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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.)
1). Domestication of Animals- led to
overgrazing, eroded soils, large
demands on water
2). Modern Agriculture- In 1800’s,
advancement in science (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)
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
4. Forest Resources- provides products,
habitats and food for organisms, moderates
climate“lungs” of the Earth”
deforestation- loss of forest. Can
lead to severe erosion.
What are two ways in which reforestation
might affect the biosphere?
a. Smog- common pollutant in large
cities. (pollutant- harmful material that
can enter the biosphere through land,
air, or water)
b. Acid rain- acidic gas released into
air and combine with water vapor forming
drops of nitric and sulfuric acid. Can kill
plants, change chemistry of soils and
standing water ecosystems
Photomicrograph of
drop of acid rain.
Serious threat to
environment
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.
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- total of the genetic 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 magnificationlevels of harmful substances
increase in organisms at
higher trophic levels.
b. Introduced Species- Introduction of
new species in new area
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
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