Question

Six white-tailed deer and six sika deer were enclosed in a pasture for observation during an eight-year study in central Texas. White-tailed deer are a native species to central Texas, while sika deer are a nonnative species to central Texas. White-tailed deer feed on flowering plants and the tips of trees and shrubs but do not eat grass. Sika deer feed on flowering plants, the tips of trees and shrubs, and grass. All other grazing animals were kept out of the pasture during the study. The number of sika deer more than doubled after the eight years, while the population of white-tailed deer decreased by 50 percent.a. The ska deer are generalists, while the white-tailed deer are specialists.b. The sika deer out competed the white-tailed deer in consuming flowering plants and shrubs.c. Parasites infected the sika deer population but did not infect the white-tailed deer population.d. Change in the local climate reduced the availability of food resources for the white-tailed deer population

Answer 1

Answer:

The correct answer is B: "The sika deer out competed the white-tailed deer in consuming flowering plants and shrubs".

Explanation:

a. The sika deer are generalists, while the white-tailed deer are specialists. Specialists are those animals that adapt to explode a specific ecological niche which is delimitated by certain characteristics. These specialist animals explode resources so well and efficiently, that they hardly have any competitor. They evolve in behavior and physical shape to specialize in their objectives and are so adapted to only one lifestyle that it is very difficult for them to readapt to a new environment. The white-tailed dear is not a specialist, because it feeds almost on the same sika dear diet. The only difference is that they do not consume grass, but their niches, in diet concern, almost completely overlapped.

c. Parasites infected the sika deer population but did not infect the white-tailed deer population. If parasites affect a dear population, this last one tends to decrease in size because animals´health is affected and their reproductive rate decreases. Sika deer duplicated its size in the 8 years of study, so it is hardly possible that this species was infected by parasites.

d. Change in the local climate reduced the availability of food resources for the white-tailed deer population. Both species feed on flowering plants and the tips of trees and shrubs. If a change in local clime would have affected these plants, then both of the species would have been affected. Even considering that the sika species feed on grass, it still would be affected by lack of resources and its size would not be able to duplicate.

b. The sika deer out-competed the white-tailed deer in consuming flowering plants and shrubs. Sika deer is a non-native species that might turn into invasive. These are the cases of new species that disperse and establish in a new area far from their original distribution range. As they expand, they compete with other species for resources. Their reproductive rate and population growth are high in comparison to native species, which are affected by interaction with the new one. Invasive species can cause huge damages in native ecosystems. In the new areas, they have less environmental pressure and better conditions than in their origin area -fewer predators, more resources, better nitches-, and these factors favor their establishment. In the exposed example sika feeds on the same resources than white-tailed dear, which leads to unavoidable competition. By duplicating its population size, it seems that it had established in the area and became the dominant competitor over the native species, that is affected by its presence.  

Answer 2

Answer:

The sika deer out competed the white-tailed deer in consuming flowering plants and shrubs.

Explanation:

Option a is not possible because they feed almost on the same type of food. Option c, cant be because is not logic that the population that was infected is more numerous. Parasites have a tendency to weaken populations. Option d makes no sense because both species feed on the same resources.

C is more logical. Both species feed on the same resource but the sika deer has an strategy to feed more effectively.