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6-1 A Changing Landscape
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2. Population and growth patterns
The size of a population is always changing.
Four factors affect the size of a population.
-immigration
-births
-emigration
-deaths
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Population growth is based on available resources.
Exponential growth is a rapid population increase due to an abundance of resources.
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Logistic growth is due to a population facing limited resources.
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Carrying capacity is the maximum number of individuals in a population that the environment can support.
A population crash is a dramatic decline in the size of a population over a short period of time.
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Ecological factors limit population growth.
A limiting factor is something that keeps the size of a population down.
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Density-dependent limiting factors are affected by the number of individuals in a given area.
Predation
Competition
Parasitism and disease
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Density-independent limiting factors limit a population’s growth regardless of the density.
Unusual weather
Natural disasters
Human activities
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Earth as an Island
Earth as an Island
All organisms on Earth share a limited resource base and depend on it for their long-term survival.
To protect these resources, we need to understand how humans interact with the biosphere.
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Human Activities
What types of human activities can affect the biosphere?
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Human Activities
Some human activities that affect the biosphere include:
hunting and gathering
agriculture
industry
urban development
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Agriculture
The Green Revolution  
The green revolution was an effort in the mid-twentieth century to increase global food production through modern plant breeding and agricultural techniques.
Over the last 50 years, the green revolution has helped world food production double.
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Agriculture
Challenges for the Future
While increasing world food supplies, modern agriculture has created ecological challenges. For example:
Monoculture leads to problems with insect pests and diseases.
Finding enough water for irrigation is difficult.
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14. Industrial Growth and Urban Development
Human society and its impact on the biosphere were transformed by the Industrial Revolution, which added machines and factories to civilization.
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16. Industrial Growth and Urban Development
The energy to power machinery comes mostly from fossil fuels—coal, oil, and natural gas.
Suburban growth consumes farmland and stresses native plants and animals.
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6-1
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6-1
Today, the most important source of environmental change on the planet is
the green revolution.
wild plants.
humans.
abiotic factors.
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6-1
The practice of planting a single crop in the same place year after year is called
uniculture.
monoculture.
the green revolution.
plant breeding.
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6-1
One problem with modern agriculture is that
chemical fertilizers don’t work.
chemical pesticides can damage beneficial insects.
it has decreased world food production.
new varieties of plants require little water.
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6-1
One impact of early hunting and gathering groups in North America might have been
changing the climate from very cold to much warmer.
the elimination of forests.
a mass extinction of large mammals about 12,000 years ago.
the development of large civilizations in Central and South America.
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6-1
Most of the energy for industry comes from
a. the sun.
nuclear power plants.
moving water.
fossil fuels.
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