Transcript Human Population Growth - Downtown Magnets High School

Ch 52
Understanding
Population
Growth
Organism
POPULATION
POPULATION
POPULATION
Community
Ecosystem
Population Ecology
•Deals with #’s of indiv. in a
species
•How and why their numbers
are the way they are
Population Density
# of indiv. of a species
unit of area
• A better way to describe size of
a pop.
Manhattan, New York City
70,595 people per sq. mile
Dhaka, Bangladesh:
2
7 million in 59 mi
Crowded
Much?!?
Competition
Spread of Disease
Lack of Natural
Resources
Lack of Jobs
Populations Change in Size…
• Births, deaths, immigrants, and emigrants
Question: How can you get
the growth rate of a
population to slow down?
Give reasonable solutions!
Make a list with your
partner 
Reproductive Strategies
Exponential Growth= r-selected
AKA J Curve
Occurs when Pops Doubling OverTime
Doubling Time
• Time for a pop. w/ a
stable growth rate
to double in size
Doubling Time =
td =
70
r (%)
Practice: With a 2 % growth rate, the
world population will double….
R-selected Species
1) Many small
offspring
2) Little/no care of
offspring
3) Most offspring die
before reaching
reproductive age
4) High population
growth rate
5) Generalists
Logistic Growth: K-selected
AKA S Curve
Carrying Capacity
K = carrying capacity (Max. pop. of a
particular species that a habitat can
support over a given time period.
Carrying Capacity
• May vary by:
– Seasons
– Changes in
environment
(fire, storm,
etc.)
K-selected Species
1) Fewer, larger
offspring
2) High parental
care
3) Most offspring
reach
reproductive
age
4) Lower
population
growth rate
5) Specialists
Density-Dependent Factors
• Increasing pop size leads to less
available resources  limiting pop
growth
• DD factors: competition, predation,
disease, poisoning…all increase
when pops grow w/in limited space.
Density-Independent Factors
• Limits placed on pop growth (not due
to space issues)
• Ex: Natural disasters or Severe
weather
Survivorship
•Proportion of a pop. to survive to breeding
age
•Type I= Late loss: K-strategists.
•Type II = Constant loss: intermediate
reproductive strategists
•Type III = Early loss: R-strategists