Population Dynamics

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Population Dynamics
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Population Dynamics

• Populations tend to grow to the maximum extent
  possible given environmental conditions
• Biotic potential
• Dependent on innate biological principles

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Not Sustained

• Biotic potential cannot be sustained
• Environmental resistance
• Population curves

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J-Curve

• Density independent
• Results from sudden crash in population size
• Outstrip resource limit
• catastrophe

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Sigmoid Curve

• Density dependent
• Recycling and renewal of resources
• Establishes equilibrium around carrying capacity

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Sigmoid Curve

• A lag phase
• B acceleration phase
• C exponential growth
• D deceleration phase
• E equilibrium
• G dynamic fluctuations

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Dynamic Fluctuation Phase

• Most populations
• Density- dependent factors
• Intraspecific competition
• Predation
• disease

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Mortality and Birthrate vs. Density

• Mortality increases as density increases
• Birthrate is density dependent
• K equilibrium point
• r recruitment or growth

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Growth and Density

• n density at which maximum growth occurs
• Used for management of wild game populations

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Predator- Prey Effect

• Delayed density dependence

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Survivorship Curve

• Type I large animals immune to predation, live
  to old age
• Type II mostly prey, predation is constant
  throughout lifespan
• Type III large numbers of young because most
  will be eaten, only few adults survive

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Reproductive Patternsr- selected vs K-selected

• r-selected
• Reproduce early and put most of their energy into
  reproduction
• Many small offspring
• High growth rate Population size fluctuates
  wildly around carrying capacity
• Low ability to compete
• Most offspring die before reaching reproductive
  age

• K-selected
• Fewer, larger offspring
• High parental care
• Most offspring survive to reach reproductive age
• Lower growth rate
• High ability to compete
• Population size fairly stable around carrying
  capacity

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Factors that Influence Population Dynamics

• Positive enhance population growth
• Negative reduce population growth

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Symbiotic Relationships

• Can be positive or negative
• Lichens
• Coral and zooxanthelae algae
• Wood termites and protozoa
• Humans and gut flora

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Behavior Patterns

• Can be positive or negative
• Migration
• Territory behavior
• Societies and hierarchies
• Mating and courtship
• Colors, patterns, physical characteristics

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Biological Controls

• Predators
• Diseases
• Pheromones