Population Ecology

Exponential growth and doubling time:

  • Exponential growth: growth at an exponential RATE of increase. If population growth is left unchecked and unrestricted it can take on a J-curve.

    Animals that grow in a J-curve often have a ___-selection reproductive strategy. They are low on the trophic level, grow quickly and mature _____, produce lots of offspring and are ______-beat parents. ex. insects, rodents, marine invertebrates, parasites and annual plants.

    Riddle: If a water lily grows at an exponential rate and covers a pond in 30 days, on what day was the pond 1/2 covered?

  • Doubling time: Amount of time it takes for the population to ________.
    • Rule of _____= 70 / annual ___ growth

Biotic Potential and Carrying Capacity

  • Biotic ___________- the maximum growth rate of a population of organisms when resources are unlimited.

    What is the biotic potential for the human female?

  • Carrying capactiy- the _________ number of individuals of a population that can be sustained __________ in an ecosystem. As an environment degrades, its carrying capacity decreases.

Population Boom and Bust Oscillations

  • Population exceeds carrying capacity or limiting factors come into effect, death rates surpass birth rates = population _____ or __________
    • Boom and bust cycles are common with R-reproductive strategists. When conditions are good, populations soar, when they soar they plummet.
  • ____________- the extent to which a population _________ the carrying capacity      
  • Irruptive/Malthusian growth-  the pattern of  population __________ followed by a population ________


Growth to a Stable Population

  • Growth rates regulated by internal and external factors limit population growth. This pattern of logistic growth is called a ___-curve.



  • The factors that reduce population growth rates are called environmental resistance. ex. space, food, water.
  • Organisms in the ___-selection reproductive strategy often exhibit logistic growth. They grow and mature more ________, have _______ offspring, and care for their young. There is a high expectation that the young will survive. ex. wolves, elephants, whales and primates.
    • Why aren't humans showing a s-curve population growth pattern then????


Factors that Increase/Decrease Populations

Natality, Fecundity and Fertility

  • Natality: production of new individuals. It is the main source of adding to populations, sensitive to environmental conditions (nutritional levels, climate, soil and water conditions, social interaction between species).
  • Fecundity: physical ability to __________
  • Fertility: measure of the actual number of _________ produced.
  • _______________: Seeds, spores, and small animals may be __________ into new ecosystems by wind, water (major source of organisms to islands), carried inside other animals, walking, swimming, flying,

Mortality and Survivorship

  • Mortality: _______ rate. The death rate is found by dividing the number of organisms that ____ in a certain time period by the number _______ at the beginning of the period.
  • Survivorship: the __________ of a certain organism that lives to be a certain age.
  • Life Expectancy: probable number of ________ of survival of an individual of a given age.
  • Life Span: __________ period of life reached by a given type of organism.
  • Emigration: the movement of members _____ of a population.

Survivorship Curves gives us the predicted life expectancy at each age interval.

  • Type I or a: Mortality mostly occurs in old age. ex. _________ in the first world.
  • Type II or b: Mortality is _____ dependent on age. ex. Hyrdas, squirrels and ___ _____ randomly die throughout their lives.
  • Type III or d: Species that mostly die when they are young would follow this curve. ex. Most marine organisms have a low survivorship- they are cast out into the waters, but once they survive that trauma they are likly to live out their ____ age. Other examples are trees and other plants that spread a lot of seeds.
  • Type "c": Some surviviorship curves include a fourth opinion in which high mortality occurs in the very _____ AND _____. ex. White tailed deer.


Factors that Regulate Population Growth


Extrinsic: limiting factors are imposed from _________ the population

  • Biotic: caused by _______ organisms. Preditor/prey cycles are common. They actually oscillate in synchrony with each other- but in a time lag.

    • Biotic factors are caused by limited food supply, predators, disease.

  • Abiotic: caused by ____-_______ components of the environment. ex. temperature, light, pH, water.

Intrinsic: limiting factors come from _______ the population: reproductive rate, adaptability, territoriality, the size of your car engine and tax returns...


Density dependent: effects are stronger or a higher percentage of the population is affected as the population density ________ (usually biotic factors like food shortages, droughts)

Density independent: the effect is the same or a _______ _________ of the population is affected regardless of the population density (usually abiotic factors like fire, climate conditions, volcano, earthquakes, severe storms)