Transcript Ch.6 - Jamestown School District

Unit 2 Ecology
Ch. 6 Humans in the Biosphere
Earth as an Island
Earth is an island, that all organisms,
including humans, live on & share a
limited resource base, & depend on for
their long-term survival
We all rely on the natural ecological
processes that sustain these resources
Earth as an Island
To protect these resources, we have to
understand how humans interact with
the biosphere
We must also learn how to predict what
will happen in the future
Human Activities
Some human activities that affect the
biosphere are hunting & gathering,
agriculture, industry, & urban
development
Human Activities
Hunting & Gathering:
For most of human history, our ancestors
got food by hunting & gathering
Today, groups of people in different parts
of the world follow the hunter-gatherer way
of life
As a result of overhunting, species have
become extinct
Human Activities
Agriculture:
Agriculture - the practice of farming
People in different regions grow wheat,
rice, & potatoes
The development of agriculture included
raising animals like sheep, goats, cows,
pigs, etc.
Human Activities
Agriculture:
Agriculture provides a stable & predictable
food supply for humans
Monoculture - large fields are planted with
a single variety of crop, year after year
Chemical fertilizers boosted plant growth &
pesticides controlled crop damaging
insects
Human Activities
Agriculture:
Green revolution - period of time in the
middle of the 20th century, when
governments began a major push toward
an increase in the world’s food supply
Over the last 50 years, the green
revolution has helped world food
production double
Human Activities
Agriculture:
While increasing food supply, modern
agriculture has created ecological
challenges
Chemical pesticides have contaminated
water supplies, usable water has declined,
etc.
Human Activities
Industrial Growth & Urban
Development:
Cities have greatly contributed to pollution
of air, water, & soil
Human wastes have been dumped into
habitats, polluting those habitats, etc.
Renewable & Nonrenewable
Resources
Environmental goods & services may
be either renewable or nonrenewable
Renewable resources - can be
replenished by biochemical cycles if
they are nonliving
Ex.) Water is a renewable resource that
can become limited by drought or overuse
Renewable & Nonrenewable
Resources
Nonrenewable resource - 1 that cannot
be replenished by natural processes
Ex.) Fossil fuels like coal, oil, & natural gas
are nonrenewable resources
Fossil fuels formed millions of years ago
from deeply buried organic materials
When they are depleted, they are gone
forever
Renewable & Nonrenewable
Resources
The classification of a resource as
renewable or nonrenewable depends on
its context
A single tree is renewable, but a
population of trees in an ecosystem,
may not be renewable because the
ecosystem may change forever once
those trees are gone
Sustainable Development
 Human activities can affect the quality and
supply of renewable resources like land,
forests, fisheries, air, & fresh water
 Sustainable development - a way of using
natural resources without depleting them & of
providing for human needs without causing
long-term environmental harm
Land Resources
Land is a resource that provides space
for human communities & raw materials
for industry
It also includes the soils where crops
are grown
If managed properly, it is a renewable
resource, but could become nonrenew.
Land Resources
Plowing the land removes the roots that
hold the soil in place, which increases
soil erosion
Soil erosion - the wearing away of
surface soil by water & wind
Land Resources
In dry climates, a combination of
farming, overgrazing, & drought has
turned once productive areas into
deserts - Desertification
Forest Resources
Deforestation - loss of forests
It can lead to severe erosion, can wash
away nutrients, grazing after
deforestation can deplete nutrients
permanently
Fishery Resources
Fishes & other animals that live in water
are a valuable source of food for
humanity
Overfishing, or harvesting fish faster
than they can be replaced by
reproduction, has greatly reduced the
amount of fish in the ocean’s
Fishery Resources
People from several countries were
taking advantage of a resource,
fisheries
Until recently, fisheries seemed to be a
renewable resource, that could be
harvested indefinitely
Overfishing has destroyed that resource
Air Resources
Air is a common resource that we use
every time we breathe
Large cities often have smog - mixture
of chemicals that occurs as a grayish
haze in the atmosphere
It is primarily due to car exhausts &
industrial emissions
Air Resources
Pollutant - harmful material that can
enter the biosphere through the land,
air, or water
Burning of fossil fuels can release
pollutants that cause smog & other
problems
Air Resources
When chemical compounds combine
with water vapor in the atmosphere,
they form drops of nitric & sulfuric acid Acid rain
Acid rain can kill plants by damaging
their leaves & change the chemistry of
soils & standing-water ecosystems
Freshwater Resources
Pollution threatens water supplies in the
following ways:
Wastes discarded on land can seep
through soil & enter underground water
Chemicals can enter streams & rivers
Sewage can encourage the growth of
algae & bacteria in aquatic habitats
The Value of Biodiversity
Biodiversity - the sum total of the
genetically based variety of all
organisms in the biosphere
Ecosystem diversity - the variety of
habitats, communities, & ecological
processes in the living world
The Value of Biodiversity
Species diversity - the # of different
species in the biosphere
Genetic diversity - all the different forms
of genetic information carried by all
organisms living on Earth today
The Value of Biodiversity
Biodiversity is 1 of Earth’s greatest
natural resources
Species of many kinds have provided
us with foods, industrial products, &
medicines - including painkillers,
antibiotics, heart drugs,
antidepressants, & anticancer drugs
Threats to Biodiversity
Human activity can reduce biodiversity
by altering habitats, hunting species to
extinction, introducing toxic compounds
into food webs, & introducing foreign
species to new environments
Threats to Biodiversity
Extinction - when a species disappears
from all or part of its range
Endangered species - a species whose
population size is declining in a way that
places it in danger of extinction
Habitat Alteration
When land is developed, natural
habitats may be destroyed
As habitats disappear, species that lived
in those habitats also vanish
Development also splits ecosystems
into pieces - habitat fragmentation
Ex.) Central Park
Demand for Wildlife Products
Humans have pushed some animal
species to extinction by hunting them for
food & other products
Today, endangered species are
protected from hunting in the U.S.
Hunting still threatens rare animals in
other countries, however
Pollution
Many forms of pollution can threaten
biodiversity, especially when toxic
compounds accumulate in the tissues of
organisms
Biological magnification - when
concentrations of a harmful substance
increase in organisms at higher trophic
levels in a food chain/ food web
Pollution
Introduced Species
1 of the most important threats to
biodiversity today comes from
apparently harmless plants & animals
that humans transport around the world
either accidentally or intentionally
Introduced Species
Introduced into new habitats, these
organisms often become invasive
species that reproduce rapidly
Invasive species - increase their
populations because their new habitat
lacks the parasites & predators that
control their popul. “back home”
Conserving Biodiversity
Conservation - describes the wise
management of natural resources,
including the preservation of habitats &
wildlife
Today, conservation efforts focus on
protecting entire ecosystems as well as
single species
Conserving Biodiversity
Protecting an ecosystem will ensure
that the natural habitats & the
interactions of many different species
are preserved at the same time
By focusing on protecting specific
ecosystems, biologists hope to preserve
global biodiversity
Charting a Course for the
Future
Researchers are gathering data to
monitor & evaluate the effects of human
activities on important systems in the
biosphere
2 of these systems are the ozone layer
high in the atmosphere & the global
climate system
Ozone Depletion
Ozone layer - 20-50Km above Earth’s
surface, a layer of high concentration of
ozone gas exists
Ozone at ground level is a pollutant, but
in the atmosphere, serves an important
function
Ozone Depletion
It absorbs a harmful UV radiation from
sunlight before it reaches Earth
Global Climate Change
Global warming - describes the
increase in average temperature of the
biosphere
1 sign is the melting polar ice cap