Download Chapter 3 Lecture #2 How Ecosystems Work

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Lecture #2
How Ecosystems Work
Biosphere Breakdown
Organism-any form of life (1 individual)
Species- all organisms of the same kind that
are genetically similar enough to breed in
nature and produce live, fertile offspring
Population-individuals of the same species in
an area
Biological Community-populations of different
species living & interacting in a given area
Ecosystem-many interacting communities in a
specific place including abiotic factors
Biome- large terrestrial regions characterized by
a distinct climate & specific life–forms,
especially vegetation, adapted to the region
Ecosphere-(=biosphere)-all of Earth’s biomes
Abiotic factors
wind speed
wind direction
current velocity
Biotic factors
What drives an ecosystem?
• Photosynthesis is at the base of all ecosystems so
photosynthesizers (usually plants) are called the
• Productivity - the amount of biomass produced in a
given area in a given period of time. Photosynthesis
is called primary productivity because it is basic to all
other growth in an ecosystem.
• Secondary productivity - manufacture of biomass by
organisms that eat plants
From Species to Ecosystems
• Ecosystem - biological community (biotic factors) and
its physical environment (abiotic factors)
– The elements are interacting to process energy
and cycle materials
– Most ecosystems are open in that they exchange
materials and organisms with other ecosystems.
– It is difficult to define the boundaries of an
Major Components of Ecosystems
Major components of aquatic ecosystems.
© Brooks/Cole Publishing Company / ITP
Food Chains and Food Webs
Food Chain - A sequence
that shows the manner
in which energy is
transferred from one
organism to another , as
each organism eats
another, in an
Food web –a complex of interconnected food chains in
an ecosystem.
• These show the many feeding relationships in an
• In an ecosystem of average complexity, numerous
pathways are possible.
• Food webs are a more realistic model of the flow of
energy and materials through an ecosystem.
Trophic pyramids
• Food Chains can also be
represented by an ecological
pyramid by arranging the
organisms at various trophic
levels diagrammatically.
• Notice that there are many
more producers than
• Each trophic level consists
of organisms that get their
energy in the same way.
Which organisms make up each
trophic level?
• Plants (producers) make up the first trophic level.
Animals are consumers.
• 2nd trophic level: Primary Consumers:- Animals that
eat plants.
• 3rd trophic level: Secondary Consumers- Animals
that eat primary consumers
• 4th trophic level: Tertiary consumers- Animals that
eat secondary consumers
* Organisms may occupy more than one trophic level!
• Organisms can also be identified by the type of food
they consume:
What they eat
– Herbivores (Plants)
– Carnivores (Meat)
– Omnivores (Plants/Meat)
– Scavengers (Carcasses)
– Detritivores (Debris)
– Decomposers (All)
Ecological Pyramids & Energy
• Due to the Second Law of Thermodynamics, energy is lost at
each level of the pyramid.
• 10% Rule (Energy / Biomass) - as an organism is consumed,
about 90% of the energy at each trophic level is lost or used
up along the way (as heat in metabolic processes).
• Only about 10% of the energy becomes part of the consumers
• This 10% is all that is available to the next trophic level when
one organism consumes another.
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