Chapter 3
Ecosystems and Energy
Overview of Chapter 3
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Ecology
Energy
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First Law of Thermodynamics
Second Law of Thermodynamics
Photosynthesis and Cellular Respiration
Flow of Energy Through Ecosystems
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Producers, Consumers & Decomposers
Ecological Pyramid
Ecosystem Productivity
Ecology
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Ecology
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Biotic- living environment
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“eco” house & “logy” study of
The study of interactions among and between
organisms in their abiotic environment
Broadest field in biology
Includes all organisms
Abiotic- non living or physical environment
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Includes living space, sunlight, soil,
precipitation, etc.
Ecology
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Biology is
very
organized
Ecologists
are
interested
in the levels
of life
above that
of organism
Ecology Definitions
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Species
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Population
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Al the populations of different species that live and
interact in the same area at the same time
Ecosystem
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A group of organisms of the same species that occupy
that live in the same area at the same time
Community
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A group of similar organisms whose members freely
interbreed
A community and its physical (abiotic) environment
Landscape
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Several interacting ecosystems
Ecology
Biosphere contains earth’s communities,
ecosystems and landscapes, and includes:
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Atmospheregaseous envelope
surrounding earth
Hydrosphereearth’s supply of
water
Lithosphere- soil
and rock of the
earth’s crust
Energy
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The ability or
capacity to do work
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Chemical, radiant,
thermal, mechanical,
nuclear, electrical
Energy exists as:
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Stored energy
(potential energy)
Kinetic energy (energy
of motion)
Thermodynamics
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Study of energy and its transformations
System- the object being studied
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Closed System- Does
not exchange energy
with surroundings (rare
in nature)
Open Systemexchanges energy with
surroundings
Laws of Thermodynamics
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First Law of Thermodynamics
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Energy cannot be created or destroyed; it can
change from one form to another
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Ex: organisms cannot create energy they need to
survive- they must capture it from another source
Focus is on quantity
Second Law of Thermodynamics
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When energy is converted form one form to
another, some of it is degraded to heat
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Heat is highly entropic (disorganized)
Focus is on quality
Photosynthesis
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Biological process by which energy from
the sun (radiant energy) is transformed
into chemical energy of sugar molecules
6 CO2 + 12 H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2
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Energy captured by plants via
photosynthesis is transferred to the
organisms that eat the plants
Cellular Respiration
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The process where the chemical energy
captured in photosynthesis is released
within cells of plants and animals
C6H12O6 + 6 O2 + 6 H2O
6 CO2 + 12 H2O + energy
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This energy is then used for biological
work
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Creating new cells, reproduction, movement,
etc.
Energy Flow
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Passage of energy
in a one-way
direction through
an ecosystem
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Producers
Primary consumers
Secondary
consumers
Decomposers
Food Chains- The Path of Energy Flow
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Energy from food passes from one
organisms to another
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Each “link” is called a trophic level
Food webs represent interlocking food chains
that connect all organisms in an ecosystem
Ecological Pyramids
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Graphically represent the relative energy
value of each trophic level
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Important feature is that large amount of
energy are lost between trophic levels to heat
Three main types
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Pyramid of numbers
Pyramid of biomass
Pyramid of energy
Web activity
Pyramid of Numbers
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Illustrates the number of organisms at each
trophic level
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Usually, organisms at the base of the pyramid
are more numerous
Fewer organisms occupy
each successive level
Do not indicate the
biomass of the
organisms at each level
or the amount of
energy transferred
between levels
Pyramid of Biomass
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Illustrates the total biomass at each
successive trophic level
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Biomass: measure of the total amt of living
material
Biomass indicates the
amount of fixed energy
at a given time
Illustrates a
progressive reduction
in biomass through
trophic levels
Pyramid of Energy
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Illustrates how much energy is present at
each trophic level and how much is
transferred to the next level
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Most energy dissipates between trophic levels
Explains why there
are so few trophic
levels
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Energy levels get too
low to support life
Ecosystem Productivity
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Gross Primary Productivity (GPP)
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Net Primary Productivity (NPP)
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Total amount of energy that plants capture and
assimilate in a given period of time
Plant growth per unit area per time
Represents the rate at which organic material
is actually incorporated into the plant tissue
for growth
GPP – cellular respiration = NPP
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Only NPP is available as food to organisms
Variation in NPP by Ecosystem
Human Impact on NPP
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Humans consume more of earth’s resources
that any other animal
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Humans represent 0.5% of land-based biomass
Humans use 32% of land-based NPP!
This may contribute to loss of species
(extinction)
Humans’ high consumption represents a
threat to planet’s ability to support both
human and non-human inhabitants
Our Net Primary Productivity Lab
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Results
My Hero Dr. Wangari Maathai
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http://www.nytimes.com/2011/09/27/worl
d/africa/wangari-maathai-nobel-peaceprize-laureate-dies-at-71.html
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http://www.cnn.com/2011/09/26/world/af
rica/wangari-maathai-tribute/