Population Growth Questions Answer Key - Bates (Page 2 of 4) in pdf

Population Growth Questions Answer Key - Bates Page 2

Bio 270 Practice Population Growth Questions

4. If the human population size in 1993 was 5.4 billion, what was the projected population

size in the year 2000 (use info from previous question)?

= population size in 1993 = 5.4 billion

t = 7 years (year 2000 - 1993)

r = 0.0139 (from question above)

= N

(0.0139)(7)

= (540,000,000) e

0.0973

/540,000,000 = e

Dust off your high school math skills. To get rid of the exponent, simply take the natural

log (ln) of both sides of the equation. Remember, when we take the natural log of a

quotient we end up taking the ln of one value and subtracting it from the ln of the other

value (see below).

0.0973

ln (N

/540,000,000) = ln (e

)

[here we're taking the natural log of the quotient]

= ln(N

) - ln(540,000,000) = 0.0973

[rewrite it as natural log of one value minus natural log of the other value]

= 595,000,000 or 5.95 billion

5. A population of Nicotiana, an annual plant, increases by 12% every year. Calculate the

doubling time for this population.

If the population increases by 12% per year, then l = 1.12

r = ln l = ln(1.12) = 0.113 individuals/(individuals x year)

= ln(2)/r

double

Therefore, t = ln(2)/0.113 = 6.1 years

Population Growth Questions Answer Key - Bates Page 2