ALL QUESTIONS ARE 4 OR 3 POINTS
1. Bacteria and fungi are found in all ecosystems on Earth. A scientist claims that fungi
are keystone species in a particular terrestrial ecosystem. To test this hypothesis, the
scientist divides an area within the ecosystem into multiple small plots of similar size.
Equal numbers of plots are then randomly assigned to one of three treatment groups.
Plots in the first group are sprayed with a water-soluble substance that selectively
kills fungi. Plots in the second group are sprayed with a water-soluble substance that
selectively kills bacteria. Plots in the third group are sprayed with the same volume of
water only. After a certain period of time, the scientist then measures the amount of
accessible nutrients in the soil in each plot.
1. (a) Describe ONE common role of both bacteria and fungi in the movement of
energy and matter in ecosystems.
2. (b) Describe how analyzing the data from the treatment group sprayed with
water only will increase the validity of the experimental results.
3. (c) Based on the scientist’s claim, predict which treatment group will have the
smallest amount of accessible nutrients in the soil at the end of the experiment.
Justify your prediction in terms of the relative impact of a keystone species in
the environment.
2. In an attempt to rescue a small isolated population of snakes from decline, a few
male snakes from several larger populations of the same species were introduced into
the population in 1992. The snakes reproduce sexually, and there are abundant
resources in the environment.
The figure below shows the results of a study of the snake population both before and
after the introduction of the outside males. In the study, the numbers of captured
snakes indicate the overall population size.
(a) Describe ONE characteristic of the original population that may have led to the
population’s decline in size between 1989 and 1993.
(b) Propose ONE reason that the introduction of the outside males rescued the snake
population from decline.
(c) Describe how the data support the statement that there are abundant resources in
the environment.
3. As part of a new suburban development, a sports complex consisting of athletic
fields and buildings is constructed in a formerly wooded area.
(a) Predict ONE ecological consequence on the local plant community that is likely to
result during the site preparation and construction of the sports complex. Justify your
prediction.
(b) To maintain the playing fields, large quantities of water and chemicals are applied
regularly to the grass- covered areas. Predict ONE effect on the local animal
community that might result from regular use and maintenance of the playing fields.
Justify your prediction.