r= (LN(N2/N1))/5
r= population growth rate
N2= population during the second observation
N1= population during first observation
5 means the date interval between first observation and second observation
This formula was used by Chau in his study about aphids, which is entitled " Influences of fertilization on Aphis gossypii and insecticide usage".
Hi Annabelle, in order to answer your question we need to know values for N1 and N2 as well as the unit for 5 (minutes, hours, days?). At the moment all we can say is that Chau measured N1 and N2 at an interval of 5. In order to obtain a more accurate growth rate I suggest you measure N over time and plot ln(N) vs time using Excel for example. Identify the region that is linear, apply the linear trendline equation (y = mx + n) and extract the specific growth rate from the slope (m). You can then use another equation to determine the doubling time: t1/2 = ln 2 / m. Hope this helps?
Hi Robert, N1 could be 5 insects and N2 could be 21 insect. 5 represents day.
Assuming that N1 and N2 data were obtained during exponential growth the calculated specific growth rate is 0.55 d-1. The doubling time is 1.25 days.
- Badges
- Science topic
- Similar topics
- Agriculture
- Horticulture
- Seeds