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  1. Science
  2. Year 9
  3. Extend Your Learning
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Microorganisms and Decay

This worksheet helps the student to explore the surprising world of microbes and how they are so important in the natural decay and rotting of dead things.

'Microorganisms and Decay' worksheet

Key stage:  KS 3

Curriculum topic:  Extend Your Learning

Curriculum subtopic:  Interesting Topics from the Old Curriculum

Difficulty level:  

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Worksheet Overview

QUESTION 1 of 10

You might expect that microbes are all bad - but in fact they're not; amazingly, there are more 'good' types of microorganisms than 'bad' ones ('bad' ones are microbes that harm us).  

One way in which different sorts of microbes are amazingly helpful is in the decay and decomposition (rotting) of things that have died, like a branch from a tree.

Basically, these microbes are nature's RECYCLERS, turning what was simply the remains of a living organism back into substances that can be used again and again. They're brilliant!

What do the billions of microorganisms in a pile of dead leaves feed on?

mud

leaves

water

What do the microorganisms in the pile of dead leaves break the leaves down into?

nutrients

oxygen

light

The process in which the microorganisms break down the pile of dead leaves is better known as what?

destruction

decomposition

fertilisation

Which TWO of the following are microorganisms which are found at work in a compost heap, helping to turn the dead plant material into soil?

viruses

bacteria

woodlice

fungi

Which of the following is NOT caused by bacteria?

tooth decay

mould on bread

turning milk into yoghurt

Why does brushing your teeth regularly help to prevent tooth decay?

brushing helps to remove the bad bacteria in our mouths

brushing helps to make our teeth shiny, helping them to resist bacteria

the toothpaste helps to make our teeth white

Here is a list of items - which ones do you think can be broken down by microorganisms in less than a year?

dead bird

grass cuttings

disposable nappy

newspaper

dead leaves

banana skin

plastic bottle

tea bag

Here is a list of items and also a list of different ways you might dispose of them. Try to match the item to the best way of disposing of it in an environmentally friendly a way as possible.

Column A

Column B

newspaper
use again
drinks can
compost heap
children's books
compost heap
dead flowers
charity shop
uneaten meat scraps
recycling centre
plastic supermarket bag
throw in the bin
old clothes, good condition
recycling centre
potato peelings
charity shop
jam jar
recycling centre
old batteries
recycling centre

Nowadays, we are trying to make plastics that don't take hundreds of years to break down. These new plastics are damaged by exposure to light and usually decompose within 6 months or so. See if you can pick out the name of these sorts of plastics:

biodegradable

biological

bionic

Imagine that in a wood all the microorganisms that cause natural decay (rotting) where killed by a chemical spray. What do you think might happen as a result?

dead leaves and branches would become knee-deep

all the animals would leave the wood

plants would not die

  • ANSWERS
  • Question 1

What do the billions of microorganisms in a pile of dead leaves feed on?

CORRECT ANSWER
leaves
EDDIE SAYS
The dead leaves themselves are the microbes' food: they consume them (just like you consume a doughnut!) and recycle the leaves into simple chemicals that plants can use again.
  • ANSWERS
  • Question 2

What do the microorganisms in the pile of dead leaves break the leaves down into?

CORRECT ANSWER
nutrients
EDDIE SAYS
What was once dead leaf becomes important nutrients for living plants - that's recycling!
  • ANSWERS
  • Question 3

The process in which the microorganisms break down the pile of dead leaves is better known as what?

CORRECT ANSWER
decomposition
EDDIE SAYS
Decomposition is the proper term for when micro-organisms change dead organisms back into the chemicals they are made of.
  • ANSWERS
  • Question 4

Which TWO of the following are microorganisms which are found at work in a compost heap, helping to turn the dead plant material into soil?

CORRECT ANSWER
bacteria
fungi
EDDIE SAYS
Bacteria and fungi (moulds) are microbes that are hard at work inside the compost heap, consuming all those leaves, twigs and so on and recycling them for re-use by living plants so that they get back into the food chain.
  • ANSWERS
  • Question 5

Which of the following is NOT caused by bacteria?

CORRECT ANSWER
mould on bread
EDDIE SAYS
Mould is a type of fungus and so is not a type of bacteria.
  • ANSWERS
  • Question 6

Why does brushing your teeth regularly help to prevent tooth decay?

CORRECT ANSWER
brushing helps to remove the bad bacteria in our mouths
EDDIE SAYS
There are billions of bacteria on your teeth and over time they can damage your teeth and gums, so it is important to brush your teeth at least twice a day to remove the build-up of bacteria and protect your teeth.
  • ANSWERS
  • Question 7

Here is a list of items - which ones do you think can be broken down by microorganisms in less than a year?

CORRECT ANSWER
dead bird
grass cuttings
newspaper
dead leaves
banana skin
tea bag
EDDIE SAYS
Interestingly, micro-organisms are so efficient at decomposing dead organisms and reproduce so rapidly that most things in the list won't last a year. In fact a disposable nappy or a plastic bottle takes 400-500 years to break down!
  • ANSWERS
  • Question 8

Here is a list of items and also a list of different ways you might dispose of them. Try to match the item to the best way of disposing of it in an environmentally friendly a way as possible.

CORRECT ANSWER

Column A

Column B

newspaper
recycling centre
drinks can
recycling centre
children's books
charity shop
dead flowers
compost heap
uneaten meat scraps
throw in the bin
plastic supermarket bag
use again
old clothes, good condition
charity shop
potato peelings
compost heap
jam jar
recycling centre
old batteries
recycling centre
EDDIE SAYS
As you can see, many things you may generally throw away can be recycled. To be honest there are several in this list with more than one possibility, so give yourself a pat on the back if, for example, you said 'use again' to a jam jar - of course you can put homemade jam in it or use it as a pencil pot on your desk!
  • ANSWERS
  • Question 9

Nowadays, we are trying to make plastics that don't take hundreds of years to break down. These new plastics are damaged by exposure to light and usually decompose within 6 months or so. See if you can pick out the name of these sorts of plastics:

CORRECT ANSWER
biodegradable
EDDIE SAYS
BIODEGRADABLE means 'breaking down naturally', so man-made substances, like plastics, can be manufactured to degrade (break down) naturally in a much shorter time.
  • ANSWERS
  • Question 10

Imagine that in a wood all the microorganisms that cause natural decay (rotting) where killed by a chemical spray. What do you think might happen as a result?

CORRECT ANSWER
dead leaves and branches would become knee-deep
EDDIE SAYS
It's unthinkable! Imagine the dustmen went on strike - the bins wouldn't be emptied, rubbish would pile up on our streets. In the wood the leaves, twigs, dead mice, dead beetles, etc. would stay just like that, not breaking down - eventually the piles would just cover the ground everywhere!
---- OR ----

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