Pyramids of biomass All learners will be able to: Describe what biomass is and where it comes from. Draw pyramids of biomass to show the relationship between different organisms. Some learners will be able to: Explain what happens to biomass at each stage of the food chain. Keywords: Primary consumer, secondary consumer, producer, herbivore, omnivore, carnivore

Food chains and energy transfer Food chains show the feeding relationships in a habitat. Food chains always start with producers. Producers are almost always green plants. Producers capture light energy from the sun using chlorophyll and use it to produce food. The other organisms in the food chain are consumers. Primary consumers gain energy by eating producers. They are usually herbivores. Secondary consumers gain energy from eating primary consumers. They are usually carnivores but can be omnivores.

Draw food chains for the following organisms. For each chain, identify the producer, primary, secondary, tertiary and quaternary consumers and explain how energy is transferred at each stage of the chain.

Food chains and energy transfer Most food chains have no more than four or five links. Why do you think that is? Energy is lost at each stage of the food chain. There cannot be too many links in a single food chain because the animals at the end of the chain would not get enough energy from the food they were eating. Most organisms are part of many different food chains. To show this we draw a food web. Can you think of examples of food chains for a desert, river or rainforest?

Biological material derived from a living, or recently living organism is called biomass. Ultimately all biomass is built up using energy from the sun. The total biomass at a particular step in a food chain is always less than the total biomass at the step before it. grassvolebarn owl Biomass Greatest biomass here Smallest biomass here Energy lost at each stage of the chain

How many blades of grass does a rabbit eat in a week? How many rabbits would a human eat in a week?

Pyramid of Numbers Secondary Consumer 1 human Primary Consumer 20 rabbits Primary Consumer 20 rabbits Producer blades of grass Producer blades of grass

Pyramid of numbers A pyramid of numbers shows the number of organisms at each stage of the food chain. The wider the bar, the more organisms there are. How could we make this look like a normal pyramid?

Pyramid of biomass A pyramid of biomass shows the relative amount of biomass at each stage of the food chain. Biomass at each stage of the food chain is less than at the previous stage, so the pyramid is always this shape. Why do you think this happens?

Why does biomass change at each stage of the food chain? The biomass at each stage of the food chain changes because: Not all organisms at one stage are eaten by the stage above Some material taken in is passed out as waste Much of the biomass eaten at each stage is used in respiration to release energy. It does not get passed on to the next consumer. These pyramids are usually drawn in proportion.

Create a pyramid of numbers and a pyramid of biomass for the food chain below. Use coloured paper, glue and scissors. Stick the pyramids into your book with a brief explanation underneath, including the advantages and disadvantages of each. Grass  Aphids  ladybirds  Blue tits  owl (5000) (500) (50) (5) (1) Grass  Aphids  ladybirds  Blue tits  owl (50kg) (10kg) (5kg) (2kg) (1kg)