LEARNING OUTCOMES
By the end of this week, you should:
 Be able to describe the ways in which energy
flows through ecosystems.
 Recognise that matter cycles within
ecosystems.
 Understand the key roles of producers and
decomposers in ecosystems.
 Become aware of trophic levels.
 Give examples of biochemical cycles.
1. Producer
1. Discuss a definition
for these 8 words
with the person next
to you.
2. Check your
understanding by
choosing the correct
definition from the
next slide.
2. Consumer
3. Herbivore
4. Detritivore
5. Carnivore
6. Food chain
7. Food web
8. Sun








I make my own food using sunlight and raw
materials.
I obtain my food by eating other living
organisms.
I only eat plant material.
I obtain my food only from animals.
I eat dead plant or animal material.
I am a simple diagram showing the flow of
energy as one organism eats another.
I am a more complicated (and more realistic)
version of this diagram.
I am the original source of energy for all living
things.
Producers
 Primary consumers
 Secondary consumers
 Tertiary consumers
 Trophic level

1
Energy can exist in many forms.
 All ecosystems
require an energy source.
2
 The energy input into ecosystems is
typically the radiant energy of sunlight.
3
 Energy flows through an ecosystem and
must be continually
supplied.
4
 Energy is captured and brought into an
ecosystem by producers.
5

Producers transform radiant energy to
6
7
7
chemical
energy in organic
matter.
 Organisms in an ecosystem can be
classified into different trophic
levels.
8

Complete Quick-check questions on
page 446 – Nature of Biology
1. How do we lose energy to the
environment?
2. What is the effect of
maintaining a constant body
temperature?






1
Not all organisms at one stage are eaten
by
the stage above.
Some energy is used for respiration
(to
2
maintain body heat).
3 and for
Some energy is used to make heat
movement
(muscle contraction).
4
5
Some energy is used to produce biomolecules
and cells.
Some energy is used to transmit nervous
6
impulses.
6
7
Some material is passed as waste.
The rule of thumb: the useful chemical
energy leaving one trophic level is
typically only 10% of the energy entering
that level.

The amounts of ……………… and ………………
contained in living things always gets less at
each stage of a ……………… from ………………
onwards. Biomass is lost as ……………… products
and used to produce ……………… in ……………… .
This is used for ……………… and to control
……………… . Only a small amount is used for
……………… .
waste
body temperature
respiration
food chain
growth
biomass
energy
energy
plants
movement

The amounts of biomass and energy
contained in living things always gets less
at each stage of a food chain from plants
onwards. Biomass is lost as waste products
and used to produce energy in respiration.
This is used for movement and to control
body temperature. Only a small amount is
used for growth.
Food Chains and Webs
1. Where does the
energy originate
from?
2. What happens to
this energy as you
go through the
food chain?
3. What do the
arrows represent?
4. Where is energy
lost?
Complete the
Quick-check
questions –
page 452
Numbers, Biomass, Energy
The population of each organism in a food
chain can be shown in a sort of bar chart
called a pyramid of numbers.
 The more organisms there are, the wider the
bar.
 The producer in the food chain always goes
at the bottom of the pyramid of numbers.


Think about this food chain:
clover
snail
thrush
hawk
› Clover is a plant and it is the producer in this
food chain. Its bar goes at the bottom of the
pyramid:

Energy is lost to the surroundings as we go from one
level to the next, so there are fewer organisms at
each level in this food chain.
› A lot of clover is needed to support the snail population.
› A thrush eats lots of snails, and a hawk eats lots of
thrushes, so the population of hawks is very small.
Sometimes the pyramid of numbers doesn't look like
a pyramid at all.
 This could happen if the producer is a large plant
such as a tree, or if one of the animals is very small.
 Still, whatever the situation, the producer always
goes at the bottom of the pyramid.


For example:
1)
An oak tree is very large so many insects can feed on it.
2)
Fleas are very small and lots of them can feed on a rabbit.



Biomass is the mass
of living material in
an animal or plant.
Biomass is made by
plants from sunlight
energy.
It is often
measured as the dry
mass of biological
material in grams.


Biomass decreases as a
food chain progresses
(at each trophic level).
A pyramid of biomass
gives a rough idea of
the amount of biomass
passed on at each
stage.
Shows the amount of
energy input at each
trophic level in a given
area of an ecosystem
over an extended
period of time (usually
one year).
 The flow of energy is
always reduced from
one trophic level to
the next, so a pyramid
of energy is never
inverted.

stinging nettles  caterpillars robin
Number
Biomass
marine plants  small fish  large fish  seals  polar bear
Number
Biomass
1. Complete Quick-check questions page 454
2. Complete the worksheet
The Carbon Cycle

How did the carbon get into this piece of coal?
What would happen if we burnt it?
Photosynthesis
 Respiration
 Decomposition
 Detritus
 Producers
 Consumers
 Excretion







All the time, a relatively small amount of available
carbon is cycled between living things and their
environment.
1
All of the main molecules that make up our bodies
(carbohydrates,
fats,
and DNA)
are based
2
3 proteins
4
5
on carbon atoms combined with other elements.
The amount of carbon on Earth is fixed.
Some is
6
found in fossil
7 fuels
7 and is only released when they
are burnt.
Limestone and chalk contain huge amounts of carbon.
8 2 in air.
Found in CO
9
Also dissolved in water.
The Nitrogen Cycle
Nitrogen-fixation
 Nitrification
 Denitrification
 Decomposition

The Water Cycle
Precipitation
 Evaporation
 Transpiration
 Percolation
 Ground water
 Return flow
 Surface run-off

(Biomagnification)
Chemical enters
ecosystem and into food
chain.
2. If not readily broken
down by organisms (ie. it
is a persistent
chemical), it accumulates
in their tissues.
3. It becomes
progressively
concentrated as it
enters organisms at
higher trophic levels.
1.
Complete the Quick-check
questions on page 467
Complete the poster
task on biochemical
cycles
True
False – combustion releases
carbon dioxide gas
False – more is found in
marine organisms and
limestone rock deposits
True
False – both animals and
plants respire
False – they respire and
release carbon dioxide
True
False – scientists think it will
cause global warming
True
True