Transcript Chapter 6 Humans in the Biosphere

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All organisms rely on resources
which are limited. Our growing
population means increasing
demands for Earth’s air, water, land,
and living things.
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Human Activities
Industry and technology give humans a strong
advantage in competing with other species for
limited resources such as food, energy, and
space. Humans are the most important source
of environmental change on the planet.
Human activities can change the flow of energy
in an ecosystem and reduce the ability of
ecosystems to recycle nutrients. Human
activities that have that have changed the
biosphere are hunting and gathering,
agriculture, industry, and urban development.
Hunting and Gathering
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For most of human history, hunting and
gathering was the primary means of survival.
Early humans hunted birds and other animals
and fished. They gathered seeds, fruits, and
nuts. Some people were nomadic, which
means they traveled to take advantage of
movements and cycles of natural plant and
animal populations.
Hunters and gatherers lived in small
groups. They often changed the
environment. They built dams to divert
water and burned grasslands to encourage
the growth of certain plants. Some
scientists believe early human hunters
caused one of the major mass extinctions of
large animals (etc: woolly mammoths, giant
ground sloths, sabertooth cats)
Today, groups of people in different parts
of the world still follow the hunting and
gathering way of life. They supplement
their diet with the meat of wild animals
through subsistence hunting. Subsistence
hunters make few demands on the
environment but use some form of
technology, such as guns, snowmobiles, or
tools.
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Agriculture
Early hunter-gatherers planted seeds near
human settlements. About 11,000 years ago,
humans began farming, or agriculture.
Agriculture spread in many directions as
people planted other varieties of seeds.
Acriculture gave people a dependable supply
of food. People settled around regions of
agricultural growth, creating town and cities,
leading to the development of elements of
civilizations such as government, laws, and
writing.
Domestication of Animals
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As crops improved and farming methods
became more reliable, farmers began to keep
herds of domesticated animals, like sheep,
goats, cows, pigs, horses, and dogs. They
supplied milk, meat, wool, companionship,
and did work. Overgrazing by goats, cows,
and others changed grassland ecosystems to
eroded soils and put large demands on water
supplies.
From Traditional to Modern Agriculture
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Between 1450 and 1700, an exchange of foods
began. In the 1800s, advancements in science
and technology led to a change in agriculture.
Large-scale watering (irrigation), new crop
varieties, and the invention of farm machines
for plowing, planting, and harvesting helped
farmers to increase their yields tremendously.
The Green Revolution
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By the 1950s, there was not enough food to
keep up with the growing population. In a
global effort to increase food production,
governments and scientists developed new,
intensive farming practices that greatly
increased yields of rice, wheat, and other crops.
This is now known as the green revolution.
The green revolution needed a few things to
increase crop production. The main strategy was
the development of new, highly productive
varieties of major food crops. Crop breeders
developed new plant varieties called “miracle
strains” that improved harvests. Another
strategy was a method called monoculture.
Monoculture calls for large fields to be cleared,
plowed, and planted with a single crop every
year. Irrigation, chemical fertilizers, and
pesticides are used. Farmers also replaced human
and animal power with machines
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The green revolution increased food
production and helped prevent food
shortages.
Disadvantages: water supplies and
energy depleted, pesticides carry
potentially harmful chemicals, fertilizer
can interfere with food webs and
biogeochemical cycles.
Industrial Growth and Urban Development
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Many ecologists are concerned about the effects
of human activity on the environment. Some
industrial processes pollute air, water, and soil.
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Resource – something that can be taken when
needed
Common Resource – environmental resource
owned by many people in common
Two types or resources: renewable and
nonrenewable
Renewable resource – can regenerate and is
therefore replaceable
Not necessarily unlimited (fresh water can
become limited by drought or overuse)
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Nonrenewable resource – Can’t be replenished
naturally
Ex – Fossil fuels (coal, oil, gas)
When these fuels are gone, they are
gone forever
Sustainable use is a way of using natural
resources at a rate that does not deplete them
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Land Resources
Plants need fertile topsoil to grow. Plowing the
land increases the rate of soil erosion –
(wearing away of surface soil by
water and wind)
Desertification – farming, overgrazing, and
drought in dry climates turn once productive
areas into deserts
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Forest Resources
Forests are an important resource for the
products they provide and functions they
perform (wood, provide oxygen)
Deforestation – loss of forests
Can lead to severe erosion of soil
Tree farms are a renewable resource because
when a tree is cut down, a new one is planted.
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Ocean Resources
People depend on sea life for food.
Overfishing can destroy a fishery.
Aquaculture – the farming of aquatic
organisms
-an efficient way to produce sea life
If not properly managed, can pollute water
with fish waste and damage local aquatic
ecosystems.
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Air Resources
Air is a resource we use every time we breathe.
Smog – a mixture of chemicals that occurs as a
gray-brown haze in the atmosphere
Pollutant – harmful material that can enter the
biosphere through land, air, or water
Burning fossil fuels can release pollutants that
cause smog. Burning fossil fuels releases acidic
gases into the air and form drops of nitric and
sulfuric acids and fall as acid rain - can kill
plants
Water Resources
Americans use billions of gallons of fresh water
daily for everything from drinking and washing to
watering crops and making steel. Although water
is renewable, the total supply of fresh water is
limited. Protecting water supplies from pollution
and managing society’s ever-growing demand for
water are major priorities. As demand for water
grows rapidly in many parts of the US, water
conservation is becoming an increasingly
important aspect of sustainable use.
6-3 BIODIVERSITY
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Biodiversity – the sum total of the genetically
based variety of all organisms in the biosphere
Ecosystem diversity - the variety of habitats,
communities, and ecological processes in the
living world
Species diversity – the number of different
species in the biosphere
So far, biologists have identified and named
about 1.5 million species and estimate that
milllions more may be discovered in the future.
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Genetic diversity – the sum total of all the
different forms of genetic information carried
by all organisms living on the earth today.
Biodiversity is one of Earth’s greatest natural
resources. Species of many kinds have
provided us with foods, industrial products,
and medicines
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Threats to Biodiversity
Human activity can reduce biodiversity by
altering habitats, hunting species to extinction,
introducing toxic compounds into food webs,
and introducing foreign species to new
environments.
As human activities change ecosystems, this
may lead to the extinction of species. (no longer
exists)
Endangered species – a species whose
population is declining in a way that places it
in danger.
Habitat Alteration and Fragmentation
When land is developed, natural habitats may be
destroyed. As habitats disappear, the species that
live in those habitats vanish. Development often
splits ecosystems into pieces. This is called habitat
fragmentation.
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Conserving Biodiversity
Conservation – the wise management of
natural resources, including the preservation of
habitats and wildlife
Today, conservation efforts focus on protecting
entire ecosystems as well as single species.
Protecting an ecosystem will ensure that the
natural habitats and the interactions of many
different species are preserved at the same
time.
6-4 CHARTING A COURSE FOR THE FUTURE
Many biologists are concerned about the biological
effects of two types of global change: the thinning
of the ozone layer and global warming
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Ozone Depletion
Ozone layer – the concentration of ozone gas
that the atmosphere contains between 20 and
50 km above the Earth’s surface
In the 1970s, scientists found evidence that the
ozone layer was in trouble. A hole was
discovered in the ozone layer. Over the years,
the hole has been growing larger. A second
has also been found. These holes allow higher
than normal levels of UV onto the Earth.
These holes were caused by CFCs, which were
used in aerosol cans, Styrofoam, and coolants.
The use of CFCs have been phased out.
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Global Warming
Global warming – the increase in the average
temperature of the biosphere
Over the past 120 years, global temperature have
risen 0.5 degrees Celsius.
Temperatures are rising at a faster rate now than
they did during the previous 100 years.
Some scientists believe that human activities have
caused global warming by adding carbon dioxide
(from burning fossil fuels) and other greenhouse
gases such as methane to the atmosphere. If global
warming continues at its current rate, the polar ice
caps will continue to melt and sea levels could rise
enough to flood some low-lying coastal areas.
Storms and other weather disturbances could
become more frequent and more severe.