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Chapter 45 Population Ecology
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Ecology:
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Overview: Earth’s Fluctuating Populations: To understand _____________________________
We must consider the general principles of _____________________
_____________________________, including the human population, can continue to grow indefinitely
Population ecology
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Including environmental influences on population _______________________and
__________________________, ______________________________, and variations in population size
The fur seal population of St. Paul Island, off the coast of Alaska is one that has experienced dramatic
fluctuations in size
Concept 52.1: Dynamic biological processes influence population _______________________,
________________________, and ________________________________
A population:
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Density
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Dispersion
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Density: A dynamic perspective
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Determining the ________________________ of natural population is possible, but difficult to accomplish
In most cases it is impractical or impossible to count _______________________________Density is the result
of a dynamic interplay
Between processes that add individuals to a population (________________________) and those that remove
individuals from it (_______________________) in a population
Patterns of Dispersion
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Environmental and __________________________ factors
Influence the _____________________ of individuals in a population
A clumped dispersion Is one in which individuals aggregate in ___________________________
May be influenced by resource _____________________________ and _____________
__________________________________ are often found together because it favors soil conditions and
other environmental factors
A uniform dispersion Is one in which individuals are ________________________________
May be influenced by social interactions such as_______________________________________
Some ____________________________ produce chemicals to inhibit the germination and growth of nearby
individuals that compete for resources.
A random dispersion is one in which the position of each individual is ________________________ of other
individuals
(c) Random. Dandelions grow from
windblown seeds that land at random and
later germinate.
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Demography
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__________________________is the study of the vital statistics of a population and how they change over
time
____________________ rates and_____________________________ rates are of particular interest to
demographers
Life Table
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A life table:
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Life table of Belding’s Squirrel
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Survivorship Curves
 A survivorship curve
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Survivorship Curve can be classified in three types
_____________________________ is flat at the start, reflecting low death rates during early and middle
life and drops steeply as many older individuals die
_______________________________ are this curve because produce few individuals are provide good
care
____________________________: Constant death over an individual life span
Examples:
_______________________________: drops sharply at the start, reflecting very high death rates for the
young, but flattens out as death rate declines for those individuals that survived to a certain critical
period
• Survivorship curves can be classified into three
general types
Number of survivors (log scale)
– Type I, Type II, and Type III
1,000
I
100
II
10
III
1
0
Figure 52.5
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50
Percentage of maximum life span
100
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The survivorship curve for Belding’s ground squirrels: Shows that the death rate is relatively
_____________________
_______________________________ Survivorship Curve
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Reproductive Rates
 A reproductive table, or ___________________schedule is an age-specific summary of the reproductive
rates in a __________________________
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A reproductive table
Describes the _______________of
a population
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Concept 52.2: Life history traits are products of ______________________________________
Life history traits are ______________________________
Reflected in the ____________________________________________________________ of an
organism
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Three basic variable: When reproduction ___________________, how
____________________________an organism reproduces, and _____________________ offspring are
reproduce
 Life histories are very __________________________.
 Species that exhibit _______________________________, or “big-bang” reproduction : Reproduce a
single ________________________________________ Species that exhibit ____________________________, or repeated reproduction: Produce offspring
repeatedly ___________________________________
Trade off and Life Histories
 Which may lead to trade-offs between ____________________________________
 Showed that survival was _____________________ to parents caring for their young.
 Some plants produce a ___________________________ number of small __________________:
ensuring that at least some of them will grow and eventually reproduce
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Other types of plants produce a moderate number of __________________seeds
That provide a large store of energy that will help seedlings become established
Parental care of smaller broods may also facilitate ________________________________
Concept 52.3: The ____________________________ model describes population growth in an idealized,
unlimited environment
It is useful to study population growth in an idealized situation
In order to understand the capacity of species for increase and the conditions that may facilitate this
type of growth
Per Capita Rate of Increase
 If immigration and emigration are ignored
 A ______________________________________ (per capita increase) equals birth rate minus death rate
 _______________________ population growth : Occurs when the birth rate equals the death rate
 The population growth equation can be expressed as
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Exponential Growth
 ____________________________ population growth: Is population increase under idealized conditions
 Under these conditions: The rate of reproduction is at its maximum, called the
______________________________________
 The equation of exponential population growth is
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Exponential population growth results in a ___________________________________
The J-shaped curve of exponential growth is characteristic of some _____________________________
that are rebounding
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Concept 52.4: The logistic growth model includes the concept of carrying capacity
Exponential growth: Cannot be sustained for _________________ in any population
A more realistic population model limits growth by incorporating _____________________________
Carrying capacity (K):
Logistic Growth Model
 In the ________________________________________________________ the per capita rate of
increase declines as carrying capacity is reached
 We construct the logistic model by starting with the __________________________________________
 And adding an expression that reduces the per capita rate of increase as _________________ increases
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The logistic growth equation includes K, the __________________________
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Hypothetical example of
logistic growth
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The logistic model of population growth produces a sigmoid (_________________________) curve
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Logistic model and real population
 The growth of laboratory populations of _____________________________
 Fits an S-shaped curve
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Some populations overshoot K
Before settling down to a relatively _________________________________
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Some_______________________________ fluctuate greatly around K
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The logistic model fits few ___________________________________
But is useful for __________________________________ possible growth
Life history traits favored by _________________________________
May vary with ___________________________________ and environmental conditions
K-selection, or ______________________________________ selection
Selects for life history traits that are sensitive to population density
Example: ________________________________________
r-selection, or ________________________________________ selection
Selects for life history traits that maximize reproduction
Example: ____________________________________________________
The concepts of K-selection and r-selection
Are somewhat controversial and have been criticized by ecologists as oversimplifications of the variation
seen in the _________________________________________ of species
 Concept 52.5: Populations are regulated by a complex interaction of _______________________ and
_____________________ influences
 There are two general questions we can ask : About regulation of ____________________________
 What environmental factors stop a population from growing?
 Why do some populations show ______________________________________ in size over time, while
others remain stable?
Population Change and Population Density
 In density-independent populations: ____________________________ and _______________________
do not change with population density
 In density-dependent populations: ___________________________ fall and
_________________________ rise with population density
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Determining equilibrium for population density
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Density-Dependent Population Regulation
 Density-dependent birth and death rates : Are an example of ________________feedback that regulates
population growth
 Are affected by many different mechanisms
Competition for Resources
 In crowded populations, increasing ____________________________
 Intensifies intraspecific _____________________________for resources
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Territoriality
 In many ________________________________ and some invertebrates
 Territoriality may limit ___________________________
 ___________________________are highly territorial
 Using ______________________ communication to warn other cheetahs of their boundaries
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Oceanic birds: Exhibit territoriality in _____________________________ behavior
Gannets nest virtually a peck apart and
defend their territories by calling and
pecking at one another.
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Health
 Population density: Can influence the _____________________________ of organisms
 In ____________________________ populations: ___________________________can spread more rapidly
Predation
 As a________________________ population builds up_____________________________ may feed
preferentially on that species
Toxic Waste
 The accumulation of toxic wastes can contribute to ___________________________ regulation of population
size
Instrinsic Factors
 For some populations________________________________ (physiological) factors appear to regulate
population size
Population Dynamics
 The study of _______________________________________ focuses on the complex interactions between
biotic and abiotic factors that cause variation in population size
Stability and Fluctuations
 Long-term population studies have challenged the hypothesis that populations of large mammals
are______________________________________ over time
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Extreme fluctuations in population size are typically more common in _________________________than in
large mammals
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Metapopulations and Immigration
 Metapopulations :
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High levels of immigration combined with higher survival can result in greater __________________________ in
populations
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Population Cycles
 Many populations undergo regular _____________________________ cycles
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Boom-and-bust cycles are influenced by complex interactions between _______________________________
factors
 Concept 52.6:________________________ population growth has slowed after centuries of exponential
increase
 No population can grow ____________________________ and humans are no exception
Global Human Population
 The human population increased ____________________ until about 1650 and then began to grow
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Though the global population is still __________________________
The rate of growth began to slow approximately__________________ years ago
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Regional Patterns of Population Change
 To maintain population ______________________ a regional human population can exist in one of two
configurations
 Zero population growth = High birth rates – High death rates
 Zero population growth = Low birth rates – Low death rates
 The demographic transition:
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The demographic transition
Age Structure
 One important demographic factor in present and future ___________________________________
 Is a country’s ___________________________, the relative number of individuals at each age
 Age structure is commonly represented in __________________________________
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 Age structure diagrams can predict a ___________________________________
 Can illuminate ____________________________________ and help us plan for the future
Infant Mortality and Life Expectancy
 _______________________________ and ________________________________ at birth vary widely among
developed and developing countries but do not capture the wide range of the human condition
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Global Carrying Capacity
 Just how many humans can the biosphere support?
 Estimate today is: __________________________ to over 1,000 billion (1 trillion) people, with an over of
_______________________________.
Estimate of Carrying Capacity
 The _________________________________ of Earth for humans is uncertain
Ecological Footprint
 The ecological footprint concept summarizes the _______________________ and ___________________
needed to sustain the people of a nation
 Is one measure of how close we are to the _________________________ of Earth
 Ecological footprints for 13 countries show that the countries vary greatly in their footprint size and their
available ____________________________
Two conclusion were found in this
graph”
1-countries vary greatly in their
individual footprint size and in their
available ecological capacity (the actual
resource based of each country).
2- The world was already in ecological
deficit when the study was conducted
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Overall analysis suggest that he world is
not at or slightly above its carrying
capacity
At more than 6 billion people the world is already in ______________________________________