Trophic levels Determines the pathways of energy flow and nutrient cycling (more on this later) Different species in the ecosystem are divided into different trophic levels depending on what they eat There are 5 main levels

Trophic levels Level 1 – Producers The bases of food chains Get their energy from the sun E.g. Plants Level 2 – Primary Consumers Herbivores Eat a range of plant material

Trophic level Level 3 – Secondary Consumers Organisms that eat Primary consumers (Herbivores) Level 4 – Tertiary Consumers Eat Secondary consumers Level 5 – Quaternary Consumers Eat Tertiary consumers

Food chains Sequence of organisms, each of which is a source of food for the next. Always begins with a producer Animals with the same number of links to other organisms are on the same trophic level PlantCaterpillarBirdCat

Food chains/food webs In real life a particular herbivore may eat more than one type of plant or a carnivore may eat lots of different herbivores Hence a more accurate way of showing trophic levels is by using a food web CatLizardSnailWormBirdCaterpiller Plants

Pyramids Another way of representing a food chain 1.Pyramid of numbers 2.Pyramid of biomass

1.Pyramid of numbers Number of each type of organism at each trophic level Not always accurate as does not take the size of organism at each level into account – E.g. One large tree could support thousands of caterpillars.

Pyramid of numbers 1,000 Flax bushes 30,000 Caterpillars 500 Birds 10 Cats

2. Pyramid of Biomass More accurate method The weight of living matter at each level is measured Most accurate to use the DRY matter weight

Pyramid of Biomass 1,000 tons of seaweed 1 ton trout 300 tons shrimp 500 kg Humans

Ways in which food chains and webs can be affected. 1.Removing one part of the food chain 2.Biological magnification 3.Introducing an exotic species 4.Removal of too much of an organism

Ways in which food chains and webs can be affected. Removing one part of the food chain – Happens through over farming, fishing and cutting down of native forest. – If you remove too much of the producer, then the rest of the food chain suffers

Ways in which food chains and webs can be affected. Biological magnification – Concentrations of poison (e.g. mercury, DDT) increase as it moves up the food chain or up the pyramid – Top predator gets the highest concentrations

Ways in which food chains and webs can be affected. Introducing an exotic species – Rabbits – Possums – Deer

Ways in which food chains and webs can be affected. Removal of too much of an organism – Can make an ecosystem unsustainable – E.g. Over fishing – not enough older fish for reproduction – E.g. Over farming – Nutrients are not returned to the soil therefore it becomes useless