Ecosystem

All biotic + abiotic features of an area.

Biotic: living organisms

Abiotic: non-living features

Through ecosystems, we study energy flow and nutrient/chemical cycling.

Ecosystem Production

• Primary production: amount of light energy converted to chemical energy.

• Trophic efficiency: amount of production transferred from one level to the next.

Energy is lost through respiration and waste

Food Webs are short

• Constrained by inefficient transfer of energy between trophic levels (~10%/level).

Predict: Areas with greater productivity should have…

• Shorter webs are more stable.

Predict: More variable environments should have…

How are trophic levels regulated?(meaning, why isn’t the whole earth covered in rabbits?)

Top-down regulation?

Bottom-up regulation?

(Can you describe how each of these might work?)

Community

Group of actually or potentially interacting species living in the same place.

How do communities form?

• Assemblage of species based on similar abiotic needs?

Prediction:

• Interdependent species clustering together?

Prediction(s):

Measuring Biodiversity

Species diversity measures the number of species (richness) and number of individuals/species (abundance) in a community.

Hot topic:

What’s the link between biodiversity, productivity, and stability?• invasion• disease

Detritus: non-living organic material (e.g. dead organisms, feces, molts, etc)

Detritivores: • linked to all levels of trophic structure• good measure of ecosystem activity (e.g.

energy flow, chemical recycling)

Difference between Detritivores and Decomposers?

Carbon, Phosphorus, Nitrogen and energy are all cycled through ecosystems

in similar pathways.