Download Populations

POPULATION GROWTH
31 October 2011
Population:
What determines if a population grows or
decreases?
Individuals of a given species that
occur together at one place and one
time and can breed.
• white-tailed deer in Indiana
• white-tailed deer in Midwest
• white-tailed deer in U.S.
What do populations do when placed into
an area with unlimited resources?
high
Dynamic equilibrium
Pop’n
no.s
GROWS!!
low
time
high
Power of twos!
high
J-shaped
curve
Popn
no.s
“Exponential
growth”
Popn
no.s
low
Growth rate
keeps increasing
low
time
Do populations grow exponentially
for ever?
NO!!
• Population limiting factors
- Factors that limit population growth
1. Density independent factors
2. Density dependent factors
Density Dependent factors:
• Factors that tend to increase mortality
rates (or decrease birth rates) as
population gets larger.
- competition
- starvation
- predation
- disease
time
Density Independent factors
Factors that reduce a population but ARE
NOT related to the size of the population.
-
fire
flood
hurricane
killing frost
high
• S-curve
Pop’n
no.s
• Sigmoid curve
• Logistic growth
low
time
high
Carrying capacity
Carrying capacity:
The number of individuals that can
be supported by the environment
in perpetuity
without negatively affecting
the environment!!
Popn
no.s
low
time
What happens if you remove some of the
population limiting factors?
High
C.C.
Popn
no.s
low
time
How many people are there on Earth?
High
C.C. ??
Does this number represent a problem?
Popn
no.s
?
Where are we on the growth curve?
low
time
What’s the human growth rate?
70
= 10 yrs
Doubling rate =
7
% growth rate
$20 = $40
$100 = $200
$8,000 = $16,000
• Don’t convert % to decimal
Is this number a problem?
Who cares? Does this crap affect me?
70
Doubling rate =
= years
• 210,000 more people by tomorrow!!
• 77,000,000 more people during year
• 8,827 more people during hour
• 250 more people during time it took to
read this (1 minute)
• Every second 5 people are born and 2 die
11:00 a.m.
• Have we exceeded the earth’s
carrying capacity?
12:00 p.m.
What time is it for humans?
When were half of all resources available?
Human Population Distribution
We aren’t the problem - It’s them!!!! It’s all of
those people having all of those babies!
U.S.
Growth rate
U.S
Mexico
India
Sierra Leone
Ethiopia
Niger
0.9
World
1.4
(Avg births/female)
2.07)
2.27
2.58
4.90
5.97
7.52
But are numbers of people the real
problem?
Or is the problem the way we use our
resources?
• U.S. has 5% of worlds population but
use 26%of the worlds energy.
• Africa has 1% of world’s population
and uses only 3% of worlds energy.
Did you know that each of you will
consume as much energy as:
•
•
•
•
•
•
•
2 Japanese
6 Mexicans
13 Chinese
32 Indians
140 Bangladeshis
284 Tanzanians
372 Ethiopians
• U.S. is responsible for 22% of world’s
industrial carbon dioxide emissions.
• Every day 9 square miles of U.S.
rural land are lost to development.
= 3 million acres of rural land lost 2000
• 1998 UN quote!!
• Landfill?