Question

 As a professor of xenobiology, you and several of your students have traveled to the ice planet Hoth to study the ecology of wampas (the picture on the right below). As an initial project, you decide to construct a life table for this ferocious predator. Below are the data you have gathered from the cohort born the year you arrived:

 (A) Using the information above, calculate the following values for this life table: (i) survivorship values, Lx (ii) mortality values, dx; (iii) net reproductive rate, R0; (iv) generation time, T, and (v) per-capita population growth rate, r.

 (B) What do the two measures R0 and r tell you about this population of wampas?

 (C) Draw a survivorship curve for this population of wampas. What type of curve does this most closely resemble: Type I, Type II, or Type III? Be sure to explain why you think this!

Answer 1

a) We are trying to create a static life table for Wampas from the given table. Life tables help to analyze birth, death and reproductive success of any cohort.

i) Survivorship (I_x) refers to the proportion of individuals surviving to each life stage (age). I_x is defined as the number of individuals surviving to the age x per the total number of individuals in the cohort.

  

ii) Mortality values refer to the proportion of individuals dying in each age. It is given by subtracting survival value of age x from survival value of age x+1.

    

iii) Net reproductive rate is the average number of offsprings produced in the cohort, given by the equation.

where Ix is the survival value and bx is the number of offspring at age x.

Calculated R₀ is R₀ = 0.72

v) Generation time T is estimated using the following equation

  

where x= age, Ix = Survivorship at age x, bx= number of offsprings at age x

Calculated generation time is T = 4.6