Download Regulation of Populations - Deans Community High School

Chapter 34
Regulation of Populations
Factors affecting population size
Define the following:
Population:
Birth rate:
Death rate:
Population dynamics:
Population density:
Carrying capacity:
What is the relationship between birth rate and death rate when dynamic equilibrium is
reached in a population?
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Chapter 34
Although each species has enormous reproductive potential, populations do not increase
in size indefinitely under natural conditions due to environmental resistance. Factors
which affect the size of a population fall into 2 categories:
Density-independent factors affect population growth regardless of population density.
These factors tend to cause a sudden drastic reduction in population number, although
after sufficient time the population normally makes a full recovery. These factors are
usually extreme and will wipe out most of a population whether it is densely packed or
sparsely distributed in the ecosystem. e.g. forest fire, lava flow, flood, drought, unusually
extreme temperatures.
In contrast, some factors affect a population only once it has reached a particular density.
Up to that point, a small population will increase - until its growth rate is affected by a
factor related to population density.
Density-dependent factors affect populations once they have reached a certain size and
density.
Write brief notes on the following density-dependent factors :
Competition for food:
Toxic wastes:
Parasitism and disease:
Predation:
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Chapter 34
Predator-prey interactions
Study graphs at Figs 34.7 and 34.8 and make sure you understand what they show.
Why is the regulation of population size seen as an example of homeostatic control?
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