Transcript Carrying Capacity (K)

Chapter 9
Population Dynamics, Carrying
Capacity, and Conservation
Biology
Miller – Living in the Environment
13th ed.
Population Dynamics changes in populations as a result of
 environmental stress
 changes in environmental conditions.
How do populations change
over time?
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POPULATION ECOLOGY  # of individuals
of a species in an area AND how/why those
numbers change over time
Effected by resource competition, predation,
disease but can be measured
Major characteristics of a population
1) Size – number of individuals
2) Density – number of individuals in a certain
space
3) Dispersion – spatial pattern of a population
4) Age distribution – proportion of individuals of
each age in a population
Generalized dispersion patterns
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Most populations live in clumps although other
patterns occur based on resource distribution.
Changes in Population Size:
Entrances and Exits
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increase through births + immigration
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decrease through deaths + emigration
biotic potential
– capacity for population growth
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Intrinsic rate of increase (r)
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Life History Characteristics
Reproduction age
Reproduction range of age
Reproductive periods
# of offspring produced
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Large Organisms have small biotic potential
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organisms with a high biotic potential
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reproduce early in life
have short generation times
can reproduce many times
have offspring each time they reproduce
Small Organisms have large biotic potential.
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EX. Bacteria reproduce by dividing in half
every 30 mins…. Plotting this growth vs.
time results in a J shaped curve.
EXPONENTIAL GROWTH results when pop
are growing at biotic potential!
environmental resistance - factors
acting to limit population growth
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No population can grow indefinitely.
There are always limits to population
growth in nature.
Unfavorable env. conditions due to
resource availability
As env conditions deteriorate, b  and d 
Carrying Capacity (K)
Over time, the pop may level out to a certain
point… called carrying capacity (K)
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the number of individuals of a given
species that can be sustained
indefinitely in a given space.
Population Growth Curves
© 2004 Brooks/Cole – Thomson Learning
Population size (N)
Population size (N)
K
Carrying capacity
Time (t)
Time (t)
Exponential Growth
Logistic Growth
Exponential and Logistic Population
Growth: J-Curves and S-Curves
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Populations grow
rapidly with
ample resources,
but as resources
become limited,
its growth rate
slows and levels
off.
Exponential and Logistic Population
Growth: J-Curves and S-Curves
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As a population
levels off, it often
fluctuates slightly
above and below
the carrying
capacity.
What Happens When Populations
Exceed Carrying Capacity
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Members of
populations which
exceed their
resources will die
unless they adapt
or move to an
area with more
resources.
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15
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14
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11
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10
9
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World Population
Growth
4
3
2
Black Death–the Plague
2-5
Mil years
Hunting and
gathering
8000
6000
4000
Time
Agricultural revolution
1
2000
2000
B.C.
0
2100
A.D.
Industrial
revolution
Billions of people
12
Population Density
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Density-independent population controls
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Affect a population’s size regardless of its population
density.
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Floods, fires, hurricanes habitat destruction, pesticides
Density-dependent population controls
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Factors that impact population’s size considering
density
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Competition of resources, predation, parasitism, disease
Types of Population Change
Curves in Nature
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Population sizes often vary in regular cycles when
the predator and prey populations are controlled by
the scarcity of resources. (predator-prey oscillation)
Reproductive Patterns and Survival
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Asexual reproduction
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Offspring are exact copies of a single parent
Sexual reproduction
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Organisms produce offspring by combining the
gametes or sex cells from both parent
Disadvantages
 Females must produce twice as many offspring
 Chance of genetic errors increases
 Mating entails costs
Advantages
 Provides greater genetic diversity
 Division of labor – males gather food and protect
females and young
Figure 9-9
Page 196 K species;
Number of individuals
Carrying capacity
experience
K selection
Reproductive
Patterns
r species;
experience
r selection
Time
K
r-Selected Species
Opportunists
cockroach
dandelion
Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental
conditions
High population growth rate (r)
Population size fluctuates wildly above and below
carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species
K-Selected Species
Competitors
elephant
saguaro
Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental
conditions
Lower population growth rate (r)
Population size fairly stable and usually close
to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species
Survivorship Curves:
Short to Long Lives
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The way to represent the age structure of a
population is with a survivorship curve.
shows different reproductive strategies thus
different life expectancies over time
shows survivors at each age group of particular
species
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Late loss population live to an old age.
Constant loss population die at all ages.
Most members of early loss population, die at
young ages.
Percentage surviving (log scale)
Survivorship Curves p. 198
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Age