DBQ on p. 181 – April 11, 2013
1) Compare the roles of Belostoma bakeri and Ranatra montezuma within the food
web.
Belostoma bakeri and Ranatra montezuma are both at the top of the food web,
although they both can be secondary, tertiary, and quaternary consumers. A
difference is that the Belostoma bakeri population has a little more than double the
biomass that the Ranatra montezuma population does.
2) Deduce, with a reason, which organism occupies more than one trophic level.
The organisms that occupy more than one topric level are both the Belostoma bakeri
and the Ranatra montezuma.
3) Deduce using P values:
a) what would be the most common food chain in this web?
b) what is the preferred prey of B. bakeri?
Hyalella montezuma
4) Construct a pyramid of energy for the first and second trophic levels.
5) Calculate the percentage of energy lost between the first and second trophic levels.
(427078 + 234342702) - 30960000
) ´100
(427078 + 234342702)
(661421022) - 30960000
% of Energy Lost = (
) ´100
661421022
% of Energy Lost = (
% of Energy Lost = (
630461022
) ´100
661421022
% of Energy Lost ≈ 95%
6) Discuss the difficulties of classifying organisms into trophic levels.
It is difficult to classify organisms into trophic levels if they consume at different levels
7) Outline the additional information that would be required to complete the pyramid
of energy for the third and fourth trophic level.
DBQ on p. 180 – April 10, 2013
1) Suggest a method that might be used to deduce the trophic level of a fish once it is
captured.
Collecting the feces of the fish and identifying undigested material in it, which in turn
helps to identify the species that the fish has consumed.
2)
a) Compare the changes in mean trophic level of landed fish from marine and
freshwater fisheries since 1970.
The mean trophic level of landed fish from both marine and freshwater
fisheries has decreased since 1970, although the decrease from 1970~2000 has been
more dramatic for freshwater fisheries at approximately 0.4 – for marine fish it
decreased by approximately 0.2.
b) Suggest why there is a difference in the two trends.
There could be a difference in the two trends because the availability of
resources is different in the two regions (saltwater vs freshwater).
3) Explain why the mean trophic level might increase with the age of an individual
fish.
The mean trophic level might increase with the age of an individual fish because
generally, the older fish are, the larger they are. Larger fish tend to consume more
species, putting them higher up in the trophic level.
4) Deduce the change in age of captured fish over the period shown.
Because there is generally a direct relationship between age and trophic level, the
graph shows that the age of captured fish seems to have decreased over the period
shown.
5) Explain two advantages of humans catching and consuming fish at a lower mean
trophic level.
One advantage of humans catching and consuming fish at a lower mean trophic level
is that energy transformations are more efficient. Because energy is lost with each
transformation, fewer transformations result in less energy that has been lost. A
second advantage is that consuming fish at lower mean trophic levels allow fish at
higher mean tropic levels to grow (because overfishing large fish has led to depletion
of the supply of such fish).
DBQ on p. 176 – April 8, 2013
1) Which of the organisms is autotrophic? Euglena and venus fly trap can be
autrotrophic.
2) Which of the organisms is heterotrophic? Ghost orchid and dodder. Euglena and
venus fly trap can also be heterotrophic.
3) Of the organisms that are heterotrophic, deduce which is a consumer, which a
detritivore and which a saprotroph. Venus fly trap is a consumer, ghost orchid and
ghost orchid are detritivores, and dodder is a saprotroph.