Ch 4 Questions
1. Charles Darwin concluded that inherited traits favorable to survival would be preserved over time. Look
at this graph of a DDT spray program aimed at eliminating a mosquito species. Explain the data contained
in the graph at points I through VI and relate the graph's data to Darwin's conclusion
I – mosquito population is sustainable, limited by limiting resources of the environment
II – population of mosquitoes declines when DDT is initially introduced, most of the mosquitoes
have no resistance to the DDT chemical.
III – due to natural variations within the mosquito population, a few mosquitoes have a trait
(resistance to DDT) that improves their chances of survival and reproductive success
IV differential reproductive success (those individuals that possess the most favorable combination
of characteristics (better adapted for the DDT environment) are more likely to survive, reproduce,
and pass their traits to the next generation)
V – mosquito population grows as the spray program ends
VI – reaches a size where the limiting resources of the environment control the extent of the
population
2. Draw a flow diagram of an old field undergoing succession. What type of succession is this?
The change in an old field over the years is an example of secondary succession. First year after
cultivation ceases, crabgrass dominates 
 third year, other weeds such
as broomsedge, ragweed, aster  years 5-15, pines  lastly, oaks and other hardwoods.
3. Compare and contrast the following terms: warning coloration and camouflage. Give examples of each.
Warning coloration causes animals to stand out from their surroundings. The coloration prompts
avoidance by experienced predators due to the toxic nature of the prey. Examples of animals with
warning coloration include the striped skunk and South American poison arrow frog.
Camouflage allows animals to blend into their surrounding to hide from predators. Certain
caterpillars resemble twigs so closely, you would never guess they are animals until they move.
Both are defensive adaptations.
4. Consider species A and B within an ecological community. These species might interact in various ways
that represent gains, losses, or no effect to the two species. In 4 of the 6 cells below, enter the terms that
describe the types of interactions might be occurring between species A and B in the community.
competition – limiting resource
competitive exclusion of species A
competitive exclusion of species B
commensalism (use twice)
mutualism
resource partitioning
predation of species A
predation of species B
parasitism of species A
parasitism of species B
Species A
Positive
Species B
Positive
mutualism
Negative
predation of species B
parasitism of species B
competitive exclusion of species B
Neutral
commensalism
Negative
Neutral
predation of species A
parasitism of species A
competitive exclusion of species A
commensalism
competition – limiting resource
resource partitioning
5. The Norway rat and the black rat were both introduced to this country from Europe. The Norway rat is
found only in cities and inhabits most cities in the U.S. The black rat can live in cities and rural areas but in
New Jersey is ONLY found in rural areas. Some cities in New Jersey, which previously had only black rats,
now have only Norway rats. Discuss this phenomenon in terms of competitive exclusion, resource
partitioning and limiting resources.
No two species can indefinitely occupy the same niche in the same community because competitive
exclusion eventually occurs. Interspecific competition for limiting resources will result in the
competitive exclusion of one of the species. In this particular case:
The black rat was driven from the cities through competition of resources with the Norway rat. The
two species of rats do not show evidence of resource partitioning that would allow the rats to
coexist in the same habitat. Instead the black rat has confined its habitat to the rural areas while
the Norway rat has taken over city existence.