AP Biology
Population Ecology
Part 3
• Population Limiting Factors (All can limit a
populations size… could even be more than
one at a time.)
– Resources (This can be food, water, space…if it is a
territorial species.)
• Competition rises as resources become scares draining
energy away from reproduction.
– Health conditions (Such as crowding and disease.)
– Predation by another species.
– Intrinsic Factors (Such as aggression, stress,
personality issues with humans.)
• Carrying capacity for the given environment
• Boom-Bust cycles of Growth (This describes a
Predator/Prey relationship mainly.)
– Shows the lag-time for other species to adjust to a
change in a species population number.
– The two population “lines” are chasing each other
because of their direct relationship.
– This relationship also promotes natural selection
as it will be the strongest that survive and
reproduce…
• so each species is causing the other to
evolve… which is referred to as co-evolution.
Boom and Bust Cycles
aculty.mdc.edu/mdelcamp/.../2_Pres_Population_Dynamics_pp.ppt
• Human Population growth pattern
– The population explosion that is occurring has
changed the dynamics of Earth tremendously.
• Environmental degradation and over-consumption of
resources is occurring.
• Species loss (extinction) is occurring at a fast rate.
• Overpopulation is being seen in India, China, and some
other Island nation.
Human Growth on Earth
aculty.mdc.edu/mdelcamp/.../2_Pres_Population_Dynamics_pp.ppt
Human Population Growth
• Human population is following
an exponential growth pattern.
With the advent of modern
medicine, better sanitation, and
increased food supplies, the
biggest constraints on population
growth were removed.
• At some point in time the world’s
population will have to stabilize.
The current increases have had
many profound effects on the
biosphere and its inhabitants.
aculty.mdc.edu/mdelcamp/.../2_Pres_Population_Dynamics_pp.ppt
Human Population Growth 2
• Man’s footprint upon the land
is great, not just in sheer
numbers of individuals, but in
the resources they consume.
How many items have you
used and then disposed of
today?
• There will be limits on the
growth of human populations.
The question is: Will we
manage it ourselves or will we
wait for natural forces to do it
for us?.
– Ethics/Freedom/Control
• China and India and United States
• China has imposed laws to get control of birth
rates. (These can be found on the internet.)
• India has not yet imposed laws, but is seeing
resource issues currently.
• The U.S. is not near the size in population as
China or India ; but the United States uses
most of the world’s resources; which is an
issue for China and India and the rest of the
world.
– Human Growth History
• The human species started as a Hunter gathers society.
(nomads)(Energy?)
• Their energy mainly went toward following the food so little
was left for reproduction (They
• were basically too tired and health issues also drained
energy.)
• Agricultural Revolution and the plow
• With the invention of the plow, more food and not having to
travel increased health and energy reserves. These could be
put toward reproducing… so the population begins to climb.
This also leads to the formation of towns and villages.
• Industrial Revolution
• This help lead to cities because now everyone didn’t
have to produce their own food, it could be grown in
the countryside and trucked into the city for sale.
Also this allowed for an increase in reserve energy to
put toward reproduction. Also health care improved
for most people.
• Technology Revolution and Medicine
• Better health causing people to live longer now and
survival of babies increases. Women, in general, are
having more children because families are becoming
more affluent. Technology, while mostly good for
society, makes most people less active and puts even
more energy toward reproduction and obesity.
– Age Structure pyramids
• These can show the number of individuals at each age
group. (called cohorts)
• These can be used to identify current trends/problems.
(life expectancy or Infant mortality)
• Can be used to identify future trends/problems.
• More elderly and less young to support them
or future unemployment for example.
Age Pyramids
Rapid growth
Afghanistan
Male
Female
Slow growth
United States
Male
Female
Age
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8
6
4
2
0
2
4
6
Percent of population
8
Decrease
Italy
Male
Female
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8
6
4
2
0
2
4
6
Percent of population
8
8
6
4
2
0
2
4
6
Percent of population
8