Ecology 3 Notes

Let’s clarify the “hierarchy of organization” 1.Species 2.Population 3.Community 4.Ecosystem 5.Biosphere

Within an ecosystem… We discussed ecological pyramids…and how energy flows up the pyramid (and gets “lost” as heat along the way…)

Pyramids…a strange yet deadly phenomenon… BIOACCUMULATION or BIOMAGNIFICATION Substances that cannot be metabolized by organisms (biodegraded) are passed up the food chain. Example: DDT dichloro-diphenyl-trichloroethane

Why does it accumulate in the higher trophic levels? It has to do with the fact that certain chemicals are non- soluble in water (meaning lower trophic levels see less of an effect), but they ARE soluble in FAT (which gets passed up the food chain…)

Something else to expand upon GPP vs. NPP Or GP vs. NP

GP vs. NP Gross Productivity vs. Net Productivity Can be measured as energy OR biomass gained per unit of time. You can look at it at the primary level (producer) or at the secondary, tertiary, etc levels (consumers). OR you can look at the entire ecosystem

GP and NP Remember the general formula… NP = GP – R (respiratory losses) And for consumers, GP (gross productivity) is the food eaten – fecal losses.

NPP Often we will talk about Net PRIMARY Productivity, meaning how much energy is left in the plant tissues after losses due to cell respiration (including the heat that is “lost” with that) Radiant energy from the sun Respiration and heat NPP

The NPP is what can be consumed by the heterotrophs… AND, consumers pass on even LESS because they lose energy not only through respiration (which they do a LOT of), but through fecal losses too.

NPP Example: The producers begin with an initial GPP of 20,000 kcal m-2 yr-1 (kilocalories per meter squared per year) They lose 86% of that to respiration. How much is available to the primary consumers? (this is the NPP) 2800 kcal m-2 yr-1

With this amount of NPP, only 10% actually gets consumed by the primary consumers (due to decomposers and other losses). How much is that? 280 kcal m-2 yr-1

The primary consumers lose 95% of THAT through their massive amounts of respiration and other losses. What is net secondary productivity then? 14 kcal m-2 yr-1

PAUSE to draw a complete flow diagram of energy moving through an ecosystem on your own paper.

We have covered the cycle of energy through ecosystems…we will get back to the cycle of nutrients when we get to Chapter 6…