Science Man and His Environment/Energy Flow in Ecosystems

Energy Flow
All of nature is driven by energy. How this energy flows through the environment is important.

It is governed by three laws:
 * Conservation of Mass
 * First Law of Thermodynamics (conservation of energy)
 * Second Law of Thermodynamics

Conservation of Mass
Conservation of Mass

 All mass is conserved - it is neither created nor destroyed. It may however, change forms

Definitions

 * Work : force acting through a distance
 * Energy : the capacity to do work
 * Heat : energy transferred due to a temperature difference

Energy can only be transferred two ways: work and heat

First Law
First law of thermodynamics

 Energy is never destroyed or created or There is no free lunch

Examples:
 * you need fuel to keep your car running
 * you need food to keep yourself running

Second Law
Questions:
 * How do we uncook rice?
 * How do we unpeel an orange?
 * A book easily falls to the floor, but takes much effort to get back up. Why?

First law says cooking and uncooking are exactly the same.

These questions lead to the second law of thermodynamics.

Second law of thermodynamics

 No system can completely convert heat to work or All systems tend toward disorder

The measure of disorder is called the Entropy

The second law therefore says that the total entropy will always increase.

Note we can convert work entirely into heat. Since heat cannot be entirely converted to work, we say heat is lower quality than work. Whenever energy is converted from one form to another, some is lost as heat.

Life
The ultimate source of energy for life processes is the SUN.

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Plants convert the sun's energy (light) into food (energy reserve) by photosynthesis

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Plants and animals then use respiration and other processes to breakdown the food releasing energy

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This energy is then used to move, think, and other actions.

Due to the second law, each step losses waste heat and the resulting energy is of lower quality



Efficiency
The percentage of energy transferred as useful work is called the efficiency.

Examples
 * Electrical Power Plant 30%
 * Fuel Cell             60%
 * Human Body            25%
 * Fluorescent Light     15%
 * Car Engine            10%
 * Incandescent Light     5%