Transcript Density-dependent limiting factor

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5-2 Limits to Growth
• The primary productivity of
an ecosystem can be
reduced when there is an
insufficient supply of a
particular nutrient.
• Limiting factor: the factor
that causes population
growth decline
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Limiting Factors
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• Examples of limiting factors:
Human disturbances
Competition
Predation
Parasitism and disease
Drought and other climate
extremes
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Limiting Factors
• Density-Dependent Factors
• Density-dependent limiting factor: A
limiting factor that depends on
population size.
• These factors come into play mostly
with a large, dense population.
• They do not affect scattered populations
as much
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Density-Dependent Factors
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• Density-dependent limiting factors
include:
• competition
• predation
• parasitism
• disease
• Competition
• When populations become
crowded, organisms compete for
food, water space, sunlight and
other essentials.
• Competition among members of
the same species is a densitydependent limiting factor.
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Density-Dependent Factors
The more individuals that live in an
area, the sooner the resources will be
used up.
• Example: The Atlantic puffin lives in
large colonies along the coast of
eastern North America from Maine to
the artic. Puffins nest in burrows dug
into the sides of cliffs. Because nesting
sites are limited, puffins must compete
for space.
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• Remember the competition exclusion
principle?
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• Competition can also occur between
members of different species.
• This type of competition is a major force of
evolutionary change.
• Over time, the species may evolve to occupy
different niches.
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• Populations in nature are often
controlled by predation.
• The regulation of a population by
predation takes place within a predatorprey relationship.
Tapeworms can
be 30 ft in
length.
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• Parasitism and Disease
• Parasites can limit the growth of a
population by taking nourishment,
causing the host to become weak,
diseased or dead.
• A parasite lives in or on another
organism (the host) and consequently
harms it.
• Environments are always changing, and
most populations can adapt to a certain
amount of change.
• Major upsets can lead to long-term
declines
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• Density-independent limiting factors
affect all populations in similar ways,
regardless of the population size.
Density-Independent Factors
• Examples of density-independent limiting
factors include:
• natural disasters
• seasonal cycles
• certain human activities—such as
damming rivers and clear-cutting
forests
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• unusual weather
• Abiotic factors
• Climate extremes
• Human
disturbances
• Building roads
• Filling wetlands
• Clearing forests
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• Biotic factors
Competition
Predation
Parasitism
Disease
Human disturbances
• Poaching
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5-2
5-2
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drought.
disease.
predation.
crowding.
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• A limiting factor that affects all populations in similar ways
regardless of their size might be
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programs that educate people about endangered species
capture of some pandas for placement in zoos
laws protecting habitat destruction
a disease that kills bamboo plants
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• Which of the following would be a limiting factor affecting the
panda population of China?
5-2
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large and dense.
large but sparse.
small and sparse.
small, but growing.
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• Density-dependent factors operate most strongly when a
population is
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increase.
decrease.
remain about the same.
become extinct.
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• Within a limited area, if the population of a predator
increases, the population of its prey is likely to
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predation
disease
a destructive hurricane
parasites
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• Which of the following is a density-independent factor
affecting populations?
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