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Biology: The Study of Life
“Bio”- living, life
“Logos”knowledge/study
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Human Impact: Humans are members of the Biosphere
Biosphere
Entire portion of planet where life
occurs
from the upper atmosphere to ocean
floor and below
Ecosystem
Consists of all the organisms living in
a particular area (plants, animals,
bacteria) as well as all the nonliving,
physical components of the
environment with which the organisms
interact (air, soil, water, sunlight)
Ex: marsh, forest, mountain lake, desert
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Organization of the Biosphere
Many types of
ecosystem
Tundra
Tropical rainforests
Deserts
Kelp forests
Coral reefs
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Organization of the Biosphere
Major determinant of which
ecosystem is found where
is climate
Deserts = low rainfall
Tropical rainforests = wet & warm
Coral reefs = shallow, clear warm
oceans
Reefs and tropical
rainforests are both homes
to wide diversity of
organisms
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Within an Ecosystem:
Community: All living organisms in an ecosystem
Organisms in communities interact with one another and are often
strongly dependent upon one another (form food webs, etc)
Population: All members of same species which may
mate with one another within an area
Many populations in one community
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Ecosystems are dynamic environments
Organisms exchange materials and energy with their
environment
Energy and nutrients are cycled through
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Ecosystems are
characterized by:
Cycling of materials
How do humans impact this?
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Ecosystems are characterized by:
Flow of energy
Food chains
Food webs
How do
humans
impact
this?
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Human Population
Human activities shape
ecosystems
cut down forests
plow grasslands
drain marshes
build houses and roads
Redirect water
Activities often result in pollution that
changes ecosystems
Effects are particularly bad in
rainforest and coral reefs
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Human Population
Human activities have
Destroyed > 10% of coral reefs
and damaged another 30%
Cut down rainforests
Polluted water
Harming ability of world’s
ecosystems to support us, our
children and other species
Just starting to realize how
strongly we depend on our
ecosystems
We may be changing our
planet in unforeseen,
negative ways
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Biodiversity
Biodiversity = number of
species, and their genetic
variability
Between 2 and 20 million
species alive today
Human activities threaten
many of them
Hundreds of species go
extinct every day
Many more have been
reduced to a very small
number of individuals
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Biodiversity
Each individual has only two sets of
chromosomes
Each can carry only 2 copies of the
gene for any trait
Fewer individuals = less genetic
diversity
Natural selection acts on diversity
If individuals don’t have needed
traits to survive in environment, all
will die
Fewer genetic options = more likely
extinction is as environment
changes
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Biodiversity
Loss of species and
loss of genetic
diversity in today’s
ecosystems is
worrying
Are human activities
leading to a “mass
extinction” like the
one 65 million years
ago when the
dinosaurs all died?
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