Transcript The Biosphere

The Biosphere
• Credit Objectives
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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).