9.4 Population Growth
Notes
Populations change in size through births, deaths, immigration and emigration.
- Exponential growth (J-shaped curve) happens when resources are unlimited.
- Logistic growth (S-shaped curve) slows and levels off at the carrying capacity, the largest population the environment can support.
- Limiting factors keep populations in check. Density-dependent factors get stronger as the population grows (food, disease, competition, predation). Density-independent factors affect a population regardless of size (fires, floods, extreme weather).
- The human population has grown very quickly over the past 200 years.
Practice
A population of deer grows quickly, then levels off at about 500 deer. The number 500 represents the:
Carrying capacity is the maximum population the environment can support.
Which is a density-dependent limiting factor?
Disease spreads more easily when individuals are crowded together.
Bacteria placed in a dish of fresh nutrients double every 20 minutes. Their growth at first is:
With unlimited resources, the population grows faster and faster.
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