biology chapter 4- population biology population limiting factor exponential growth carrying...
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Biology Chapter 4- Population BiologyPopulation
Limiting factorExponential growthCarrying capacity
Life-history patternsDensity
R strategyK strategy
Competition
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More Vocabulary
• Stress
• Crowding
• Demography
• Birthrate
• Deathrate
• Doubling time
• Age structure
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Population Growth
• J Curve
• http://cauchy.math.colostate.edu/Applets/ExponentialGrowth/exponentialgrowth.htm
• Limits to growth (Limiting Factors y’all)– Biotic and abiotic
• Carrying Capacity
• Exponential growth
• Page 94 growth graph and explaination
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More graphing
• Add carrying capacity
• http://cauchy.math.colostate.edu/Applets/LogisticGrowth/logisticgrowth.htm
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Life History patterns
• Rapid Life history
• Slow life history
• K reproduction strategy (but intrinsic, not conscious)
• R reproduction strategy
• http://www.sumanasinc.com/webcontent/animations/content/tradeoffs.html
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Population DensityPatterns
– Random– Clumped– Uniform
Limiting Factors
• Density-dependent– Disease– Competition
• Density-independent– Usually abiotic
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Organism interactions
• Predation– Graph p 98
• Interspecies competition
• Intraspecies competition
• Effects of crowding
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Addendum
• An S shaped curve is logistic growth
• This is the more common representation of population growth
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Basic Characteristics of Populations
• The suitability of habitats influences the geographic distribution of a species.
• Insights can be gained by studying the spatial distributions of populations within habitats.
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Population Age Structure
• Differences in environmental conditions and past history may cause populations to differ in their age distributions.
• The future growth of a population depends on its current age distribution.
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Density-Independent Population Growth
• Simple models describe how idealized populations would grow in an infinite environment.
• In these models, populations increase to infinity or decrease to zero.
• Continuous Model – Reproduction occurs in the
population at all times.
• Discrete Model – Populations reproduce only at
certain times.
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Density-Dependent Population Growth
• In density dependent population growth, the per capita growth rate decreases as the population approaches a carrying capacity.
• When population growth rate depends on current population size, the population smoothly approaches carrying capacity.
• When there is a delay such that population growth depends on past population sizes, the population may cycle or have chaotic dynamics.
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Dynamics of Lagged Logistic Growth Models
• As growth rate increases, populations overshoot carrying capacity (K).
• Further increases cause the population to cycle.
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Human Population Growth
• Human population growth does not currently show density effects that typically characterize natural populations.
• In natural populations, per capita population growth rate decreases with population size, whereas global human population growth rate has a positive relationship.
• Human population growth rate has been growing more than exponentially.
• Limited resources eventually will cause human population growth to slow, but global human carrying capacity is not known.
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Density-Dependent and Density-Independent Effects on
Populations• In many habitats, the forces that limit population
sizes are independent of population density. For example, extreme weather events may decrease populations.
• For most species, density-dependent factors limit birth rates or increase death rates at least some of the time. This type of population determination often is referred to as “regulation.”
• Disease outbreaks and starvation are two factors that may increase with population density.
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r-selected Reproductive Strategy
• r-selected Species: – have high
reproductive rates– tend to occur in
unpredictable environments
– typically have type III survivorship curves
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K-selected Reproductive Strategy
• K-selected Species: – occur near carrying
capacity – experience effects of
population density – have low
reproductive rates, high parental care
– have type I survivorship curves.
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Populations
• Groups of organisms of the same species that live within a given area
• Key characteristics:– Dispersion patterns– Population density – Growth rate
Ostriches are nomadic, wandering
in small groups.
Aspen trees are quick to pioneer areas that have been disturbed
by fire.
BioEd Online
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Dispersion Patterns Within Populations
Three common patterns of population distribution are:
BioEd Online
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Population Density• Population density is total population size per unit of
area.
• Population densities depend on:– Interactions within the environment
– Quality of habitat
– Density dependent factors
– Density independent factors
• Carrying capacity is the maximum number of organisms that can be supported in a given habitat.
• Population size can be measured by several sampling techniques.
BioEd Online
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Population Growth
Exponential vs. Logistical Growth
BioEd Online
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Survivorship in Populations
BioEd Online
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Reproductive Strategies
• r- Selected (maximum growth rate, below carrying capacity)– Early reproduction– Short life span– High mortality rate– Little or no parental care– Large investment in
producing large numbers of offspring
– Below carrying capacity– Examples:
• Bony fish• Grasshoppers
• K-Selected (maximizes population size near carrying capacity)– Late reproduction– Long life span– Low mortality rate– Extensive parental care– Greater investment in
maintenance and survival of adults
– At or near carrying capacity– Examples:
• Sharks• Elephants
BioEd Online
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Limits on Population Growth
• Density Dependent Limits– Food– Water– Shelter– Disease
• Density Independent Limits– Weather – Climate
Water and shelter are critical limiting factors in
the desert.
Fire is an example of a
Density independent
Limiting factor.BioEd Online