Breeding earlier makes a population grow faster
- The idea
- Predict
- See it
- Why
- Check
The idea
“If each female has the same number of young, the populations grow at the same rate.”
Young per female is the number you can count, so it looks like the whole story. When those young arrive never shows up in that count.
The short version
The mistake: If each female has the same number of young, the populations grow at the same rate.
What's actually true: A shorter generation time makes a growing population grow faster, even when each female has the same number of young.
- Generation time is the average age of mothers when their young are born. Breeding earlier makes it shorter.
- New young join the population and soon have young of their own. Each generation builds on the one before, so growth compounds.
- Shorter generations pack more rounds of compounding into the same time. That raises the per capita growth rate, r, with no change in young per female.
On the exam: Count young per female and generations per year. Shorter generations mean more rounds of growth.