Carrying capacity

REVIEW

Organism

Population

Community

Ecosystem

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

• Logistic growth curve is oversimplified; real populations can behave differently

Carrying capacity can change.

Factors that may influence?

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

III. Humans and carrying capacity

A. Global human population

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?

C. Regional patterns

D. Global carrying capacity1. Difficult to estimate

2. Limits on human population size?

a. ecological footprint

IV. What does this have to do with matter and energy?