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Ecology
Food Chains and Food Webs
Standards:
• BI 6.a-Students know biodiversity is the sum
total of different kinds of organisms and is
affected by alterations of habitats.
• BI 6.e-Students know a vital part of an
ecosystem is the stability of its producers and
decomposers.
• BI.6.f-Students know at each link in a food web
some energy is stored in newly made structures
but much energy is dissipated into the
environment as heat. The dissipation may be
represented in an energy pyramid.
Objectives:
SWBAT:
• Explain the role of biodiversity in
maintaining the balance of an ecosystem.
• Demonstrate how energy is transferred
and lost in an ecosystem.
• Explain the various roles of organisms in
maintaining the stability of an ecosystem.
• Understand the interaction between living
and nonliving factors in an ecosystem.
Review-Key Concepts So Far
• Every ecosystem includes both living (biotic) and
nonliving (abiotic) factors.
• Life in an ecosystem requires a source of
energy.
• The biodiversity of an ecosystem maintains the
stability of an ecosystem, and altering habitats
decreases this biodiversity.
What are food chains?
• Key Concept: Food chains and food webs
model the flow of energy in an ecosystem.
• Food chains-A sequence that links species
by their feeding relationships.
• Follows the connections between one
producer and a single chain of consumers.
What are food chains?
• Owl
• Mouse
• Grasshopper
• Grass
What are the different types of
consumers?
• Herbivores-eat only plants (grasshopper)
• Omnivores-eat both plants and animals
(kangaroo mouse)
• Carnivores-eat only other animals (owl)
What are the different types of
consumers?
• Detritivores-organisms that eat only dead
or decaying organic matter (detritus).
(Millipedes)
• Decomposers-Detritivores that break down
organic matter into simpler compounds.
They return vital nutrients back to the
ecosystem. (Fungi)
What are the different types of
consumers?
• Herbivores
• Omnivores
• Carnivores
• Detritivores
• Decomposers
What are trophic levels?
• Trophic levels-are the levels of nourishment in a
food chain.
• Energy flows up the food chain from the lowest
trophic level to the highest.
• Producer-Herbivore-Carnivore
• Primary consumer, Secondary Consumer,
Tertiary Consumer
What are food webs?
• Food web-is a model that shows the
complex network of feeding relationships
and the flow of energy within an
ecosystem.
• At each link some energy is stored by an
organism and some is lost.
• The stability of an ecosystem depends on
the producers.
What are food webs?
What happens to the energy in a
food web?
• Energy pyramid-A diagram that compares
energy used by producers, primary consumers,
other trophic levels.(kilocalories)
• Shows how energy is distributed among trophic
levels
• Start with large base (producers) and each level
gets smaller because energy is lost (10%) as
heat
Energy Pyramid
Energy Pyramid
What happens to the energy in the
pyramid?
• SunlightProducersHerbivores
Carnivores
• Producers-use energy to make food
• Herbivores-use energy to grow and for cellular
respiration. Most of the energy is lost as heat.
• Carnivores-Most of the energy is lost as heat
• Each level in food chain contains less energy
Summary Questions:
• What is the difference between food webs
and food chains?
• Why does the stability of ecosystems
depend on producers?
• What is the role of decomposers in
ecosystems?
• What are trophic levels?
• What happens to energy at each trophic
level?