Transcript Chap 3 PowerPoint

Chapter 3
Ecosystems and Energy
Overview of Chapter 3
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What is Ecology?
The Energy of Life
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Laws 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 and their abiotic environment
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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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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All 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 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
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Biosphere contains earth’s communities,
ecosystems and landscapes, and includes:
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Atmosphere gaseous envelope
surrounding earth
Hydrosphere earth’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
Chemical, Thermal, Mechanical, Nuclear,
Electrical, and Radiant/Solar (below)
Energy
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Energy exists as:
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Potential energy
(stored energy)
Kinetic energy
(energy of motion)
Potential energy is
converted to kinetic
energy as arrow is
released
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 System exchanges 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
Second Law of Thermodynamics
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When energy is converted from one form to
another, some of it is degraded to heat
Heat is highly entropic (disorganized)
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
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
Photosynthesis and Cellular Respiration
Energy Flow
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Passage of energy 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
organism to another based on their
Trophic Level
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An organism’s position in a food chain
determined by its feeding relationships
First Trophic Level: Producers
Second Trophic Level: Primary Consumers
Third Trophic Level: Secondary Consumers
Decomposers are present at all trophic
levels
Food Web
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 amounts 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
Pyramid of Numbers
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Illustrates the number of organisms at each
trophic level
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Fewer organisms
occupy each
successive level
Does not indicate:
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biomass of organisms
at each level
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
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
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 represent 0.5% of land-based
biomass, but use 32% of land-based NPP!
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This may contribute to loss of species
(extinction)
This represents a threat to planet’s ability
to support both human and non-human
inhabitants