What Limits the Size of a Food
Chain?
By Jason and Joel
3 major limitations on a Food
Chain
• Energetic Hypothesis
• Dynamic Stability Hypothesis
• Loss of Keystone Organisms
Energetic Hypothesis
• The length of a food chain is limited by the
inefficiency of energy transfer along the chain.
Energetic Hypothesis
• About 10% energy stored in organic matter of
each trophic level is converted to organic
matter in the next trophic level.
Dynamic Stability Hypothesis
• Long food chains are less stable than short
food chains.
• Population fluctuations in lower trophic levels
are magnified at higher levels, potentially
causing local extinctions.
Dynamic Stability Hypothesis
• Top predators must be able to recover from
environmental shocks that can reduce food
supply all the way up the chain.
• If they chain is long it takes longer for the top
predators to have shock be suppressed.
Effects of Keystone Species
• Keystone species- a species that is not
necessarily abundant in a community yet
exerts strong control on community structure
by the nature of its ecological role or niche.
• If a keystone species is not present, the chain
collapses
• Example of a keystone species: sea otter
Keystone Species cont.
• Sea otters are important to the offshore kelp
forest ecosystem.
• Kelp are fast-growing seaweeds that live in
submerged forests near the ocean shore.
• Otters feed and play in the kelp forests, where
they dine on sea urchins
Keystone species cont.
• When sea otters are hunted for their fur, it
caused their population to decline
precipitously
• As a result, sea urchins destroyed kelp forests
by eating the holdfasts that attach the
seaweeds to the ground, destroying the kelp
forest leaving fish and shellfish homeless.
Other Keystone Species
• Other keystone species
include the gray wolf,
sea stars, prairie dogs,
and northern spotted
owls.