Radiation from the sun is the source of
energy for most communities of living
organisms
Green plants and algae absorb a
small amount of light that reaches
them.
Green plants
transfer the solar
energy to chemical
energy which is
then passed along
the food chain.
This transfer occurs during photosynthesis
The energy is stored in the substances that make up the cells of
the plant
A pyramid of biomass represents
the mass of the organisms at each
stage in a food chain. +accurate
than pyramid of numbers
e.g a bush may have insects feeding on it but the
mass of the bush would be far larger than the
mass of the insects and so the bush would be the
first thing in the pyramid
The mass of each living material (biomass) at each stage
of the pyramid is less than that of the previous stage
The biomass can be drawn to scale and as a pyramid
Energy Transfers
There is wastage at each stage of a food chain
The amounts of material and energy contained
in the biomass of organisms is reduced at each
successive stage in a food chain.
This means that not all of the energy
that is taken in by an organism is
used for growth
Not all food eaten can be digested and
so some energy is stored in faeces or in urea in
urine (waste materials)
Some of the biomass (food) is used for respiration, which releases
energy for living processes, including movement, so the more
something moves, the more energy it uses and the less is available for
growth
Animals need to keep a constant temperature, so energy
from the previous stage of the food chain is used to keep
the animal at its normal body temp
Much of the energy which is released in
respiration is eventually released into the
surroundings.
Decay Processes
Living organisms must remove materials from the environment for growth and other processes.
These materials are eventually returned to the environment either in waste
materials or when the organisms dies or decays
Materials decay because they are broken down
(digested) by micro-organisms.
These mirco-organisms (bacteria and fungi) are called decomopsers and they work faster if they
are in a warm, moist aerobic conditions
Many decomposers also need oxygen.
The decay process releases substances that plants need to grow
In a stable community the processes that remove materials are balanced by those that return materials. They are constantly recycled
Humans can recycle waste in sewage plants and compost heaps
Detrius feeders e.g.
some worms start the
process of decay by
eating dead plants or
animals & producing
waste materials
Decay organisms then break down the waste or dead plants and
animals
The Carbon Cycle
The constant cycling of carbon is called the carbon cycle.
CO2 is removed from the
environment by green plants
and algae and is used for
photosynthesis
carbon from CO2 is used to make
carbohydrates, fats & proteins which
make up the body of plants and algae
When green plants
and algae respire
some of this carbon
becomes CO2 and is
released back into
the atmosphere
When animals respire some
carbon become CO2 and is
released back into the
atmosphere
When plants, animals and
algae die, some animals and
microorganisms feed on their
bodies. Carbon is released
into the atmosphere as
carbon dioxide when these
organsims respire
Combustion of wood and fossil fuels release CO2 back into the atmosphere