Human Population Flashcards
The human population is currently growing at a rate of ___ million per year; that is 2.8 people added every second.
88
The human population didn’t reach ____ until after 1800.
1 billion
This is an example of ___________, where a small percentage growth rate still produces a large increase due to the size of the base population.
exponential growth
Global doubling time is 70/1.2%, or ________
58 years.
Improved sanitation, modern medicine, and higher agricultural output have all helped to reduce the ___________, the frequency of children dying in infancy.
infant mortality rate
British economist___________-argued that the number of people would eventually outgrow the available food supply.
Thomas Malthus
Paul and Anne Ehrlich of Stanford University have been called “___________” because they have made similar warnings.
neo-Malthusians
Despite a quadrupling of the human population, these predictions have not fully materialized.
____________ has intensified.
Enhanced prosperity, __________, and ________________ have helped to slow birth rates.
Food production
education
increasing gender equity
The I P A T model represents how our total ________ (I) on the environment results from the interaction of _____ (P), __________ (A), and __________ (T).
I = PAT
impact
population
affluence
technology
Increased population means that more ________ take up space, use resources, and generate waste.
Affluence leads to greater per capita resource ___________.
Technology can _______ impact by enhancing our ability to exploit resources or ______ impact by improving efficiency.
individuals
consumption
increase
decrease
A sensitivity factor (S) may also be added to denote the _________ of a given environment.
I = PAT*S
For example, the arid lands of western China are more sensitive to human disturbance due to the slow growth rate of the plants there.
vulnerability
Modern-day _____ has many examples of how I P A T elements can create environmental impact.
Intensive agriculture has caused _____ in western China similar to the _______
____________are heavily withdrawn.
Air quality is very ______
China
erosion
Dust Bowl.
Aquifers and rivers
poor
demography
Principles of population ecology can be applied to the study of statistical changes in the human population.
Demographers study several characteristics of the human population:
Size
Distribution
Age structure
Sex ratio
Rates of birth, death, emigration, and immigration
Predicted to surpass __________ by 2050
9.8 billion
Age structure diagrams, also called ___________ describe the relative numbers of individuals in each age class within a population.
population pyramids,
A pyramid with a ______denotes a potential for rapid future growth.
A pyramid with an ______ indicates a stable population.
A pyramid with a ____________ indicates a shrinking population.
wide base
even age distribution
narrow base
The global population is aging: the median age today is ___; in 2050 it is predicted to be 38.
This creates _____ in social welfare programs as ____ young workers are supporting more elderly.
28
strain
fewer
The naturally occurring sex ratio is ___ males born per every ___ females born.
106
100
The cultural gender preference for male children, coupled with the one-child policy, has resulted in roughly _______ born for every 100 girls.
116 Chinese boys
Infant mortality rates are closely tied to a nation’s level of __________.
industrialization
In recent decades, falling __________ in many countries has led to an overall decline in the global growth rate.
This is primarily due to a steep drop in _______
growth rates
birth rates.
______ describes the movement of individuals between countries.
Migration
_______ is people entering a country.
Immigration
__________ is people leaving a country.
Emigration
Total fertility rate (T F R)
is the average number of children born per woman during her lifetime.
Replacement fertility
is the T F R that keeps the size of a population stable. For humans, this is 2.1.
Europe’s ____________, which only includes birth and death rates, was between 0.0% and 0.1% in 2016.
rate of natural increase
Industrialized countries tend to have the highest increases in __________, the average number of years a person in an age group is expected to live, due to a drop in infant mortality.
life expectancy
Countries still industrializing will pass through a series of stages of economic and cultural change called the __________
demographic transition.
During the _______________ death rates are high due to widespread disease, rudimentary health care, and unreliable food supplies.
Birth rates are also ____, leading to a stable population size.
pre-industrial stage, high
Death rates decline during the _________ due to improved food production and health care.
Birth rates remain ______, so the population increases.
transitional period
high
During the ____________ opportunities increase for women and birth control becomes more widely available, decreasing birth rates.
Population growth slows and begins to ______.
industrial stage, employment
stabilize
The population growth stabilizes or begins to shrink during the ___________
post- industrial stage.
Some developing countries are so overpopulated that they may not be able to complete a transition, creating _____________
demographic fatigue.
Family planning
is the effort to plan the number and spacing of one’s children.
Birth control
includes all efforts to reduce the frequency of pregnancy.
Contraception
is a deliberate attempt to prevent pregnancy despite engaging in sexual intercourse.
Access to family planning gives women control over their _________, the time at which they can become pregnant.
reproductive window
If humanity’s ecological footprint exceeds Earth’s biocapacity, it is termed an __________
If the footprint is less, there is an _____________
ecological deficit.
ecological reserve.
K Selected species tend to be _____, few offspring per reproduction event, live in stable environments, ______ for each offspring,mature after many years of youth and _________, have long life spans life expectancy, and reproduce more than once in their ________.
Competition for resources in K-Selected species habitats is usually _____.
large
expand lots of energy
expand lots of energy
lifetime
high
R-selected species expand _______ energy for each offspring, mature ______, have ____ life spans, and reproduce once in their lifetime, Competition for resources is normally __.
minimal
early
short
low
Life history theory
A scientific approach that explains how natural selection influences patterns in reproduction, survival, and life span.
Biotic potential
the maximum reproductive rate of a population in ideal conditions
Population density
the number of individuals per unit area in a population
Population distribution
the spatial arrangement of organisms in an area
Sex ratio
population of males to females
1:1 ratios are seen in monogamous species; rates vary in others
Age structure
the relative numbers of individuals of different ages within a population
this can help predict whether a population will grew or shrink in near future
rate of natural increase
birth rate - death rate
Survivor ship curve is a line that displays the ____________ of a chart, group of individuals of the _________, in population, from birth to __________ age reached by any one cohort member. Type I, Type II, and Type III ______.
relative survival rates
same age
maximum
curves
Random distribution
shows no particular pattern
Uniform distribution
individuals spaced evenly
Clumped distribution
when individuals concentrate in certain areas
_________ species are more affected by invasive species than _________ species. Most invasive species are _______ species.
K-selected
r-selected
r-selected
(birth rate - death rate) + (immigration rate- emigration rate)
Population growth rate
K-selected species typically following __________, and r-selected species following a _______ curve.
Type I / Type II
Type III
_____ population density makes it easier for organisms to group and find mates. It can also lead to _______ and conflict if space, food, or mates are ______. Overcrowding also increases the transmission of infectious ______. Low population ________, individuals benefit from space and _________ but may be harder to locate mates and _________.
High
competition
limited
disease
densities
resources
companions
Older individuals oten reproduce in _________
greater numbers
Natality
Births within the population
Mortality
Deaths within the population
Immigration
Arrival of individuals from outside the population
Emigration
Departure of individuals from the population
Growth rates may be expressed as percentages:
population growth rate * 100%
Population increase by a fixed percentage each year, undergoes exponential growth
J-shaped curve
Only occurs in nature when population is small, competition is minimal, and environmental conditions are ideal.
Carrying Capacity
the maximum population size of a species that a given environment can sustain
Logistic growth
Ecologist use the S-shaped curve to show how an initial exponential increase is slowed and eventually brought to a standstill by limiting factors
Density-dependent
Condition of limiting factors whose effects on a population become stronger or weaker dpending on the population density
Density-independent
factors are those whose influence is independent of population density
-Temp extremes, catastrophic natural disasters
-Predation disease
Environments are complex and dynamic carrying capcities can change
-Forest fires decrease carrying capacity for most animals
-Humans altered their environment to increase its carrying capacity for our population
