APES Unit 3: Populations

K-related species

organisms that tend to be large, have few offspring per reproduction event, live in stable environments, expend significant energy for each offspring, mature after many years of extended youth and parental care, have long life spans/life expectancy, and reproduce more than once in their lifetime.

r-related species

organisms that tend to be small, have many offspring, expend or invest minimal energy for each offspring, mature early, have short life spans, and may reproduce only once in their lifetime

survivorship curve

Graph showing the number of survivors in different age groups for a particular species.

population overshoot

Occurs when the population of a species exceeds the carrying capacity. As a result, resources run out faster and the population plummets, also decreasing the carrying capacity.

population crash

A sudden population decline.

reproductive strategies

a method an organism uses to reproduce

biotic potential

the maximum reproductive rate of a population in ideal conditions.

famine

an extreme shortage of food

exponential growth

Growth pattern in which the individuals in a population reproduce at a constant rate

fecundity

fertility; fruitfulness

sex ratio

the ratio of males to females in a population

Total Fertility Rate (TFR)

The average number of children a woman will have throughout her childbearing years.

Replacement level fertility

the number of children a couple must have to replace themselves (2.1 developed, 2.7 developing)

infant mortality rate

The percentage of children who die before their first birthday within a particular area or country.

population density

the number of individuals in a population per unit area.

Age Distribution

the relative numbers of organisms of each age within a population

Population distribution

the spatial arrangement of organisms in an area.

random distribution

organisms arranged in no particular pattern

uniform distribution

individuals are evenly spaced

clumped distribution

individuals are found in groups or patches based on availability or resources

Immigration

individuals moving into an area

Emmigration

individuals moving out of an area

demographic fatigue

governments face overwhelming challenges related to population growth

demographic transition

change in a population from high birth and death rates to low birth and death rates

pre-industrial stage

birth and death rates high, population grows slowly, infant mortality high

Transitional stage

death rate lower, better health care, population grows fast

post-industrial stage

both birth and death rates have fallen to low and stable levels.

Industrial stage

the third stage of the demographic transition model, characterized by falling birth rates that close the gap with falling death rates and reduce the rate of population growth

Population size

the total number of individuals within a defined area at a given time

Population density

A measurement of the number of people per given unit of land

Random density

position of each individual is independent of others

Uniform density

Organisms in a population are evenly spaced; reflects evenly distributed resources

Clumped density

resources are clustered and individuals enhance each other's survival

Type 1 survivorship

high survivorship through early and middle ages (humans)

Type 2 survivorship

relatively constant survivorship throughout life (birds)

Type 3 survivorship

indicates that death rates for a population peaks early in life ; species that produce many small offspring and provide little or no parental care

Exponential population growth

Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.

Demography

The scientific study of population characteristics.

Doubling Time

The number of years needed to double a population, assuming a constant rate of natural increase.