Carrying capacity
Jan 02, 2016
I. What is carrying capacity?
• Carrying capacity is the maximum population size of a species that a given environment can sustain.
• Limiting factors constrain population growth.
• Physical factors• Chemical factors• Biological factors
Populations tend to increase exponentially, followed by a slowdown, then stopped by limiting factors.
logistic growth curve
II. Carrying capacity and real populations
A. Density-dependent factors influence populations
1. Benefits of high population density?
2. Problems with high population density?
B. Density independent factors influence populations
1. Examples?
C. Real populations do not always follow predicted models (e.g., logistic growth model)
D. Why not?– Logistic model assumes populations adjust
immediately to growth– Allee effect
E. Biotic potential 1.K-selected species- stabilize at or near
their carrying capacity
2.r-selected species- devote energy to producing as many offspring as possible, fluctuate around carrying capacity
B. Rate of growth of human populations began to slow in 1960’s
– 2.2% in 1962– 1.15% in 2005– Projected 0.4% in 2050– Why?
D. Global carrying capacity1. Difficult to estimate
2. Limits on human population size?
a. ecological footprint