The Biosphere

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The Biosphere

• Revision

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Sub-topic (a)

• Investigating an Ecosystem

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What is the biosphere?

• The biosphere is the zone of life around Earth,
  from the deepest ocean to high in the atmosphere
• Within the biosphere there are numerous
  ecosystems which are natural biological areas
  such as woodlands, ponds, hillsides, rivers etc

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Ecosystems are usually very large and complex

• Ecosystems are made up of animal and plant
  communities plus habitats
• Living factors in the ecosystem are called BIOTIC
  factors
• Non living factors are called ABIOTIC factors

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Sampling

• Because ecosystems are usually large and complex
  It is impossible to count every organism and
  habitat in the ecosystem
• We therefore have to sample the ecosystem to
  identify numbers

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Sampling Biotic factors

• A quadrat is used to sample Plants or slow moving
  animals
• It is thrown at RANDOM on the area of ground
  being sampled. This is step is repeated several
  times
• The number of squares which contain an identified
  plant are counted

0.5m
0.5m
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Measuring Abundance

• Abundance is a measure of how rare or common a
  plant type is

grass
dandelion
pansy
Only the squares that contain a particular plant
are counted NOT the total number of
plants Calculate the abundance ratio for each of
the plants shown
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Errors during quadrat sampling

• Errors or mistakes must be kept to a minimum to
  ensure results from sampling are reliable
• Quadrats must be thrown at random
• If the sample area is large it must also be
  thrown numerous times to give a accurate
  representation of the area

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Sampling Biotic factors continued

• A pitfall trap is used to obtain samples of small
  animals that move along the grounds surface
• The stones prop up the lid of the trap which
  could be leaves/wood etc
• The lid prevents flooding and camouflages the trap

bait
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Measuring Abiotic Factors

• Light and moisture are 2 easily measured abiotic
  factors
• To measure light intensity we use a light meter
• To measure moisture we use a moisture meter

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Measuring light and moisture

• The moisture meter probe is carefully pushed into
  the ground being careful not to hit any stones
• A light meter is held at the soil surface and
  pointed in the direction of maximum light and the
  reading taken
• Both meters are not very accurate they are only
  used for comparing readings

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Possible sources of error

• Care must be taken not to shade light with your
  body when taking a reading
• Readings must also be taken at the same time of
  day under similar conditions

• The probes of the moisture meters must be pushed
  into the same depth at each site
• The probe must be cleaned/dried between samples

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Errors made with pitfall traps

• The top of the trap must be LEVEL with the ground
• The soil rod about the trap should remain as
  undisturbed as possible
• Traps should be checked often
• The traps should have adequate drainage

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Sub-topic (b)

• How it Works

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How ecosystems work

• There are certain words you must know the
  definitions of
• An ecosystem
• Community Habitat

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Food Chains

• A food chain shows the feeding relationship
  between organisms within an ecosystem
• The arrows show the direction of energy flow

Producer
Consumers
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Food webs

• A food web is a number of food chains that
  interconnect
• When an organism is removed from the web, this
  has a knock on effect on other organisms in the
  web

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Energy Loss

• Not all energy conserved inside an organism is
  passed onto the next when it is eaten
• Energy is lost from a food chain/web by movement
  and heat
• Because an organism only converts a small amount
  of food into making new cells, there are usually
  fewer organisms at each stage in a food chain
• This can be represented in a pyramid of numbers

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Pyramid of numbers
Least numbers
Fewer numbers
Greatest number of organisms

• This diagram shows the NUMBER of organisms
  present at each stage in a food chain

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Are Pyramids of numbers reliable?

• With PONs you can get odd results if organisms
  are really big or really small
• A better way of representing food chains are
  PYRAMIDS OF BIOMASS

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Pyramids of Biomass

• Pyramids of biomass show the amount of biological
  material at each stage in a food chain.
• Pyramids of biomass are always pyramid shaped

Least Mass
Greatest Mass
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Factors that affect population growth

• The no. of organisms in a population depends on
  the BIRTH rate and DEATH rate
• Populations are limited due to several factors
  such as
• Space
• Food/water supply
• Disease
• predators

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A typical growth curve

• 1st stage shows little growth as there arent a
  lot of organism to reproduce
• 2nd stage shows a rapid increase in numbers de to
  plentiful food and few predators
• 3rd stage shows growth slowing due to food being
  used up and other growth limiting factors

3
2
1
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Competition

• Competition occurs when 2 organism need the same
  resource
• Competition can be for
• Space
• Mates
• Food
• Light
• Usually the strongest and fittest survive and the
  weakest organism will eventually become extinct
  in the ecosystem

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The recycling of resources

• Some resources are in short supply for all
  organisms such as carbon and nitrogen
• Nitrogen makes up about 80 of out air but it is
  unreactive in this form
• Special types of bacteria can fix nitrogen into
  useful nitrates
• The recycling of nitrogen can be illustrated in
  the Nitrogen Cycle

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N-Cycle simplified(!!!)

• Plants can absorb nitrates through their roots to
  make protein.
• Animals eating the plants can convert this
  protein into their own protein.
• When protein is excreted or the animals die
  decomposers change the protein into ammonia in
  the soil.
• Soil bacteria convert the ammonia into nitrites
  in the soil.
• Soil bacteria convert the ammonia into nitrates
  in the soil.

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Nitrogen fixing bacteria

• Some plants have nitrogen fixing bacteria living
  in root nodules (swellings on the roots)
• These bacteria can convert N gas from the air and
  convert it to forms that a plant can use such as
  nitrate
• Other bacteria called DENITRIFYING bacteria can
  change soil nitrates into nitrogen gas (the
  opposite process from above)

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The Nitrogen Cycle in all its glory!!
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Sub-Topic (c)

• Control and Management

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What is pollution?

• Pollution is the contamination of our
  surroundings by substances which harm living
  things
• Often pollution cause disease and in extreme
  cases death
• Pollution affects 4 main ecosystems AIR, LAND,
  FRESH WATER and the SEA

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Sources of pollution

• Domestic pollution such as raw sewage (faeces),
  household rubbish and old car parts

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Sources of pollution

• Agricultural pollution caused by excess use of
  fertilisers and pesticides
• Excess liquids run off into rivers and streams
  affecting aquatic life.

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Sources of pollution

• Industrial pollution caused by the burning of
  fossil fuels, inorganic chemical wastes and
  nuclear power stations

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Burning of Fossil Fuels

• Poisonous gases such as carbon monoxide, nitrogen
  oxides and sulphur dioxide are produced
• These gases react with light, water and oxygen in
  the atmosphere to form acid rain
• Acid rain falls and affects trees at high
  altitudes by causing yellowing of leaves/needles
  or even death
• Acid rain also interacts with soil leading to it
  being run off into water causing the death of
  aquatic animals that cannot withstand acidic
  waters

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Nuclear Power

• Nuclear power is used in some power stations
  instead of fossil fuels to make electricity
• Radioactive waste is produced from this which
  give out harmful radiation for many years to come
• Radiation can cause diseases such as leukemia and
  other forms of cancer

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Controlling pollution

• Domestic recycling and alternative methods of
  disposal, lead free petrol, catalytic converters
  in cars
• Agricultural use minimum concs of fertilisers
  or pesticides
• Industrial scrubbers in chimney which removes
  SO2 from gases, sealing of radioactive waste in
  lead containers and dumping on ocean bed,
  alternative energy sources (sun, wind waves etc)

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Organic Waste

• Organic waste is the unwanted remains of living
  things such as sewage, dead leaves and stale food
• Organic waste is and ideal food source for
  decomposing micro-organisms that bring about
  decay
• Sewage is usually treated at sewage works by
  being fed to these micro organisms which break it
  down into harmless substances

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River Pollution

• Some sewage can end up untreated in rivers and
  waterways
• Because they provide a food source for
  micro-organisms, when they feed on it they
  rapidly multiply and use up the rivers supply of
  dissolved oxygen
• This oxygen shortage leads to the death of
  aquatic organisms

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Organisms found in polluted rivers

• Clean water - mayfly nymph, stonefly nymph
• Partly polluted water freshwater shrimp, caddis
  fly larva
• Badly polluted water bloodworm, water louse
• Very badly polluted water sludge worm, rat
  tailed maggot

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Indicator species

• These are organisms which only thrive well under
  certain environmental conditions such as the
  organisms discussed
• Trout need oxygen rich water whereas roach are
  more tolerant of lower O2 concentration
• Different types of lichen differ in their
  sensitivity to sulphur dioxide gas

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Poor management

• Example overuse of fertilsers and pesticides
• Effect excess chemicals are washed into rivers
  and lakes by the rain. They are difficult to
  decompose so end up in the food chain
• Solution use minimum fertilisers on land near
  waterways. Develop biodegradable pesticides

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Poor Management

• Example overgrazing of grassland
• Effect overgrazed plants die and so no longer
  retain water in the soil so the area becomes
  desert like. People become poorer and more prone
  to disease and malnutrition
• Solution crop rotation, develop irrigation
  schemes