Energy Flow through

Ecological Systems

The other balance of life…

Photosynthesis

Again, the equation for photosynthesis is:

6 CO2 + 6H2O + light energy C6H12O6 + 6 O2

This equation leaves out important details:

1. Where does the O2 gas come from?

2. How is light energy converted into chemical bond energy?

PhotosynthesisWhy is it so important to life?

It is estimated that 99% of the energy used by living cells comes from the sun!!!!!

Incorporation of sunlight into chemical bonds occurs through the process of photosynthesis

"Invented" by cyanobacteria about 2 billion years ago

Oxygen is a waste product of photosynthesis

All oxygen in atmosphere is believed to originate from photosynthesis

Photosynthesis

Also…...

Photosynthesis begins the carbon cycle by fixing CO2 (carbon dioxide in the atmosphere)

The oxygen released as a by-product has a major impact on the biosphere. Today's atmosphere would not have 21% oxygen if not for photosynthesis.

Energy Flow Charts

Your plot receives 10,000 kcal/m2/day of energy

Tell us where it all goes!!!

On butcher paper create an Energy Flow Diagram from a simple imaginary food chain, which demonstrates how this energy enters and exits your plot.

What scientific laws apply to energy?

First and Second Laws of thermodynamics

First law: energy is neither created or destroyed!!! General accounting…

Second law: every step of energy transformation and flow through a system = gradual loss of the ability to do work.

What happens to all of that energy anyway?

Equator most light--- poles about ½ the amount

1/3 reflects off clouds, snow fields bounces back to space

1/3 warms sea/land

1/4 absorbed in evaporation drives water cycle

1% - 2% of light striking a forest is used by all other living beings.

Equivalent only 1/5 of the gasoline you put in your car gets you to your destination…..bummer hey….

Trophic Levels

Effects of Lindeman’s Efficiency

(10% Rule)

Top predators are sensitive to changes in the energy flow of an ecosystem

Cannot have more than 4 or 5 levels on a trophic pyramid. Why?

The amount of energy and space needed to feed animals on a higher trophic level would be larger than the amount of energy expended to forage for it

Effects of Lindeman’s

Efficiency (10 % Rule)

Omnivores (i.e., bears, humans, raccoons, opossums, coyotes, etc.) can switch trophic levels depending on the food sources that are available

Eating at lower trophic levels can support more members of a population in an ecosystem/environment

Humans and Energy Flow

Humans are omnivores

Humans use approximately 40% of the net

primary production on land

Net primary production: the amount of available

energy that is produced in photosynthesis (after

plants use what they need for survival)

Energy Flow and Eating

Habits Meat eating (higher on the trophic pyramid) uses

more energy than eating veggies

90% of the grain that we grow is used to feed livestock

100 kg of grain can feed:

10 kg of cow and 1 kg of steak eating people

10 kg of grain eating people (10x more)

A simple food web……….

Implications

We observe this dynamic balance of energy flow at all levels of scale from the ecological system to the individual organism.

Also, this is the algebra with which we can understand the consequences of our actions.