You need to be able to construct pyramids of biomass
Theres less energy and less biomass every time you
move up a stage (trophic level) in a food chain. There
are usually fewer organisms every time you move up a
level too
100 dandelions..feed..10 rabbits..which feed..one fox
Each bar on a pyramid of biomass
shows the mass of living material at
that stage of the food chan - basically
how much all the organisms at each
level would weigh if you put them all
together
The bar along the bottom of the pyramid always
represents the producer. The next bar will be the
primary consumer (the animal that eats the plant) then
the secondary consumer (the animal that eats the
primary consumer and so on up the food chain
Energy transfer
All that energy just disappears somehow
1. Energy from the sun is the source of energy for nearly all life on earth
2. Green plants and algae use a small percentage of the light
energy from the sun to make food during photosynthesis. This
energys stored in the substances which make up the cells of plants
and algae and then works its way through the food chain as animals
eat them and each other
3. Respiration supplies the energy for all life processes including movement. Most
of the energy is eventually lost to the surroundings as heat. This is especially true
for mammals and birds whose bodies must be kept at a constant temperature which
is normally higher than the surroundings
4. Some of the material which makes up plants and animals is
inedible (e.g. bones) so it doesnt pass to the next stage of the food
chain. Material and energy are also lost from the food chain in the
organism waste materials
5. This explains why you get biomass pyramids. Most of
the biomass is lost and so does not become biomass in
the next level up
6. It also explains why you hardly ever get food chains
with more than about five trophic levels. So much
energy is lost at each stage that theres not enough left
to support more organisms after after four or five stages
Decay
Living things are
made of materials
they take from the
world around them
1.Plants take elements like carbon, oxygen, hydrogen and
nitrogen for the soil or the air. They turn these elements
into the complex compounds (carbohydrates, proteins
and fats) that make up living organisms, and these then
pass through the food chain
2. These elements are returned to the environment
in waste products produced by the organisms or
when the organisms die. These materials decay
because they are broken down by
microorganisms thats how the elements get put
back into the soil
3. Microorganisms work best in warm moist
conditions. Many microorganisms also break
down material faster when theres plenty of
oxygen avaliable. Compost bins recreate these
ideal conditions
Compost bin: Kitchen waste can be made into
compost. Compost is decayed remains of animal
and plant matter that can be used as fertiliser. It
recycles nutrients back into the soil
4. All the important elements are thus
recycled they return to the soil ready to be
used by new plants and put back into the
food chain again
5. In a stable community the
materials taken out of the soil and
used are balanced by those that are
put back in. Theres a constant cycle
happening
The carbon cycle
1. Theres only one arrow going down from the
atmosphere. The whole thing is powered by
photosynthesis. CO2 is removed from the
atmosphere by green plants and algae and the
carbon is used to make carbohydrates, fats and
proteins in the plants and algae
2. Some of the carbon is returned to the
atmosphere as CO2 when the plants and algae
respire. Some of the carbon becomes part of the
fats and proteins in animals when the plants and
algae are eaten. The carbon then moves through
the food chain
3. Some of the carbon is returned to the atmosphere
as CO2 when the animals respire
4. When plants, animals and algae die other animals (detritus
feeders) and microorganisms feed on their remains. When
these organisms respire CO2 is returned to the atmosphere
5. Animals also produce waste and this too is broken
down by detritus feeders and microorganisms.
Compounds in the waste are taken up from the soil by
plants as nutrients they are put back into the food
chain again
6. Some useful plant and animal products e.g. wood
and fossil fuels are burnt (combustion). This release
CO2 back into the air
7. So the carbon is constantly being
cycled from the air, through food chains
and eventually back out into the air again