1. 5.1 Communities and Ecosystems
Outcomes 5.1.6, 5.1.7, 5.1.8

2. 5.1.6 – Define Trophic level Trophic Levels T5 Quaternary consumer T4
An organism’s trophic level refers to its position in a food chain.
Trophic levels classify organisms by their feeding relationships with other organisms in the same ecosystem.
There must be a large number producers and decreasing numbers of each subsequent level.
Trophic Levels T5
Quaternary consumer T4
Tertiary consumer T3
Secondary consumer T2
Primary consumer T1
Producer

3. 5.1.7 – Deduce the trophic level of organisms in a food chain, and a food web
A food chain begins with a producer.
For Example: algae – Mosquito Larva – Dragonfly Larva – Fish – Raccoon
So to determine the trophic level of each organism we begin with the producer, which is the only organism in the chain which photosynthesizes.
Second Trophic Level, which is occupied by the primary consumer, is determined by finding out which organism eats the producers: from the example mosquito larva.
Next levels are occupied by the secondary then tertiary consumers and so on.

4. 5.1.7 – Deduce the trophic level of organisms in a food chain, and a food web (cont.)
Highest trophic level in a food chain is occupied by a top predator ( For example, it would be the raccoon). Other top predators are birds of prey, bears, sharks, or humans.
Some food chains have 6 trophic levels, most however have 4.
Number of levels can be limited by how much energy enters the ecosystem. So since so much is lost at each level, low energy at the start will quickly disperse whereas abundant energy for producers can last for several trophic levels

5. 5.1.7 – Deduce the trophic level of organisms in a food chain, and a food web (cont.)
Food webs are more complex than food chains; therefore, determining trophic levels is more challenging.
Best method is to isolate a single food chain inside the web and analyse it in the same way as above
For Example:
A river food web which includes the food chain: Algae – Mayfly Larva – Juvenile Trout – Kingfisher
From this example we should be able to determine why the juvenile trout, for example, is a secondary consumer ( on the third trophic level)

6. 5.1.8 – Construct a food web containing up to 10 organisms, using appropriate information
Always begin with the producer at the bottom of the diagram.
After this, include all of the primary consumers.
Continue until you reach the top predator.

8. 5.1.8 – Construct a food web containing up to 10 organisms, using appropriate information (cont.)
For example, one could construct a food web from these statements.
Algae is eaten by the mayfly larva
Leaf debris is eaten by the caddis fly larva and blackfly larva.
The mayfly larva and the blackfly larva are eaten by juvenile trout.
The juvenile trout is eaten by the kingfisher
The mayfly larva is also eaten by the sculpin and the stonefly larva, all of which are eaten by adult trout

9. 5.1.8 – Construct a food web containing up to 10 organisms, using appropriate information (cont.)
King Fisher
Juvenile Trout
Sculpin
Adult Trout
Caddis Fly Larva
Blackfly Larva
Mayfly Larva
Stonefly Larva
Leaf Debris
Algae