1. What Limits the Size of a Food Chain? By Jason and Joel

2. 3 major limitations on a Food Chain Energetic Hypothesis Dynamic Stability Hypothesis Loss of Keystone Organisms

3. Energetic Hypothesis The length of a food chain is limited by the inefficiency of energy transfer along the chain.

4. Energetic Hypothesis About 10% energy stored in organic matter of each trophic level is converted to organic matter in the next trophic level.

5. 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.

7. 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.

8. 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

9. 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

10. 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.

11. Other Keystone Species Other keystone species include the gray wolf, sea stars, prairie dogs, and northern spotted owls.