Trophic levels Flashcards
What is a top-down model of trophic levels?
a community energy flow model that suggests the structure of lower trophic levels depends on effects of consumers at high trophic levels – consumers affect primary producers, primary producers affect secondary etc…
It places more importance on predation
What is a bottom-up model of trophic levels
a community energy flow model that suggests the structure of higher trophic levels depends on factors that influence it from below (such as nutrient concentration, prey availability) – primary producers affect consumers etc…
Places importance on resources
Which trophic model focuses on predator-prey interaction?
Top-down
Which trophic model focuses on energy/ nutrient transfer?
Bottom-up
Which direction does energy flow in a bottom-up model?
Nutrients -> Vegetation -> Herbivores -> Predators
What is a top-down model also known as?
A trophic cascade
Which direction are organisms limited by in a top-down model?
Nutrients
Give a case study example of biomanipulation
Lake Vesijarvi in Finland
How was biomanipulation used in Lake Vesijarvi in Finland?
Scientists removed 80% of the 3rd trophic level (roaches) and introduced pike as a 4th trophic level. This increased the number of zooplankton which used up the phytoplankton, reducing algal blooms due to trophic cascades.
Define keystone species
a plant or animals that plays a unique and crucial role in the way an ecosystem functions
Name a case study of a keystone species
The pisaster starfish - Paine 1966
What did Paine (1966) do with the Pisaster starfish?
He deliberately removed it from an intertidal zone.
Found that species richness declined due to mussels monopolising the rocks (eliminating most other invertebrates). Found that the Pisaster was a keystone species for this ecosystem as it preys on mussels
Which trophic level are key stone predators found at?
Any
