Chapter 5- Populations Flashcards
What are 3 important characteristics of a population?
geographic distribution, density and growth rate
What is population density?
number of individuals per unit area
What are 3 factors that affect population size?
number of births, number of deaths, and the number of individuals that enter or leave the population
What is immigration?
the movement of individuals into an area; causes population to grow
What is emigration?
the movement of individuals out of an area; causes a population to decrease in size
When does exponential growth occur?
when the individuals in a population reproduce at a constant rate; at first, population increases slowly then it becomes large until it approaches an infinitely large size
Under what condition will a population grow exponentially?
if its resources are unlimited
What happens as resources become less available for a population?
Its growth slows or stops
When does logistic growth occur?
When a population’s growth slows or stops following a period of exponential growth
What is carrying capacity?
the largest number of individuals that a given environment can support
What are some density-dependent limiting factors?
competition, predation, parasitism, and disease
What are some examples of density-independent limiting factors?
unusual weather, natural disasters, seasonal cycles, and certain human activities like damming rivers and clear-cutting forests
What is a limiting factor?
a factor that causes population growth to decrease
What is a density-dependent limiting factor?
a limiting factor that depends on population size
What is a predator-prey relationship?
the regulation of a population by predation
What is a density-independent limiting factor?
affects all populations in similar ways, regardless of the population size
What is demography?
the scientific study of human populations
What helps predict why some countries have high growth rates while other countries grow more slowly?
birthrates, death rates, and the age structure of a population
What is demographic transition?
a dramatic change in birth and death rates
When is demographic transition complete?
when the birthrate falls to meet the death rate and population growth stops
