In order to maintain stable population size, must there be a constant 50/50 sex ratio?
Stable Population size: Require a 50/50 sex ratio?
- Thread starter SaintJude
- Start date
- Joined
- Dec 30, 2009
- Messages
- 2,641
- Reaction score
- 527
I don't see a correlation between the two. You can have a population disappear or grow exponentially while still having 50/50 ration. You should also be able to have a stable population with a different ration, provided that individuals don't mate for life. Actually, even that should not be important as a requirement - if say only half of the individuals need to reproduce to maintain the population, you can get by with a sex disbalance even if they do mate for life. All this is just theoretical - I don't know any specific species to give you as an example.
Here is one, actually: bees.
Here is one, actually: bees.
- Joined
- May 18, 2009
- Messages
- 444
- Reaction score
- 29
All you need is mortality rate =birth rate
Think of it this way, if pop had a low mortality rate, and each female gave birth to 10 young at a time, a 50/50 sex ratio would cause massive population increase.
For the pop to be stable, you need a much lower ratio.
Think of it this way, if pop had a low mortality rate, and each female gave birth to 10 young at a time, a 50/50 sex ratio would cause massive population increase.
For the pop to be stable, you need a much lower ratio.
- Joined
- Jan 12, 2010
- Messages
- 674
- Reaction score
- 1,380
Think of it like a farm.
1 Bull, 100 cows. Bull nails each cow. Each cow has a crib midget.
Mommy cow goes off to the beef factory. Baby cow grows into a new mommy cow. Population stays stable.
(I realize some of the new offspring will be male yes, but the farmer would sell those, knock up some of the females a couple extra times, and still have 100 head to send to slaughter. The point of the example still works)
1 Bull, 100 cows. Bull nails each cow. Each cow has a crib midget.
Mommy cow goes off to the beef factory. Baby cow grows into a new mommy cow. Population stays stable.
(I realize some of the new offspring will be male yes, but the farmer would sell those, knock up some of the females a couple extra times, and still have 100 head to send to slaughter. The point of the example still works)
- Joined
- May 18, 2009
- Messages
- 444
- Reaction score
- 29
Remember that example only works if all of the original cows die.
Or else there will be a population of 200 cows for an amount of time.
Or else there will be a population of 200 cows for an amount of time.
- Joined
- Oct 4, 2011
- Messages
- 226
- Reaction score
- 5
Think fitness. As was mentioned, it depends more on the fitness of the offspring to survive than if you have a 50/50 ratio. If you have a 50/50 ratio and no offspring live to reproduce you will have a declining population size. If the opposite were true, high fitness and not a 50/50 ratio, you could maintain a stable population size. Therefore, the 50/50 ratio is not necessary.
