Title: Chapter 52 (pgs. 1151- 1172) Population Ecology
1Chapter 52 (pgs. 1151- 1172) Population Ecology
- AP minknow
- How density, dispersion, and demographics can
describe a population. - The differences between exponential and logistic
models of population growth. - How density-dependent and density-independent
factors can control population growth
2- Characteristics of Populations
- 1.Define the scope of population ecology
- 2.Define and distinguish between density and
dispersion. - 3.Explain how ecologists measure the density of a
species. - 4.Describe conditions that may result in the
clumped dispersion, uniform dispersion, and
random dispersion of populations. - 5.Describe the characteristics of populations
that exhibit Type I, Type II, and Type III
survivorship curves. - 6.Describe the characteristics of populations
that exhibit Type I, Type II, and Type III
survivorship curves. - Life History Traits
- 7.Define and distinguish between semelparity and
iteroparity. - 8.Explain how limited resources affect life
histories. - 9.Give examples of the trade-off between
reproduction and survival.
3- Population Growth
- 10.Compare the geometric model of population
growth with the logistic model. - 11.Explain how an environment's carrying capacity
affects the intrinsic rate of increase of a
population. - 12.Distinguish between r-selected populations and
K-selected populations. - 13.Explain how a "stressful" environment may
alter the standard r-selection and K-selection
characteristics. - Population-Limiting Factors
- 14.Explain how density-dependent factors affect
population growth. - 15.Explain how density-dependent and
density-independent factors may work together to
control a population's growth. - 16.Explain how predation can affect life history
through natural selection. - 17.Describe several boom-and-bust population
cycles, noting possible causes and consequences
of the fluctuations. - Human Population Growth
- 18.Describe the history of human population
growth. - 19.Define the demographic transition.
- 20.Compare the age structures of Italy, Kenya,
and the United States. Describe the possible
consequences for each country. - 21.Describe the problems associated with
estimating Earth's carrying capacity.
4- Population ecology is the study of populations in
relation to environment - Including environmental influences on population
density and distribution, age structure, and
variations in population size
552.1 Dynamic biological processes influence
population density, dispersion, and demographyA
population
- A population
- Is a group of individuals of a single species
living in the same general area
6Density and Dispersion
- Density
- Is the number of individuals per unit area or
volume - Dispersion
- Is the pattern of spacing among individuals
within the boundaries of the population
7Density A dynamic perspective.
- Determining the density of natural populations
- Is possible, but difficult to accomplish
- In most cases
- It is impractical or impossible to count all
individuals in a population - Density is the result of a dynamic interplay
- Between processes that add individuals to a
population and those that remove individuals from
it
8Patterns of Dispersion
- Environmental and social factors
- Influence the spacing of individuals in a
population. - There are three different Patterns of Dispersion
- Clumped Dispersion
- Uniform Dispersion
- Random Dispersion
9- A clumped dispersion
- Is one in which individuals aggregate in patches
- May be influenced by resource availability and
behavior
10- A uniform dispersion
- Is one in which individuals are evenly
distributed - May be influenced by social interactions such as
territoriality
11- A random dispersion
- Is one in which the position of each individual
is independent of other individuals
Figure 52.3c
(c) Random. Dandelions grow from windblown seeds
that land at random and later germinate.
12Life Tables
- A life table
- Is an age-specific summary of the survival
pattern of a population - Is best constructed by following the fate of a
cohort
13Survivorship Curves
- A survivorship curve
- Is a graphic way of representing the data in a
life table
14- Survivorship curves can be classified into three
general types - Type I, Type II, and Type III
Many species fall somewhere between these basic
types of survivorship curves. Some
invertebrates, such as crabs, show a
stair-stepped curve, with increased mortality
during molts.
Figure 52.5
1552.2 Life histories are highly diverse, but they
exhibit patterns in their variability.
- Life histories entail three basic variables
- when reproduction begins
- how often the organism reproduces
- how many offspring are produced during each
reproductive episode. - These histories are evolutionary outcomes
reflected in the development, physiology, and
behavior of an organism. - Some organisms, such as the agave plant, exhibit
semelparity. Big Bang Production. (then death) - By contrast, some organisms exhibit iteroparity.
- They produce only a few offspring during repeated
reproductive episodes.
16- Some plants produce a large number of small seeds
- Ensuring that at least some of them will grow and
eventually reproduce
17- Other types of plants produce a moderate number
of large seeds - That provide a large store of energy that will
help seedlings become established
18What factors contribute to the evolution of
semelparity versus iteroparity?
- In other words, how much does an individual gain
in reproductive success through one pattern
versus the other? - The critical factor is survival rate of the
offspring. - When the survival of offspring is low, as in
highly variable or unpredictable environments,
big-bang reproduction (semelparity) is favored. - Repeated reproduction (iteroparity) is favored in
dependable environments where competition for
resources is intense. - In such environments, a few, well-provisioned
offspring have a better chance of surviving to
reproductive age.
19Population Growth is measured byPer Capita Rate
of Increase
- If immigration and emigration are ignored
- A populations growth rate (per capita increase)
equals birth rate minus death rate
Growth rate rN It can be found using the
equation---
20Exponential Population Growth
- Exponential population growth
- Is population increase under idealized conditions
- Under these conditions
- The rate of reproduction is at its maximum,
called the intrinsic rate of increase
- Exponential population growth
- Results in a J-shaped curve
21The J-shaped curve of exponential growth
- Is characteristic of some populations that are
rebounding
2252.4 The logistic growth model includes the
concept of carrying capacity
- Exponential growth
- Cannot be sustained for long in any population
- A more realistic population model
- Limits growth by incorporating carrying capacity
- Carrying capacity (K)
- Is the maximum population size the environment
can support
23The Logistic Growth Model
- In the logistic population growth model
- The per capita rate of increase declines as
carrying capacity is reached
We construct the logistic model by starting with
the exponential model And adding an expression
that reduces the per capita rate of increase as N
increases
24The logistic growth equation
- Includes K, the carrying capacity
25- The logistic model of population growth
- Produces a sigmoid (S-shaped) curve
Figure 52.12
26- As N approaches K for a certain population, which
of the following is predicted by the logistic
equation? - The growth rate will not change.
- The growth rate will approach zero.
- The population will show an Allee effect.
- The population will increase exponentially.
- The carrying capacity of the environment will
increase.
27The Logistic Model and Real Populations
- The growth of laboratory populations of paramecia
- Fits an S-shaped curve
- Some populations overshoot K
- Before settling down to a relatively stable
density - Some populations
- Fluctuate greatly around K
28The Logistic Model and Life Histories
- Life history traits favored by natural selection
- May vary with population density and
environmental conditions - K-selection, or density-dependent selection
- Selects for life history traits that are
sensitive to population density - K-selection tends to maximize population size and
operates in populations living at a density near
K. - r-selection, or density-independent selection
- Selects for life history traits that maximize
reproduction - r-selection tends to maximize r, the rate of
increase, and occurs in environments in which
population densities fluctuate well below K, or
when individuals face little competition.
Controversy
29- 52.5 Populations are regulated by a complex
interaction of biotic and abiotic influences - In density-independent populations
- Birth rate and death rate do not change with
population density - In density-dependent populations
- Birth rates fall and death rates rise with
population density - Determining equilibrium for population density
30Density-Dependent Population Regulation
- Density-dependent birth and death rates
- Are an example of negative feedback that
regulates population growth - Are affected by many different mechanisms
- Competition for Resources
- Territoriality
- Health (Disease/Parasites)
- Predation
- Toxic Wastes (think bacteria)
31Competition for Resources
- In crowded populations, increasing population
density - Intensifies intraspecific competition for
resources
32Territoriality
- Cheetahs are highly territorial
- Using chemical communication to warn other
cheetahs of their boundaries
33Population Dynamics
- The study of population dynamics
- Focuses on the complex interactions between
biotic and abiotic factors that cause variation
in population size
34Stability and Fluctuation
- Long-term population studies
- Have challenged the hypothesis that populations
of large mammals are relatively stable over time
35Extreme fluctuations in population sizeAre
typically more common in invertebrates than in
large mammals
Fluctuating Wind pushing eggs out to
sea Cannibalism
36Metapopulations and Immigration
- Metapopulations
- Are groups of populations linked by immigration
and emigration - High levels of immigration combined with higher
survival - Can result in greater stability in populations
- Are groups of populations linked by immigration
and emigration
37Population Cycles
- Many populations
- Undergo regular boom-and-bust cycles
- Three main hypotheses have been proposed to
explain the lynx/hare cycles. - The cycles may be caused by food shortage during
winter. - The cycles may be due to predator-prey
interactions. - The cycles may be affected by a combination of
food resource limitation and excessive predation.
38Limiting Factors
Density Dependant Factors
Density Independent Factors
39- 52.6 Human population growth has slowed after
centuries of exponential increase - No population can grow indefinitely
- And humans are no exception
The Global Human Population
Increased relatively slowly until about 1650 and
then began to grow exponentially
40Global population Growth Rate
- Though the global population is still growing
- The rate of growth began to slow approximately 40
years ago
41Age Structure
- One important demographic factor in present and
future growth trends - Is a countrys age structure, the relative number
of individuals at each age - Usually presented in Pyramids
42Infant Mortality and Life Expectancy
- Infant mortality and life expectancy at birth
- Vary widely among developed and developing
countries but do not capture the wide range of
the human condition
43Global Carrying Capacity
- Just how many humans can the biosphere support?
- It is complex and we just dont know, but we
have.
44Ecological Footprint
- The ecological footprint concept
- Summarizes the aggregate land and water area
needed to sustain the people of a nation - Is one measure of how close we are to the
carrying capacity of Earth
At more than 6 billion people The world is
already in ecological deficit