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The Biosphere
Chapter 3
What is ECOLOGY
1866 German Biologist Ernst Haeckel
first coined the term ecology.
 Came from the Greek word oikos
meaning “house”
 Defined today as the study of
interactions among living organisms
and their environment

Energy Flow



The sun is the main
source of energy for
life on earth.
< 1 % of all sunlight
that reaches earth
is used by living
organisms.
What happens to
the rest?

Most is reflected off
as heat energy.
Producers or
Autotrophs
Use sunlight or chemicals to make
their own food.
 Examples:


6CO2 + 6H2O
C6H12O6 + 6O2

Performed on land by plants and in
water by algae.
Can organisms make their
own food without the aid
of sunlight?
Chemosynthesis: using chemical
energy to make carbohydrates.
 Usually performed bacteria found in
harsh environments

– Ocean vents, volcanoes, hot-acidic
Consumers or
heterotrophs
 Herbivores
 Carnivores
 Omnivores
 Detritivores
 Decomposers
Food Chains
Producer
(algae)
primary consumer
(plankton)
secondary consumer
(small fish)
tertiary consumer
(large fish)
Food Webs
More complex than food chains
 A complex net of interactions among
organisms. (interdependence)

Trophic Levels
Each location or step in a food chain or
food web represents a trophic level.
 Examples: producers, primary
consumers, secondary consumers,
etc.

Ecological pyramids

Only about ten
percent of the
energy available
within a trophic
level is transferred
to oragnisms at the
next higher level.
Other pyramids:

Biomass and numbers
Cycles of matter
Unlike energy, matter is constantly
being recycled in an ecosystem.
 Known as biogeochemical cycles

Transpiration
The release of water from the leaves
of plants.
 Water is exchanged through a plant’s
stomata.
 Evaporation is the second process that
releases water into the atmosphere.

Carbon Cycle
1.
2.
3.
4.
Biological processes
(photosynthesis, respiration,
decomposition)
Geochemical processes (volcanoes)
Biogeochemical (fossil fuels)
Human activity (factories,
deforestation, car exhaust)
Nitrogen Cycle
All organisms need nitrogen to live.
 Most abundant gas in atmosphere
(80%)
 Nitrogen gas is unusable for plants
 Must be “fixed” or changed into the
nitrate or nitrite form by bacteria in the
soil. Known as nitrogen fixation

Nitrogen Cycle
Phosphorus cycle
P is important in the production of DNA
and RNA.
 Unlike water,oxygen, and nitrogen,
phosphorus is NOT found in the
atmosphere. Found in rocks and
minerals.

Nutrient Limitation

When a single nutrient is scarce for a
particular ecosystem and limits the
growth of organisms in that
ecosystem.