|
Whoever wrote the paper is being a little simplistic and general in the way they have approached this, so I shall attempt to clarify as best I can;
Q1.
a) - competitive exclusion of other predators could possibly increase diversity, but where other predators prey on particularly vigourous and invasive species which the keystone predator does not, eradication of other predatory species may actually reduce diversity by reducing pressure on that invasive species.
b) - predation of dominant species - this depends if the dominant species is dominant to the detriment of other species, or if its domination is co-existant with an appropriate diversity level. As an example, upland heathland is maintained by grazing, thus, if the grazing animals are the dominant species and are heavily predated, this will reduce the ability of the habitat to remain intact and will allow succession to take place. Perhaps this could increase diversity but at the expense of habitat. Remember, absolute diversity is not always the most preferred aim in all habitats
c) - immigration of other predators - nope, this is a red herring, immigration of other predators will only occur where those predators exploit different ecological niches, or where sufficient biomass and low predator numbers permit, but in the latter case, the more likely outcome would be increased breeding within the keystone predator and territoriality to defend a "choice spot"
d) - reducing the number of disruptions in the community will again depend on the community type, but this answer does not make any ecological sense, predators are not the police, they do not "reduce" any disruptions, they simply take advantage of an ecological niche and food source as efficiently as their biology and behaviour and population dynamics allows
e) - again, too general, this depends again on the habitat, the predator, the threats and oppurtunities. No keystone predator will be that exclusive, where least abundant species are predated, it is likely to be by a series of predators, possibly including some specialist predators. But in general, if a food source reaches low volumes, most predators will (if their ecology permits) either utilise an alternative food source or migrate to another habitat
Q2.
a) - this does not shorten the food chain, because there are too many other factors which are not mentioned. Although each floral species may be predated by only one herbivore species, the levels of predation on the herbivore species may vary, thus, a rabbit has more potential predators than a horse. There are also other factors to be discussed, such as the microbial diversity of different species dung, symbiotic relationships, parasitic relationships, pollenation, seed dispersal, nutrient cycling etc etc.
b) - not always, it depends on the interplay between species and how interdependant they are. As an example, if a population of Roach in a freshwater is exterminated, but a healthy population of Rudd and Bream remains, the niche in which the Roach existed as a food source is filled by the others. Also, extinction of a species may cause an INCREASE in other species, due to a loss of predation. Remember that food chains go in both directions at the same time.
c) Yes, it can be, but again, this is too general, and depends on the energy density within each trophic level and the direction of energy cycling. Whilst a cow, for example, may require a vast amount of plant material for a given population, the energy which is not absorbed and is passed through as dung, is recycled by other organisms, so the energy goes sideways into a different chain, and even goes backwards to a lower trophic level as waste cellulose is slowly digested by soil dwelling microorganisms and made available to upper trophic levels again
d) Not really. An african plain may have a limited diversity of prey (eg wildebeest), which are preyed on (either directly or scavenged) but a large diversity and mass of organisms which rely in one way or another upon that limited source. However, where prey biomass is minimal, although predator species may be limited in diversity and extent, this does not shorten the food chain, it merely reduces the number of predators at the apex. All the other trophic levels will remain intact and diverse as long as they remain ecologically viable (ie sufficient space, nutrient levels, presence of other species, lack of disease, climate etc)
e) nope, because even inedible producers have trophic value, as they die, their tissues provide nutrient for soils. They provide food for pollinators, create micro-habitats for symbiotic and parasitic organisms and are thus an intimate contributor within the food chain.
Sorry that doesn't help, the question is rather poorly written, too general, too many assumptions, not enough information.
|
Quick Reply
