Download 05 Populations and Demography

Chapter 5
Populations
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5-1 How Populations Grow
How do researchers study populations?
Researchers focus on 4 major groups when they study
populations:
1. Geographic Range
2. Density and Distribution
3. Growth rate
4. Age structure
1. This is the area in which a population inhabits.
Geographic range can vary enormously in size
depending on the species. Think bacteria in a given
area compared to people.
2. Population density refers to the number of
individuals per unit area. This like #1 is dependant on
species. (Duck in on a pond compared to fish in it)
Distribution refers to how individuals in a population
are spaced out. There are three recognized
distribution types:
1. Random- Spaced out sporadically in an area
(flowers in a field)
2. Uniform- Set distance between each (nesting
sites)
3. Clumped- tightly packed pods or groups
(school of fish)
3. The populations growth rate
determines whether the size of the
population will increase, decrease, or stay
the same. Again this is mainly decided by
the species type.
4. Age structure is a breakdown of how
many males and females of the
population at specific ages. This is
important because most species have a
certain age they can begin to reproduce
at.
Population Growth
•Number of births
•Number of deaths
•Emigration (out) & Immigration (in)
In Springfield, 45 babies are born in the
year 2008. 15 people died that same year.
What is the growth rate for the city?
Positive Growth rate = population
increase
Negative Growth rate = decrease
Exponential Growth –reproduce at a
constant rate. Occurs under ideal
conditions (no limits)
J-shape curve
Logistic Growth – resources become
less available, growth slows or stops
S-shape curve
Carrying Capacity
– the number an
environment can
support
5-2 Limits to Growth
Limiting Factor – causes population
growth to decrease
Most common are:
Density-Dependent Factors –
Population size depends on:
• Competition
• Predation
• Parasitism and disease
• Human disturbances
DensityIndependent
Factors – does not
depend on
population size
1. Unusual weather
2. Natural disasters
3. Some human
activities
5.3 DEMOGRAPHY
•the study of human population growth
- explains how populations change over
time.
Change in our world population over time
Page 143 Graph
•Agriculture
•Irrigation
•Plagues
•Industrial revolution
Demographic Transition – a dramatic
change in birth and death rates
•United States, Japan, and Europe
population growth has stopped
•ZERO POPULATION GROWTH
In order to achieve ZPG, each couple
has only 2 children
AGE STRUCTURE DIAGRAMS
•Show percentage of people alive at each
age group
Choose two and draw a diagram
that would fit each:
•1. A country where the king orders
the deaths of all the baby boys
•2. A country at war, many young
men die in that war
•3. A country with poor health care
for women, many die in childbirth
•4. A country where AIDS kills
people in their 30s