Question

Suppose that a population of skunks lives on an isolated island is 500 skunks are present today and the birth rate is 65 per week and the death is 47 per week how many skunks to you predict will be on the island 105 days from now and what would a graph population versus time look for this population?

Answer choices:
230 skunks; graphs shows a downward trend
550 skunks; graph shows a stable trend
770 skunks; graph shows an upward trend
432 skunks; graph shows a downward trend

Answer 1

105 days represent 105/7 = 15 weeks
Number of births = 15 x 65 = 975
Number of deaths = 15 x 47 = 705

Number of skunks after 105 days = 500 + 975 - 705 = 770.

There is an increase in the number of skunks, so it shows an upward trend.

Answer 2

First we need to calculate what is the natural increase.
natural increase = birth rate - death rate = 65 - 47 = 18.
That means that every week island is getting 15 new skunks.

since there are 15 weeks (105 days/ 7 days per week = 15 weeks), after that period there will be
500 + 15*18 = 770

Answer is c) (graph will show an upward trend because population is growing as the time pass)