Biodiversity and Ecosystem Stability  Objectives:  Explain why biodiversity is essential to the survival of organisms using food web models  Catalyst:  What is a trophic level?  What percentage of the Sun’s energy do producers receive? Primary consumers? Secondary consumers?

Agenda  Homework Review  Catalyst Review  Biodiversity  Benefits  Ecosystem Stability  Stations  Closing  Exit Question

Homework Review

Catalyst Review  What is a trophic level?  Step in a food chain  What percentage of the Sun’s energy is received by…  Producers?  Primary consumers?  Secondary consumers?  100%  10%  1%

Biodiversity is…  Biodiversity is a measure of how many different species live in an ecosystem.

Low Biodiversity

High Biodiversity

Low or High Biodiversity?

Benefits of Biodiversity  Key Point #1: There are three primary benefits to biodiversity  Beautiful for people to enjoy  Provides medicines—many plants contain treatments/cures for illnesses  Preserves ecosystem stability If biodiversity provides us with so many services, don’t we owe it to the environment to preserve biodiversity?

Ecosystem stability… What that is!?  Stable = things stay the same  Key Point #2: An ecosystem is stable if it does not change easily when disturbed  When an ecosystem is resistant to change, it is stable  When an ecosystem can be easily changed, it is unstable  In this class, we will measure “change” by the number of species that live somewhere

This food web has low biodiversity Rabbits eat grass. Foxes eat rabbits Grass Rabbit Foxes

This food web has low biodiversity  A disturbance hits… A drought happens and kills all the grass. Grass Rabbit Foxes

This food web has low biodiversity  What happens to the foxes? Grass Rabbit Foxes How many species do we have left? 0! BIG change?

After the disturbance  The food web started with low biodiversity  Low biodiversity = unstable ecosystem  One change wiped out all the species!

This food web has high biodiversity Let ’ s add a few more species to our original ecosystem Grass Rabbit Foxes Chickens Lettuce

This food web has high biodiversity  A disturbance hits… A drought happens and kills all the grass. Grass Rabbit Foxes Chickens Lettuce

This food web has high biodiversity  What happens to the foxes? Population size decreases… a little BIG change? Grass Rabbit Foxes Chickens Lettuce  The food web started with high biodiversity  High biodiversity = stable ecosystem  One change… didn’t really do anything!

Comparing Multiple Ecosystems  Key Point #3: We can figure out which of two ecosystems has higher biodiversity based on how stable each one is  Ecosystems with high biodiversity change less than ecosystems with low biodiversity.  If ecosystem “A” changes less than ecosystem “B” in response to the same disturbance, “A” must have higher biodiversity than “B.”

Stations (GP)  Designed to get you moving, and practice understanding some of what we’ve been talking about  6 stations  Each asks you to complete something  THINK. About what you’re reading and what you’re drawing. Really. Think.  Work hard. Talk when you’re finished, not before.

Stations Review (GP)  Any questions?

Closing  There are three primary benefits to biodiversity  Beautiful, medicines, ecosystem stability  An ecosystem is stable if it does not change easily when disturbed  “Change” = number of species that live there  We can figure out which of two ecosystems has higher biodiversity based on how stable each one is  More stable = higher biodiversity  Less stable = lower biodiversity

Exit Questions Read the passage at right to answer the questions below:  How does trawling affect coral reef biodiversity?  Would the coral reef be more or less stable after trawling? Explain why, and be SPECIFIC.  (Hint: describe what happens to all the organisms in the coral reef ecosystem, and use the word “biodiversity.”) Read the passage at right to answer the questions below:  How does trawling affect coral reef biodiversity?  Would the coral reef be more or less stable after trawling? Explain why, and be SPECIFIC.  (Hint: describe what happens to all the organisms in the coral reef ecosystem, and use the word “biodiversity.”) Many organisms live in coral reefs, such as plankton and algae, hundreds of species of fish, sea urchins, and eels. All of these organisms depend on the coral to survive: they live inside of it, use it for shelter, eat it, etc. Trawling is the process of dragging a gigantic rake across the bottom of the ocean floor to scoop up organisms. This is a very good way to catch fish, but has the unfortunate side effect of destroying nearly all the coral in the trawler’s path. Many organisms live in coral reefs, such as plankton and algae, hundreds of species of fish, sea urchins, and eels. All of these organisms depend on the coral to survive: they live inside of it, use it for shelter, eat it, etc. Trawling is the process of dragging a gigantic rake across the bottom of the ocean floor to scoop up organisms. This is a very good way to catch fish, but has the unfortunate side effect of destroying nearly all the coral in the trawler’s path.