WM Chapter 5 Population Ecology

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WM Chapter 5 Population Ecology

• A population is a group of interbreeding
  individuals found in the same area.
• Example 2 populations below
• A population of robins in West Central Illinois
• A population of robins in Chicago
• Population Density / area

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Population Growth Carrying Capacity

• K maximum number sustain by environment
• N number in population
• T time lapsed
• Growth equation N/T run (K-N)/K

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Potential Growth measured for any species using
growth equation

• Used to predict numbers at a distant time
• After 5, 10, 20 years
• Must consider life history characteristics
• R vs. K
• Biotic potential
• Life survivorship

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R vs K life history and survivorship

• I elephants, human K
• Long lived
• Low biotic potential
• II prey squirrel
• intermediate
• III prey fish, insects R
• Short lived
• High biotic potential

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Variation in survivorship between M F
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Field studies of populations

• Field census
• Trap count
• Radio collar
• Hunter kills
• Aerial survey
• tracking

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Fluctuations in populations

• Difficult to predict population year to year
• Natural fluctuations
• Unusual weather, abnormal kills
• disease

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Sex Ratios and Mating System

• Primary
• 50/50 M/F at birth
• Secondary
• Sex specific mortality
• Ex. Nutritional stress affects F
• Tertiary
• Sex ratio of juveniles
• Increase in F due to male mortality
• Quaternary
• Adult sex ratios
• Sometimes sharply skewed.
• Ex diving ducks

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Effect of Quaternary Sex Ratios on breeding
success monogamous species

• Ratio M/F max of nest/ 100 birds
• 50/50 50 (100)
• 60/40 40 (80)
• 40/60 40 (80)

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Effect of Quaternary sex ratio on polygamous
species

• Ratio M/F max of nest/ 100 birds
• 40/60 60 (100 )
• 50/50 50 (83)
• 60/40 40 (60)

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Age Specific Birth Rates

• Crude birth rate Number of births per
  individual
• Age specific birth rate age classes important in
  determining rates

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Eggs produced by brook trout varies with age of
female

• Class age number of eggs
• I 2.5 1.7 million
• II 1.5 0.5 million
• III 1.0 0.04 million

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Mortality

• Death of individuals in a population
• Disease, Predation, Malnutrition, Severe weather
• Additive mortality several factors work impact
  at the same time
• Compensatory mortality some factors lessened
  when 1 mortality factor kills many individuals.

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Life Tables
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Metapopulations

• Metapopulations groups of local populations of
  species.
• Occupy separate patches of land
• Often connected by a corridor

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Population models

• Simulated harvest strategies