Population ecology
A major sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment.
Population density
The number of individuals of a species per unit of area or volume at a give time.
Demography
The statistical study of human populations.
Carrying capacity
The maximum number of individuals a particular environment can sustainably support.
K- selected species
Strong competitors in crowded niches, and invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood.
R-selected species
Species with this reproductive strategy reproduce quickly and have many offspring, most of which usually do not survive very long.
Survivorship curves
The probability that a given individual in a population will survive to a particular age, three different types (Type I, Type II, Type III)
Density dependent factors
An environmental factor that affects the size of a population and is impacted by changes in population density. Examples include food availability, predation, competition and disease.
Boom bust cycle
A pattern of population growth in which exponential growth leads to a period when the population exceeds its carrying capacity, causing the population to decrease rapidly or crash (lemmings)
Density independent factor
A factor that affects the size of the population regardless of the population density ex. climate, drought, floods, hurricanes
Doubling time
The amount of time it would take for a population to double in size, assuming its current growth rate does not change. Rule of 70 is that 70 divided by the percent annual growth in population tells you how many years it will be before a population doubles
Infant mortality rate
The number of infant deaths under age 1 per 1,000 live births.
Developing countries
Countries where infant mortality rates are higher than highly developed countries.
Logistic growth
A model describing population growth that levels off as population size approaches carrying capacity (S-shaped curve)
Replacement-level fertility
The number of children a couple must produce to "replace" themselves.
Total fertility rate
The average number of children born per woman, given the population's current birth rate.
Demographic transition
Consists of four demographic stages in which population growth rate of a country changes as its society becomes industrialized.
Transitional stage
The second demographic stage that has a lowered death rate, characterized by rapid population growth.
Population Age structure
The number and proportion of people at each age in a population. Can be visualized in a "Population Pyramid
Population growth momentum
The potential for future increases or decreases in a population based on the present age structure.
Crude birth Rate
Number of childbirths per 1000 people per year
Crude death Rate
Number of deaths per 1000 people per year
Population growth rate
The change in a population over time, and can be quantified as the change in the number of individuals of any species in a population.
Exponential growth
The accelerating population growth that occurs when optimal conditions allow a constant reproductive rate over a period time.
Pre Industrial Stage
Birth and death rates high, population grows slowly, infant mortality high
Industrial Stage
(demographic transition) decline in birth rate, population growth slows
Post Industrial Stage
the fourth and final stage of the demographic transition model, in which both birth and death rates have fallen to a low level and remain stable there, and populations may even decline slightly
Highly Developed Countries
countries with complex industrialized bases, low rates of population growth, and high per capita incomes
Less Developed Countries
Also known as developing country, a country that is at a relatively early stage in economic development