Food Web Notes
“The Circle of Life”
“Players”
• Producers
• Primary Consumers
• Secondary Consumers
• Tertiary, & Quaternary Consumers
• Scavengers
• Decomposers
Quaternary
Consumers
Tertiary
Consumers
Primary Consumers
Producers
Scavengers &
Decomposers
Secondary Consumers
Producers
• Plant life fills this role for most webs
– Convert the Sun’s energy into “chemical
energy” (food) through photosynthesis
• Some bacteria also play this role
Consumers
• May occupy different roles within different
food chains
• What they are eating determines their role
Primary Consumers
• Eat Producers
• Most primary consumers only ever appear
as a primary consumer.
• On land these are Herbivores
Secondary Consumers
• Eat Primary Consumers
Tertiary Consumers
• Eat Secondary Consumers
Quaternary Consumers
• Eat Tertiary Consumers
• Top predator
Scavenger
• Eat carrion (dead animals)
Decomposers
• Some insects, bacteria, and fungi
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
Any arrow going away from a
producer points to a possible
Primary Consumer
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
Any arrow going away from a
Primary Consumer points to a
possible Secondary Consumer
killer whale
Notice that some of the
Primary Consumers can also
sometimes be a Secondary
Consumer.
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
Any arrow going away from a
Secondary Consumer points to
a possible Tertiary Consumer
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
Any arrow going away from a
Tertiary Consumer points to a
possible Quaternary Consumer
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
phytoplankton
killer whale
leopard seal
penguin
baleen
whales
herring
zooplankton
Not many food webs will have food
chains that are long enough to need
a 5th or higher consumer.
phytoplankton
Quaternary
Consumers
Tertiary
Consumers
Secondary Consumers
Primary Consumers
Producers
Only 10% of the
mass (or energy)
from any level
can be used to
support the level
above it.
Heat
Energy
Loss
Quaternary
Consumers
Tertiary
Consumers
Decomposers
Secondary Consumers
Solar
Energy
Primary Consumers
Producers
How the 10% rule is used:
Only 10% of the mass or energy available at one level can
be used to support the next level.
If the Producers had 1,000,000 Kcal of energy, how much
could be used by the Primary Consumers?
𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝐸𝑛𝑒𝑟𝑔𝑦 = 0.1 𝑃𝑟𝑜𝑑𝑢𝑐𝑒𝑟 ′ 𝑠 𝐸𝑛𝑒𝑟𝑔𝑦
𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝐸𝑛𝑒𝑟𝑔𝑦 = 0.1 1,000,000 𝐾𝑐𝑎𝑙
𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝐸𝑛𝑒𝑟𝑔𝑦 = 100,000 𝐾𝑐𝑎𝑙
Primary Consumers
Producers
How the 10% rule is used:
Quaternary
Consumers
Tertiary
Consumers
Secondary Consumers
Primary Consumers
Producers
How the 10% rule is used:
Quaternary
Consumers
Tertiary
Consumers
If a Quaternary Consumer had a mass of 200 Kg, what is
the smallest combined mass of Tertiary Consumers that
would be required to support it?
200𝐾𝑔 𝑖𝑠 10% 𝑜𝑓 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑇𝑒𝑟𝑡𝑖𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝑚𝑎𝑠𝑠
200𝐾𝑔 = 0.1 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑇𝑒𝑟𝑡𝑖𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝑚𝑎𝑠𝑠
200 𝐾𝑔
= 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑇𝑒𝑟𝑡𝑖𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝑚𝑎𝑠𝑠
0.1
2,000 𝐾𝑔 = 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑇𝑒𝑟𝑡𝑖𝑎𝑟𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑟 ′ 𝑠 𝑚𝑎𝑠𝑠
How the 10% rule is used:
Quaternary
Consumers
Tertiary
Consumers
Secondary Consumers
Primary Consumers
Producers