More mouths split a fixed supply
- The idea
- Predict
- See it
- Why
- Check
The idea
“Each animal still gets its usual share. A bigger population just uses more food in total.”
When food is plentiful, more animals really do just eat more in total. That picture stops working once the supply runs out.
The short version
The mistake: Each animal still gets its usual share. A bigger population just uses more food in total.
What's actually true: A fixed supply is divided among everyone sharing it, so more individuals means less for each one.
- Food, light, water and space come in limited amounts. When more individuals share a fixed amount, each one gets less.
- Competition within one species is intraspecific competition. When a share falls below what an individual needs, it grows slower, breeds less and is more likely to die.
- This effect grows with density, so it's density-dependent. It slows population growth as a population nears carrying capacity.
On the exam: Divide the supply by the number sharing it. The total stays capped, so each share shrinks.