How to Calculate Population Size at T+1 Using Life Tables?

Click For Summary

Discussion Overview

The discussion revolves around calculating the population size at T+1 using life tables, specifically focusing on mortality and offspring production rates for different age classes of a species. Participants are attempting to apply these concepts to a homework problem involving population dynamics over a one-year period.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a homework statement and an equation related to population growth, seeking verification of their calculations.
  • Several participants question the initial values used in the calculations, indicating a need for clarification on how these values were derived.
  • There is a discussion about the interpretation of Mx values, which represent the average number of offspring produced per individual per year, and how to apply these to the population at T+1.
  • One participant suggests that the offspring calculation should consider the number of individuals alive at T+1, factoring in mortality rates, leading to uncertainty about whether reproduction occurs before or after mortality is accounted for.
  • Another participant proposes that mortality should not be considered in the calculation of offspring, suggesting that individuals reproduce before dying.

Areas of Agreement / Disagreement

Participants express differing views on how to incorporate mortality rates into the population calculations, indicating that there is no consensus on whether reproduction occurs before or after accounting for mortality. This leaves the discussion unresolved regarding the most logical approach to take.

Contextual Notes

Participants are working with specific mortality and offspring production rates, but there are unresolved assumptions about the timing of reproduction relative to mortality, which affects the final population size calculation.

atomant
Messages
27
Reaction score
1

Homework Statement


http://imgur.com/OInF6O2

The blue table shows the mortality and offspring production rates per year per age class by individuals of an unnamed species. The orange tables shows the starting population at time t, I have to find the number of individuals at T+1 (next year)


Homework Equations



Not sure if relavent but an equation is given: r = ln (NT+1)/NT)/T

The Attempt at a Solution


http://imgur.com/pilNkOP

Would love if someone could check the workings though or see if this makes sense
 
Physics news on Phys.org
How did you get the first value?
I agree with the others.
 
mfb said:
How did you get the first value?
I agree with the others.

Well the basic idea was to calculate the Mx values for the age groups that had an initial population at times t, which means age groups 2 and 3 which has Mx values of 3 and 2 respectively. Therefore the number of 0 age offspring should be 5 (I think)..don't really know how I got 7. Is this correct?
 
Those mx values are "offspring per individual and year". It mean a single individual at age 1 will (on average) get 2 children.

How many do 10 at age 2 get then? And the other groups?
 
  • Like
Likes   Reactions: 1 person
mfb said:
Those mx values are "offspring per individual and year". It mean a single individual at age 1 will (on average) get 2 children.

How many do 10 at age 2 get then? And the other groups?

Ah, I see - so the 10 at age 2 will on average have 30 offspring at t+1 (10 individuals and mx of 3).

The question now then is do I assume that all 10 individuals are alive at t+1 to reproduce? i.e- at age 2 the have a mortality rate of 10%, which means 9 individuals will survive at t+1 to become 3yr olds so do I assume that reproduction occurs after the death based on mortality rate happens or do I assume that these 2yr olds will reproduce before dying? Depending on these assumptions the offspring will either be 30 or 27. The question doesn't specify so I am unsure which is the most logical assumption to take.
 
I would read the table in a way that mortality does not have to be taken into account - in other words, they get children before they can die.
 
Thank you so much for your help, you have been amazing!
 
  • Like
Likes   Reactions: 1 person

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
9K
Replies
13
Views
3K
Replies
5
Views
3K
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
6K
  • · Replies 4 ·
Replies
4
Views
2K