5.1 + 5.2 pyramids of biomass

© Oxford University Press 2011

IB1.19.1 Objectives

5.1 + 5.2 Pyramids of Biomasswhat pyramids of biomass show and how they are useful.WAL:

The outcomes

• Can you describe what a food chain shows?

• Can you explain what relationship food chains and pyramids of biomass show?

• Can you interpret and construct a pyramid of biomass in terms of organism populations?

Starter: Review your understanding of the previous topic.

Starter: Review your understanding of the previous topic.


IB1.19.1 Objectives

What do we get from food?


IB1.19.1 Objectives

What do we get from food?

Energy!


IB1.19.1 ObjectivesEnergy in Food ChainsEnergy is stored in organisms as chemical energy.

When one organism eats another, this energy is passed on.


IB1.19.1 ObjectivesEnergy in Food ChainsNot all of this energy is passed on, however. Some is lost in other ways; Released in respiration to allow

movement and to keep the rabbits body temperature constant.

Only a small amount is used for growth – this is passed onto predators.

A lot of the chemical energy is passed out as

undigested food.


IB1.19.1 ObjectivesEnergy in Food ChainsNormally, there are fewer organisms as you go along

a food chain, because energy is lost at each stage.

10 3 1


IB1.19.1 ObjectivesWhat is a food chain?A food chain is a diagram which shows the flow of energy from one organism to another as they

eat one another.


IB1.19.1 ObjectivesPyramids of NumbersWe can show these stages in a food chain using a pyramid of numbers;

Fox

Rabbits

Lettuces

(Secondary Consumer)

(Primary Consumer)

(Producer)

Each level on a pyramid of numbers is called a trophic level.


IB1.19.1 ObjectivesPyramids of NumbersPyramids of numbers do not always look like pyramids, however. For example, one rose bush can feed many aphids;

Ladybirds

Aphids

Rose bush

(Primary Consumer)

(Producer)



IB1.19.1 ObjectivesPyramids of NumbersPyramids of numbers do not always look like pyramids, however. For example, one rose bush can feed many aphids;

Ladybirds

Aphids

Rose bush

(Primary Consumer)

(Producer)


What would be a better way of showing the flow of energy?


IB1.19.1 ObjectivesPyramids of BiomassPyramids of numbers do not take into account the size of the organisms. A better way of showing the transfer of energy is to use a pyramid of biomass.

This shows the mass of each organism at each trophic level.

Bigger organisms = more energy


IB1.19.1 ObjectivesPyramids of BiomassA sample of organisms is taken and they are dried out before they are weighed.

How wet or dry the weather is can affect the mass of the organisms, so their dry weight is taken to ensure that the measurements of biomass are accurate.

Ladybirds 5g

Aphids 10g

Rose bush 1000g

(Primary Consumer)

(Producer)



IB1.19.1 ObjectivesPyramids of BiomassPyramids of numbers do not take into account the size of the organisms. A better way of showing the transfer of energy is to use a pyramid of biomass.

This shows the mass of each organism at each trophic level.

Ladybirds 5g

Aphids 10g

Rose bush 1000g

(Primary Consumer)

(Producer)



IB1.19.1 ObjectivesHow to construct a pyramid of biomassConstruct a pyramid of biomass for the following food chain. Use the graph paper below where 1 small square will represent 100kg:

Grass Rabbit Fox

50,000 1,200 5000.1kg 3kg 5kg



Grass Rabbit Fox

50,000 1,200 5000.1kg 3kg 5kg5000kg 3,600kg 2,500kg



Grass Rabbit Fox5000kg 3,600kg 2,500kg100 100 100

50 squares 36 squares 25 squares

Grass

Rabbits

Foxes

5.1 + 5.2 pyramids of biomass

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