Page 152 - Big Ideas Year 9 sciPAD 2025

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152 SCIPAD - BIG IDEAS - BOOK 1
LIFE AND THE TAIAO
1. State the type of organisms always found on the bottom of ecological pyramids.

2. State how the consumers in one level of a pyramid obtain energy from the organisms at
the lower level of the pyramid. 

3. Referring to the ‘Pyramid of Numbers’, explain why the large number of producers can
only support a very small number of tertiary consumers. 




4. A grass-eating cow supports a large number of parasitic ticks. These ticks are in turn eaten
by birds.
(a) Write a food chain for this feeding relationship.

(b) Circle the pyramid of numbers that represents this food chain.
1 2 3 4
(c) Justify your answer to (b). 



Ecological Pyramids
Ecological pyramids are models that show the number of organisms (pyramid of numbers), the
mass of organisms (pyramid of biomass), or the amount of energy (pyramid of energy) at each
feeding (trophic) level.
Ecological pyramids begin with producers on the bottom (such as plants) and proceed through
the various trophic levels (i.e. herbivore to carnivore). The highest level is the top of the food chain.
100 %
Producers
10 %
Primary
consumers
1 %
Secondary
consumers
0.1 % Tertiary
consumers
Availble energy decreases
1,000,000
Producers
10,000
Primary
consumers
100
Secondary
consumers
1 Tertiary
consumer
Population size decreases
Pyramid of Energy Pyramid of Numbers
In a pyramid of energy, each level represents the
amount of energy that is available to that level.
With each step up, there is an ~90 % loss in energy.
In a pyramid of numbers, each level represents the
number of individuals consumed by the trophic
level above it.
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