Starter Activity: On a show me board answer these

questions:

1. What does a food chain always start with?

2. What does the arrow in a food chain represent?

3. How much energy is passed on to the next level in a food chain?

4. Give an example of how energy is lost at each stage in a food chain.

Pyramids of biomass, energy

and number.

Learning Intention: Show the biomass, energy and numbers of organisms within a food chain as a diagram.

Success Criteria: •Define ‘Pyramid of biomass’ and construct one from data about a food chain.•Define ‘Pyramid of energy’ and construct one from data about a food chain.•Define ‘Pyramid of number’ and construct one from data about a food chain.

Why aren’t food chains very long?

This tiger is a top predator; the final level in a food chain.

Energy is lost at all levels in food chains.

Animals at the top of a long food chain would not get enough energy to survive.

Most food chains only contain four or five species, why is this?

Food chains and pyramidsWhat can pyramids show about energy transfer?

Pyramids of numbers only give an accurate impression of the flow of energy in a food chain if the organisms are of similar size. Measuring the biomass at each trophic level can give a more accurate picture.

Pyramids of numbers are a way of representing food chains.

What are the problems of representing food chains in pyramids of numbers?

They record the number of organisms at each feeding level in a specified area.

What are pyramids of numbers?

In a pyramid of numbers, the length of each bar represents the number of organisms at each feeding level in a specified area.

As a single tree can support many organisms, this food chain produces an irregular pyramid.

Understanding pyramids of numbersnumbers

Understanding pyramids of biomassbiomassIn a pyramid of biomass, the length of each bar represents the

volume of organic matter – biomass – at each feeding level in a specified area.

At each trophic level, the volume of biomass and energy available is reduced, giving a pyramid shape. The units of measurement is g/m².

Understanding pyramids of energyenergyIn a pyramid of energy, the length of each bar represents the volume of energy available– at each feeding level in a specified area.

At each trophic level, the volume of biomass and energy available is reduced, giving a pyramid shape. The units of measurement is KJ/m²/year.

Irregular PyramidsThere are some exceptions to the classis pyramid shape. These pyramids are said to be irregular. Some food chains have a single large producer e.g. a tree. Another exception is when a parasite is the top carnivore in the food chain:

Fleas

Fox

Rabbit

Lettuce

Draw and label the irregular pyramid of numbers for this food chain:

Oak tree greenfly ladybird blue tit

Irregular pyramid of numbers with a parasite.

Pyramids Task

Draw and label each type of pyramid for each food chain:

1.Oak tree Caterpillar Blackbird Fox2.Green algae Water flea Tadpole Trout3.Grass Aphid Ladybird Robin4. Lettuce Vole Fox Fleas

Pyramids of biomass, energy

and number.

Learning Intention: Show the biomass, energy and numbers of organisms within a food chain as a diagram.

Success Criteria: •Define ‘Pyramid of biomass’ and construct one from data about a food chain.•Define ‘Pyramid of energy’ and construct one from data about a food chain.•Define ‘Pyramid of number’ and construct one from data about a food chain.