Ecology

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What is Ecology?Ecology is the study of how

living things relate to each other and to their environment

Their environment refers to all the conditions in which the organism lives, which affect the growth and development of the organism.

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What is an Ecosystem?An ecosystem is a community of living

organisms interacting with one another and their non-living environment within a particular area.

The earth itself is a true ecosystem as no part of it is completely isolated from the rest.

**Ecosystem = Communities + Environment

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Diversity of ecosystemsWoodland, Hedgerow,

Seashore, Marine,Grassland, Freshwater,

Tree, etc. Can you name some more?

Ecosystems can be very large or very small

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To study an ecosystemWe divide the ecosystem into a

number of smaller, more manageable areas (habitats).

Individual habitats are then studied.

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What is the Biosphere?The biosphere is that part of the

earth inhabited by living organisms, including land, ocean and the atmosphere in which life can exist.

It is the global ecosystem.

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Relationships in the biosphere

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What is a Habitat?

A habitat is the particular place within the ecosystem where an organism lives and to which it is adapted

As a living organism (you) what is your Habitat, Ecosystem and Biosphere?

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SummaryBiosphere = that part of the earth and its

atmosphere in which life can exist composed of ecosystems

Ecosystems = composed of communities of organisms and their environment

Communities = populations of different species of organisms

Habitats = is the place where an organism lives and to which it is adapted

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Learning check1. What is ecology?

2. What is an ecosystem?

3. What is the biosphere?

4. What is a habitat?

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Definition of NicheA niche is the functional role of

an organism in an ecosystem.

A niche is a term describing the relational position of a species or population in an ecosystem.

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Niche Explanation (cont’d)This includes how a population responds to

the abundance of its resources and enemies

(e.g. by growing when resources are abundant, and predators, parasites and pathogens are scarce)

and how it affects those same factors (e.g. by reducing the abundance of resources through consumption and contributing to the population growth of enemies by falling prey to them).

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Niche Explanation (cont’d)The abiotic (non-living) or physical

environment is part of the niche because it influences how populations affect, and are affected by, resources and enemies.

The description of a niche may include descriptions of the organism's life history, habitat, and place in the food chain.

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Niche Explanation (cont’d)

No two species can occupy the same niche in the same environment for a long time.

When plants and animals are introduced into a new environment, they can occupy new niches or niches of native organisms, outcompete the native species, and become a serious pest.

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LichensTwo lichens on a

rock, in two different ecological niches.

Can you explain why they are different niches?

Lichenes on a rock

Author: Johann Dréo

Date: 2005, august, 10

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SummaryFor a species to maintain its population,

its individuals must survive and reproduce.

Certain combinations of environmental conditions are necessary for individuals of each species to tolerate the physical environment, obtain energy and nutrients, and avoid predators.

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Summary cont’dThe total requirements of a species for

all resources and physical conditions determine where it can live and how abundant it can be at any one place.

These requirements are termed the ecological niche.

Environmental Factors

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Environmental factors that affect organisms

Abiotic These are non-living factorsBiotic These are living factorsClimatic These are the average

weather conditions that affect the community in an ecosystem

Edaphic These refer to the soil

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Abiotic factorsThese are the non-living features

of an ecosystem (i.e. the physical and chemical conditions) that affect the community.

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Abiotic factors include:TemperatureLight intensityAir speedWater currentHumiditypH

Dissolved oxygen

SalinityNitrate,

phosphate and other plant nutrients

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Abiotic factors in a woodland

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Biotic factorsThese are the living features of

an ecosystem that affect the other members of the community.

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Biotic factors include: Plants for food and shelterPredatorsPreyParasites and pathogensDecomposers CompetitorsPollinators

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Climatic factorsThese are elements of the climate

(weather) that influence the life and distribution of the organisms that live in a particular environment.

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Climatic factors include:TemperatureRainfallHumidityWind Light intensity (including seasonal

variations)Day length

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Edaphic factorsThese are the physical,

chemical and biological characteristics of the soil that influence the community.

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Edaphic factors include:Soil type, Soil pH, Available (soil) water, Air and Mineral content, Humus, Soil texture and Structure.

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Aquatic Environmental FactorsThe following are also considered as

factors:Light penetrationCurrentsWave action

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Learning check1. What is meant by abiotic factors? Give

examples.

2. What is meant by biotic factors? Give examples.

3. What are edaphic factors? Give examples

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Energy FlowEcosystems are unable to function unless

there is a constant input of energy from an external source.

Where does this energy come from?The Sun

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The Sun

The sun is the primary source of energy for our planet.

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Energy Flowis the pathway of energy transfer

from one organism to the next in an ecosystem due to feeding, e.g. along a food chain

Feeding allows energy to flow from one organism to another in an ecosystem.

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Energy flow in the ecosystem

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Food ChainIs a flow diagram that begins with a plant

and shows how food/energy is passed through a series of organisms in a community.

Each organism feeds on the one before it.

A food chain ends when there is not enough energy to support another organism.

An example of a food chain: grass rabbit fox.

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A Grazing food chain- is one where the initial plant is living e.g.

Grass grasshoppers frogs hawks

Honeysuckle aphids ladybirds thrushes

Seaweed winkles crabs herring gulls

Phytoplankton zooplankton copepod herring

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Grazing Food Chains

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A Detritus food chain- is one where the chain begins with dead

organic matter and animal waste (detritus) e.g.

Detritus edible crab seagull

Fallen leaves earthworms blackbirds hawks

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Food WebThis is a chart showing all the

feeding connections in the habitat/ecosystem.

Constructed by showing the links between all the interconnecting food chains in the habitat.

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Food Webthe interconnected food chains in an ecosystem

e.g.

41A woodland food web

Construct a two food chains (4 ‘links’) from the above food web

42Another food web

What is the longest food chain you can construct from this food web?

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Producers

Producers are organisms capable of making their own food by photosynthesis, e.g. green plants.

Primary producers are the first members of a food chain

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ConsumersConsumers are organisms that feed on

other organisms. They cannot make their own food. There are three types:

Primary consumers – feed on producers

Secondary consumers – feed on primary consumers

Tertiary consumers – feed on secondary consumers

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Woodland food chainHoneysuckle aphids ladybirds thrushes

Primary consumer

Secondary consumer

Tertiary consumerProducer

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Learning check1. What is the primary source of energy?2. Energy flow/transfer through an

ecosystem is achieved by …3. What is meant by a Grazing food chain?

Give an example4. Construct a simple food web

Two food chains e.g.Plant caterpillar thrush foxPlant earthworm blackbird foxCombine them to form a food web

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Trophic LevelThis refers to the position of an organism

in a food chain.Plants are at the 1st trophic level (T1) andHerbivores occupy the 2nd trophic level

(T2).Carnivores that eat herbivores are at the

3rd trophic level (T3). The 4th trophic level (T4) is often occupied

by the top carnivore.

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Trophic levels

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Pyramid of NumbersA diagram that represents the numbers of

organisms at each trophic level in a food chain.

Bottom layer is the largest and represents a very large number of primary producers

The next layer smaller and represents a smaller number of primary consumers

The next layer – the no. of secondary consumers

The uppermost layer where there may be only one tertiary consumer

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Pyramid of Numbers

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Learning checkExplain the following terms:1. Producer 2. Consumer 3. Primary Consumer 4. Secondary Consumer 5. Tertiary Consumer

6. What is meant by trophic level?

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To construct a pyramid of numbers

1. Count the primary producers and place them at the base of the pyramid

2. Count each consumer and include them according to their status (primary or secondary consumer) in the pyramid

3. The apex of the pyramid should include tertiary or top carnivores

4. Draw the pyramid so that the area/volume of each level is proportional to the number of organisms found

Nutrient Recycling

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Nutrient Recycling (1/3)

There is a limited amount of nutrients on earth e.g. you are probably aware of the water cycle – where water is constantly being recycled in nature. There are similar cycles for all nutrients.

When plants and animals die, their nutrient content is not wasted.

Bacteria and fungi decompose the remains and release the nutrients back into the abiotic environment (i.e. into the soil, nearby water and air).

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Nutrient Recycling (2/3)

These nutrients are then taken up by other plants and used to make new organic material.

This material is passed on down the food chains and is reused by all the chain members.

When death occurs for these members, the nutrients are again returned to the abiotic environment and the cycling of nutrients continues in this circular way.

57Recycling nutrients within an ecosystem

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Nutrient RecyclingThis ensures that there is no real longterm

drain on the Earth’s nutrients, despite millions of years of plant and animal activity.

In summaryNutrient recycling is the way in which elements are continuously being broken down and/or exchanged for reuse between the living and non-living components of an ecosystem.

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Carbon Cycle

Carbon forms part of all organic nutrients – carbohydrates, fats and proteins.

Carbon dioxide is removed from the environment by photosynthesis in plants, and under certain conditions, over long periods of time, some of these plants may form fossil fuels such as coal, oil, peat and natural gas.

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Carbon Cycle

Carbon dioxide is returned to the environment by:1. Respiration in plants, animals &

micro-organisms.2. Decay caused by micro-organisms.3. Combustion i.e. burning fossil fuels

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The Carbon Cycle (1/3)

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Summary of Carbon CycleClick on the link below to see a summary of the

Carbon Cycle

The Carbon CycleFor Animated Cycle click here

FlashShochwave

Click on this link to go to the next slide

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The Nitrogen Cycle

All organisms need nitrogen for protein, DNA & RNA manufacture

78% of the Earth’s atmosphere is nitrogen gas, but it cannot be used in this form by plants and animals.

Nitrogen gas must first be ‘fixed’, i.e. changed to a suitable form (ammonia or nitrate) before it can be used.

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Nitrogen Fixation♣ Nitrogen-fixing bacteria in the soil convert

N2 gas in the air into ammonia (NH3). This accounts for the majority of all N2 fixation.

♣ Lightening storms and fuel burning in car engines produce nitrates, which are washed by rain into the soil water.

♣ Nitrates are absorbed by plant roots and converted to plant protein.

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The Nitrogen Cycle§ Plant proteins are passed along food chains to

become animal protein.§ When organisms die, their proteins are

converted to ammonia by bacterial decomposition.

§ Nitrifying bacteria in the soil then convert ammonia (NH3) into nitrites (NO2

2 _) then into nitrates (NO3

_).§ Nitrates can be absorbed by other plants to

continue the cycle.

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The Nitrogen Cycle§ Denitrifying bacteria convert soil nitrates

into N2 gas.This is a loss of N2 from the cycle.Only happens in anaerobic conditions (when O2 levels are low) – due to flooding or accumulation of sewage.

§ Nitrate also enters the cycle through the addition of nitrogen rich fertilisers to the soil – made industrially from nitrogen gas.

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The

Nitro

gen

Cycle

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Summary of Nitrogen Cycle

Click on the link below to see a summsry of the Nitrogen Cycle

The nitrogen cycleFor Animated Cycle click here

FlashShochwave

Click on this link to go to the next slide

69Summary of Nitrogen Cycle

1. Nitrogen Fixation & Lightning

2. Absorbed by roots and used by plants – Assimulation

3. Animal feeding, digestion & assimulation

4. Excretion: urea Ammonia

5. Death & decomposition – putrefying bacteria

6. Nitrification: NH3 NO2

7. Nitrification: NO2 NO3

8. Denitrification: NO3 NO2 N

Nitrogen in Air

Nitrite NO2

Ammonia NH3

Nitrate in Soil NO3

Plant Protein Animal Protein

1

2 3

4

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6

78

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Learning check1. What is meant by nutrient recycling?2. What process(es) remove Carbon dioxide

from the atmosphere?3. What process(es) add Carbon dioxide to the

atmosphere?4. Nitrogen gas must be ‘fixed’ – what does this

mean?5. In what form is nitrogen absorbed by plants?6. What is nitrification?7. What do denitrifying bacteria do?

Human Impact on the Environment

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PollutionPollution is any human addition

(contamination) to a habitat or the environment that leaves it less able to sustain life.

It is the most harmful human impact and affects air, fresh water, sea, soil and land.

Chemicals of human origin that harm the environment are called pollutants.

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Some types of Pollution

Industrial/Air Pollution

Domestic Pollution

River/Water

Pollution

Agricultural Pollution

– slurry, if it gets into a river/pond

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Learning check1. Explain the difference between Pollution and

Pollutant.2. List some types of pollution3. CO2 is produced by all living things as a reuslt

of respiration. Is CO2 a pollutant? Explain your answer.

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Pollutants: are produced by human activities

CO2 from respiration is not a pollutant – : excess CO2 from burning fossil fuels is

SO2 from marshes & volcanoes is not – :SO2 from factory chimney is

Some pollutants are normally present in an environment, e.g. CO2, but levels are increased by human activity.

Other pollutants never exist in an environment e.g. oil slick, CFCs

76From the Syllabus & Guidelines

The Syllabus states: “Study the effects of any one pollutant.”

The Guidelines for Teachers states: “Give the effects of one pollutant from any of the following areas: domestic, agricultural, industrial.” and

“Give an example of one way in which pollution may be controlled in the selected area.”

What follows is only a sample of the pollutants available.

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Effect of one pollutant from one area- Agricultural, Industrial or Domestic

Area Pollutant Source Effects

Agricultural Slurry & Fertiliser

Washed or leached from land

Formation of algal blooms and eutrophication

Industrial Sulphur dioxide

Burning fossil fuels

Forms ‘acid rain’More detail later

Domestic Plastic bags ShoppingNon-biodegradable Suffocate small animals, Litter

78Eutrophication & Algal bloom

Eutrophication: a condition where lakes become over-enriched with nutrients, resulting from excess artificial fertilisers washed into rivers and lakes.

There is a rapid increase in the growth of alga (algal bloom) as they use up the nutrients.

When all the nutrients are used up the algae die and are broken down by bacteria, which use up the oxygen in the water resulting in the death of aquatic organisms such as fish.

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Control of Pollutants in the selected area - Agricultural, Industrial or Domestic

Area Pollutant Control Measures

Agricultural Slurry & Fertiliser

Avoid spreading these:• on wet, waterlogged, frozen or steeply sloping land• within 1.5m of any watercourse.

Industrial Sulphur dioxide

Fit catalytic scrubbers in factory chimneys

Domestic Plastic bags Bag tax/levy. Reuse/Recycle bags

Ecological impact of one human activity

Burning Fossil Fuels

81Acidic oxides and acid rain All rain is acidic – but not the same pH- CO2 in the air dissolves in rainwater to form carbonic acid – pH = 5.5 in unpolluted air

Acid rain refers to very acidic rain with a pH of 4.5 or less

Burning of fossil fuels releases acidic oxides into the air, especially SO2 and nitrogen oxides (NOx)

SO2 dissolves in rainwater to form sulphurous acid (H2SO3) or reacts with particles in the air to form sulphuric acid (H2SO4)

The resulting rain is very acidic and can be carried far by the wind

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Effects of acid rain Reduces soil pH Phosphorus (P) binds to soil particles and is

unavailable to plant roots Al becomes soluble and poisonous and with K, Ca

and Mg is washed (leached) from the soil into lakes and water suppliesSoil is impoverished and fish die in highly mineralised water. Why?

Erodes limestone buildings Causes breathing difficulties – irritates the

delicate lining of the lungs Inhibits chlorophyll formation and burns the

leaves of plants

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Dealing with acid rain Reducing the quantity of fossil fuels

burned Using catalysts to treat chimney gases

(‘scrubbers’ are fitted to the insides of chimneys)

Catalytic converters fitted to modern cars

Developing alternative ‘clean’ energy sources

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Learning check1. What is acid rain?

2. How is acid rain formed?

3. List at least 4 of the effects of acid rain

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What is Conservation?**Conservation is the protection and wise

management of natural resources and the environment.

Benefits of Conservation 1. Existing environments are maintained 2. Endangered species are preserved for

reproduction 3. The balance of nature is maintained 4. Pollution and its effects are reduced

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One Conservation practice from one of the following areas

Area Conservation Practice

AgricultureMixed farming, Crop rotationBiological controls, Gene banks

Fisheries Fishing Net size, Quotas, Re-stockingForestry Re-planting, Broadleaf/conifer mix

There is a need for continual monitoring of the environment to ensure its protection and the wise management of its natural resources.

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FisheriesOne Conservation practice from one of the

following areas is required:Fishing Net size Quotas Re-stocking

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Fishing Net sizeWhat is net mesh size? This refers to how large or small the openings or

spaces enclosed by the threads of a net are.

The use of small-mesh nets can result in too many young fish being caught

Using larger meshed nets to allow the young to escape, mature and reproduce

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Different types of nets

Square mesh – does not alter its shape under tension – allows young fish to escape

Diamond mesh netting (left) – closes under tension (right) and prevents young fish escaping

Go to next topic: Waste Management

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Fishing QuotasWhat is a fishing quota? A fixed proportion of the total allowable catch

allocated to each fishing nation. This national quota allocation is further sub-divided

into quotas for specific areas, seasons, fisheries or organisations, e.g. producers' organisations.

Why have quotas? Over fishing has reduced fish stocks at sea Fish quotas (maximum amount allowed to be caught)

have been assigned to different countries to ensure that enough fish are left to replenish the stock.

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Conservation and Fishing Quotas Helps to prevent the extinction of a fish

species Gradually increases fish stock and helps

to re-establish populations Attempts to maintain fishing at highest

possible levels

Go to next topic: Waste Management

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Re-stockingWhat is the purpose of re-stocking? To achieve a permanent increase in the sustainable

population of that species Translocation of species into areas where they have

not naturally occurred is not encouraged Re-stocking attempts to maintain the balance in

the ecosystem Increases stocks for recreational fishing

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Waste ManagementWhat is waste management? Waste management is the collection, transport,

processing, recycling or disposal of waste materials, produced by human activity, in an effort to reduce their effect on human health or local aesthetics or amenity.

It also tries to reduce waste materials' effect on the natural world and the environment and to recover resources from them.

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Waste Management Urban rubbish is mostly dust, dirt, hair, paper,

food scraps, metal, glass and plastic. Traditional disposal has been to bury rubbish in

landfill sites or incinerate.The area being filled has a rubberized landfill liner

is in place (exposed on the left).This prevents leaching materials migrating

downward through the underlying rock.

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Waste Management in Forestry Leaves from coniferous trees should not be

allowed fall into rivers – make the water acidic Chemicals and fertilisers should not be allowed

run off into waterways - algal blooms and eutrophication

When trees are harvested only bare poles are removed so a lot of tree debris (called brash) and the stumps are left behind

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Forestry solutions Waste Management in the forestry sector is all

based on recycling. When the trees are harvested brash and the

stumps are left behind. The stumps are sprayed with a urea-type

compound which speeds up the decomposition process

The brash is either left to decompose on the forest floor or collected and sold as a fuel source.

In some of the larger sites the sawdust and debris is sold on for conversion to fibreboard e.g. MDF

97Problems with Waste Disposal

Availability of suitable landfill sites The toxic or polluting content of fumes from

incineration (CO2, other acidic oxides and dioxins – produced from burning plastic)

Decaying waste produces methane gas which contributes to the “greenhouse gases”

Harmful substances may leak into groundwater supplies (wells, lakes, reservoirs)

Plants and animals in rivers and lakes are killed through direct poisoning or eutrophication

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Possible solutions Lifestyle changes and education programmes

for all ages are needed to alter the attitudes to littering and waste minimisation and disposal

Use micro-organisms to degrade the rubbish and produce fuel pellets

Reduce the use of paper and recycle more paper

Biodegradable materials (e.g. paper bags) should be used in place of plastic ones.

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Suggestions for waste minimisation Reduce – use less, minimise waste.

Re-use – use again, without changing but maybe for a different purpose.

Recycle – change, recover some material and use again.

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Role of micro-organisms in Waste Management

Composting is an aerobic process during which micro-organisms decompose organic matter into a stable substance called compost which recycles all the nutrients required for plant growth.

Since it is aerobic the organic waste mixture must be turned and loosened to allow air into it.

This increases the size and number of air pores.

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Micro-organisms in Waste Management Fungi break down the ‘tougher’ materials in the

waste such as lignin and cellulose.

Their filamentous structure penetrates the composting material and helps to improve aeration and drainage in the compost heap.

Temperatures within a compost heap can reach 70°C as the bacteria and fungi work to breakdown the material.

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VermicompostingThis is another method of recovering the nutrients

from organic waste, uses worms to consume the food waste and utilizes the worm castings as compost.

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Role of micro-organisms in Pollution Control

Composting can reduce environmental pollution caused by disposal of organic wastes in landfills and streams or by incineration.

Bacteria and fungi break down organic matter into compost that recycles all the nutrients required for plant growth.