4.7 explain why only about 10% of energy is transferred from one trophic level to the next

This is mainly explained in point 4.6, but I will cover the main points again...

Much energy is lost so not all energy an organism takes in is conserved until it dies and then transferred onto he next trophic level when it is eaten. the main causes of energy loss are...

- Heat energy
- Energy needed for the 7 life processes
- Energy in indigestible foods (e.g fibre) is not 'absorbed'

this results in around 90% of the energy being used, so only 10% is passed onto he next trophic level.

4.5 understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

Food chain
A food chain shows the flow of energy up the food chain. It can only show one organism at each trophic level, also you cannot tell whether the organism is feeding at more than one.


Here is an example of a food chain...

Food web
A food web gives a better understanding of a certain ecosystem by linking several animals within a habitat showing which organisms consumes which etc. A food web basically just shows multiple different food chains, that are all linked together. They show multiple different trophic levels including multiple prey and multiple predators. This means an organism has the potential to be a secondary or tertiary consumer at the same time.

Here is an example of a food chain...

Pyramid of numbers
A pyramid of number shows the number of each organism (of each trophic level of a certain food chain) by the area of the block in the pyramid. E.g a large block is lots of that animal, a little block means few of that animal.

Here is an example of a pyramid of numbers...

Pyramid of biomass

A pyramid of biomass is a bit like a pyramid of numbers, only it represents the dry mass of each consumer (and producer), again, by the area of a pyramid block.


Here is an example of a pyramid of biomass...

Pyramid of energy

A pyramid of energy, again looks like a pyramid of numbers/biomass, but it shows the transfer/flow of energy through the food chain.

Here is an example...

NOTE: The amount of energy transferred decreases by 10% each time, this is important (this is explained in 4.6).

4.6 understand the transfer of substances and of energy along a food chain

Plants use energy from the sun in photosynthesis, this energy makes its way through the food chain as animals eat the plants and each other.

However, not all the energy that's available to the organisms in a trophic level is passed on to the next trophic level, this is because 90% of the energy is lost in various ways. These include...

- Indigestible energy is not taken in in the first place (e.g. fibre), it is just digested out
- Lots of energy is used for the 7 life processes
- Lots of the energy is lost in heat

NOTE: Only around 10% of energy becomes biomass (e.g. it is stored for growth etc). This is transferred onto the next trophic level once the organism is eaten.

4.4 explain the names given to different trophic levels to include producers, primary, secondary and tertiary consumers and decomposers

Producers are the first trophic level because they are at the bottom of the food chain. They turn sunlight into usable energy, in other words, the produce energy.

The second tier are known as the primary consumers, as they are the first consumer in the food chain. They consume the producers.

The third tier are known as secondary consumers as they are the second consumer in the food chain, they consume the primary consumers.

And so on.

NOTE: Eventually all of the above die, they are eaten by decomposers (who break down dead material/waste.