Unit 3 - Populations

population growth rate

population growth rate

the number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period

biotic potential

under ideal conditions with unlimited resources available, every population has a maximum potential for growth

K-selected species

a species with low intrinsic growth rate that causes the population to increase slowly until it reaches the carrying capacity of the environment

carrying capacity

the limit to the number of individuals that can be supported by an existing habitat or ecosystem, and is denoted as K

r-selected species

a species with high intrinsic growth rate, and their population typically increases rapidly

overshoot

when a population becomes larger than the environment’s carrying capacity

dieback

a rapid decline in a population due to death

survivorship curve

a graph that represents the distinct patterns of species survival as a function of age

type I survivorship curve

a pattern of survival over time, in which there is a high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age

type II survivorship curve

a pattern of survival over time in which there is relatively constant decline in survivorship throughout most of the life span

type III survivorship curve

a pattern of survival over time in which there is low survivorship (a high death rate) early in life with few individuals reaching adulthood

density-dependent factor

a factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population

density-independent factor

a factor that has the same effect on an individual’s probability of survival and reproduction at any population size

population growth models

mathematical equations that can be used to predict population size at any moment in time

fecundity

the ability to produce an abundance of offspring

exponential growth model

a growth model that estimates a population’s future size after a period of time based on the biotic potential and the number of reproducing individuals currently in the population

J-shaped curve

the curve of the exponential growth model when graphed

logistic growth model

a growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment

S-shaped curve

the shape of the logistic growth model when graphed

limiting resource

a resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size

demography

the study of human populations and population trends

demographer

a scientist in the field of demography

immigration

the movement of people into a country or a region, from another country or region

emigration

the movement of people out of a country or region

crude birth rate (CDR)

the number of births per 1,000 individuals per year

crude death rate (CDR)

the number of deaths per 1,000 individuals per year

net migration rate

the difference between immigration and emigration in a given yer per 1,000 people in a country

life expectancy

the average number of years that an infant born in a particular year in a particular country can be expected to live, given the current average life span and death rate in that country

infant mortality

the number of deaths per children under 1 year of age per 1,000 live births

child mortality

the number of deaths of children under age 5 per 1,000 live births

environmental justice

the study of the disproportionate exposure to environmental hazards experienced by people of color, recent immigrants and people of lower socio-economic backgrounds; and is both an academic field and a social movement

age structure diagram

a visual representation of the number of individuals within specific groups for a country, typically expressed for males and females

population pyramid

an age structure diagram that is widest at the bottom and smallest at the the top, typical of developing countries

developing countries

countries with relatively low levels of industrialization and income

developed countries

countries that have relatively high levels of industrialization and income

population momentum

continued population growth after growth reduction measures have been implemented

total fertility rate (TFR)

an estimate of the average number of children that each woman in a population will bear throughout her childbearing years

family planning

the regulation of the number of spacing of offspring through the use of birth control

replacement-level fertility

the total fertility rate required to offset the average number of deaths in a population to maintain the current population size

doubling time

the number of years it takes a population to double

rule of 70

a method which indicates that by dividing the number 70 by the percentage population growth rate we can determine a population’s doubling time

theory of demographic transition

a theory that states that a country moves from high to lower birth and death rates as development occurs and that country moves from a preindustrial to an industrialized economic system

IPAT equation

a conceptual representation of 3 major factors that influence environmental Impact: Population of humans, Affluence, Technology