Question 1. You are studying an endangered population of orchids, for which the

Question

Question 1. You are studying an endangered population of orchids, for which the birth rate b-0.20 births per individual per year and the death rate d-0.18 deaths per individual per year. The current population size (No) is 50 plants A. A new shopping mall is planned that will eliminate part of the orchid habitat and reduce the current population to 25 individuals. Given that the probability of extinction for a population is: Pextinction (d/b)N (where b and d birth and death rates and No initial population size), estimate the potential effect of the proposed development on the probability of extinction for this population. State your answer in words. Show your work. B. The logistic growth model accounts for the idea that in the real world, resource availability ultimately limits population growth. Is resource availability a density-dependent or density independent factor in such a model? Explain.

Explanation / Answer

A. ans: Given;

birth rate, b = 0.20,

death rate, d=0.18

Initial population, No=50

Final population, N=25

So, For initial population, Pextinction=(d/b)No = (0.18/0.20)50 =0.0051

And for the final population, Pextinction=(d/b)N = (0.18/0.20)25 =0.0717

Therefore, the proposed development increases the probability

of extinction by a factor = 0.0717-0.0051=0.0666

B. ans:

Resource availability is a density-dependent factor in logistic growth, however, in our model since the population has declined from 50 to 25 resource availibilty is not a limiting factor.

In the normal scenario, density-dependent factors such as resource availability cause a reduction in the rate of per capita growth with the increase in density in a population. For example, consider a population, say a population of deer—with access to limited amount of food. To the point when the population is small in size, the restricted food will be sufficient for each member of the population. However, with the growth of the population extensively, the restricted amount of food that stays constant may never again be adequate, prompting intraspecific competition among the individuals. On account of the competition, some individuals may die due to starvation or fail to reproduce or the young ones may die before reaching reproductive stage. As a result per capita growth rate will decrease and the population will reach a plateau.

However, in our model, since the population has not reached carrying capacity, resource availability will not limit the logistic growth. The population will rise freely as there is no resource competition.

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