It’s a green world

1. It’s a green world Decay Part 1

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3. Decay Learning objectives Success criteria • Understand what causes decay and why decay is useful. • What conditions speed up decay. • Explain the role of detritivores and saprophytes 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

4. 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.

5. B4g1 -Decay by decomposers Look at the experiment and answer the questions.

6. 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

7. 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.

8. 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.

9. 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.

10. 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

11. What is a saprophyte? A saprophyteis 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?

12. 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

13. PlenaryWhat 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

14. Decay Learning objectives Success criteria • Understand what causes decay and why decay is useful. • What conditions speed up decay. • Explain the role of detritivores and saprophytes 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