Unit 3 Notes Packet KEY: Human Population Growth
Vocabulary Terms are italicized
Chapter 8, Section 1: How Populations Change in Size
I.
What is a population?
Population- Is all the members of the species living in the same place, at the same time.
Organisms usually breed with members of the same population. The word “population” refers to
the group of organisms in general and their size (the number of individuals that group counts).
II. Properties of populations
-Populations may be described in terms of size, density, or dispersion.
Density- A population’s density is the number of individuals per unit area of volume.
Dispersion- A population’s dispersion is the relative distribution or arrangement of its
individuals within a given amount of space. It may be: even, clumped or random.
III. How does a population grow?
Growth Rate- A change in the size of the population over a given period of time in that
population. Growth rates can be positive, negative or zero, depending of the number of births
and deaths in a particular time period. If the birth rates are greater than the death rates, the
population will increase. If the birth rates are lower than the death rates, the population is
decreasing. If the average birth rates are equal with the average number of death rates, than
the population will be zero (stabile).
IV. How fast can a population grow?
A. Reproductive Potential- The maximum number of offspring that each member of the
population can produce.
Biotic Potential- The fastest rate at which the species’ populations can grow.
B. Exponential Growth- Where the organism’s population grows faster and faster.
Exponential growth occurs in nature only when populations have plenty of food and
space, and have no competition or predators.
V. What Limits Population Growth?
A. Carrying capacity- of an ecosystem for a particular species is the maximum population
that the ecosystem can support indefinitely.
B. Resource Limits- A species reaches its carrying capacity when it consumes a particular
natural resource at the same rate at which the ecosystem produces the resource. That natural
resource is referred to as “limiting resource” for the species in that area.
C. Competition within a Population
- The members of the population use the same resources so they will eventually compete with
one another as the population approaches its carrying capacity. The members of the same
species could compete directly or indirectly (by fighting for a territory which contains that
particular resource, as well as food, shelter and/or breeding sites).
VI. Two Types of Population Regulation
Density dependent- Death in a population occurs more quickly in a crowded population
than in a sparse population.
Density independent- A number of the population may die due to regardless of the
population’s density (weather related causes: natural disasters like floods, hurricanes,
tornadoes).
VII. An Organism’s Niche
A niche includes the species’ physical home, the environmental factors necessary for the
species’ survival, and all of the species’ interactions with other organisms. (A niche is different
from a habitat. An organism’s habitat is a location. A niche is an organism’s way (pattern) of
using its habitat).
VIII. Ways of which species interact
There are five major ways of species interactions: competition, predation, parasitism, mutualism
and commensalism.
IX. Competition
-Competition is a relationship in which different individuals or populations attempt to use the
same limited resources. For many organisms, competition is part of daily life. Competition can
occur both within and between species.
A. Indirect Competition
-Species can compete even if they never come into contact with each other. Example: an insect
species can feed on a certain plant during the day, and another insect species feed on the same
plant during the night.
B. Adaptation to Competition
-When two species with similar niches are placed together in the same ecosystem, we might
expect one species to be more successful than the other species. The better adopted species
will be able to use more of the resources. One way competition can be reduced between
species is by dividing up the niche in time and space.
Chapter 9, Section 1: Studying Human Populations
Demography- is the study of population, but most often refers to the study of human population.
It studies the historical size and makeup of the populations of countries to make comparisons
and predictions.
I. Human Population Over Time
-Up until the 1800’s, the human population was in a steady and slow growth. After the 1800’s
the human population underwent exponential growth, meaning that population growth rates
increased during each decade. This was as a result of the industrial and scientific revolution.
II. Forecasting Population Size
A. Age Structure- The distribution of ages in a specific population at a certain time.
Population Pyramid- Age structure is graphed on a population pyramid- a type of boublesided bar graph. One side represents the males and the other side the females. Ages from
0-14 is the pre-reproductive age. Ages from 15-49 are the reproductive age. Ages from
50+ are the elderly are group. We can tell if a population is increasing, decreasing or is
stabile by looking at the age structure on a population pyramid graph.
B. Survivorship- is the percentage of members of a group that are likely to survive to any
given age.
Survivorship curves- There are 3 types of Survivorship curves: Type I, II and III. Type I
represents people that live to be very old. Type II represents similar death rates at all
ages. Type III represent a population that remain the same size or grow slowly.
C. Fertility Rate- The number of babies born each year per 1,000 women in a population is
called the fertility rate.
Total Fertility Rate- the average number of children a woman gives birth to in her lifetime.
Replacement Level- is the average number of children each parent must have in order to
“replace” themselves in the population.
D. Migration- The movement of individuals between areas (different countries).
Immigration vs. Emigration- Movement into an area is immigration and movement out of
an area is emigration.
III. Declining Death Rates
A. Life Expectancy- The average number of years a person is likely to live.
Infant Mortality- the death rate of infants less than a year old. It differs greatly among
countries that have the same average income. It depends of parents’ education, fuel,
food, and clean water.
IV. The Demographic Transition
-
Is a model that describes how changes in population size can occur in a particular area.
A. Stages of the Transition- In the first stage of demographic transition, a society is in a
preindustrial condition. The birth and death rates are both in a high levels and the
population size is stabile. In the second stage, a population explosion occurs. Death
rates decline as hygiene, nutrition and education improve. But birth rates remain high
which results in fast population growth. In the third stage of the demographic transition,
population growth slows because birth rate decreases. As the birth rate becomes close
to the death rate, the population size stabilizes.
B. Women and Fertility- the factors important for decline in birth rates are: increasing
education and economic independence for women.
Chapter 9, Section 2: Changing Population Trends
Infrastructure- Is the basic facilities and services that support a community, such as: public
water supplies, sewer lines, power plants, roads, subways, schools, and hospitals. The
symptoms of overwhelming population growth include suburban sprawl, overcrowded
schools, polluted rivers, barren (infertile) land and inadequate housing.
I.Problems of Rapid Growth
-People can’t leave without sources of clean water, burnable fuel and fertile land (land that can
be farmed to produce food).
A. A Shortage of Fuelwood
-
In many of the poorest countries, wood is the main fuel source. If the population is
stabile, there is enough deadwood. But if the population grows rapidly, that people start
to cut down live trees, thus reducing the amount of wood available in each new year.
B. Unsafe Water
-
In places with no infrastructure, the sewage water is mixed with the drinking and
washing water. As a result, the drinking water becomes a breeding ground for organisms
that causes diseases such as: dysentery, typhoid, and cholera.
C. Impacts on Land
-
People need space to live in. They prefer space with easily reachable resources and a
comfortable lifestyle.
Arable Land- land that can be used to grow crops.
Urbanization- More people are living in cities that in rural areas. (People find jobs in the
cities but tend to live in the suburban areas around the cities).
Suburban sprawl- it leads to traffic jams, inadequate infrastructure and the reduction of
land for farms, ranches, and wildlife habitat.
II. A Demographically Diverse World
Least developed countries- countries that show few signs of development and in some
cases have increasing death rates, while birth rates remain high.
Case Study: Thailand’s Population Challenges
In Thailand, there was an increasing problem with birth rates, population growth and pollution.
Before the 1970’s, the average number of children in one family was about 6.4. The government
realized that certain sanctions and actions must be done to lower the number of births in their
developing country. In 1970, the Thailand’s government adopted a policy to reduce its country’s
population growth. This policy included better education, healthcare, contraceptive usage and
increase in women’s rights and ability to earn income. The policy was successful. In Thailand,
by the year 2000, the growth rate had fallen to 1.1 percent and the age structure was more
evenly distributed.
III. Managing Development and Population Growth
Throughout history, people have observed the negative effects of population growth. Many
developing countries are struggling with the population growth issue. If their population is
increasing, that might slow them in developing and becoming a more developed county.
IV. Growth is slowing
- In both- more developed and less developed regions, fertility rates have declined. However,
rates are still much higher in developing regions. The demographers predict that this trend will
continue and by the year 2050, the world population growth will eventually stop.
A. Projections to 2050
- The United Nations projections of the world population growth by 2050 projected on a graph
with a medium-growth line. Most demographers predict a medium growth rate and a world
population of 9 million in 2050.