The Biosphere

1
The Biosphere

• Credit Objectives

2

• Sub-topic (a) Investigating an Ecosystem
• Identify possible errors that may arise when
  using techniques for sampling and measurement.
• Pit fall trap
• Possible errors The numbers and types of
  organisms may not be typical of the whole
  ecosystem. Birds may eat trapped animals. Some
  animals may eat others.

3

• Quadrats numbers and types of plant may not be
  representative of the whole area.
• Light Intensity Observer may stand in shadow, in
  the way of the light. Light intensity may change
  from one moment to the next.
• Moisture content Moisture from previous
  measurement may be left on the probe.
• Explain how errors can be minimised when using
  techniques for sampling and measurement.
• Pit fall trap Set up several traps. Disguise the
  opening. Check traps regularly Or put
  preservative liquid at the bottom of traps.

4

• Quadrats Take large numbers of random samples.
• Light intensity Ensure all observers are
  standing to one side of the light meter. Take all
  the measurements as near to the same time as
  possible or take several readings at one site and
  take an average.
• Moisture content Wipe the probe before each
  reading.

5

• Explain how an abiotic factor has an effect on
  the distribution of organisms.
• Light Intensity Green plants make their food by
  photosynthesis using light energy. In conditions
  of low light intensity , it is possible that they
  are unable to obtain sufficient solar energy to
  produce food. They are therefore unable to
  survive in the dimly lit conditions. For example
  daisies would be unable to grow within an oak
  wood. Therefore light intensity plays a part in
  determining the distribution of daisies.

6

• Sub-topic (b) How it Works
• Explain the effects of the removal of one species
  from a food web.
• When explaining the effects use the terms
  INCREASE, DEACREASE or STAY THE SAME. Fully
  explain the effect given.
• Explain what is meant by pyramid of
  numbers/biomass.
• Pyramid of numbers
• Shows the relative numbers of organisms at each
  stage of a food chain the further from the
  producer the smaller the number.

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• Pyramid of Biomass
• This represents the relative biomass possessed by
  the organisms at each stage of a food chain.
• Describe and explain population growth under
  ideal conditions.
• The growth of a population under ideal conditions
  continues to rise indefinitely because the birth
  rate is high and the death rate is low and
  therefore the population continues to increase
  and realise its full reproductive potential
  without being controlled by factors such as
  disease.

8

• Describe the sequences or processes in the
  nitrogen cycle.
• All living things need nitrogen to make protein.
• Plants and animals cannot make use of nitrogen
  gas directly.
• Plants absorb nitrogen from the soil in the form
  of NITRATE.
• Animals must eat plant or animal protein to
  obtain their supply of nitrogen.
• Study and learn the nitrogen cycle in your notes.

9

• Sub-topic (c) Control and Management
• Explain the possible problems related to the use
  of fossil fuels and nuclear power.
• The burning of fossil fuels can have an adverse
  effect on the environment because the sulphur
  dioxide and other poisonous gases released
  pollute the atmosphere and may even be converted
  into acid rain.
• Nuclear power is used instead of fossil fuels in
  some power stations. Many of the radioactive
  wastes produced are extremely dangerous since
  they continue to give out harmful radiation for
  many years.

10

• Explain the relationship between level of
  pollution with organic waste, numbers of
  micro-organisms, oxygen concentration and numbers
  of species.
• As the level of pollution increases so will the
  level of organic waste.
• The number of micro-organisms will also increase
  as they have a rich food supply and will
  multiply.
• As the bacteria multiply they will use up
  available oxygen causing the oxygen concentration
  to decrease.
• This will cause surrounding species to decrease
  as their oxygen supply will be depleted.

11

• Explain what is meant by an indicator species.
• Some types of living things only thrive well
  under certain environmental conditions. Such
  organisms are called INDICATOR SPECIES because
  their presence shows that these conditions are
  present in the environment.
• Mayfly nymph thrive in rivers with a high oxygen
  concentration.
• Rat-tailed maggots thrive in rivers with low
  oxygen concentrations.

12

• Explain how the parts of an ecosystem are
  controlled in either agriculture or forestry.
• Agriculture
• By employing agricultural practices, people
  deliberately interfere with an ecosystem in order
  to produce vast numbers of a useful species (eg.
  crops).
• Parts of the ecosystem are controlled.
• Nutrient supply fertilisers (natural and
  unnatural).
• Crop habitat clearing the land of other possible
  competitors (herbicides, weed killers, fences and
  maintains water).