Decomposition Flashcards
(29 cards)
What is decomposition?
-breakdown of dead matter, which is often called rotting
What is the rate of decay?
-speed at which dead matter is broken down by decomposers
How can we estimate the rate of decay?
measure changes in: -pH
-mass
-temperature
What factors affect the rate of decay?
-temperature
-water
-oxygen
-chemicals
How is decomposition useful for an ecosystem?
-dead organisms contain energy that is locked up within organic molecules
-decomposers break these down (by releasing enzymes) making nutrients available for the ecosystem
How does temperature affect the rate of decay?
-at warmer temperatures, enzymes will be more active, so rate of decomposition increases
-at extremely high temperatures, enzymes will be denatured and will stop
How does oxygen affect the rate of decay?
-decomposers need oxygen to survive (so they can respire, enabling them to grow/multiply)
How does water affect the rate of decay?
-decomposers cannot survive without it
-many secrete enzymes onto decaying matter and absorb dissolved molecules
-without water, these reactions cannot occur
How can we preserve food?
-put it in a fridge
-put it in a container with lid
-wrap it in foil
-put salt on it
-pickle it
-use preservatives
How do chemicals affect the rate of decay?
-decomposition requires the absence of chemicals
How do decomposers versus detritivores digest?
decomposers:
-external digestion, release enzymes onto their food and absorb it later
detritivores:
-internally eat
What is compost?
-made of dead matter that are broken down into minerals by decomposers or detritivores
What is manure?
-solid animal waste used as fertiliser
Why do gardeners put dead material on their compost heap?
-so that over time they can be decomposed by bacteria, fungi and detritivores to produce minerals, that the plants can then use to grow
Why is compost used as a natural fertiliser?
-rich in minerals that plants need to grow
Why do some compost bins have holes?
-to allow oxygen in, so that the decomposes work faster
Why do gardeners mix the compost heap regularly?
-to allow more oxygen to pass into the centre
How do we calculate the rate of decay?
change in mass (g)/time (hrs)
Why do gardens put grass cuttings, potato peelings and egg shells in the compost?
-makes nutrient rich compost to return minerals to soil
What are the types of energy that are contained in organic molecules?
-carbohydrates
-protein
-lipid
-DNA/RNA
What do detritivores do?
-feed on waste material and use it for energy and matter
-break up material into pieces, giving a larger surface area for tiny decomposes to work on
temp. 0h24h48h72h
5 6.5 6.4 6.4 6.0
20 6.5 6.1 5.5 4.8
35 6.5 5.1 4.8 4.8
What conclusion can you draw from this data?
-at 5°C the pH of the milk reduced the least
> least decay has occurred at this temperature
-milk incubated at 20°C and 35°C both reduced to pH 4.8
>decay after 72 hours is similar at these temperatures
-but the reduction in pH occurs much quicker at 35°C
-pH reaches its lowest after 48 hours not 72 hours with the 20C milk
>show the decay of milk occurs quickest at 35°C and then stops
Required practical:
What limitations might there be in drawing these conclusions?
-did not take repeat readings to look for concordant results
-they should to this to be more confident in their conclusions (as they will have repeatable results)
Required practical:
How would you modify the procedure described above to find out if skimmed milk decayed less quickly than fresh milk?
-use same quantities of fresh and skimmed milk but keep both samples at 35°C.
-pH of the milk would need to be measured at the start, and after 24 and 48 hours, but not 72 hours
