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Edexcel Biology Gcse > natural cycles and decomposition > Flashcards

natural cycles and decomposition Flashcards

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1
Q

boigas

definition

A

A type of biofuel (methane) derived from the action of bacteria on animal manure or other organic waste.

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2
Q

crop rotation

definition

A

When fields are used to grow the same crop in alternate years. This helps to maintain soil fertility.

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3
Q

decompose

definition

A

If a substance decomposes, it breaks down into simpler compounds or elements.

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4
Q

decomposer

definition

A

An organism which eats dead organisms, fallen leaves, animal droppings, etc, and breaks them down into simpler materials.

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5
Q

decomposition

definiton

A

The process of breaking down material to release nutrients back into the soil.

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6
Q

desalination

definition

A

The removal of salt from water. This is an energy-intensive process. Also known as desalinisation.

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7
Q

detrivores

definition

A

Animals that obtain nutrients by consuming detritus (decomposing plant and animal tissue as well as waste e.g. faeces).

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8
Q

distillation

definition

A

A separation technique which involves a solution being heated so that the solvent evaporates before being cooled to form a pure liquid.

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9
Q

drought

definiton

A

A long period of low rainfall that creates a major shortage of water.

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10
Q

eutrophication

definition

A

‘Hyper-nutrition’ resulting from fertiliser pollution of aquatic ecosystems.

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11
Q

indicator species

definiton

A

The presence, abundance or absence of these organisms provides information such as the level of pollution in the environment.

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12
Q

nitrate

defintion

A

The chemical absorbed from the soil by plants to produce their protein.

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13
Q

nitrifying bacteria

definition

A

The bacteria that produce nitrate which is released into soil.

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14
Q

nitrogen cycle

defintion

A

The sequence of events or processes involved in the recycling of nitrogen in the environment.

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15
Q

nitrogen-fixing bacteria

definition

A

The bacteria found free-living in the soil or in the root nodules of some plants such as peas and clover that convert nitrogen gas into nitrate.

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16
Q

potable

definiiton

A

Safe to drink.

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17
Q

water cycle

definition

A

The continuous movement of water on, above and below the Earth.

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18
Q

Peat bog

definition

A

Peat bogs are poorly drained areas made up of partially decomposed organic matter due to waterlogging.

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19
Q

How materials are cycled in an ecosystem
atoms
Carbon and water

A

Atoms exist in different forms or compounds at different times in history and cycle between them. This cycling can be seen in the element carbon and the compound water.

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20
Q

How materials are cycled in an ecosystem

Living organisms

A

Other elements and compounds also exist in cycles. Elements pass along food chains when animals eat plants and other animals. Many humans eat protein in the form of meat from other animals. The body breaks this down into amino acids and then uses these to make proteins within the body for growth and repair. When someone dies these building blocks are returned to the environment to be used by other living organisms.

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21
Q

How materials are cycled in an ecosystem

Decomposing bacteria and fungi

A

Decomposing bacteria and fungi break down dead organisms. They help recycle minerals and nutrients to the environment, which can then be used by other organisms. As they decompose dead matter, the decomposers also respire and so release carbon dioxide to the environment, contributing to the carbon cycle.

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22
Q

How materials are cycled in an ecosystem

biotic and abiotic

A

Materials cycle through both the non-living abiotic and living biotic factors within the ecosystem.

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23
Q

What is the carbon cycle?

A

Carbon is passed from the atmosphere, as carbon dioxide, to living things, passed from one organism to the next in complex molecules, and returned to the atmosphere as carbon dioxide again. This is known as the carbon cycle.

The carbon cycle shows how atoms of this element can exist within different compounds at different times.

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24
Q

Which cells contain carbon?

A

All cells - whether animal, plant or bacteria - contain carbon, because they all contain proteins, fats and carbohydrates. Plant cell walls, for example, are made of cellulose - a carbohydrate.

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25
Q

Importance of carbon

A

Carbon is an essential element for life on Earth and parts of each of the cells in our bodies are made from it. The carbon cycle shows how atoms of this element can exist within different compounds at different times.

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26
Q

Removing carbon dioxide from the atmosphere

A

Green plants remove carbon dioxide from the atmosphere by photosynthesis. The carbon becomes part of complex molecules such as proteins, fats and carbohydrates in the plants.

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27
Q

Returning carbon dioxide to the atmosphere

A

Organisms return carbon dioxide to the atmosphere by respiration. It is not just animals that respire. Plants and microorganisms do, too. Carbon dioxide is also released by combustion. The burning of fossil fuels releases large quantities into the atmosphere.

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28
Q

Passing carbon from one organism to the next

A

When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Decomposers and some animals, called detrivores, feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these organisms.

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29
Q

Stage one of the carbon cycle

A

Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

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30
Q

Stage two of the carbon cycle

A

Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.

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31
Q

Stage three of the carbon cycle

A

Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.

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32
Q

Stage four of the carbon cycle

A

Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

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33
Q

Three key processes in the carbon cycle

A
  • Photosynthesis
  • Respiration
  • Combustion (burning)
34
Q

In the process photosynthesis:

What does carbon dioxide start as?

What does carbon end as?

A

In the process photosynthesis:

Carbon dioxide starts as carbon dioxide

Carbon dioxide ends as glucose

35
Q

In the process Respiration:

What does carbon dioxide start as?

What does carbon end as?

A

In the process Respiration:

Carbon dioxide starts as glucose

Carbon dioxide ends as carbon dioxide

36
Q

In the process Combustion:

What does carbon dioxide start as?

What does carbon end as?

A

In the process Combustion:

Carbon dioxide starts as fuel (eg methane or wood)

Carbon dioxide ends as carbon dioxide

37
Q

Purpose of the water cycle

A

Water is a key compound for life on Earth. All living organisms need water. Some can survive in a dormant state without it for long periods of time, but all organisms will eventually die without it.

38
Q

Process pf the water cycle

A

Water is constantly recycled. Energy from the Sun evaporates water from the land and sea forming water vapour. This rises up into clouds and then cools, condenses and falls as rain onto the ground. The water then drains into the sea and the water cycle starts again.

39
Q

Key processes in the water cycle

A
  • Evaporation
  • Condensation
  • Transport
  • Precipitation
  • Surface runoff
  • Infiltration
  • Transpiration
40
Q

What happens to water in the key process of the water cycle:

Evaporation

A

Water turns from a liquid to a gas when it evaporates. Energy from the Sun can evaporate water from all places on the Earth’s surface such as puddles, ponds, lakes and oceans.

41
Q

What happens to water in the key process of the water cycle:

Condensation

A

After evaporation water can cool and convert from gas to liquid, often forming clouds.

42
Q

What happens to water in the key process of the water cycle:

Transport

A

Water within clouds can be blown many miles by strong winds and so transported to other areas.

43
Q

What happens to water in the key process of the water cycle:

Precipitation

A

Precipitation occurs when rain, snow, hail and sleet fall from the sky.

44
Q

What happens to water in the key process of the water cycle:

Surface runoff

A

Much water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet some water can run along the surface of the ground.

45
Q

What happens to water in the key process of the water cycle:

Infiltration

A

This occurs when water that has fallen as precipitation is absorbed into the ground. This can then be stored within underground rocks called aquifers.

46
Q

What happens to water in the key process of the water cycle:

Transpiration

A

Plants need to maintain a constant stream of water to their leaves for transport and support. They allow some water to evaporate as water vapour from their leaves so it is continually ‘pulled’ to their leaves from the soil.

47
Q

The production of potable water

How drinking water is provided

A

Drinking water is usually provided by precipitation.There are problems in supplying potable, drinkable water in some areas of the world, especially where there is drought.

48
Q

The production of potable water

Seawater

A

Seawater is a very abundant source of water, but its high salt content makes it unsuitable as drinking water. However, pure water can be produced from seawater by distillation. This is also known as thermal desalination.

49
Q

Distillation of seawater

A

During distillation, the seawater is boiled. The water vapour is then cooled and condensed to form pure water - leaving the salt behind.

50
Q

The disadvantages of producing drinking water by distillation of seawater include:

A
  • it is expensive because large amounts of thermal energy are needed to heat the seawater
  • it increases the use of fossil fuels - which are non-renewable resources
  • carbon dioxide emissions from burning fossil fuels contribute to global warming
51
Q

Another method of desalination is reverse osmosis:

step by step

A

1) salt water is forced at high pressure into a vessel with a partially permeable membrane
2) the pressure causes water molecules to move in the opposite direction to osmosis from a concentrated salt solution (low water concentration) to a lower salt concentration (higher water concentration)
3) water molecules pass across the membrane leaving the salt behind, so pure water is available for drinking

52
Q

Osmosis and reverse osmosis

A

Osmosis is the movement of water across a partially permeable membrane from a region of higher water concentration to a lower water concentration. Reverse osmosis water moves, due to pressure, in the opposite direction.

53
Q

What is nitrogen needed for?

A

Nitrogen is essential for the formation of amino acids which form proteins.

The nitrogen cycle is a model that explains how nitrogen is recycled.

54
Q

Nitrogen in the air

A

There’s lot of nitrogen in the air – about 78% of the air is nitrogen. Because nitrogen is so unreactive, it cannot be used directly by plants to make protein. Only nitrates are useful to plants, so we are dependent on other processes to convert nitrogen to nitrates in the soil.

55
Q

Stage one of the nitrogen cycle

A

Nitrogen gas from the air is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules. Lightning also converts nitrogen gas to nitrate compounds. The Haber process is a man-made process where nitrogen gas is converted into ammonia which is used to make fertilisers. Farmers use fertilisers like ammonium nitrate to help crops to grow and increase yields.

56
Q

Stage two of the nitrogen cycle

A

Ammonia is converted to nitrates by nitrifying bacteria in the soil.

57
Q

Stage three of the nitrogen cycle

A

Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.

58
Q

Stage four of the nitrogen cycle

A

Decomposers break down the bodies of dead organisms, urine and faeces resulting in nitrogen being returned to the soil as ammonia. This ammonia is converted to nitrates by nitrifying bacteria.

59
Q

Stage five of the nitrogen cycle

A

In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen back to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile by retaining more nitrates.

60
Q

Farmers can increase the nitrate content of soil using two methods:

A
  • Crop rotation

- Using fertilisers

61
Q

Crop rotation and improved soil fertility

A

Farmers often grow crops such as peas, beans or clover as these crops can form nitrate, as they have nitrogen-fixing bacteria in their roots. This will increase the nitrate content and fertility of the soil. Crop plants will take in the nitrate and use it to make proteins for growth. One year the farmer will grow one of these crops and then the following years, the farmer will plant another crop in the nitrate rich soil. Growing different crops each year in a cycle is called crop rotation.

62
Q

Using fertilisers

A

Natural fertilisers such as manure or compost are used by farmers to provide a source of nitrate to increase crop yield. Expensive artificial fertilisers such as ammonium nitrate can be applied to the fields.

63
Q

Pollution indicators

A

The level of pollution in air or water can be indicated by the species living there. This is known as an indicator species. Data obtained using indicator species will only show if an area is polluted or not. Indicator species cannot measure pollution levels only chemical analysis using electronic meters and laboratory tests can do this.

64
Q

Species that indicate water pollution levels

A

If water is polluted by raw sewage or fertilisers, eutrophication can happen, which decreases the oxygen concentration in the river or lake. Some freshwater animals are very sensitive to the oxygen levels such as stonefly larvae and freshwater shrimps. If these animals are found in a river, it shows that the river is clean. However, some animals are adapted for surviving in polluted conditions and can survive in low oxygen concentrations. Examples are blood worms and sludge worms. The presence of these species indicates there is a high level of water pollution.

65
Q

Species that indicate air pollution

A

Pollutants in the air such as sulfur dioxide are released from power stations. Air pollution can be monitored by indicator species. Some species of lichens and blackspot fungus are very sensitive to sulfur dioxide, if there are very high levels in the air then they will not be able to grow. By looking at the number and type of lichens present in various locations, scientists can determine how clean or how polluted the air is.

66
Q

Decomposition

detailed

A

Decomposition is the breakdown of dead matter, which is often called rotting. Decomposing bacteria and fungi are organisms that help the process of decomposition. Decomposition is crucial to the cycling of elements, such as carbon from one living organism to another. You can learn more about the carbon and water cycles here.

67
Q

The rate of decay

A

The rate of decay is the speed at which dead matter is broken down by decomposers. The rate can be estimated by measuring changes in pH, (for example in milk), change in mass (decaying fruit and vegetables) or change in temperature (grass cuttings). Rates of decay are affected by a number of key factors.

68
Q

The effect of temperature, water & oxygen on the rate of decay

Temperature

A

At colder temperatures decomposing organisms will be less active, therefore the rate of decomposition remains low. This is why we keep food in a fridge. As the temperature increases, decomposers become more active and the rate of decay increases. When decomposers break compost down, the compost heap becomes warmer due to the respiration of the bacteria and fungi generating heat. At extremely high temperatures decomposers will be killed and decomposition will stop.

69
Q

The effect of temperature, water & oxygen on the rate of decay

Water

A

With little or no water there is less decomposition because decomposers cannot survive. As the volume of available water increases, the rate of decomposition also increases. Many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules. Without water these reactions cannot occur.

The Egyptians mummified their dead kings and queens. This process removed all water from the mummy and so stopped decomposers from breaking down the dead tissue.

70
Q

The effect of temperature, water & oxygen on the rate of decay

Oxygen

A

Similar to water, decomposers need oxygen to survive and without it there is little or no decomposition. Oxygen is needed for many decomposers to respire, to enable them to grow and multiply. This is why we often seal food in bags or cling film before putting it in the fridge. As the volume of available oxygen increases, the rate of decomposition also increases. Some decomposers can survive without oxygen. These are used in biogas generators.

71
Q

The effect of temperature, water & oxygen on the rate of decay
Oxygen

example: peat bogs

A

Archaeologists have found very old remains of people who have fallen into peat bogs. A famous example of this was the Tollund man. In peat bogs there is low oxygen, a low temperature and acidic water which can naturally mummify dead remains.

72
Q

Rate of change equation

A

Rate of change = change in value ÷ Change in time

73
Q

Rate of change can also be calculated from graphs. Here we use this equation:

A

x axis = time (hours)
y axis = pH

Rate of change = vertical change ÷ horizontal change

74
Q

Which process removes carbon dioxide from the atmosphere?

A

Photosynthesis

75
Q

Which conditions make decay happen at a faster rate?

A

Warm and moist

76
Q

What do nitrogen-fixing bacteria do?

A

Nitrogen-fixing bacteria convert nitrogen gas into nitrates.

77
Q

What does Denitrifying bacteria do?

A

Denitrifying bacteria convert nitrates into nitrogen gas.

78
Q

What do nitrifying bacteria do?

A

Nitrifying bacteria convert ammonia into nitrates.

79
Q

Which process releases water vapour into the atmosphere?

A

Transpiration from the leaves of plants releases water vapour into the atmosphere.

80
Q

Which gas is needed for decomposers to respire?

A

Oxygen

81
Q

What is potable water?

A

Safe to drink

Edexcel Biology Gcse (36 decks)

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