Chapter 5 Populations Flashcards
What is population density?
refers to the number of individuals per unit area
What is an age structure?
the number of males and females of each age a population contains
Immigration vs Emigration
Immigration- individuals move into range of population from somewhere else (increases size)Emigration- individuals move out of the population’s range (decreases size)
What is exponential growth?
a function that has a number risen to a certain power, in this case a positive number. The larger the population gets, the faster it grows. (J-shaped curve)
What is logistic growth?
occurs when a population’s growth slows and then stops, following a period of exponential growth. (S-shaped curve)
What is carrying capacity?
the maximum number of individuals of a particular species that a particular environment can support
How do population ecologists study populations?
researchers study populations’ geographic range, density and distribution, growth rate, and age structure
What factors affect population growth?
birthrate, death rate, and the rate at which individuals enter or leave the population
What happens during exponential growth?
Under ideal conditions (unlimited resources and no danger to population) a population will grow exponentially
What is logistic growth?
occurs when a population’s growth slows and then stops, following a period of exponential growth
What is a limiting factor?
a factor that controls the growth of a population
Describe density-dependent limiting factor. What are a few examples?
operate strongly only when population density (number of organisms per unit area) reach a certain level.Examples include: competition, predation, herbivory, parasitism, disease, and stress from overcrowding
Describe density-independent limiting factors. What are a few examples?
Affect all populations in similar ways, regardless of population size and density.Examples- unusual weather events like hurricanes, droughts, floods, natural disasters such as wildfires, tsunamis, earthquakes, and supervolcanic eruptions can act as density independent limiting factors.
What factors determine carrying capacity?
Acting separately or together, limiting factors determine the carrying capacity of an environment for a species
What limiting factors depend on a population?
(density-dependent) limiting factors include competition, predation, herbivory, parasitism, disease, and stress from overcrowding
What limiting factors do not typically depend on population density?
(density-independent) limiting factors
What is demography?
scientific study of human populations
How has human population size changed over time?
the human population, like populations of other organisms, tends to increase. The rate of that increase has changed dramatically over time.
Why do population growth rates differ among countries?
birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly
What is demographic transition?
a dramatic change from high birthrates and death rates to low birthrates and death rates. To date, United States, Japan, and Europe have completed the demographic transition. Parts of South America, Africa, and Asia are passing through stage II. A large part of ongoing human population growth is happening in only ten countries, with India and China in the lead. Globally, human population is still growing rapidly, but the rate of growth is slowing down. (transition from J-shape to S shape logistic growth)
