Carrying capacity belongs to the habitat
- The idea
- Predict
- See it
- Why
- Check
The idea
“Each species has its own carrying capacity, so it levels off at the same size wherever it lives.”
K sits in the equation next to r, the species' built-in growth rate, so it reads like a fact about the animal. Yet one species can level off at very different sizes.
The short version
The mistake: Each species has its own carrying capacity, so it levels off at the same size wherever it lives.
What's actually true: Carrying capacity is set by what a habitat supplies, so one species levels off higher where resources are plentiful.
- Carrying capacity, K, is the largest population a habitat can support over time. It depends on the food, water and space there, and on what each individual needs.
- As a population nears K, each individual gets a smaller share, so births fall and deaths rise. The 1 - N/K term in the logistic model brings growth to zero at K.
- The intrinsic rate of increase, r, is how fast a population grows with plenty of resources. It comes from the species' biology and sets how steep the climb is.
On the exam: K belongs to the habitat. When food or space changes, K changes with it.