Chapter 8: Population Change (Terms and Definitions)

G. F. Gause

"A Russian ecologist who conducted experiments during the 1930s, grew a population of a single species, Paramecium caudatum, in a test tube. He supplied a limited amount of food (bacteria) daily and replenished the media occasionally to eliminate the buildup of metabolic wastes. Under these conditions, the population of P. caudatum increased exponentially at first, but then their growth rate declined to zero, and the population size leveled off." (pg. 172)

Metapopulation

"A group of local populations among which individuals occasionally disperse (emigrate and immigrate)." (pg. 179)

Population crash

"An abrupt decline from high to low population density." (pg. 173)

Life tables

"Ecologists construct life tables for plants and animals that show the likelihood of survival for individuals at different times during their lives. Insurance companies originally developed life tables to determine how much policies should cost; Life tables show the relationship between a client's age and the likelihood the client will survive to pay enough insurance premiums to cover the cost of the policy." (pg. 177)

Source habitats

"Habitats that increase the likelihood of survival and reproductive success for the individuals living there." (pg. 179)

Sink Habitats

"Lower-quality habitats - areas where the local birth rate is less than the local death rate." (pg. 179)

Thomas malthus

"One of the first to recognize that the human population cannot increase indefinitely was Thomas Malthus, a British economist. He pointed out that human population growth is not always desirable - a view contrary to the beliefs of his day and to those of many people even today - and that the human population can increase faster than its food supply. The inevitable consequences of population growth, he maintained, are famine, disease, and war." (pg. 180)

S Shape of logistic population growth

"When a population affected by environmental resistance is graphed over a long period, the curve has the characteristic S shape of logistic population growth. The curve shows an approximate exponential increase initially, followed by a leveling out as the carrying capacity of the environment is approached. In logistic population growth, the rate of population growth is proportional to the amount of existing resources, and competition leads to limited population growth." (pg. 172)

Zero population growth

"When the birth rate equals the death rate ... At that time, exponential growth of the human population will end, and the J curve may be replaced by the S curve. It is projected that [it] will occur toward the end of the 21st century." (pg. 181)

Rolf Peterson

"Wildlife biologists, such as Rolf Peterson of Michigan Technological University, have studied the effects of both density-dependent and density-independent factors on the Isle Royale population of moose and wolves. They found that the two populations fluctuated over the years. Generally, as the population of wolves decreased, the population of moose increased. The reverse was also true ..." (pg. 175)

Less developed countries (LDCs)

A developing country with a low level of industrialization, a high fertility rate, a high infant mortality rate, and a low per capita income (relative to highly developed country.

Moderately developed countries

A developing country with a medium level of industrialization, a high fertility rate, a high infant mortality rate, and a low per capita income (all relative to highly developed countries)

Population

A group of individuals of the same species that live in the same geographic area at the same time.

K selection

A reproductive strategy in which a species typically has a large body size, slow development, long life spawn, and does not devote a large proportion of its metabolic energy to the production of offspring.

r selection

A reproductive strategy in which a species typically has a small body size, rapid development, and a short life span, and devotes a large proportion of its metabolic energy to the production of offspring.

Negative feedback mechanism

A system in which a change in some condition triggers a response that counteracts, or reverses, the changed condition.

Immigration

A type of dispersal in which individuals enter a population and thus increase its size.

Emigration

A type of dispersal in which individuals leave a population and thus decrease its size.

Density-independent factor

An environmental factor that affects the size of a population but is not influenced by changes in population density.

Density-dependent factor

An environmental factor whose effects on a population change as population density changes.

Highly developed countries (also called developed country)

An industrialized country that is characterized by a low fertility rate, low infant mortality rate, and high per capita income.

The growth rate equals (birth rate minus death rate) plus (immigration minus emigration): r = (b - d) + (i - e)

Growth rate (r) = (birth rate (b) - death rate (d)) + (immigration (i) - emigration (e))

The growth rate (r) of a population is equal to the birth rate (b) minus the death rate (d): r = b - d

Growth rate (r) = birth rate (b) - death rate (d)

Frank Notestein

In 1954, a Princetone demographer [that] recognized four demographic stages, based on his observations of Europe as it became industrialized and urbanized.

Source

In environmental science, the part of the environment from which materials move; economies depend on sources for raw materials.

Sink

In environmental science, the part of the natural environment that receives an input of materials; economies depend on sinks for waste products.

Environmental resistance

Limits set by the environment that prevent organisms from reproducing indefinitely at their intrinsic rate of increase; includes the limited availability of food, water, shelter, and other essential resources

Postindustrial stage

Low birth and death rates characterize this fourth demographic stage. In heavily industrialized countries, people are better educated and more affluent; they tend to desire smaller families, and they take steps to limit family size. The population grows slowly or not at all in the fourth demographic stage. (pg. 184 - 185)

Immigration and Nationality Act (now called the "Immigration Reform and Control Act", or "IRCA")

Passed in 1952, although it had to be revised since (now called the Immigration Reform and Control Act), it is still the basic immigration law in effect. (pg. 189)

Natural increase Growth rate

See growth rate The rate of change of a population's size, expressed in percent per year. ("Is also called natural increase in human populations." (pg. 170))

Exponential population growth

The accelerating population growth that occurs when optimal conditions allow a constant reproductive rate over a period of time.

Demographics

The application of demographic science that provides information on the populations of various countries or groups of people.

Demography

The applied branch of sociology that deals with population statistics and provides information on the populations of various countries or groups of people.

Replacement-level fertility

The average number of children a couple must produce to "replace" themselves; the number is greater than two because some children die before reaching reproductive age.

Total fertility rate

The average number of children born per woman, given the population's current birth rate.

Population ecology

The branch of biology that deals with the numbers of a particular species that are found in an area and how and why those numbers change (or remain fixed) over time.

Population growth momentum

The continued growth of a population after fertility rates have declined, as a result of a population's young age structure; population growth momentum can be either positive or negative but is usually discussed in a positive context.

Intrinsic rate of increase

The exponential growth of a population that occurs under ideal conditions

Preindustrial stage

The first stage, in which birth and death rates are high, and population grows at a modest rate. Although women have many children, the infant mortality rate is high. Intermittent famines, plagues, and wars also increase the death rate, so the population grows slowly or temporarily declines. (pg. 184)

Carrying capacity (K)

The maximum number of individuals of a given species that a particular environment can support for an indefinite period, assuming no changes in the environment.

Dispersal

The movement of individuals among populations, from one region or country to another.

Age structure

The number and proportion of people at each age in a population.

Birth rate (b)

The number of births per 1000 people

Death rate (d) (Also called mortality)

The number of deaths per 1000 people per year.

Population density

The number of individuals of a species per unit of area or volume at a given time.

Infant mortality rate

The number of infant deaths (under age 1) per 1000 live births.

Population growth momentum

The potential for future increases or decreases in a population based on the present age structure.

Survivorship

The probability a given individual in a population will survive to a particular age.

Demographic transition

The process whereby a country that is industrializing moves from relatively high birth and death rate to relatively low death rates, followed within a few generations by reduced birth rates.

Growth rate (r)

The rate of change of a population's size, expressed in percent per year.

Transitional stage

The second demographic stage, which has a lowered death rate as a result of improved healthcare and more reliable food and water supplies that accompany the beginning of an industrial society. (pg. 184)

Industrial stage

The third demographic stage, characterized by a decline in birth rate and takes place at some point during the industrialization process. The decline in birth rate slows population growth despite a relatively low death rate. (pg. 184)

Doubling time

The time it takes for a population to double in size, assuming that its current rate of increase doesn't change.