- #36
- 12,175
- 182
I mean, when you can identify an expression that contains only constants, then that expression is also a constant. This is what I did in Post #25 when I came up with the new constant g'. The previous equation contained the expression [itex]g(1+k2/k1)[/itex] with all constants. So that expression is a constant too. All those constants get combined into a single constant g'.HeLiXe said:When you say that we can rearrange things and combine A into k...how is this done? I am not asking for you to work it out for me, just an indication of what you mean exactly.
In Post #28, I had written
[tex]\frac{dp}{dt}=p(kp/A−g)[/tex]
Focus on the term kp/A, which contains two constants. If we define a new constant k'=___(?), then we can reduce that to one constant.
Yes, strickly speaking you're right. We could have even more than two variables to model different age groups, since newborns and extremely aged rhinos have a different mortality rate than adult males.ehild said:Should not this be a two variable problem? If I remember well, there has to be a male and a female to produce a baby, but only females can give birth. So the growth rates of both male and female rhinos are proportional to the probability that a female rhino meets a male during the mating period, and the number of female rhinos.
The baby can be a male or female, say, with equal probability and you have to subtract the dying rate. But it can be even more complicated than that.
ehild
But for an introductory problem on population models, it's probably best to keep things simple. If this is the first time you're modelling a population, just model it as a single population to familiarize yourself with the concepts.