Chapter 3: Ecosystems and Energy
Brant Wells
Ecology: Greek word for house “study of one’s house”
 The study of the interactions among organisms and between
organisms and their abiotic environments.
o The environment consists of two parts…
 1. Biotic (living) things
 2. Abiotic (nonliving, or physical) things
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There are many levels of biological organizations
o Biosphere: The layer of Earth containing all living organisms
 Earth’s four realms:
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Biosphere: all other three realms combined
Atmosphere: the gaseous envelope surrounding
Earth
Hydrosphere: Earth’s supply of water, frozen or
liquid
Lithosphere: soil and rock of Earth’s crust
o Landscape: a spatially heterogeneous region that includes
several interacting ecosystems
 Landscape ecology: a subdiscipline of ecology that
studies ecological processes that operate over large
areas.
o Ecosystem: A community and its physical environment
o Community: A natural association that consists of all
populations of species that live and interact together within
an area at the same time
o Population: A group of organisms of the same species that
live together in the same area at the same time
o Species: A group of similar organisms whose members freely
interbreed with one another in the wild in order to produce
fertile offspring
 Example: Elephant=species
Many elephants=population
Elephants, zebras, giraffes=community
African wilderness=ecosystem
Chapter 3: Ecosystems and Energy
Brant Wells
Energy: The ability to do work
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Forms of Energy
o Chemical: energy stored in the bonds of molecules
o Radiant: energy, such as radio waves, visible light, and X
rays, which is transmitted as electromagnetic waves
o Solar: radiant energy from the sun
o Thermal: heat energy that flows from an object with a higher
temperature to an object with a lower temperature
o Mechanical: energy in the movement of matter
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Nuclear: energy found within atomic nuclei
Electrical: energy that flows as charged particles
Potential: energy that is stored
Kinetic: energy that is in motion
The study of energy and its transformations is called
thermodynamics
o System: consists of multiple interacting parts enclosed in a
definite boundary that forms a unified whole
The rest of the universe would be considered
surroundings
o Closed System: self-contained and isolated—does not
exchange energy with its surroundings
o Open System: exchanges energy with its surroundings
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The First Law of Thermodynamics
o Defined: energy cannot be created nor destroyed, although it
can change form one form to another
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The amount of energy on Earth today and Earth 20
billion years ago is exactly the same!!
Photosynthesis is a good example of how this works
The Second Law of Thermodynamics
o Defined: When energy is converted from one form to another,
some of it is degraded into heat, a less usable form that
disperses into the environment
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When energy enters the atmosphere as heat, there is
no way to recapture that energy
Entropy: a measure of this disorder or randomness
Photosynthesis and Cellular Respiration
o Photosynthesis is the biological process in which light
energy from the sun is captured and transformed into the
chemical energy of carbohydrate (sugar) molecules.
 This energy is used to manufacture the carbohydrate
glucose (C6 H12 O6) from Carbon Dioxide (CO2) and
Water (H2O), with the liberation of oxygen (O2)
6CO2 + 12H2O + radiant energy  C6H12O6 + 6CO2
o The chemical energy that plants store in carbohydrates and
other molecules is released within cells of plants, animals, or
other orgasms through cellular respiration.
C6H12O6 + 6O2 + 6H2O  6CO2 + 12H2O + energy
Chapter 3: Ecosystems and Energy
Brant Wells
Energy Flow: The passage of energy in a one-way direction through an
ecosystem
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Producers, Consumers, and Decomposers
o Producers, also called autotrophs, manufacture organic
molecules from simple inorganic substances, generally carbon
dioxide and water, usually using the energy of sunlight.
o Consumers, use the bodies of other organisms as a source
of food energy and bodybuilding materials. Consumers are
also called heterotrophs.
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Consumers that eat producers are primary consumers
or herbivores.
Secondary Consumers eat primary consumers,
whereas tertiary consumers eat secondary
consumers. Both secondary and tertiary consumers are
carnivores.
Omnivores eat both plants and animals
Detritus feeders or detritivores consume detritus,
organic matter that includes animal carcass, leaf litter,
and feces.
o Decomposers, also called saprotophs, are microbial
heterotrophs that break down dead organic material and use
the decomposition products to supply themselves with
energy.
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In an ecosystem, energy flow occurs in food chains, in which energy
from food passes from on organism to the next in a sequence.
o Trophic Level: An organism’s position in a food chain, which
is determined by its feeding relationships
o Food Web: A representation of the interlocking food chains
that connect all organisms in an ecosystem.
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Ecological Pyramids
o Ecological Pyramids often graphically represent the relative
energy values of each trophic level.
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Three types of Pyramids
 Pyramid of numbers: shows the number of
organisms at each trophic level in a given
ecosystem
 Pyramid of biomass: illustrates the total biomass
at each successive trophic level.
 Biomass is a quantitative estimate of the
total mass, or amount, of living material; it
indicates the amount of fixed energy at a
particular time.
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Pyramid of energy: illustrates the energy content,
often expressed as kilocalories per square meter
per year, of the biomass of each trophic level
Ecosystem Productivity
o Gross Primary Productivity (GPP): the total amount of
photosynthetic energy that plants capture and assimilate in a
given period
o Net Primary Productivity (NPP): Productivity after
respiration losses are subtracted. That is, NPP is the amount
of biomass found in excess of that broken down by a plant’s
cellular respiration. NPP represents the rate at which this
organic matter is actually incorporated into plant tissues for
growth.