Humans in the Biosphere

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Chapter 6
Humans in the Biosphere
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VIII. Humans in the Biosphere

• Earth as an Island-
• 1. all organisms that live on Earth share
  limited resource base

2. Understanding how humans interact is crucial
to protecting resources
The iiwi (Hawaiian honeycreeper), a native
species in Hawaii is becoming scarce due to
disease, habitat loss, and predation by
introduced species
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B. Human Activities
1. Industry and Technology give humans
advantage in competing with other species for
limited resources such as food, energy, and space
2. Today, humans most important source for
environmental change
a. Hunting and Gathering-have changed
environment since pre-historic times
Human hunters arrived in North America about
12,000 years ago. They caused one of major mass
extinctions of large animals (woolly mammoths,
giant ground sloths, sabertooth cats, cheetahs,
zebras, etc.)
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b. Agriculture- humans began practicing
farming 11,000 years ago (after last ice age)
1). Domestication of Animals- sheep,
goats, cows, pigs, horses, dogs (led to
overgrazing, eroded soils, large demands on
water
2). Modern Agriculture- In 1800s,
advancement in science led to remarkable
changes in agriculture and increased yields
(irrigation, new crop varieties, invention of
farm machines
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3). Green Revolution- global effort to
increase food production for fast- growing
world population (new, intensive farming
practices that increase yields)
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• Renewable and Nonrenewable Resources

1. Two types of environmental resources
a. Renewable- can regenerate (are
replaceable) not necessarily unlimited
b. nonrenewable- one that cannot be
replenished by natural processes (eg. Fossil
fuels, oil and natural gas
2. Sustainable use- using natural resources
so that you dont deplete them (based on
principles of ecology and economics)
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This proud, tall tree is no match for a huge
chainsaw. Once cut, it will be used to make many
consumer products
A tiny tree will be placed in its stead.
Varieties of trees that reach harvesting size in
fewer years have been developed
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3. Land Resources- provides space for cities,
materials for industry, soils in which crops are
grown.
desertification- in certain parts of the world
with dry climates, a combination of farming,
overgrazing, and drought have turned once
productive areas into deserts
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4. Forest Resources- provides products,
habitats and food for organisms, moderates
climate, limits soil erosion, protects
freshwater supplies, lungs of the Earth
deforestation- loss of forest. Can lead to
severe erosion. Sustainable-use strategies
include selective harvesting and replanting.
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What are two ways in which reforestation might
affect the biosphere?
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5. Ocean Resources- provides valuable food
resources.

How do you explain graph 2 (fish catch per
person remains the same despite steady increase
in world fish catch)?
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6. Air Resources- Air is common resource.
Preserving air quality remains a challenge for
modern society.
a. Smog- common pollutant in large cities.
(pollutant- harmful material that can enter the
biosphere through land, air, or water)
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b. Acid rain- acidic gasses released into
air and combine with water vapor forming drops
of nitric and surfuric acid. Can kill plants,
change chemistry of soils and standing water
ecosystems
Photomicrograph of drop of acid rain. Serious
threat to environment
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7. Water Resources- water is renewable resource
but must be protected because supply is limited.
a. Water pollution- threatened by chemicals,
domestic sewage, wastes discarded on land- all
can seep into underground water supplies.
City sewage must be treated in sewage-treatment
plants. Organic wastes are broken down by
bacteria and then chemicals are added to kill
harmful microorganisms.
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Where does all of your trash end up? Why do we
have to be careful about what goes into our
garbage landfills?
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Trawlers clean up an oil spill caused by a
disaster at sea. A system of floats called booms
helps keep the oil from spreading during the
cleanup process.
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b. Domestic sewage, which is the wastewater from
sinks and toilets, contains nitrogen and
phosphorous compounds that can encourage the
growth of algae and bacteria in aquatic habitats
Algae bloom
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D. Biodiversity- sum total of the genetically
based variety of all organisms in the biosphere
1. Forms of diversity
a. Ecosystem diversity- includes variety of
habitats, communities, and ecological processes
in the living world
b. Species diversity- number of different
species in the biosphere
c. Genetic diversity- sum total of all the
different forms of genetic information carried by
all living organisms
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2. Biodiversity is one of Earths greatest
natural resources. Species of many kinds have
provided us with foods, industrial products,
medicines, etc.
3. 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 into new environments
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a. Pollution- many forms of pollution can
affect biodiversity.
Biological magnification- concentrations of
harmful substances increase in organisms at
higher trophic levels. Affects all levels, but
top-level carnivore are at highest risk
By what number is the concentration of DDT
multiplied at each successive trophic level?
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b. Introduced Species- one of most important
threats. Introduced either intentionally or
unintentionally they have destroyed habitats of
species native to those ecosystems.
Fire ants were accidentally imported from Brazil
about 45 years ago. Now found in San Clemente
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Kudzu was introduced into the U.S. from Russia
and Japas as an ornamental and to reduce soil
erosion. It grows and reproduces rapidly,
smothering areas of native plants
Zebra mussels were introduced into Great Lakes
from ballast of ships. Fast-growing mussels
filter food from the water, blocking many food
chains
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Can you name any introduced species that have
created problems locally?
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4. Conserving Biodiversity- many conservation
efforts focusing on entire ecosystems as well as
single species
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D. Charting a Course for the Future- two major
concerns
1. Ozone depletion- naturally occurring ozone
gas (20-50 km above Earths surface) absorbs good
deal of harmful ultraviolet radiation from
sunlight before it reaches Earths surface.
a. Beginning in 1970s scientists found evidence
showing ozone hole over Antarctica
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b. Problem caused by compounds called
chlorofluorocarbons (CFCs) (CFCs act as
catalysts that enable UV light to break apart
ozone
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2. Global Warming- an increase in average
temperature of the biosphere.
a. Hypothesize that human activities have added
carbon dioxide and other greenhouse gasses
(methane, H20) into the atmosphere
b. Scientific models suggest that could cause
polar ice caps to melt and raise sea level. This
could also cause more severe weather disturbances
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D. The Value of a Healthy Biosphere
1. Human society depends on healthy, diverse,
and productive ecosystems because of the
environmental and economic benefits they provide
2. People need to make wise choices in use of
resources and disposal or recycling of materials
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Review
Chapter 6 Humans in the Biosphere
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In the very distant past, most people a. lived in
small groups. b. lived in permanent
settlements. c. did not gather plants. d. did
not hunt animals.
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In the very distant past, most people a. lived in
small groups. b. lived in permanent
settlements. c. did not gather plants. d. did
not hunt animals.
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The arrival of Europeans in the Hawaiian Islands
changed the islands by introducing a. ranching. b
. predators. c. disease. d. all of the above
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The arrival of Europeans in the Hawaiian Islands
changed the islands by introducing a. ranching. b
. predators. c. disease. d. all of the above