BIOL 115 Environmental Science

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BIOL 115Environmental Science

• Professor
• Dr. E. Binney Girdler

To keep every cog and wheel is the first
precaution of intelligent tinkering. -Aldo
Leopold
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QUIZLET Which of these assertions are in the
realm of science?

• a. The Detroit Tigers are a great baseball team.
• b. Geese fly south in the winter.
• c. Dust from agricultural fields is causing
  allergic reactions in area schoolchildren.
• d. My roommate is the most qualified candidate
  for president of the Student Commission.
• e. Overharvesting of blue crabs in the Gulf of
  Mexico causes sawgrass marsh to die off.
• f. Restricting harvest of blue crab is
  ill-advised because it will decimate the local
  economies of many Gulf Coast communities.

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Human Population Growth

• Number of people on the planet
• Amount of resources used by each one

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Two population growth models
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Feedback Loops
-

!

-
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Negative feedback acts to stabilize a system
The switch is open in this diagram and the
furnace is off. As the temperature falls the
bimetallic coil curves and the glass capsule
tilts to the left. The mercury flows to the left
and when the mercury fills the space between the
contacts, the furnace turns on.
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Negative feedback acts to stabilize a system
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Positive feedback acts to de-stabilize a system
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Positive feedback acts to de-stabilize a system
B K Fig. 3.6
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A system can have both positive and negative
feedback loops
B K Fig. 3.8
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Time delays can destabilize system

• Thermostat example
• What happens when the heater is very far from the
  thermostat?

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Time delays can destabilize system

• Thermostat example
• What happens when the heater is very far from the
  thermostat?
• Residence hall showers?

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Two population growth models
K carrying capacity
Feedback in these systems?
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Two population growth models
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Examples of logistic growth
Model organisms in a test tube Paramecium
caudatum (1,2) and Paramecium aurelia (3)
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Assumptions of logistic growth

• Constant environment
• Constant carrying capacity (K)
• Homogeneous population
• Not characters the human population exhibits

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Predicting Human Population Growth

• Changing demographics
• Factors that affect future growth
• TFR
• Age structure
• Migration

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Demographic determinants of future growth

• Total Fertility Rate (TFR)
• Age structure
• Migration

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Demographic determinants of future growth

• Total Fertility Rate (TFR)
• Age structure
• Migration

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Factors that affect TFR

• Culture and fertility
• Socioeconomic status of women
• Family planning

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Factors that affect TFR

• Culture and fertility
• Role of children in economy/society

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Factors that affect TFR

• Culture and fertility
• Effects of infant mortality rate

What is the dependent variable in this graph?
The independent variable?
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Factors that affect TFR

• Socioeconomic status of women
• Age at first reproduction

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Factors that reduce TFR

• Socioeconomic status of women
• Age at first reproduction

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Factors that affect TFR

• Socioeconomic status of women
• Age at first reproduction
• Education

What is the dependent variable in this graph?
The independent variable?
Figure from Raven Berg (2001) Environment, 3rd
ed., p. 203
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Factors that affect TFR

• Socioeconomic status of women
• Age at first reproduction
• Education
• Income

Dependent variable?
image source Addison-Wesley
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Factors that affect TFR

• Family planning
• Societal mores

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Factors that affect TFR

• Family planning
• Societal mores
• Contraception

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Factors that affect TFR

• Family planning
• Societal mores
• Contraception
• Abortion

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Factors that affect TFR

• Family planning
• Societal mores
• Contraception
• Abortion
• Government policies

United Nations Population Summit (1997)
Photo Histoire de l'ONU en photos
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Demographic determinants of future growth

• Total Fertility Rate (TFR)
• Age structure
• Migration

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Age Structure of Populations
In 2003, 30 of the people on the planet were
under 15 years old.
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Age Structure of Populations
Miller Fig. 11-13
remember the TIME LAG this bulge imposes upon
this system
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Age Structure of Populations
Miller Fig. 11-13
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Demographic determinants of future growth

• Total Fertility Rate (TFR)
• Age structure
• Migration

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Migration

• Relief is temporary and finite
• Short term effects exacerbate problem
  immigration is usually in the direction of higher
  standards of living.

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High
TFR 2.6
High 10.9
10
Medium
TFR 2.1
TFR Total Fertility Rate children to be born
per female if birth rates remain as status quo
Low
TFR 1.7
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Medium 9.3
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Population (billions)
7
6
Low 7.3
5
4
3
2
1950
1960
1970
1980
1990
2000
2010
2020
2030
2040
2050
Year
Miller Fig. 11-6
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Even if a countrys TFR falls below replacement
(2.1 in developed and 2.7 in developing nations),
that countrys population may continue to
increase.
High
Medium
Low
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What is our fate?
K?
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Your Ecological Footprint
"The ecological footprint is the corresponding
area of productive land and aquatic ecosystems
required to produce the resources used, and to
assimilate the wastes produced, by a defined
population at a specified material standard of
living, wherever on Earth that land may be
located."
--William E. Rees, Professor of Community and
Regional Planning at the University of British
Columbia
http//www.myfootprint.org/ http//www.ecologyfund
.com/registry/ecology/res_bestfoot.html http//www
.carbonfootprint.com/ http//www.rprogress.org/new
projects/ecolFoot/faq/index.html