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Chapter 16
Ecosystems
Section 1- What is an Ecosystem?
• Ecology – study of interactions of living
organisms with one another and with their
physical environment.
– Soil
– Water
– Climate
– Etc.
• Habitat – place where a particular
population of a species lives.
• Community – the
many different
species that live
together in a
habitat.
• Ecosystem – consists of a community and
all the physical aspects of its habitat.
– Soil
– Water
– Weather
• Abiotic Factors – non-living parts of an
ecosystem.
• Biotic Factors – living parts of an
ecosystem
Diverse Communities in Ecosystems
• Biodiversity – variety of organisms, their
genetic differences, and the communities
and ecosystems in which they occur.
Change in Ecosystems Over Time
• Pioneer Species – first organisms to live in
a new habitat where soil is present tend to
be small, fast-growing plants.
• Succession – somewhat regular
progression of species replacement
• Primary Succession – succession where
life has never existed before
• Secondary Succession – succession that
occurs in areas where there has been
previous growth, such as abandoned fields
or forest clearings
*No 2 successions are the same
Section 16.2
Energy Flow in Ecosystems
Movement of Energy Through Ecosystems
• All activities that organisms perform in
ecosystems require energy
• The flow of energy in an ecosystem
determines what kind and how many
organisms an ecosystem can support.
Primary Energy Source
• Most life on earth depends on photosynthetic
organisms
• Primary Productivity
– Rate at which organic material is produced by
photosynthetic organisms in an ecosystem
• Producers
– Organisms that first capture
energy
• Plants, bacteria, and algae
• Consumers
– Organisms that consume plants
or other organisms to obtain energy
Trophic Levels
• Used to study how energy moves through
an ecosystem.
• Trophic Level
– Graphic organizer based on the organisms
source of energy
– p. 345 – fig. 6
Trophic Levels
• First Level
– This level is occupied by producers
– Get their energy from the sun
• Food Chain
– The path of energy through the trophic levels
of an ecosystem
• p. 346 – fig. 7
Trophic Levels
• Second Level
– Primary consumers
– Organisms that are able to digest cellulose
• Herbivores
– Animals that eat plants or other primary
producers
Trophic Levels
• Third Level
– Secondary consumers
• Carnivores
– Animals that eat other animals
• Omnivores
– Eat plants and animals
• Detritivores
– Obtain energy from organic wastes and dead
organisms
– Decomposers
Trophic Level
• Food Web
– Develops from organisms feeding at several
different trophic levels
Loss of Energy in a Food Chain
• When organisms obtain energy they are
never able to obtain 100% of the
resource’s supply.
Energy Transfer
• Large amount of energy lost as heat as various
organisms capture/obtain energy.
• Plants capture about 1% of the sun’s energy.
• Herbivores obtain about 10% of plant’s energy.
• Carnivores obtain about 10% of herbivores
energy.
The Pyramid of Energy
• Used to illustrate the flow of energy in an
ecosystem
• Energy Pyramid
– Diagram in which each
trophic level is
represented by a block
with the lowest trophic
level on the bottom.
Limitations of Trophic Levels
• Not much available energy as levels increase
– Usually only 3 trophic levels
• Limited by the amount of available resources
• Ability of digestive system
• Size of organism
• Biomass
– Dry weight of tissue and other organic matter found
in an ecosystem
– Decreases with each trophic level
• Think of the animals and other organisms
in our area.
• Construct a food chain of at least 10
animals and plants that you can find in our
area.
Food Web
• Use the same organisms you chose for
your food chain to create a food web.
Section 3
Cycling of Materials in
Ecosystems
Biogeochemical Cycles
• Materials are constantly cycling through our
ecosystems
– Energy
– Water
– Carbon
– Phosphorus
– Nitrogen
• Biogeochemical Cycle
– Pathway of substances that enter living
organisms, stay for a period of time within the
organism, then return to the nonliving
environment and starts over.
The Water Cycle
• Has the largest impact on the organisms of an
ecosystem.
• Ground Water
– Water that is retained beneath the surface of the earth
– Nonliving part of environment
• Transpiration
– Water that evaporates from the leaves of plants
– Living part of the environment
The Water Cycle
• Condensation
• Precipitation
• Evaporation/Transpiration