Transcript File

Chapter 6
Humans in the
Biosphere
VIII. Humans in the Biosphere
A. 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
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.)
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 1800’s,
advancement in science led to
remarkable changes in agriculture and
increased yields (irrigation, new crop
varieties, invention of farm machines
3). Green Revolution- global effort to
increase food production for fastgrowing world population (new,
intensive farming practices that
increase yields)
C. 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 don’t deplete them (based on
principles of ecology and economics)
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
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
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.
What are two ways in which reforestation
might affect the biosphere?
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)?
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)
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
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.
Where does all of your trash end
up?
Why do we have to be careful about
what goes into our garbage landfills?
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.
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
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
2. Biodiversity is one of Earth’s
greatest natural resources. Species of
many kinds have provided us with foods,
industrial products, medicines, etc.
3. Threats to Biodiversityhuman activity can reduce
biodiversity by altering
habitats, hunting species to
extinction, introducing toxic
compounds into food webs,
and introducing foreign
species into new
environments
a. Pollution- many forms of
pollution can affect biodiversity.
Biological magnificationconcentrations 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?
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
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
Can you name any introduced species
that have created problems locally?
4. Conserving Biodiversity- many
conservation efforts focusing on entire
ecosystems as well as single species
D. Charting a Course for the Future- two major
concerns
1. Ozone depletion- naturally occurring
ozone gas (20-50 km above Earth’s
surface) absorbs good deal of harmful
ultraviolet radiation from sunlight before it
reaches Earth’s surface.
a. Beginning in 1970’s
scientists found evidence
showing ozone “hole” over
Antarctica
b. Problem caused by
compounds called
chlorofluorocarbons (CFCs)
(CFCs act as catalysts that enable
UV light to break apart ozone
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
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
Review
Chapter 6
Humans in the
Biosphere
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.
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.
The arrival of Europeans in the Hawaiian Islands
changed the islands by introducing
a.
ranching.
b.
predators.
c.
disease.
d.
all of the above
The arrival of Europeans in the Hawaiian Islands
changed the islands by introducing
a.
ranching.
b.
predators.
c.
disease.
d.
all of the above