Understanding:
• Most species occupy different trophic levels in multiple food chains
The position an organism occupies within a feeding sequence is known as a trophic level
- Producers always occupy the first trophic level in a feeding sequence
- Primary consumers feed on producers and hence occupy the second trophic level
- Further consumers (e.g. secondary, tertiary, etc.) may occupy subsequent trophic levels
The trophic levels in a community are:
Food Chains
A food chain shows the linear feeding relationships between species in a community
- Arrows represent the transfer of energy and matter as one organism is eaten by another (arrows point in direction of energy flow)
- The first organism in a food chain is always a producer, followed by consumers (primary, secondary, etc.)
- Most species feeding requirements will consist of multiple food chains, with organisms occupying different trophic levels
Understanding:
• A food web shows all the possible food chains in a community
A food web is a diagram that shows how food chains are linked together into more complex interrrelated feeding relationships
A food web is more representative of actual feeding pathways within an ecosystem because:
- Organisms can have more than one food source
- Organisms can have more than one predator
This means that, unlike a food chain, organisms in a food web can occupy more than one trophic level
- Hint: When constructing food webs, position organisms at their highest trophic level (keeps all arrows pointing in same direction)
Example of a Food Web (Pond Ecosystem)
