Water cycle, Decomposition

Question 1

Describe the stages of the water cycle

how water is cycled around ecosystems

Answer 1

Almost all of the water on Earth is found in the oceans, and this is salt water

Energy from the sun causes the water to evaporate from the surface of the sea. (water also evaporates from plants)
Plants take up water in their roots
This water moves up the plant in the xylem and passes out of the leaves through the stomata as water vapour
This process is called transpiration

The warm water vapour now travels into the air (is carried upwards) and cools down

When it cools, the water vapour condenses to form clouds

The water in clouds then falls to the ground as precipitation. Precipitation includes rain, snow, hail and sleet.

All forms of precipitation contain fresh water. This water does not contain salt

Once the water hits the ground, some of it evaporates back into the atmosphere as water vapour. Some of the water passes through rocks and forms aquifers.
And a lot of the water forms rivers or streams
The water in rivers and streams eventually drains back into the sea
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Living organisms also play a role in the water cycle
Plants take up water in their roots
This water moves up the plant in the xylem and passes out of the leaves through the stomata as water vapour
This process is called transpiration

Animals take in water through drinking and in their food
Animals release water in their urine, in their faeces and when they exhale

Question 2

importance of water

Answer 2

water major constituent of all living cells,
chemical reactions of life (photosynthesis and respiration)
take place in solution in water,
water needed by plants for support

Question 3

Importance of water cycle

Answer 3

The water cycle provides fresh water for plants and animals on land
before draining into the seas.

Water is continuously evaporated and
precipitated.

Question 4

in terms of a stable community how is the minerals taken out of the soil and minerals put back in related - carbon cycle

Answer 4

In a stable community, the materials that are taken out of the soil and used by plants are balanced by those that are put back in.(materials that they need to grow) There is a constant cycle happening

Question 5

Describe the conditions required for decomposition (decay)

Answer 5

Temperature
Amount of water
Amount of oxygen

Question 6

Describe the optimal conditions for decompositions (the conditions that make decomposition take place most rapidly)

Answer 6

Warm temperature
Moist environment
Good amount of oxygen

Question 7

Describe how temperature affects the rate of decay of biological material

Answer 7

Decomposition takes place faster at warmer temperatures
That is because the decomposers use enzymes to break down the plant materials, and these enzymes work at a faster rate in warm conditions

It is important that the compost does not get too hot/temperatures do not get too hot.
If that happens then the enzymes in decomposers can denature and the decomposers can die (decomposition slows down or stops because enzymes are destroyed and organisms die)

Really cold temperatures slow the rate of decomposition too. Enzymes in the decomposers do not work at a fast enough rate/work too slowly

Question 8

Explains why compost heaps (areas where decay occurs) tend to be quite warm

Answer 8

This is because decomposers release energy when they carry out aerobic respiration

Question 9

Explain why it is important that the compost (areas/sites where decay occur) does not get too hot

Answer 9

It is important that the compost does not get too hot
If that happens then the enzymes in decomposers can denature and the decomposers can die

(decomposition slows down or stops because enzymes are destroyed and organisms die)

Question 10

Explain how the rate of decay is affected in cold temperatures

Answer 10

Really cold temperatures slow the rate of decomposition too. Enzymes in the decomposers do not work at a fast enough rate/work too slowly

Question 11

Describe how the amount of water affects the rate of decay of biological material

Answer 11

Decomposing microorganisms work faster if the compost is moist (In moist conditions/environments)
That is because many of the chemical reactions in decay require water.
(because organisms need water to carry out biological processes)

So it important that gardeners do not allow a compost heap to dry out

Question 12

Why is it important that gardeners do not allow a compost heap to dry out

Answer 12

Decomposing microorganisms work faster if the compost is moist (In moist conditions/environments)
That is because many of the chemical reactions in decay require water.

So, if gardeners allow the compost heap to dry out, then rate of decay slows down

Question 13

Describe how the amount of oxygen affects the rate of decay of biological material

Answer 13

Decomposers carry out aerobic respiration and this requires a good supply of oxygen

(probably increases rate of decay)

Question 14

Explain why some compost bins have holes in the walls

Answer 14

This compost bin has holes in the walls to allow oxygen to enter
decomposers need a good supply of o2
Decomposers carry out aerobic respiration and this requires a good supply of oxygen

increase rate of decay

Question 15

Explain why many gardeners use a gardening fork to mix their compost regularly

Answer 15

Many gardeners use a gardening fork to mix their compost regularly allowing more oxygen to pass into the centre

decomposers need a good supply of o2
Decomposers carry out aerobic respiration and this requires a good supply of oxygen

increase rate of decay

Question 16

Explain the effect of mixing compost

Answer 16

Many gardeners use a gardening fork to mix their compost regularly allowing more oxygen to pass into the centre

decomposers need a good supply of o2
Decomposers carry out aerobic respiration and this requires a good supply of oxygen
- this increase rate of decay

Mixing the compost also breaks up large clumps and it increases the surface area for decomposers to act on.

Question 17

In a compost heap, what do decomposing microorganisms carry out

Answer 17

In a compost heap, decomposing microorganisms carry out aerobic respiration

Question 18

How do the decomposing microorganisms respond if there is no oxygen

Answer 18

In the absence of oxygen, the decomposing microorganisms carry out anaerobic decay

Question 19

What does anaerobic decay produce

Answer 19

Anaerobic decay produces methane gas

Anaerobic decay produces a mixture of gases including methane. This is called biogas

(green house gas -\ which contribute towards global warming)

Question 20

What are biogas generators used for

Answer 20

Biogas generators can be
used to produce methane gas as a fuel.

in many parts of the world, small-scale biogas generators are used to provide fuel for homes
these often use plant materials such as food waste or animal manure

Question 21

garden and kitchen waste added to a compost bin rot down and become compost much more rapidly in summer than in winte

Answer 21

Rate of chemical reactions in microorganisms acting as decomposers
speeds up with increase in temperature.
Average temperatures much warmer in summer than in winter,
so rate of decomposition increases

Question 22

when do decomposers produce biogas

Answer 22

Decomposers produce biogas under anaerobic conditions

Question 23

Describe why the processes of decay are so important in keeping the soil fertile

Answer 23

Plants remove minerals from the soil constantly.

When animals eat plants these minerals are passed on through food chains and webs.

If minerals were never returned to soil, soil would soon be infertile.

Decay enables minerals that have become part of bodies of living organisms to be recycled and returned to environment.

Question 24

what is decomposition

Answer 24

Decomposition
is the breakdown of dead matter,

Question 25

what is anaerobic decay

Answer 25

Anaerobic decay occurs when bacteria and fungi break down dead matter without oxygen

Question 26

turning over the contents of a compost bin every so often can increase the rate at which decomposition takes place. explain why

Answer 26

Many microorganisms involved in decomposition need oxygen for
aerobic respiration.
Turning over compost bin contents increases air in mixture.
Turning compost bin contents increases rate of decomposition as
microorganisms have plenty of oxygen for aerobic respiration.

Question 27

during a particularly hot, dry summer compost formation may slow down. suggest a possible explanation for this

Answer 27

Moisture makes it easier for microorganisms to digest food and
prevents them from drying out,

so they grow better in moist conditions.

Rate of decomposition slows down in dry conditions, even if
temperature is high.

Question 28

what is compost used for

Answer 28

Gardeners and farmers try to provide optimum conditions for rapid decay of waste biological material

The compost produced is used as a
natural fertiliser for growing garden plants or crops.

gardeners put dead plant material such as grass onto the compost heap and over time, bacteria and fungi decompose the plant material and produce compost

Question 29

why do gardeners use compost as a natural fertiliser

Answer 29

this is because compost is very rich in the minerals that plants need to grow