A population can be defined as the total number of individuals that belong to the same species and inhabit a particular geographical region with the capacity to interbreed only amongst themselves. The term "population" can be defined using two parameters: density and dispersion. Density of a population can be explained as the number of individuals of a species per unit area. Population dispersion is how the density of the population is spaced out in a particular area. The rate of increase of a population depends on many factors like death rate (mortality rate), birth rate (natality rate), immigration, emigration, etc. Not all individuals of a population survive to reach a particular age. A survivorship curve is basically a graph that shows the number of individuals of a species or a particular group that survive at each age. In simpler words, it traces the decline of a group of individuals over time. Survivorship curves help us to determine various evolutionary strategies of different species. It also helps us in understanding how the population density of a species is maintained. In this, the age of the individuals is plotted on the X-axis and the log of the total number of individuals surviving at each age is taken as the Y-axis, on a semilogarithmic graph. According to the curve that is generated, we may be able to comment on the rate of survival and the evolutionary strategies undertaken by the species or the group. Survivorship curves can be broadly classified into three basic types: You can construct a survivor curve in the following few steps. Your survivorship curve will be as accurate as the data you have recorded. This can also be used to check the accuracy of the data. Open a new spreadsheet and fill in the heading and the columns as given in the table. Do this by selecting the cells and type in them. Number the column A from 0-11 (A43-A14). ◆ In A3, give the value zero. ◆ In A4, give the formula = A3+1. Copy this formula in cell A5 and do the same for cells A6-A15. Enter the values in column B (B3-B14) These are the data that have been recorded for each of the survivorship curve and is called survivorship schedule, every entry is the number of survivors at each age. Enter the formulae used to calculate the standardized survivorship, given as l_x, in column E (E3-E14) ◆ In E3, enter the formula = B3/$B$3, continue this from E4-E14. ◆ This corresponds to: (Standardized Survivorship) = (No. of individuals surviving at age x)/(No. of individuals surviving at 0) l_x=S_x/S₀ ◆ Similarly, in F3 the formula = C3/$C$3 and so on; in G3= G3/$G$3 and so on. This part of your spreadsheet work is complete; make sure to save this data before you proceed. Make a graph of the standardized survivorship (l_x) vs. age. ◆ Select the cells A2-A14. ◆ Hold the control key and Select the cells E2-G14. ◆ Create an XY scatter graph. * Source: Data is obtained from the University of Vermont Change the Y-axis to a logarithmic scale. ◆ Double click on the Y-axis and choose the 'number' tab from the dialog box that appears. ◆ Set the number of decimal places to 3. ◆ Choose the 'scale' and select the box for Logarithmic Scale. ◆ Adjust the minimum unit to 0.001, major unit to 10, and Value (x) Crosses at 0.0001. * Source: Data is obtained from the University of Vermont There you have a survivorship graph created by you. Kudos!