Trophic Cascades
Abundance and productivity of populations are influenced by what?
Top-down and bottom-Up
Both Top-down and Bottom-Up controls influence what?
abundance and productivity of populations
What are nutrients?
anything that a plant or animal needs to live and grow
An odd number of trophic links results in:
control of primary producers by grazing (topdown)
What was the previous belief on eutrophication in marshes?
marshes are very big and have a lot of plants and animals that use nutrients; for a long time people thought that a little excess nutrients would not hurt as long as the water did not go anoxic
What are the nutrients plants need?
nitrogen and phosphorous (like in amino acids)
Describe excess nutrients:
not all of the nutrients humans add to the soil are used by the plants and these "excess" nutrients can wash into the water where they are used by algae (this can make dead zones)
Describe nutrients and their effect on plants:
nutrients limit how well plants can grow
What can still increase producer biomass and have effects that propagate up the food web?
nutrients or other factors limiting producers
Which nutrients affect which areas?
on land and freshwater ecosystems, the limiting nutrient is phosphorous; in saltwater and marsh ecosystems, the limiting nutrient is nitrogen
An even number of trophic links results in control of:
primary producers by resources (bottom-up)
What are the things plants need to live, in order from bigger to lower amounts?
sunlight, water, and nutrients (nitrogen and phosphorous)
Which process is infinitely important to producing nitrogen fertilizer, and allows there to be as many people on the planet as there are today?
the Haber Bosch process
What is the main thing used to show the nutrients humans need?
the food pyramid
Where do most nutrients come from?
the soil
Describe humans and nutrients:
usually plants get plenty of sunlight and water, but the nutrients run low and plants stop growing; humans help the plants by adding these nutrients back to the soil
What are Bottom-down effects?
we add something to the bottom of the food web, and those effects go all the way to the top; production increases, and thus organism groups that consume the first group will grow
What are Top-down effects?
we add something to the top of the food web, and those effects cascade all the way to the bottom
What is the effect excess nutrients have on the water?
when algae receive excess nutrients the algae can "bloom"; these blooms can be harmful to animals that live in water by using up all the oxygen in the water (this can make dead zones)
Define trophic cascades:
when predators in a food web suppress the abundance or alter the behavior of their prey, thereby releasing the next lower trophic level from predation
