Decay
Part 1
Starter
On Ilkley Moor bah tat
Wheear 'as ta bin sin ah saw thee,
On Ilkla Moor baht 'at?!
Wheear 'as ta bin sin ah saw thee?
Wheear 'as ta bin sin ah saw thee?
On Ilkla Moor baht 'at?!
On Ilkla Moor baht 'at?!
On Ilkla Moor baht 'at?!
Then t'worms 'll cum and eat thee oop
On Ilkla Moor baht 'at
Then t'worms 'll cum and eat thee oop
Then t'worms 'll cum and eat thee oop
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Tha's been a cooartin' Mary Jane
On Ilkla Moor baht 'at
Tha's been a cooartin' Mary Jane
Tha's been a cooartin' Mary Jane
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Then ducks 'll cum and eat oop t'worms
On Ilkla Moor baht 'at
Then ducks 'll cum and eat oop t'worms
Then ducks 'll cum and eat oop t'worms
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Tha's bahn t'catch thi deeath o'cowd
On Ilkla Moor baht 'at
Tha's bahn t'catch thi deeath o'cowd
Tha's bahn t'catch thi deeath o'cowd
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Then we shall ha' to bury thee
On Ilkla Moor baht 'at
Then we shall ha' to bury thee
Then we shall ha' to bury thee
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Then we shall go an' ate oop ducks
On Ilkla Moor baht 'at
Then we shall go an' ate oop ducks
Then we shall go an' ate oop ducks
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
Then we shall all 'ave etten thee
On Ilkla Moor baht 'at
Then we shall all 'ave etten thee
Then we shall all 'ave etten thee
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
On Ilkla Moor baht 'at
What does all this mean?
Decay
Learning objectives
 Understand what causes
decay and why decay is
useful.
 What conditions speed
up decay.
 Explain the role of
detritivores and
saprophytes
Success criteria
Students should be able to:
 State the key factors in
the process of decay.
 State the optimum
conditions for making
compost
 Understand the role of
detritivores and
saprophytes
What is decay?
In all ecosystems, dead organisms and waste material are
broken down by bacteria and fungi called decomposers.
This process is decay or decomposition, and it releases
nutrients back into the environment ready to be reused by
other organisms.
Some food chains have decaying matter as the first stage.
Under what conditions will decay occur the fastest?
A warm, moist, oxygen-rich environment is the most
favourable for decay to occur.
B4g1 -Decay by decomposers
Look at the experiment and answer the questions.
B4g1 -Decay by decomposers
1. The heated soil will be drier, lighter, have no living things
2. Flask A: limewater turns white/milky
 Flask B: limewater is unchanged or only very slightly
white/milky
3. The fresh soil must have contained living organisms that
produced carbon dioxide from respiration; the limewater in
Flask B would be reacting to the small amount of carbon
dioxide in the air
4. Very little carbon dioxide would be produced from dry or
cold soil, so these conditions slow down decay
5. Shaun should keep his compost bin in a warm place, not let
it dry out and keep mixing up the contents
What is a detritivore?
Detritus is dead and decaying matter,
such as dead leaves.
A detritivore is an organism that
feeds on detritus. The detritus
may already be partially
decomposed by fungi or bacteria.
Earthworms, maggots and
woodlice are detritivores.
Detritivores
 Detritivores speed up the rate of
decay by breaking down the
detritus are creating a larger
surface area for other
microorganisms to work.
 By gaining minerals from the
decaying matter, detritivores
reintroduce essential nutrients
back into food chains.
Compost
What speeds up decay?
Warm temperatures, good supply of water and
oxygen.
Microorganisms living
in the compost respire
and heat is produced
which warms up the
compost, which
speeds up decay.
Aerobic and anaerobic bacteria
Aerobic bacteria break down ________quickly,
they need a good supply of _______.
Anaerobic bacteria grow in a ____ of oxygen,
they produce ____ conditions that ____ down
decay
lack
detritus
slow
acid
oxygen
What is a saprophyte?
A saprophyte is an organism that gains nutrients from dead
organic matter. This is usually the first stage of decay.
Saprophytes produce
enzymes that break
down dead matter. They
can then absorb the
released nutrients.
Bacteria and fungi feed
saprotrophically. What
would happen if they
didn’t exist?
Speeding up compost production
Answer questions 9 – 11 in the textbook p81
9. Aerobic bacteria will release heat during
respiration.
10. To encourage aerobic bacteria and anaerobic
bacteria forming silage.
11. To keep moisture and oxygen out so it does
not decay
Plenary
What are the ideal conditions for
making compost?
Conditions that speed up the decay process are:
 Warmth, such as placing the compost bin in
the sun
 Moisture
 Good aeration, such as regular mixing of the
contents to allow oxygen in
Decay
Learning objectives
 Understand what causes
decay and why decay is
useful.
 What conditions speed
up decay.
 Explain the role of
detritivores and
saprophytes
Success criteria
Students should be able to:
 State the key factors in
the process of decay.
 State the optimum
conditions for making
compost
 Understand the role of
detritivores and
saprophytes