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Examination Scores

Class Average:52.45

Females:52.42

Males:52.48

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Time Spent Studying for the Exam

Females:Less than 2.5 days before the exam

Males:Less than 2.2 days before the exam

1. Time spent studying was positively associated with higher or lower test scores.

2. More importantly, individuals that initiated studying ~ 7 days or more before the exam scored significantly higher than those student who initiated studying 3 days before the exam(> 8 hours total).

Hypothesis: there is no significant association between test scores and the amount of time devoted to studying.

Days Before Studying for Exam0 1 2 3 4 5 6 7 8

TestScores

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When to Study?

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Patterns to establish for the rest of the class:

1. Note-taking habits.2. Study together as a group.3. Exchange notes.4. Quiz each other.5. Ask questions6. Participate in class.

Examination I

Upcoming Quiz

Population Ecology:

▲ Definition▲ Factors Affecting Population

Growth/Decline▲ Exponential Growth▲ Logistic Growth▲ Density-dependence/Independence▲ Predation, Competition, Spatial

Distributions

Text Readings

Chapter Reading:Chapter #26 in Audesirk, Audesirk and Byers:

“Population Growth and Regulation”Pg. #513-534.

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Questions to Answer in the Chapter

• How Does Population Size Change? p. 514• How Is Population Growth Regulated? p. 515• How Are Populations Distributed

in Space and Time? p. 524• How Is the Human Population

Changing? p. 526

Population Dynamics

Sooo…….What if

resourcesbecomelimiting?

“J” Crash

What if resources are limited ?Paul Verhulst (1804 – 1849)

How does the formula change?

Nt = N0e r t dNdt

= r N ( k – N )k

Incorporates the instantaneous rate of changein populations

Population Dynamics

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Environmental Resistance

Logistic Growth

dNdt = rN ( k – N )

k

Environmental ResistanceFinite Resources?

Source: Bolen and Robinson (1999) Wildlife Ecology and Management

Environmental Resistance: The limitinginfluences ofenvironmental factorson the numbers ofindividuals in acommunity.

Carrying CapacityFinite Resources?

Source: Bolen and Robinson (1999) Wildlife Ecology and Management

Carrying Capacity (k): The abundance (size) of a species’ population that a habitat can support for a specified period of time (an upper limit).

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Population DynamicsLogistic Growth

• Environmental resistance can reduce the reproductive rate and average life span and increase the death rate of young.

• As environmental resistance increases, population growth slows and eventually stops.

Population DynamicsLogistic Growth

dNdt = rN ( k – N )

k

Acceleratingphase

Deceleratingphase

Inflection Point (k/2)

k

The Verhulst-Pearl Equation

Environmental Resistance Time

Abundance

k/2

Carrying Capacity

• In nature, conditions are never completely stable, so both K and the population size (n) will vary somewhat from year to year.

• However, environmental resistance ideally maintains populations at or below the carrying capacity of their environment.

Population DynamicsLogistic Growth

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• If a population far exceeds the carrying capacity, excess demands decimate crucial resources.

• This can permanently and severely reduce K, causing the population to decline to a fraction of its former size or disappear entirely.

Population DynamicsLogistic Growth

Population DynamicsLogistic Growth

Population DynamicsPopulation Cycles

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Population DynamicsEffect of “r” on cycles

r = 1.9

Population DynamicsEffect of “r” on cycles

r = 2.4

Population DynamicsEffect of “r” on cycles

r = 2.5

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Population DynamicsEffect of “r” on cycles

r = 2.8

Population DynamicsEffect of “r” on cycles

r = 1.9 r = 2.5

r = 2.4 r = 2.8

Prey Switching and Availability

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Home Range: an area in which an animal normally lives and is not necessarily associated with any type of aggressive behavior. Dominance hierarchy may exist among individuals with overlapping home ranges.

Territory: a defended, more or less fixed and exclusive area maintained by an individual or social unit occupying it.

Social Behavior Limits Access to Resources

Ecological “Lines of Dependency”

Individual to IndividualTerritory, Home Range, Density

Species to SpeciesPredator-PreyCompete (?) for access to essential resources

Species to Abiotic (non-living) ComponentsSoil, Topography, Weather

Population Resources: Food, Water, Cover, and Space

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• Logistic Growth Curve• Formula• Carrying Capacity (k)/Environmental Resistance• Portions of the Curve (phases, inflection point)• Factors Affecting Population Cycles• Home Range/Territory Resources

dN

dt= rN

( k – N )

k

Environmental Resistance

Logistic Growth

In Summary: