Question

A given population of bugs inhabiting a habitat X consisted of 200 bugs at the beginning of the year. Throughout the year there were 75 bugs born and 90 bugs that died. Around 35 bugs from a neighbouring habitat entered this population of habitat X in the middle of the year and started living with the original population. 15 bugs left the population by the end of the year to find a new habitat. What is the final size of the population living in habitat X at the end of the year?

• A. 250
• B. 205
• C. 305
• D. 175

Answer 1

The correct option is B 205

Initial size of the population ($N_t$) = 200 bugs

Number of births during the given time period of a year, i.e, natality (B) = 75 bugs

Number of deaths during the given time period of a year, i.e, mortality (D) = 90 bugs

Number of bugs entering the population during the given time period of a year, i.e, immigration (I) = 35 bugs

Number of bugs leaving the population during the given time period of a year, i.e, emigration (E) = 15 bugs

Therefore the final population density at the end of the year $\left(N_{t+1}\right)$ can be calculated as,

$N_{t+1}$= $N_t$[(B+I)-(D+E)]

= 200+[(75+35) - (90+ 15)] = 205 bugs