Midterm 2

• Why do animals migrate?

  Allows animals to tolerate seasonally unsuitable conditions
• How do animals navigate in migration?

  Time compensated sun compass, wind direction, and geographic features
• What is the difference between dispersal and migration?

  Dispersal refers to the movement of individuals away from their birthplace, while migration refers to the seasonal movement of individuals between different habitats or regions
• What characteristics of a population can be measured?

  Population size, density, biomass, age structure, dynamics, spatial variation
• How do ecologists determine the size of a population?

  -Census: all individuals are counted

  -Estimated local density: count all individuals in an area, divide by area and multiple by total area

  -Mark recapture: marking every animal caught then counting how many marked you caught the second time
• Mark Recapture Formula

  $Marked Caught/ Total Caught=$$Marked / N (total pop)$
• Geometric Population Growth Formula


  $N(t)=$$N(0)λ^t$
• Geometric Growth Rate Formula


  $λ=$$N(t+1)/N(t)$
• What factors influence the growth rate of the human population?

  Education, use of contraceptives, delayed reproduction, and wealth
• How should the size of the human population change in the future?

  Will either stabilize or overshoot and crash
• What is the difference between the per capita growth rate and the total population growth rate?

  Per capita growth rate: Growth rate per individual

  Total population growth rate: Growth rate of the entire population
• How would you determine the per capita growth rate for an age-structured population?

  Life table lxbx or births-deaths per individual
• In an age structured population, how would changes in survivorship affect the per capita growth rate if those changes occurred early versus late in an organism's lifetime?

  It would affect more earlier in it's lifetime as most species produce less offspring as they age
• What is the difference between density-dependent and density-independent population growth?

  Density-dependent: factors that affect population growth based on the population size

  Density-independent: factors that affect population growth regardless of population size
• What are the implications of logistic population growth for the per capita and total population growth rates?

  Per capita: growth rate decreases with population density

  Total population: growth rate is highest when carrying capacity is 1/2
• How can information about growth rates help in fisheries management?

  Can harvest fish to produce the maximum sustainable yield
• Why does MSY approach typically not work?

  Environmental variability and overfishing may cause prediction to be wrong
• What are genetic factors that affect small populations?

  -Inbreeding depression

  -Loss of genetic diversity

  -Fragmentation of populations and loss of gene flow

  -Genetic issues with captivity and reintroduction
• What conservation approaches can be used to counteract genetic effects?

  Prevent loss of genetic diversity by mixing populations and encourage rapid population growth after decline
• Exponential Growth Formula


  $N(t)=$$N(0)e^(rt)$
• Can a population grow exponentially?

  Yes but there are limits