 10% of the energy passed from one level to the next is released as heat.

about 10% of the stored energy of one level becomes stored energy at the next higher level.

the energy at each level increases by about 10% with each move up in trophic level.

the total energy at all trophic levels is constant, but only about 10% is available for use by

organisms for life functions.

6. autotroph is to producer as heterotroph is

herbivore.

consumer.

decomposer.

carnivore.

7. which of the following is true of population cycles?

population cycles signal an imbalance in an ecosystem.

keystone species are necessary to establish population cycles.

a new species introduced to an ecosystem tends to stabilize population cycles in the

ecosystem.

population cycling maintain a healthy ecosystem.

8. an example of a pioneer species is

a sparrow.

a lichen.

an earthworm.

a spider.

9. why are human disturbances often of more concern than natural disturbances?

human disturbances last much longer than natural disturbances so that a damaged ecosystem

may have little or no chance of recovery.

human disturbances are stronger than natural disturbances and so the recovery needed is

much greater.

human disturbances often cover much wider areas than natural disturbances, which means

that more ecosystems are affected.

human disturbances affect all types of ecosystems, whereas natural disturbances are limited

to certain types of ecosystems.

10. suppose a particular community is concerned about a fox population that kills and eats chickens on the

local farms. what is the best course of action by this community?

kill the foxes.

trap and transport the foxes out of the region.

introduce rabbits as an alternative source of food for the foxes.

build enclosures for the chickens that the foxes cannot access.