Population/Growth Problem

[Guest cluster]

I posted this in homework help but wasnt getting any responses so now trying here...

 

Hey All - new poster here and would gladly appreciate a push in the right direction for my Global Environment class...I'll set up the problem and show you the work I have done so far...

 

Question:

 

Imagine a hypothetical population with three assumptions:

 

1) Males and females are in the same abundance in all age classes beginning in year 0

2) Newborn males produced @ the same rate as newborn females by mothers of all ages

3) Males and females have same per capita survival rate in all of the different age classes

 

After knowing this I am supposed to find out how many males of each age are present in the population starting @ age 2...

 

Ok what I have done so far...

 

I know this is a trick question whos answer is not readily apparent, and I know I shouldnt have to use a calculator to solve it...

 

I tried setting up a tree w/ a fake population to determine the ratio...

 

_____(Year 0) (Year 1) (Year 2)

Age 1(1m, 1f)

Age 2(1m, 1f)

Age 3(1m, 1f)

 

At this point, I follow rule #1 "Males and females are in the same abundance in all age classes beginning in year 0" - I said 1 m, and 1 f are present in each age group @ Year 0

 

_____(Year 0) (Year 1) (Year 2)

Age 1(1m, 1f) (2m, 2f)

Age 2(1m, 1f) (2m, 2f)

Age 3(1m, 1f) (2m, 2f)

 

At this point, I know that if the birth rate of males/females is the same then that one f in each age group will produce, lets say, 1 m and 1 f...and in this situation I also say that the survival rate is 100% (so each newborn carries on to next age)

 

_____(Year 0) (Year 1) (Year 2)

Age 1(1m, 1f) (2m, 2f) (4m, 4f)

Age 2(1m, 1f) (2m, 2f) (4m, 4f)

Age 3(1m, 1f) (2m, 2f) (4m, 4f)

 

So I expand the process again and find that the same number of males and females exist in each age group @ year 2...but something seems wrong b/c this answer is too obvious...

 

Can anyone point out flaws in my logic?

[Anarchaus]

Yes I can, you think too much.

[ecoli]

Yes...there is something seriously wrong. Why would there be 4 m and 4 females at two years of age?

 

since survival rate is 100%, is there is one new male and female at year zero, two years later...the number of males and females at age 2 will still be 1 male and 1 female.

 

Where are you getting the extra people from?

 

I honestly don't see how you are supposed to answer this question...your not given any specific population figures or rates.