E n v i r o n m e n t a n d E n e r g y

Environment and Energy

Vocabulary• Biotic• Abiotic• Ecosystem• Consumer• Producer• Decomposer• Autotrophs• Heterotrophs• Biomagnification

• Bioaccumulation• Biomass• Photosynthesis• Non-Renewable• Renewable• Fossil Fuels• Geothermal• Hydroelectricity

• 5.10a) distinguish between biotic and abiotic features of the local environment

• 5.10b) describe the importance of cycles of materials in ecosystems

• 5.10c) describe some impacts of human activities on ecosystems

• 5.11.1a) discuss the importance of energy as a resource • 5.11.1b) identify properties that make some natural resources

economically important and describe their uses• 5.11.2a) relate pollution to contamination by unwanted

substances• 5.11.2c) discuss strategies used to balance human activities

and needs in ecosystems with conserving, protecting and maintaining the quality and sustainability of the environment

• 5.12b) discuss the benefits and problems associated with medical and industrial uses of nuclear energy

What is energy?

• Energy is the ability to do work and is measured in joules (J). Organisms require energy for the ‘work’ of living.

• This work includes growth, reproduction, respiration, repair of body tissues and digestion.

• Consider this simple food chain

green plant →insect→frog→snake→kookaburra

Recall

• Here, we can see that the energy from the green plant (a producer) goes into the insect (a primary or 1st consumer), which then provides energy for the frog (a secondary or 2nd order consumer).

•The frog is a source of energy for the snake (tertiary or 3rd order consumer), which in turn provides energy for the kookaburra (4th order consumer).

• In this food chain, the kookaburra is the highest order consumer, as it is unlikely that anything else will be able to catch and eat it.

•If by chance a dingo or some other animal caught it, that animal would be considered a fifth order consumer.

Plants• Convert light energy into chemical energy

(Photosynthesis). Organisms that produce food in this way are referred to as producers or autotrophs. All other organisms rely on the energy stored by plants to meet their energy needs.

• Organisms that eat plants are referred to as consumers or heterotrophs. In the food chain, energy is not the only thing being transferred from one organism to the next—matter is also being transferred.

•Most of this material is used directly by the next organism for its growth and survival, some is lost to the environment as waste products or heat.

Food pyramids• Consider this summarised food chain;

producers (plants) →herbivores →carnivores

• There are vast numbers of plants. We would expect to find a smaller number of herbivores eating those plants and an even smaller number of carnivores eating the herbivores.

• In any ecosystem the number of individuals at each level decreases as we move from the producers up to the higher orders of consumers. A food pyramid shows the mass of organisms change and that the total amount of energy at each level decreases.

we would expect a pyramid-shaped diagram.

•If we were to gather all the producers, herbivores and consumers in a food chain, and represent either their numbers or their dry weight diagrammatically,

Pesticides and herbicides• Crops have been a readily available source of food for

many insects and pests. The use of fertilisers and ploughing of the land has also encouraged weeds to grow among the crops. Both weeds and animal pests are known as competitors.

• Humans have developed chemicals to control these pests, called herbicides and pesticides.

• Herbicides kill pest plants or weeds, while pesticides kill animal and insect pests.

Biomagnification.• With use, these chemicals have

become part of the natural food chains. The chemicals are absorbed by plants and small animals.

• When these plants and animals are consumed by other animals, the chemicals are also consumed and passed up the food chain.

• Chemicals also wash into rivers, lakes and the ocean, where they are absorbed by algae. The algae are consumed by aquatic animals and again the chemicals are passed up the food chain.

• This is called Biomagnification.

Bioaccumulation• Is the process of organisms

accumulating (building up) higher and higher levels of these chemicals in their bodies.

• These chemicals become more concentrated in organisms as we move up a food chain. Animals at the top of the food chain must consume very large amounts of other organisms, and so more and more chemicals become concentrated in their tissues.

Problems include:• the deaths of many large

sea mammals such as dolphins and whales, which is thought to be related to bioaccumulation

• the thinning of egg shells of birds such as the American eagle, leading to this animal becoming endangered

• increased rates of cancer, disease and deformities in humans

The concentration of chemicals in a foodchain is shown by this energy pyramid.

Recycling in Nature

• Dead organisms are returned to the ecosystem by the action of decomposers

• Decomposition involves the breakdown of organic materials, releasing the requirednutrients to the air, water and soil. Two important elements that are recycled are carbon and nitrogen.

• Organic matter basically means containing Carbon, and is found in all living things.

• Inorganic matter does not contain carbon and includes simple substances such as water, minerals and glass.

• All cycles rely on the flow of atoms between the biotic (living) and the abiotic (non-living) environment. In healthy ecosystems, this flow remains balanced.

Natural Cycles

• An Abiotic environment for a fish would include coastal currents, tides, temperature, water salinity, and chemicals added by human activities.

• Its Biotic environment would include the organisms on which it feeds, or those which compete for food and space, and those which may feed on it.

• All these environmental factors influence the survival of the fish.

The water cycle

• Of all the water on Earth, almost 98% is found in the salt water of the oceans.

• Of the remaining 2%, some is found in the form of atmospheric water vapour and as permanent ice deposits in various parts of the Earth.

•Less than 1% is available as fresh water to the organisms that live on the Earth.

•It is only because water is recycled that life on our planet has been able to exist for millions of years.

•The Sun is the only source of energy that powers the essential process that we know as the water cycle.

• Of these, evaporation from the oceans provides most of the water vapour present in our atmosphere.

• Carried by air currents, much of the water vapour falls as either rain or snow when it reaches land. Eventually the water finds its way back to the sea, allowing the cycle to continue.

Heat energy from the Sun causes water molecules to evaporate from:• moist soil surfaces• living organisms such as plants (by transpiration) and animals (sweat)• lakes, rivers and oceans.

The carbon cycle• Carbon is found in all living

things, and in our atmosphere as CO2. It is the movement of carbon atoms between the living and the non-living environment that we call ‘the carbon cycle’.

• In our biosphere, land plants take up the carbon dioxide directly from the atmosphere through tiny pores in their leaves called stomata, while aquatic algae absorb carbon dioxide, dissolved in the water surrounding them, over their entire surface.

• Once inside the plant, the carbon atoms detach from their oxygen atoms and rearrange to form glucose (photosynthesis). Glucose is used for energy or further rearranged into cellulose (a structural component in plant cell walls) and starch (an energy store).

• Photosynthesis: is driven by energy from the Sun. It is the process that provides the foundation for most of life on Earth.

• Herbivores eat and digest plant matter, using the carbon and other elements contained within the plant to provide for their own energy and growth. Higher order consumers rely on digestion to convert the carbon obtained from eating animal or plant tissue into a form they can use. Carbon gets back to the atmosphere by

• the release of carbon dioxide via respiration, which can be summarised as:

• sugar + oxygen →water + carbon dioxide + energy• Sugar breaks down to provide energy. Carbon dioxide

and water are waste products that are released back into the ecosystem.

• • the return of carbon to the ecosystem through animal wastes (faeces and urine) and the decomposition of dead plants and animals and animal wastes by the action of decomposers (bacteria, fungi and worms) in the soil.

• CARBON CYCLE.• The balance of CO2 and

O2 is changing due to:• • large-scale felling of

rainforest trees• • increased production of

carbon dioxide by industry• • increased burning of

fossils fuels such as petrol.

• This imbalance is referred to as the enhanced greenhouse effect

• The nitrogen cycle

• Nitrogen makes up about 78% of the air around us. Most organisms cannot use nitrogen directly. Before it can be used it needs to undergo a process called nitrogen fixation. Most of this happens during lightening strikes, where the electrical energy from the storm converts atmospheric nitrogen into various useful nitrogen compounds.

• One group of those compounds is the nitrates (NO3). These dissolve in rain droplets and fall onto the Earth’s surface, and are taken up by the roots of plants. Once inside the plant, nitrogen plays an essential part in the formation of amino acids and nucleic acids (the building blocks of genetic material).

• These nitrogen compounds are then consumed by animals when the plants are eaten.

• Energy sources • are classified as non-

renewable or renewable.• Energy sources that cannot

be replaced are referred to as non-renewable.

• These energy sources include:

• • fossil fuels such as coal, gas and crude oil.

• • uranium and other nuclear fuels used in nuclear power plants.

• Fossil fuels• Coal forms from decaying plant material buried in swampy

areas under muds to prevent total decomposition. Over millions of years the plants turn into coal from chemical changes caused by heat and pressure. Oil and gas generally form from decaying marine organisms buried in shallow seas over millions of years.

• Uranium

• When uranium atoms are bombarded with neutrons, they often split, releasing more neutrons and enormous amounts of energy. So much energy, in fact, that splitting just one uranium atom releases 26 million times more energy than the burning of one molecule of natural gas!

• This process is referred to as nuclear fission. Nuclear reactors were built to produce energy however we have problems of how to dispose of the dangerous waste products. Radioactive

• waste can cause cell damage in living organisms and lead to cancer. Many methods of storing nuclear waste have been tried in the past but all are only short-term solutions.

• The waste can remain radioactive for many thousands of years.

• Renewable energy sources• Renewable energy comes from

sources that can be used over and over again with minimal impact on the environment.

• Renewable forms of energy include:

• • energy from the Sun• • energy from the vast quantities

of heat stored within the Earth• • energy from the action of wind• • energy from water—the action of

waves, currents or tides, the falling of water due to gravity, or differences in salt content

• • ‘green energy’—energy derived from wood and other plant matter (sometimes called biomass).

• Energy from the Sun• Solar ponds• In a shallow pool, sunlight passes through

the water and is absorbed by the base and sides of the pool, gradually warming them. Water that is in contact with the sides and base slowly gets warmer too. Warm water rises and cool water drops, causing

• Convection currents throughout the pond. These continue until the temperature of the pond is uniform throughout. If salt is added to the water, however, the warm water does not rise, but stays warm at the bottom of the pond. Water pipes running along the bottom of

• the pond can be used as a way to heat fresh water passing through the pipes.

• The temperature of the water at the bottom of a solar pond can be as high as 107°C—hot enough to turn special turbines to generate electricity.

• Solar cells• Solar cells convert light energy

into electrical energy.• They are extremely useful in

remote areas because they have no moving parts to service and require no fuel except sunlight. Unfortunately the process used for the production of solar cells is not energy efficient and also produces pollution.

• Recent research has led to the development of a ‘solar concentrator’—the Winston tube. This instrument concentrates light to intensities similar to that of the Sun’s surface, generating enormous quantities of cheap, non-polluting energy

Energy from within the Earth (Goethermal)• Some countries, such as New Zealand, have hot

magma very close to their surface because they lie on fault lines in the Earth’s crust.

• They are able to use this geothermal energy to produce electricity: water is pumped into the ground, where it is heated by the molten rock until it boils and produces steam. The steam is tapped and turns turbines that produce electricity. Although this system appears to be ideal, there are some disadvantages:

• • Only countries near fault lines have easy access to molten rocks beneath the surface.

• • When water is extracted from or pumped into rocks, underground pressures change, leading to increased likelihood of earthquakes and rock cracking.

• • Geothermal energy produces a number of gaseous pollutants, particularly carbon dioxide, hydrogen sulfide, sulfur dioxide and methane.

Geothermal energy is used in areas where active volcanoes and lava lows are present, or

where water heated by deeply buried rocks makes its way to the surface. Water can be

pumped down into the ground to be heated bythe hot rocks, then pumped back out again.

Australia makes only limited use of geothermal energy

production.The Mulka Cattle Station in South Australia has used it since 1987, and the Garden

East Apartments (also in South Australia) have been operational

since 1994.Funding has also been provided

for a pilot plant in the Hunter Valley, New South Wales. In

contrast, New Zealand meets up to 75% of its energy needs

through geothermal sources.

• Energy from the wind• Global winds are the result of hot

air rising over the equatorial regions. This process creates a space into which cooler air from the poles rushes. We call this movement of air ‘wind’.

• Sailing boats and windmills have used wind energy for thousands of years. Now we have wind turbine generators, they convert the energy of wind movement into electricity. This electricity is used directly to do mechanical work, or fed directly into the electricity grid, or it can be stored in batteries for later use.

• Factors that influence the amount of electrical energy produced include:

• • the wind speed. The power supplied by the wind turbine• generators depends on the wind speed cubed. Thus when

the• wind speed doubles, the power produced increases eightfold.• • the length of the blades. The power supplied is related to

the length of the blades squared. This means that when the blade length is doubled, the power is quadrupled.

• At Blayney, west of Bathurst, New South Wales, 15 turbines generate 10 MW of power. This is enough power for 7000 homes and replaces older technologies that would produced 16 000 tonnes of carbon dioxide emissions yearly. The largest single wind generator is on Kooragang Island, Newcastle.

• Energy from water (Hydroelectricity)

• Gravity pulls water downhill until it reaches the lowest possible point—the sea. The gravitational potential energy it contains can be harnessed by passing it through turbines to generate electricity.

• Electricity produced in this manner is referred to as hydroelectricity. There are two ways we can maximise the amount of electricity produced.

• • Make a small volume of water fall from a great height.

• • Make a large volume of water fall from a much smaller height.

• The largest hydroelectric scheme in Australia is the Snowy Mountains Scheme in New South Wales, which generates almost 3800 MW (megawatts) of power. Consisting of 16 dams and 145 km of tunnels, this series of seven power stations provides 50% of Australia’s hydropower. A further 30% comes from Tasmania.

Using water currents, tides, waves and salinity

• Wave energy generators; Waves are forced into a narrow gully, causing the air above them to rise and fall. This moving air passes

• through a turbine to produce electricity. • Tidal power generation; place a barrier across a bay’s entrance so that the

incoming tide turns a turbine. At the maximum height of the tide, the water flow is blocked until the tide is low. The stored water is then released at low tide turning the turbine making more electricity.

• An oscillating wave column (OWC); generates energy by using ocean waves. The waves push air past a turbine, causing it to spin and as they recede they suck air past the turbine causing it to spin again. This creates power in both directions.

• Biomass • Is the term used to

describe organic material that has recently died and which can be used to generate energy. It includes everything from wood from fallen trees or industrial processes to the faeces from humans and animals.

• Biomass can be used directly by burning it or by collecting and burning the gases produced from biomass decay eg methane.

• Indirect use of biomass involves converting it into a suitable fuel. This most occurs with crops such as sugar cane, corn, rice and wheat. Waste products from their harvesting are processed into fuels such as ethanol and biodiesel.

• Energy from industrial and household waste

• The commercial food industry produces vast quantities of both solid and liquid wastes.

• These wastes contain dissolved organic matter, including sugars and starches, and have the potential to produce ethanol when combined with certain anaerobic bacteria.

• Of the total household waste collected each day, more than 80% is biomass, and of this 46% is organic matter (food scraps and garden waste). This type of waste can be converted into energy directly, by burning, or it can be ‘digested’ by anaerobic bacteria in landfill gas plants to produce biogas (methane and carbon dioxide), which can then be used to generate heat and power.

• Energy from animal and human waste

• In many developing countries, the manure from cows, camels and other animals is shaped into ‘pancakes’ or ‘bricks’, dried and stored.

• It is then burned to provide heat mainly for cooking. Animal and human wastes can also be converted to biogas using anaerobic bacteria.

QUESTIONS…

• 1 a Identify how energy resources are classified into two major types.

• b List examples of each type.• 2 Define the term ‘fossil fuel’.• 3 Define the term ‘nuclear fission’

and explain why some think it is a desirable energy source.

• 4 Discuss two disadvantages of nuclear energy.

• 5 List three ways we use energy from the Sun.

• 6 State the two major benefits of using the Sun as an energy source.

• 7 Define the term ‘geothermal energy’.

• 8 Describe how geothermal energy is used to produce electricity.

• 9 Discuss two disadvantages of geothermal energy.

• 10 State the benefits of using wind-powered electricity generators.

• 11 a Propose a likely meaning for the term ‘wind farming’.

• b Discuss the advantages and disadvantages of this form of energy production.

• 12 List the various ways in which water can be used to generate electricity.

• 13 Define the term ‘biomass’.• 14 Explain two ways in which

biomass can be used to supply energy.

• 15 Describe how fossil fuels are produced.

• 16 Your friend cannot understand why coal and gas are called ‘fossil fuels’. Explain to him why these terms are being used correctly.

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