Download Chapter 35-Population Dynamics 2

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 35
Population Dynamics
Modules 35.6 – 35.10
From PowerPoint® Lectures for Biology: Concepts & Connections
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LIFE HISTORIES AND THEIR EVOLUTION
35.6 Life tables track mortality and survivorship in
populations
• Life tables and survivorship curves predict an
individual's statistical chance of dying or
surviving during each interval in its life
• Life tables predict how long, on average, an
individual of a given age can expect to live
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– This table was compiled using 1995 data from
the U.S. Centers for Disease Control
Table 35.6
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• Population ecologists have adopted this
technique, constructing life tables for various
plant and animal species
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• Survivorship curves plot the proportion of
individuals alive at each age
• Three types of survivorship curves reflect
important species differences in life history
Figure 35.6
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35.7 Evolution shapes life histories
• An organism's life history is the series of events
from birth through reproduction to death
• Life history traits include
– the age at which reproduction first occurs
– the frequency of reproduction
– the number of offspring
– the amount of parental care given
– the energy cost of reproduction
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• The effects of
predation on
life history
traits of
guppies has
been tested
by field
experiments
for several
years
Experimental
transplant of
guppies
Predator: Killifish;
preys mainly on
small guppies
Guppies:
Larger at
sexual maturity
than those in “pike-cichlid”
pools
Predator: Pike-cichlid;
preys mainly on large
guppies
Guppies: Smaller at
sexual maturity than
those in “killifish” pools
Figure 35.7A
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• In nature, every population has a particular life
history adapted to its environment
• The agave illustrates
what ecologists call
"big-bang
reproduction"
– It is able to store
nutrients until
environmental
conditions favor
reproductive success
Figure 35.7B
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• Natural selection favors a combination of life
history traits that maximizes an individual's
output of viable, fertile offspring
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• Selection for life history traits that maximize
reproductive success in uncrowded,
unpredictable environments is called
r-selection
– Such populations maximize r, the intrinsic rate
of increase
– Individuals of these populations mature early
and produce a large number of offspring at a
time
– Many insect and weed species exhibit
r-selection
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• Selection for life history traits that maximize
reproductive success in populations that live at
densities close to the carrying capacity (K) of
their environment is called K-selection
– Individuals mature and reproduce at a later
age and produce a few, well-cared-for
offspring
– Mammals exhibit K-selection
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THE HUMAN POPULATION
35.8 Connection: The human population has been
growing exponentially for centuries
• The human population as a whole has doubled
three times in the last three centuries
• The human population now stands at about 6.1
billion and may reach 9.3 billion by the year
2050
• Most of the increase is due to improved health
and technology
– These have affected death rates
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• The history of human population growth
Figure 35.8A
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• The ecological footprint represents the amount
of productive land needed to support a nation’s
resource needs
• The ecological capacity of the world may
already be smaller than its ecological
footprint
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• Ecological footprint in relation to ecological
capacity
Figure 35.8B
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• The exponential growth of the human
population is probably the greatest crisis ever
faced by life on Earth
Figure 35.8C
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35.9 Birth and death rates and age structure affect
population growth
• Population stability is achieved when there is
zero population growth
– Zero population growth is when birth rates
equal death rates
• There are two possible ways to reach zero
population growth (ZPG)
– ZPG = High birth rates - high death rates
– ZPG = Low birth rates - low death rates
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• The demographic transition is the shift from
high birth and death rates to low birth and
death rates
– During this
transition,
populations
may grow
rapidly until
birth rates
decline
Figure 35.9A
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• The age structure of a population is the
proportion of individuals in different agegroups
– Age structure affects population growth
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RAPID GROWTH
SLOW GROWTH
ZERO GROWTH/DECREASE
Kenya
United States
Italy
Male
Female
Male
Female
Ages 45+
Ages 45+
Ages 15–44
Ages 15–44
Under
15
Percent of population
Male
Female
Under
15
Percent of population
Percent of population
Figure 35.9B
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• Age-structure diagrams not only reveal a
population's growth trends
– They also indicate social conditions
• Increasing the status and education of
women may help to reduce family size
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35.10 Connection: Principles of population ecology
have practical applications
• Principles of population ecology may be used
to
– manage wildlife, fisheries, and forests for
sustainable yield
– reverse the decline of threatened or
endangered species
– reduce pest populations
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• Renewable resource management is the
harvesting of crops without damaging the
resource
– However, human economic and political
pressures often outweigh ecological concerns
– There is frequently insufficient scientific
information
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• The collapse of the northern cod fishery
– Estimates of cod stocks were too high
– The practice of discarding young cod (not of
legal size) at sea caused a higher mortality rate
than was predicted
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• Collapse of northern cod fishery
Figure 35.10A
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• For species that are in decline or facing
extinction, resource managers try to increase
population size
• Carrying capacity is usually increased by
providing additional habitat or improving
the quality of existing habitat
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• Endangered species
often have subtle
habitat requirements
– The red-cockaded
woodpecker was
recently recovered
from near-extinction
by protecting its pine
habitat and using
controlled fires to
reduce undergrowth
Figure 35.10B
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• Integrated pest management (IPM) uses a
combination of biological, chemical, and
cultural methods to control agricultural pests
• IPM relies on knowledge of
– the population ecology of the pest
– its associated predators and parasites
– crop growth dynamics
• One objective of IPM is to minimize
environmental and health risks by relying on
natural biological control when possible
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