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Decay Processes

AQA GCSE Biology - B1.6.1

Peter Fearon

on 3 October 2013

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Transcript of Decay Processes

Key Points
Living organisms remove materials from the environment as they grow. They return them when they die through the action of decomposers.
Dead materials decay because they are broken down (digested) by microorganisms.
Decomposers work more quickly in warm, moist conditions. Many of them also need a good supply of oxygen.
The decay process releases substances which plants need to grow.
In a stable community the processes that remove materials (particularly plant growth) are balanced by the processes that return the materials.
Key Terms
detritus feeders
There is a finite number
of atoms on the planet.
These atoms are constantly being recycled as part of different cycles and processes eg. Carbon and Nitrogen cycle.
In order for these minerals to be recycled, there needs to be an organism that can break down dead organic matter (dead bodies of animals and plants) into its component minerals.
Decomposers do this job - they break down dead organic matter and return the minerals to the environment to be used by other organisms.
The decomposers are a group of microorganisms that include bacteria and fungi. They feed on waste droppings and dead organisms.
Maggots and worms are detritus feeders
Detritus feeders start the process of decomposition - they eat dead animals and produce waste material.
Bacteria & Fungi
Bacteria and fungi then digest everything - dead animals, plants and detritus feeders plus their waste.
They use some of the nutrients to grow and reproduce.
They also release waste products.
waste products
of decomposers
carbon dioxide
process of

fertile soil allowing
plants to grow

Conditions for
The rate of decay depends partly on temperature.
The chemical reactions that happen in decomposers are like those in most other living things, they work better in warmer conditions.
They slow down and even stop if the conditions are too cold.
However, as the chemical reactions are controlled by enzyme activity, if the temperature gets too hot, the enzymes will denature and the reactions will stop.
Most microorganisms also grow better in moist conditions - the moisture makes it easier to dissolve food and stops the food from drying out.
Therefore, the decomposition of organic matter happens much quicker in warm, moist conditions as opposed to cold, dry conditions.
Some microbes work without oxygen, but most decomposers respire like any other organism.
This means that they need to release energy to grow and reproduce.
This is why decay requires a ready supply of oxygen.
The hypothesis makes a prediction only.
The method does not follow a step-by-step guide. Steps are not justified in scientific knowledge.
Variables are unclear.

The hypothesis contains some science to back up prediction.
The method is step-by-step.
steps are justified with science. Some variables unclear.

The hypothesis uses scientific knowledge and terms to support prediction.
The method is step-by-step. The
variables are clearly identified.
control variables are identified.

The hypothesis uses scientific knowledge and terms to support the prediction.
The method is step-by-step with
variables clearly identified. Controls are explained and their consequences justified.
Peer assess our investigation plans
Using the mark scheme
To improve our investigation skills
[Self Manager]
Full transcript