5 In a conservation project in a nature reserve, scientists are modelling the population of one species of animal.

The initial population of the species, $P _ { 0 }$, is 10000 . After $n$ years, the population is $P _ { n }$. The scientists believe that the year-on-year change in the population can be modelled by a recurrence relation of the form\\
$\mathrm { P } _ { \mathrm { n } + 1 } = 2 \mathrm { P } _ { \mathrm { n } } \left( 1 - \mathrm { k } \mathrm { P } _ { \mathrm { n } } \right)$ for $n \geqslant 0$, where $k$ is a constant.
\begin{enumerate}[label=(\alph*)]
\item The initial aim of the project is to ensure that the population remains constant.

Show that this happens, according to this model, when $k = 0.00005$.
\item After a few years, with the population still at 10000 , the scientists suggest increasing the population. One way of achieving this is by adding 50 more of these animals into the nature reserve at the end of each year.

In this scenario, the recurrence system modelling the population (using $k = 0.00005$ ) is given by\\
$P _ { 0 } = 10000$ and $\mathrm { P } _ { \mathrm { n } + 1 } = 2 \mathrm { P } _ { \mathrm { n } } \left( 1 - 0.00005 \mathrm { P } _ { \mathrm { n } } \right) + 50$ for $n \geqslant 0$.\\
Use your calculator to find the long-term behaviour of $P _ { n }$ predicted by this recurrence system.
\item However, the scientists decide not to add any animals at the end of each year. Also, further research predicts that certain factors will remove 2400 animals from the population each year.
\begin{enumerate}[label=(\roman*)]
\item Write down a modified form of the recurrence relation given in part (b), that will model the population of these animals in the nature reserve when 2400 animals are removed each year and no additional animals are added.
\item Use your calculator to find the behaviour of $P _ { n }$ predicted by this modified form of the recurrence relation over the course of the next ten years.
\item Show algebraically that this modified form of the recurrence relation also gives a constant value of $P _ { n }$ in the long term, which should be stated.
\item Determine what constant value should replace 0.00005 in this modified form of the recurrence relation to ensure that the value of $P _ { n }$ remains constant at 10000 .
\end{enumerate}\end{enumerate}

\hfill \mbox{\textit{OCR Further Additional Pure 2024 Q5 [10]}}