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RATIONALES
What is a tropic cascade?
✓ A Trophic Cascade is when the impact of a predator on its prey's ecology trickles
down one more feeding level to affect the density and/or behavior of the prey's prey
What is the minimal number of trophic levels that must be involved in a trophic
cascade? Use scientific names to describe each tropic level (e.g., tertiary consumer).
✓ The minimum of trophic levels that must be involved in a Trophic Cascade is 3. It
involves the Primary Producer, Primary Consumer, and Secondary Consumer.
What is the difference between the bottom-up and top-down paradigms for regulating
the primary productivity of ecosystems?
✓ A top-down cascade is a trophic cascade where the food chain or food web is
disrupted by the removal of a top predator, or a third or fourth level consumer. On
the other hand, a bottom-up cascade occurs when a primary producer, or primary
consumer is removed, and there is a reduction of population size through the
community.
What arguments did Hairston and colleagues put forth in 1960 that challenged the
bottom-up paradigm and supported the top-down paradigm?
✓ Hairston and Colleagues came up with the view that consumers play an important
role in structuring plant-dominated ecosystems. They argued that the world is/was
green because higher Trophic Levels control herbivore abundance. This challenged
the bottom up paradigm and supported the top-down paradigm because the top
down cascade paradigm states that the food web is distributed by the removal of a
top predator, hence exemplifying how crucial predators are to the ecosystem. This
theory challenged the bottom up paradigm because this paradigm states that the
removal of consumers will negatively affect an ecosystem where as Hairston and
,Page2
,Page3
, Page4
RATIONALES
What is a tropic cascade?
✓ A Trophic Cascade is when the impact of a predator on its prey's ecology trickles
down one more feeding level to affect the density and/or behavior of the prey's prey
What is the minimal number of trophic levels that must be involved in a trophic
cascade? Use scientific names to describe each tropic level (e.g., tertiary consumer).
✓ The minimum of trophic levels that must be involved in a Trophic Cascade is 3. It
involves the Primary Producer, Primary Consumer, and Secondary Consumer.
What is the difference between the bottom-up and top-down paradigms for regulating
the primary productivity of ecosystems?
✓ A top-down cascade is a trophic cascade where the food chain or food web is
disrupted by the removal of a top predator, or a third or fourth level consumer. On
the other hand, a bottom-up cascade occurs when a primary producer, or primary
consumer is removed, and there is a reduction of population size through the
community.
What arguments did Hairston and colleagues put forth in 1960 that challenged the
bottom-up paradigm and supported the top-down paradigm?
✓ Hairston and Colleagues came up with the view that consumers play an important
role in structuring plant-dominated ecosystems. They argued that the world is/was
green because higher Trophic Levels control herbivore abundance. This challenged
the bottom up paradigm and supported the top-down paradigm because the top
down cascade paradigm states that the food web is distributed by the removal of a
top predator, hence exemplifying how crucial predators are to the ecosystem. This
theory challenged the bottom up paradigm because this paradigm states that the
removal of consumers will negatively affect an ecosystem where as Hairston and
