Energy Flow in Ecosystems
Environmental Science | |
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Topics | What is the Environment | Population | Ecological Footprint, Food, and Urbanization | Ecology - Definitions and Outline | Energy Flow in Ecosystems | Population and Community Ecology | Biogeochemical Cycles | Biodiversity | Energy | Atmosphere and Climate | Global Warming | Air Quality | Water Quantity | Water Quality | Solid Waste |
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Contents
Energy Flow
All of nature is driven by energy. How this energy flows through the environment is important for understanding ecolgy.
It is governed by three laws:
- Conservation of Mass
- Conservation of Energy (First Law of Thermodynamics)
- Second Law of Thermodynamics
Conservation of Mass
Conservation of Mass
All mass is conserved - it is neither created nor destroyed.
Definitions
- Work
- force acting through a distance
- Energy
- the capacity (ability) 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.
Important notes about the Second Law:
- 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.
- Each step above involves changing the form of energy. Therefore, by the second law of thermodynamics each step losses waste heat and the resulting energy is of lower quality.
Thermodynamics - A wikieducator project on this topic |