Download Introduction to Ecology What sustains Life on Earth

Introduction to Ecology
• Organisms
• Populations – actually
interbreeding
organisms
• Communities –
interacting species
• Ecosystems –
interacting species and
their inorganic
environment
• Biosphere – The thin
skin of living space on
the earth
What sustains Life on Earth?
• One-way flow of energy
THERE ARE NO ENERGY CYCLES ON
EARTH!!!!!
Energy has a oneway trip from the sun,
through the biosphere and out into space
• Cycling of Matter
Bucky Fuller was right! We live on a
spaceship. There will be no more
materials added.
Spaceship Earth
• Buckminster Fuller
coined the term
“spaceship earth”
• We are on a lightpowered spaceship
– Nothing is added but
energy
– Implication is that
resources are finite
The Sun is the source of Energy
that drives the biosphere
• Ultimate source is
thermonuclear
reactions in sun
• The sun is a huge,
self- sustaining
hydrogen bomb
• Good thing that is it
93,000,000 miles
away
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What Happens to Solar Energy
Reaching the Earth?
• Most is reflected back
into space
• The rest is used to
drive materials
(biogeochemical)
cycles
• Constant energy input
from sun keeps
biosphere functioning
Energy Transfer Within the
Biosphere
Ray Lindeman
• Applied the ideas of
physics to ecology
• Organisms transfer
energy
– But energy is lost at
each step
• Result is food chain
Representative Food Chain
Food chain
– Animals and plants pass energy between each other
– Plant gets energy from sun
• Fixes Carbon to make sugar
• Primary producers (1st trophic level)
– Animals get energy from plants
• Primary Consumers (2nd trophic level, herbivores)
• Secondary Consumers (3rd trophic level, carnivores)
• Tertiary Consumers (4th trophic level, top carnivores)
– Detritivores eat the left-overs
Decomposers and Detritivores
Recycle Materials
About 10% of the Energy from
one trophic level is available to
the next level
The other 90% is lost as heat
This is ecological efficiency
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Antarctic Ocean Food Web
Illinois Forest Food Web
• Food Webs are more
likely than food chains
• The trophic status
story still holds
Pyramid of Energy Flow
• 2nd Law of
Thermodynamics
says that energy is
lost at every transfer
• Less and less
biomass as you go up
the food chain
Implications of Pyramid of Energy
• You can support more humans as
vegetarians than as carnivores
– You don’t lose as much energy to lower
trophic levels
• Food Chains tend to be short
• It is easier to exploit low trophic level
organisms than high trophic level ones
– High trophic level organisms are more likely to
be hunted to extinction
Feeding Humpback Whales
Biogeochemical Cycling
Whales are large animals that feed low on the food chain
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All Material Cycles in Biosphere
• Biogeochemical
Cycling causes
chemicals to turn up
in unexpected places
• Nutrients
– Nitrogen
– Phosphorus
– Sulfur
– Methyl Mercury and
Minamata disease
– Discharges of methyl
mercury taken up by
fishes
– Caused horrible
disease in people and
cats
• Toxicants also cycle
– Dioxin
– DDT
– Mercury
– Lead
Species
Minamata Bay
Mercury Concentrations
In sediment from
Minamata Bay
Robert MacArthur
• Biological Species Concept
- Interbreeding or potentially interbreeding
populations
• Ecological Niche
– What a species does in the environment
• Demonstrated
that each
species has its
own ecological
niche
• MacArthur’s
Warblers
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MacArthur’s Warblers
• All Live together in
the same woods
• They do different
things
• Species are selected
to do different things
in the environment
• Fill an ecological
niche
Ecological Niche
• The total way of life
or role of a species
in an ecosystem. It
includes all
physical, chemical,
and biological
conditions as
species needs to
live and reproduce
• Species have
environmental
tolerances
• They “fit” particular
environments
• If you change the
environment, you may
cause the species to
go extinct
The ecological niche of an
organism depends not only on
where it lives but also on what it
does. By analogy, it may be said
that the habitat is the organism’s
“address”, and the niche is its
“profession”, biologically
speaking
E.P. Odum
• You can see the ecological niche as a
species role in an ecosystem
• Niches may be “broad” or “narrow”
– Broad – Rats
– Narrow
• Red Cockaded Woodpecker
• Spotted Owl
• Panda
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Biodiversity
• Earth is home to a wide range of species
• They keep ecosystems functioning
• Why is Biodiversity important
– Natural world provides us with food, fiber,
energy
– Free recycling
– Water and Air purification
– Natural Pest control
Problem of Loss of Biodiversity
• Threatens “ecosystem services”
• Airplane rivets analogy
• Extinction and species endangerment are
real problems
• So, is the problem of endangered
species one that we should worry
about???
Winds on a Rotating Earth
Earth Ecosystems
Climatic Zones of the Earth
Biological Communities on Earth
organized into “Biomes”
• Groups of organisms
with similar
environmental
requirements live
together
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Lots of Different Kinds of Biomes
Deciduous Forest
Populations
Illinois Praire
Lake
Tundra
Rainforest
• Population growth could be very fast
– There are more babies of most animals (and
plants) born than could ever be accomodated
on earth
• Exponential growth
– Can’t continue forever
• Limits to growth
– Space
– Food
– Nest Sites
• Sheep in Tasmania
– Illustrate
population
growth
– Initial
exponential
growth
– Reach a carrying
capacity
Does this Apply to Humans?
Is there a limit to human
population growth?
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