13.4 Food Chains And Food Webs
Bell Ringer
• Look at figure 13.9 on page 408.
• 1-What is the original source of energy?
• 2-How do the cottontail and hawk differ as
consumers?
• 3-Think about your typical meal. What do
you get from these foods? How does
energy and matter come to be in these
foods?
• 4-What other way could you obtain energy
for your body?
13.4 Food Chains And Food Webs
Thinking back to chapter 12…………..
• How might chemosynthetic organisms help
scientist to understand how life developed
on Earth????
13.4 Food Chains And Food Webs
• -Lived in environments similar to those that
existed on earth BYA when life was beginning to
develop.
• -Studying these organisms enables scientist to
infer how different life forms may have evolved
as Earth changed.
13.4 Food Chains And Food Webs
KEY CONCEPT
Food chains and food webs model the flow of energy
in an ecosystem.
13.4 Food Chains And Food Webs
A food chain is a model that shows a sequence of feeding
relationships.
• A food chain links species by their feeding relationships.
• A food chain follows the connection between one producer
and a single chain of consumers within an ecosystem.
Ex. In a desert ecosystem…
GRAMA GRASS
DESERT COTTONTAIL
HARRIS’S HAWK
13.4 Food Chains And Food Webs
• Consumers are not all alike.
13.4 Food Chains And Food Webs
– Herbivores eat only plants.
Ex. cottontail
– Carnivores eat only animals.
Ex. hawk
– Omnivores eat both plants and
animals.
Ex. rodent
carnivore
13.4 Food Chains And Food Webs
– Detritivores eat dead organic matter.
Ex. millipede
– Decomposers are detritivores that break down organic
matter into simpler compounds.
Ex. Fungus & bacteria
decomposer
13.4 Food Chains And Food Webs
• Specialists are consumers that primarily eat one specific
organism or a very small number of organisms.
– Are very sensitive to changes in food availability.
Ex. Florida snail kite eats apple snails
• Generalists are consumers that have a varying diet.
Ex. Gray wolf eats moose, elk, deer, beavers, mice, etc
13.4 Food Chains And Food Webs
• Trophic levels are the nourishment levels in a food chain.
– Primary consumers are herbivores that eat producers.
– Secondary consumers are carnivores that eat
herbivores.
– Tertiary consumers are carnivores that eat secondary
consumers.
– Omnivores, such as humans that eat both plants and
animals, may be listed at different trophic levels in
different food chains.
13.4 Food Chains And Food Webs
Bell Ringer
• On page 411 answer questions #1 and
#3
13.4 Food Chains And Food Webs
• Carnivores are at the highest trophic level.
• Energy flows up the food chain.
– Lowest to highest.
13.4 Food Chains And Food Webs
“What is the connection between food chains & trophic
levels?”
13.4 Food Chains And Food Webs
A food web shows a complex network of feeding
relationships.
• An organism may have multiple feeding relationships in an
ecosystem.
• The food web is a model that shows complex networks of
feeding relationships.
• A food web emphasizes complicated feeding relationships
and energy flow in an ecosystem.
13.4 Food Chains And Food Webs
• At each link energy is stored within an organism while
some energy is lost to the environment.
Identify the different trophic levels
13.4 Food Chains And Food Webs
“How might the introduction of a new predator affect the
flow of Energy through the food web?”