Download Carrying Capacity

Thursday, August 27th
Limiting Factors Restrict Growth
Learning Goals
• Factors that slow a population’s growth or
prevent it from existing in certain areas
• Outline the characteristics of populations that help
predict population growth
• Assess logistic growth, carrying capacity, limiting factors,
and other fundamental concepts in population ecology
Agenda
• Population Notes
• Lesson of the Kaibab WS
Homework
• Ch. 3 Quiz Monday
Limiting Factors Restrict Growth
• Density-independent factors: factors that
affect a population regardless of its density
− EX: Events such unusual weather, natural disasters,
seasonal cycles, certain human activities—such as
damming rivers and clear-cutting forests
• Density-dependent factors: factors that affect a
population related to its density
− EX: Increased risk of predation, competition for mates,
disease, stress, food availability
− Operate only when the population density reaches a
certain level.
These factors operate most strongly when a
population is large and dense.
They do not affect small, scattered populations as
greatly
Carrying Capacity
• The maximum population size
of a species that its
environment can sustain
− An S-shaped logistic growth
curve
− Limiting factors slow and stop
exponential growth
1
Carrying Capacity
• When a population grows larger than carrying capacity,
there aren’t enough resources and deaths outnumber
births, population size brought back to carrying capacity
• When a population shrinks smaller than carrying capacity,
there are more resources and births outnumber deaths,
bringing the population size back to carrying capacity
Activity: Lesson of the
Kaibab WS
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