populations and exponential growth ecocapital · 2016-03-15 · • limiting factors • many...
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populations and ecocapital
unit 2
population growth• how do populations grow?• exponential growth
• bigger populations grow faster• begins slow, then ramps up
• even if rate of increase stays the same• limits on population growth
• biotic and abiotic factors• carrying capacity
biotic factors• efficiency of energy flow
• biomass pyramid• higher levels support lower biomass
• dietary choices?• food prices?
primary consumers
tertiary consumers
secondary consumers
producers
10 kcal
100 kcal
1000 kcal
10,000 kcal
1,000,000 kcalsunlight
Abiotic Factors• Limiting Factors
• Many limiting factors define the viability of life.• temperature, light, oxygen, carbon dioxide, and precipitation
• Optimum / ideal range for factors• Zones of stress -- above or below the ideal• Range of tolerance – includes optimum plus zones of stress• Limits of tolerance – upper and lower limit beyond which
organism cannot survive
time
popu
lati
on s
ize
(N)
population growth• exponential growth model
• growth occurs exponentially if no limiting factors• G=rN
• logistic growth model• growth with limiting factors• carrying capacity (K)
• G=rN• asymptotic
• TFR - total fertility rate• life expectancy• infant mortality
(K-N)K
time
popu
lati
on s
ize
(N)
population growth• density-dependent factors
• intraspecific competition• density-independent factors
• seasonal factors• disturbance
month
popu
lati
on s
ize
(N)
apr may jun jul aug sep oct nov dec
population growth
lynx
snowshoe hare
• boom / bust cycles• predator / prey population cycles
• classic example • snowshoe hare / lynx
human population • population growth continues
• birth rate and death rate• age structure?• china’s one child policy• infant mortality rate?
declining expanding
stable
15
30
45
60
75
agemale female
life expectancy• living longer?
human population• human population growth
• carrying capacity?• fertilizer
• 1909 - Haber process• other technology - farming in new places• health care
The Human Factor• Three major revolutions for humanity• 1. Neolithic revolution – 12,000 years ago
• conversion from a hunter-gatherer to an agricultural society• long term settlements• Better care and protection
• reduced mortality rate • reliable food production
• Population growth supported
http://www.flickr.com/photos/museumwales/3654034824/sizes/m/in/photostream/
The Human Factor• 2. The Industrial Revolution - 200 years ago
• Created the modern world• Reliant on fossil fuels – coal, oil and gas• Pollution and exploitation of natural resources increased• Uninterrupted population growth and economic expansion
http://cuwhist.wordpress.com/worldviews-hist-103/industrial-revolution/
The Human Factor• 3. The Environmental Revolution –21st Century
• Building a sustainable society• Commitment to the ethic of stewardship• Caring for the environment• Reduce waste products and pollutants• Conservation
Ecosystem Capital• Ecosystems -> functional units of sustainable life on earth
• provide the good and services – ecosystem capital - that humans depend upon
• humans in ecosystems• We are part of the food web – using organic matter provided by
producers and other consumers• We influence the way food webs function – both positively and
negatively• We must learn to manage ecosystems in order to keep them
healthy and productive
footprint• ecological footprint
• to accommodate the expected population by 2025, food production must double
ecological footprint• what is your ecological footprint?
IPAT model• factors affecting environmental impact
• IMPACT= POPULATION x AFFLUENCE x TECHNOLOGY• I = P x A x T• for less-developed countries population has greatest effect• for more developed countries consumption has greatest
effect
discussion questions• How are humans altering biotic and abiotic factors in our
ecosystems? • are we at or near carrying capacity?• What is the role of science in conserving our ecosystems?• should everyone have the right to have as many children as
they want?• what is your ecological footprint?
• http://www.footprintnetwork.org/en/index.php/GFN/page/calculators/