ECCB 403 FINAL EXAM QUESTIONS
WITH VERIFIED ANSWERS. A+ GRADE
2025/2026.
Allee Effects - ANS Population growth rates that decrease below replacement level at low
population density, potentially leading to extinction.
Balance of Nature - ANS The belief that natural populations and communities exist in a stable
equilibrium and maintain that equilibrium in the absence of human interference.
Density-Dependent Rate - ANS As population density rises, births or immigration decrease or
deaths or emigration increase, and consequently a graph of population density versus the rate
will have a positive or negative slope.
Density-Independent Rate - ANS As population density rises, the rate does not change in any
systematic manner, so that a graph of population density versus the rate will have a slope of
zero.
Limiting Factor - ANS A factor is defined as limiting if a change in the factor produces a
change in average or equilibrium density.
Metapopulations - ANS Local populations in patches that are linked together by dispersal
among the patches, driven by colonization and extinction dynamics.
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,Regulating Factor - ANS A factor is defined as potentially regulating if the percentage of
mortality caused by the factor increases with population density or if per capita reproductive
rate decreases with population density.
Self-Thinning Rule - ANS The prediction that the regression of organism size versus
population density has a slope of -1.5 for plants and animals that have plastic growth rates and
variable adult size.
Sink Population - ANS Local populations in which the rate of production is below
replacement level so that extinction is inevitable without a source of immigrants.
Source Populations - ANS Local populations in which the rate of production exceeds
replacement so that individuals emigrate to surrounding populations.
Population Regulation is important for: - ANS Conservation, Land Management, and
Fisheries.
We can make two fundamental observations about populations of any plant or animal.
The first observation is that: - ANS Abundance varies from place to place; there are some
"good" habitats where the species is, on the average, common and some "poor" habitats where
it is, on the average, rare.
We can make two fundamental observations about populations of any plant or animal.
The second observation is that: - ANS NO population goes on increasing without limit, and
the problem is to find out what prevents unlimited increase in low- and high-density
populations.
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,We can make two fundamental observations about populations of any plant or animal.
The second observation is that no population goes on increasing without limit, and the problem
is to find out what prevents unlimited increase in low- and high-density populations.
This is the problem of explaining: - ANS Fluctuations in Numbers!
Figure 14.1 illustrates this!
A population in a closed system will increase until it reaches an equilibrium point at which: -
ANS Per Capita Birth rate = Per Capita Death Rate
A population in a closed system1 will increase until it reaches an equilibrium point at which:
Per Capita Birth rate = Per Capita Death Rate
Figure 14.2 illustrates three possible ways in which this equilibrium may be defined.
As a population goes UP: - ANS 1. Birth Rates may FALL
OR
2. Death Rates may RISE
OR
3. BOTH changes may occur
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Figure 14.2 illustrates three possible ways in which a pop, in a closed system will reach a
equilibrium point.
To determine the equilibrium population size for any field population, we need only: -
ANS Determine the curves shown in Figure 2.
- Note that this simple model in no way depends on the shapes of the curves, provided that
they rise or fall smoothly.
- In particular, these curves need NOT be straight lines.
The Per Capita Death Rate is said to be Density-Dependent IF: - ANS It INCREASES as density
INCREASES!
- Figure 14.2a & c
The Per Capita Birth Rate is called Density-Dependent IF: - ANS It FALLS as density RISES
- Figure 14.2a & b
Rates are called Density-Independent IF: - ANS Birth OR Death Rates DO NOT change as
density RISES!
Note that Figure 14.2 does not include all logical possibilities.
Birth rates might, in fact, INCREASE as population density RISES,
OR
Death Rates might DECREASE.
Such rates are called: - ANS Inversely Density-Dependent Rates!
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
WITH VERIFIED ANSWERS. A+ GRADE
2025/2026.
Allee Effects - ANS Population growth rates that decrease below replacement level at low
population density, potentially leading to extinction.
Balance of Nature - ANS The belief that natural populations and communities exist in a stable
equilibrium and maintain that equilibrium in the absence of human interference.
Density-Dependent Rate - ANS As population density rises, births or immigration decrease or
deaths or emigration increase, and consequently a graph of population density versus the rate
will have a positive or negative slope.
Density-Independent Rate - ANS As population density rises, the rate does not change in any
systematic manner, so that a graph of population density versus the rate will have a slope of
zero.
Limiting Factor - ANS A factor is defined as limiting if a change in the factor produces a
change in average or equilibrium density.
Metapopulations - ANS Local populations in patches that are linked together by dispersal
among the patches, driven by colonization and extinction dynamics.
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,Regulating Factor - ANS A factor is defined as potentially regulating if the percentage of
mortality caused by the factor increases with population density or if per capita reproductive
rate decreases with population density.
Self-Thinning Rule - ANS The prediction that the regression of organism size versus
population density has a slope of -1.5 for plants and animals that have plastic growth rates and
variable adult size.
Sink Population - ANS Local populations in which the rate of production is below
replacement level so that extinction is inevitable without a source of immigrants.
Source Populations - ANS Local populations in which the rate of production exceeds
replacement so that individuals emigrate to surrounding populations.
Population Regulation is important for: - ANS Conservation, Land Management, and
Fisheries.
We can make two fundamental observations about populations of any plant or animal.
The first observation is that: - ANS Abundance varies from place to place; there are some
"good" habitats where the species is, on the average, common and some "poor" habitats where
it is, on the average, rare.
We can make two fundamental observations about populations of any plant or animal.
The second observation is that: - ANS NO population goes on increasing without limit, and
the problem is to find out what prevents unlimited increase in low- and high-density
populations.
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,We can make two fundamental observations about populations of any plant or animal.
The second observation is that no population goes on increasing without limit, and the problem
is to find out what prevents unlimited increase in low- and high-density populations.
This is the problem of explaining: - ANS Fluctuations in Numbers!
Figure 14.1 illustrates this!
A population in a closed system will increase until it reaches an equilibrium point at which: -
ANS Per Capita Birth rate = Per Capita Death Rate
A population in a closed system1 will increase until it reaches an equilibrium point at which:
Per Capita Birth rate = Per Capita Death Rate
Figure 14.2 illustrates three possible ways in which this equilibrium may be defined.
As a population goes UP: - ANS 1. Birth Rates may FALL
OR
2. Death Rates may RISE
OR
3. BOTH changes may occur
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Figure 14.2 illustrates three possible ways in which a pop, in a closed system will reach a
equilibrium point.
To determine the equilibrium population size for any field population, we need only: -
ANS Determine the curves shown in Figure 2.
- Note that this simple model in no way depends on the shapes of the curves, provided that
they rise or fall smoothly.
- In particular, these curves need NOT be straight lines.
The Per Capita Death Rate is said to be Density-Dependent IF: - ANS It INCREASES as density
INCREASES!
- Figure 14.2a & c
The Per Capita Birth Rate is called Density-Dependent IF: - ANS It FALLS as density RISES
- Figure 14.2a & b
Rates are called Density-Independent IF: - ANS Birth OR Death Rates DO NOT change as
density RISES!
Note that Figure 14.2 does not include all logical possibilities.
Birth rates might, in fact, INCREASE as population density RISES,
OR
Death Rates might DECREASE.
Such rates are called: - ANS Inversely Density-Dependent Rates!
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
