2. 5.1 Communities and
Ecosystems
5.1.4: Describe what is meant by a
food chain giving three examples,
each with at least three linkages
(four organisms).
• A food chain is a sequence of
relationships between trophic levels
where each member feeds on the
previous one.
3. 5.1 Communities and
Ecosystems
5.1.5: Describe what is meant by a
food web.
• A food web is a a diagram that
shows the feeding relationships in a
community. The arrows indicate the
direction of energy flow.
4. 5.1 Communities and
Ecosystems
5.1.6: Define trophic level.
• A trophic level is where an organism
is positioned on a food web.
– Producer
– Primary consumer
– Secondary consumer
– Tertiary consumer
5. 5.1 Communities and
Ecosystems
5.1.9: State that light is the initial
energy source for almost all
communities.
• Reference to communities that start
with chemical energy is not required.
Such as deep sea ocean vents.
6. 5.1 Communities and
Ecosystems
5.1.10: Explain the energy flow in a
food chain.
• Energy losses between trophic levels
include material not consumed or
material not assimilated, and heat
loss through cell respiration.
7. 5.1 Communities and
Ecosystems
5.1.11: State that when energy
transformations take place, including
those in living organisms, the
process is never 100% efficient,
commonly being 10–20%.
8. 5.1 Communities and
Ecosystems
5.1.12: Explain what is meant by a
pyramid of energy and the reasons
for its shape.
• A pyramid of energy shows the flow
of energy from one trophic level to
the next in a community. The units
of pyramids of energy are therefore
energy per unit area per unit time,
e.g. J/m2/yr.
11. 5.1 Communities and
Ecosystems
5.1.13: Explain that energy can enter
and leave an ecosystem, but that
nutrients must be recycled.
• Energy enters as light and usually
leaves as heat.
• Nutrients do not usually enter an
ecosystem and must be used again
and again. Nutrients such as Carbon
dioxide, Nitrogen, and Phosphorus
12.
13. 5.1 Communities and
Ecosystems
5.1.14: Explain the role of
saprotrophic bacteria and fungi
(decomposers) in recycling nutrients.
• The digestive enzymes secreted by
saprophytes breaks down the organic
molecules in dead material releasing
the nutrients that were ‘locked up’
