Transcript Human Ecology

Human Ecology
Exponential Growth
• Bacteria placed in
nutrient broth of optimal
temperature
Exponential growth:
•
when population
growth at any point is 2N ,
N= # of generations
• will occur under ideal
conditions with unlimited
resources
• Ex. After 5hrs, 25 = 32
• J-shaped graph
• Exponential Growth CANNOT continue
indefinitely due to limiting factors:
– Factors that stop or control population
growth
– Examples: Food, light, water, space,
parasitism and disease, predators,
energy resources, oxygen, accumulation
of waste products, competition,
disasters – fire, floods, drought, etc.
Carrying Capacity and Logistic
Growth
• Logistic Growth:
– Exponential at first 
then levels off as it
reaches carrying
capacity
– Growth rate = 0
– S-shaped graph
• Carrying Capacity:
– Maximum population
that environment can
support
Population Growth of Humans
Factors affecting human population
growth
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Agricultural revolution/food production
Increase in knowledge of diseases
Better health care and hygiene/sanitation
Advances in Medicine and technology
Resulting in a decrease in death rate, a
longer life span, and an increased birth
rate in some areas
• NOTE: there has been a decrease in
fertility rates in underdeveloped nations
Limiting Resources
• Renewable Resources
– Can be replaced
– Food supply, solar energy, wind/air, water,
soil, living things (trees), geothermal energy,
nuclear energy
• Non-Renewable Resources
- cannot be replaced in one’s lifetime
- fossil fuels
•Human population is
estimated to rise
over 9 billion by the
year 2150.
• Many think it will
then level off or
decline at this point.
•If growth continues,
may result in
population crash due
to overcrowding and
competition for food.
•May also result in
famines, disease and
wars.
Source: United Nations, World Population Prospects, The 1998 Revision;
and estimates by the Population Reference Bureau.
Human Population Growth and
the Environment
As the human population grows, we take
up more space, consumer more resources,
and produce more wastes!
Disruption of Existing Ecosystems
• Urbanization
– Shift from rural (farming) areas to cities
– Increased Industrialization
– Destruction of farmland and deforestation
– Results in
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Decreased amount of space for other species
Loss of habitats
Decreased biodiversity
Disruption of ecosystem by introducing new
species into an area w/no known predator
Poor Farming Practices
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Over farming and over grazing
– result in areas w/o a cover of vegetation
– No plants…no roots to hold soil
– Leads to soil erosion: removal of soil by
wind or water and desertification
Deforestation – can also lead to soil erosion,
washing away of nutrients
Pollution
• Noise
• Water – ex. Sewage, animal wastes, toxic
chemicals (DDT, fertilizers), thermal
pollution
• Air – ex. burning of fossil fuels leads to
increased levels of carbon dioxide, acid
rain, smog
• Land – ex. solid wastes, garbage
RESTORING ENVIRONMENT
• PRESERVING RESOURCES: 3 R’s
– Reduce: avoid using resource, ex. Walk, bike,
carpooling
– Reuse: use product over again instead of
throwing it out, ex. Dishes instead of paper
plates
– Recycle: using a product to make another
product, ex. Paper, metal, plastic, glass
• Use biological pest control, not pesticides
– ex. Using lady bugs to control aphids
– Use phermones – sex hormones to attract
pests
• Compost heaps: natural recycling of
nutrients, no need for chemical fertilizers,
reduces amount of waste in landfill
The Value of Biodiversity
• Species diversity – the # of different
species in a biosphere
• Genetic diversity – the sum total of all
genetic differences
• Provide us with foods, industrial products,
medicines, etc.
Threats to Biodiversity
• Habitat alteration
• Demand for wildlife products
• Pollution – biological magnification (ex.
bald eagle and DDT)
• Introduced species – invasive species