Download Population Growth

Populations
How they change over time…
What is a population and how is it
measured?
• POPULATION: A group of
organisms that belong to
the same species living in
the habitat at the same
time.
• GROWTH RATE = Births –
Deaths
– Immigration: moving
INTO an area
– Emigration: EXITING an
area
How are populations distributed?
POPULATION DENSITY:
Number of individuals per
unit area.
CLUMPED (in groups)
RANDOM (all over)
UNIFORM (spread evenly)
How do populations grow?
J-shaped curve
• Exponential Growth:
population increases
rapidly very quickly
only after a few
generations
Grow forever? Micro-organisms can
if given enough nutrients and space!
S-shaped curve
• Logistic Growth: starts
as exponential growth
with limiting factors
and levels off (due to
carrying capacity)
Limiting factors prevent MOST
populations from growing forever.
What factors limit population
growth?
• Limiting Factors control • Carrying Capacity is
the growth of a
the MAXIMUM
population
number of individuals
an environment and
– Available resources
its resources can
(food, space, mates)
support
– Competition,
predation, parasitism,
disease
– Natural disasters,
unusual weather
Limiting factors determine the carrying
capacity for a species.
What factors limit population
growth?
• Environmental changes (ex. drought)
• Other species
– Predators, prey, competitors
– Lynx and snowshoe hare example
How is the human population
growing?
12
Human Population (Billions)
11
2100
10
9
Old
Stone
7 Age
8
New Stone Age
Bronze
Age
Modern
Age
Iron Middle
Age Ages
6
2000
Future
5
4
1975
3
1950
2
1
Black Death—The Plague
1900
1800
1+ million7000 6000 5000 4000 3000 2000 1000 A.D. A.D. A.D. A.D. A.D. A.D.
years B.C. B.C. B.C. B.C. B.C. B.C. B.C. 1 1000 2000 3000 4000 5000
• Earth - 5 Billion
Years
• Multi-cell Biota
- 600 Million
Years
• Human Beings
~ 2 Million Years
• Human
Population
Growth into
Billions- Last 200
years
What’s Behind the Human Population
Explosion?
• Three Factors
•
– Fertility
– Infant Mortality
– Longevity
• Animal
Domestication and
Agriculture
– Provided for a few
to feed many
Industrial Revolution
– Growth of Cities and
Infrastructure
•Water
•Energy
•Transportation
– Increased Productivity
– Nutrition
– Sanitation
– Medicine
How are humans affecting the
environment?
• Limited Resources
– Land, food, water
• Agriculture
• Industries
• Ecosystem Goods
– Renewable
– Nonrenewable
• Desertification &
Deforestation
• Water pollution
• Biological magnification
• Air pollution
• Acid rain
• Habitat Fragmentation
• Introduced Species
 What is the size of YOUR
ecological footprint?
(take the quiz online!)
2060-
2040-
2020-
2000-
1980-
1960-
1940-
1920-
1900-
1880-
1860-
1840-
3 929 214
5 308 483
7 239 881
9 638 453
12 866 020
17 069 453
23 191 876
31 443 321
39 818 449
50 155 783
62 947 714
75 994 575
91 972 266
105 710 620
122 669 275
131 669 275
151 325 798
179 323 175
203 211 926
223 889 000
248,709,873
281,421,906
3. Can
1.
2.
Whatthe
type
factors
human
of growth
contributed
population
is this,
to keep
the
exponential
human
growingor
logistic?
population
like
this forever?
growing
Why
likeorthis?
why not?
1820-
1790
1800
1810
1820
1830
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
3303102902602302101801501209060300-
1800-
Population of
Year
the
United States
Population of the United States
(millions)
Human Population
Growth
Graph
350-
Any Questions?