ENERGY FLOW AND MATTER CYCLES

CHAPTER 3

What do you think of when you hear the word “energy”?

• Some terms we will use are:• Chemical, mechanical, stored, electrical…• Efficiency• Solar, nuclear, wind• Primary, secondary consumers• Energy pyramid• Food webs and chain• Energy cannot be created or destroyed, but

it can change from one form to another.• No energy conversion is 100%. Some

energy is always lost.

3.1 Energy Flow In Nature And Human-built Systems

Where Do Most Organisms Get Their Energy?

The sun!Plants, algae and some kinds of

bacteria capture the sun light and produce sugar, an energy rich food.

This process is called photosynthesis.

6CO2 + 6H20 + → C6H12O6 + 6O2

• Producer (autotroph)- an organism that gets its energy from the sun. Examples are grass, clover, trees

• Consumer (heterotroph)- organisms that eat other organisms. Examples are rabbits, lions and spiders

• Consumers get their energy indirectly from the sun by eating producers or other organisms that eat producers.

Types Of Consumers

• Herbivores- eat only producers such as cows, sheep, deer and grasshoppers

• Carnivores- eat only other consumers such as hawks and lions

• Omnivores- eat both plants and animals such as humans, pigs and bears

• Scavengers – eat remains of dead animals such as vultures and hyenas.

• Decomposers- get their food by breaking down dead organisms such as bacteria and fungi

What is Cellular Respiration?

It is the process of breaking down food to get energy.

C6H12O6+ 6O2 → 6CO2 +6H20 + energy

Is an aerobic process

Energy Transfer

• Each time an organism eats another, a transfer of energy occurs.

• We use food chains, food webs and trophic levels to follow the flow of food energy.

• Trophic= feeding level

Food ChainsA simple representation of how

energy is transferred.

Food WebsIs a more accurate representation

of what is really happening when organisms eat.

Energy Pyramids• Each layer is a trophic (feeding) layer• Producers form the base level• Heterotrophs make up the second level

and carnivores are on the rest of the levels

• As you go up the side of the pyramid, the amount of energy decreases and the number of organisms also decreases.

How Does Energy Loss Affect an Ecosystem?

1. There are fewer organisms at the higher trophic levels.

2. The loss of energy to each trophic level limits the number of levels in an ecosystem.

3. There are usually no more than 4-5 levels because there is not enough energy left to support higher trophic levels.

This is an energy pyramid- Notice there is a 90% loss of energy as you go up the pyramid. Only 10% of energy is

available for the next level.

3.2 Resource Recycling In Nature: The Biogeochemical

CyclesThere are 4 major cycles:• Hydrologic (water)• Mineral/nutrient• Carbon• Nitrogen

The Water Cycle

Mineral/Nutrient Cycle

• Includes all the nutrients needed by organisms.

• Minerals originate in rocks and are released when rocks weather.

• Eventually these minerals end up in the water and soil.

The Carbon Cycle

The Carbon Cycle• A key element in organic molecules. • Plants take in CO2 during photosynthesis

and all organisms release it during respiration (returned to the air).

• Stored as a carbohydrate (C6H12O6)• Returned to air when organisms die and

decompose.• Can be stored for long periods of time in

waters, plants, shells and skeletons of marine organisms (CaCO3)

The Carbon Cycle• Carbon is stored in fossil fuels and

released when they burn.

• Fossil fuels = oil, coal, natural gas, oil shale, tar sands

• CO2 is a greenhouse gas and is believed to contribute to global warming.

• Carbon sinks= ocean and forests

Nitrogen Cycle

Nitrogen CycleOrganisms need nitrogen to make proteins.Nitrogen gas (N2) makes up 78% of the

atmosphere.Plants need nitrogen to grow, but cannot use it

directly from the atmosphere.Nitrogen-fixing bacteria convert the N2 into a

useable form. This is called nitrogen fixation.Some plants have nitrogen-fixing bacteria in

nodules on their roots which house the bacteria- a mutualistic relationship. These plants are legumes such as peas, soy beans and alfalfa.

Other bacteria live in the soil and add the nitrogen to the soil.

Nodules On The Roots Of A Legume

Nitrogen Cycle• How does nitrogen get “fixed”?• Atmospheric nitrogen is converted by

bacteria into ammonia (NH3). Ammonia is then converted into nitrite and then nitrate by nitrifying bacteria. Plants then take in the fixed nitrogen.

• Animals get their needed nitrogen by eating plants.

• Not a lot of nitrogen in the soil, so it is added to the soil as animal manure and fertilizer.

3.3 Matter And Energy3.4 Kinetic And Potential

Energy• Mass, matter and energy• Potential and kinetic energy• Identify the type of energy in each situation.• Burning candle• Kinetic• Tree growing• Kinetic• Gallon of gasoline• Potential• Rock balanced on a cliff• potential

3.5 Closed and Open Systems• All cycling occurs in a system.• A system is a designated area,

space or region under study.• Earth is a closed system as far as

matter goes.• Earth is an open system as far as

energy goes.

Closed and Open Systems• Closed system: nothing enters or leaves.

Everything is used and reused.

• Open system: things both enter and leave.

• Steady state: properties are constant because substances enter and leave at the same rate.

• Using figure 3.15, answer question 1 on page 85.

3.6 Conservation Laws• Law Of Conservation Of Matter – total

mass on earth is constant.

• Law of Conservation of Energy- energy cannot be created or destroyed. It can, however, be transformed from one form to another ( mechanical → heat i.e. rubbing hands together ).

• This law is also known as the First Law Of Thermodynamics.

Why are these laws important in environmental science?

• Think about recycling, mining, garbage, pollution and food chains.

• As a group, discuss the questions on page 86.

3.7 Forms Of Energy

• Mechanical• Heat (thermal)• Radiant (including light)• Electrical• Chemical• Nuclear

Identify The Form Of Energy• Food Cooked In A Microwave • Radiant• Light From A Light Bulb• Electrical• Energy Stored In Bonds• Chemical• Electromagnetic Waves• Radiant

• Moving cars• Mechanical• Burning wood• Chemical, light and heat• Fusion and fission• Nuclear• Photosynthesis• Chemical

3.8 Energy Sources• The Sun– Energy drives the winds,

waves, and climate.– Provides energy for

photosynthesis.– Fuels all life processes!– Only 0.1% of sun’s

radiation reaches Earth, and only 70% of that reaches the atmosphere and surface.

– Solar energy is stored in living plants. These plants can form oil, coal, natural gas, oil shale, tar sands .

More Energy Sources• Tides• Earth’s Heat– Geothermal energy

• Fission Fuels– Energy stored in unstable uranium and thorium

nuclei – Nuclear energy

• Fusion Fuels– Involves combining small nuclei into larger nuclei.

By combining nuclei (deuterium and tritium), energy is released. (the sun)

3.10 The 3 Forms of the Second Law of Thermodynamics

• 1. In any transformation of energy from one form to another, there is always a decrease in the amount of useful energy.

• 2. Heat cannot, by itself, flow from cold to hot. It spontaneously flows from hot to cold.

• http://www.youtube.com/watch?feature=fvwrel&v=C0NBosKaznA&NR=1

• 3. In any closed system, disorder has a natural tendency to increase. (chaos, randomness, entropy)

Special Focus: The Kinetic Theory

Of MatterThe kinetic theory is based on 3 assumptions.

• 1. All matter is made of atoms, molecules or ions.

• 2. Atoms, molecules and ions are in constant motion. The greater the motion of the particles, the warmer the object.

• 3. Moving particles do not lose energy when they collide with each other or with a rigid container.

3.11 Energy and Efficiency

• Efficiency = useful energy or work x 100% energy or work in

OR

• Efficiency = work output x 100%

work input

Determine the efficiency of …• A device in which the energy input is 100 calories and the

output is 30 calories. 30 cal x 100 = 30% 100 cal

• A device in which 10 Btu of energy were produced from an original 250 Btu. (Btu is an energy unit, most often used with heating and air systems)

10 Btu x 100 = 4% 250 Btu

No Efficiency Can Be Greater Than 100%

• You can’t get more work out of any process than what you put in.

• Energy is often lost to friction (heat) so industry tries to reduce friction by using lubricants, making machines smooth….

• Heat engines and lighting are very inefficient.

3.12 System Efficiency

• See figures 3.39 and 3.40• Study figures 3.41 and 3.42• Complete the Questions/Tasks on pages 112

and 113 of your text.

3.13 Net Energy and 3.14 Energy Quality

• Net Energy - Ratio of total energy produced over the lifetime of the system to the total energy, direct and indirect, used to produce that energy.

• Energy Quality – how useful is the energy?High quality energy can be used to move things or

generate electricity. It is organized and concentrated.Ambient temperature heat is low quality. It is heat

at a temperature near that of the surroundings. It cannot be used to produce mechanical or electrical energy.

Developed Countries Are Energy Dependent

• Therefore, energy quality is important.• Most activities result in matter becoming more

disorganized and as energy is transformed, it goes to less useful forms. Our energy supply is continuously losing its ability to move objects and produce electricity.

• What can be done to improve our use of energy?

• http://www.youtube.com/watch?v=HOQSAjc37Y8