Physical patterns on the earth’s surface (and one evolution problem)
Homework
1. Predation may work through the mechanism of natural selection to modify the
behavior of prey species. Bosmina longirostris is a freshwater North American shellfish.
Two kinds of predators feed on B. longirostris:
a)
fish that are large enough to eat the eggs as well as the adults of B. longirostris,
and that locate their prey by sight.
b)
invertebrates (called Cylops sp. and Chaoborus sp.) that are small, and only can
consume small prey. Soon after hatching, B. longirostris grow too large to be eaten by
these predators.
In Frains Lake, Michigan, fish predators are common from April through September
(summer), but rare during the months of October through February (winter). During the
summer, B. longirostris females lay large clutches (groups of eggs) but the eggs are very
small and therefore not easily seen by the fish. By producing many cryptic eggs the
negative effects of predation by fish are minimized. During the winter, when Cyclops sp.
and Chaoborus sp. are the only significant predators (but note that these crustaceans also
are present in the summer), the B. longirostris females lay fewer eggs per clutch but the
eggs have significantly larger yolks. This allows their offspring to grow quickly beyond
the size range that can be handled by Cyclops sp. and Chaoborus sp. Although fewer
eggs are laid per clutch by each female, each egg has a greater chance of survival due to
its size.
a)
What changes might be expected to occur in this pattern if fish somehow became
extinct in Frains Lake?
b)
With reference to the process of evolution by natural selection, devise a scenario
to explain how the change you have suggested above might occur.
2. If a mass of air is moving from southern Florida (find out the latitude) toward the
equator, which way will the wind be deflected?
3. Name two areas of the earth that receive over 500 cm of rain annually.
4. Describe three textures of soil. Which texture is the best for plant growth? Why?
5. After reading the section on fire in the textbook, discuss how programs that prevented
forest fires in many areas of the U.S. (remember Smoky the Bear?) for many years may
have affected the frequency and intensity of fires.
6. What are the characteristics of regions in which fire is an important agent of
disturbance?