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Biology A-level > 5B Energy Transfer and Nutrient Cycles > Flashcards

5B Energy Transfer and Nutrient Cycles Flashcards

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1
Q

How do plants produce biomass?

A

They photosynthesise

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2
Q

What is an ecosystem?

A

All the organisms living in a particular area and all the non-living conditions

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3
Q

What are producers?

A

Organisms that make their own food

e.g. plants & algae produce their own food through photosynthesis

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4
Q

Why do plants photosynthesise?

A

To make glucose and other sugars

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5
Q

What are the sugars produced in photosynthesis used for?

A
  • Used in respiration, to release energy for growth

- To make other biological molecules i.e. cellulose - used to make up the plants biomass

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6
Q

What is biomass?

A

The mass of living material

Or

Can also be thought of as the chemical energy stored in the plant

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7
Q

How is energy transferred in an ecosystem?

A

It is transferred through the living organisms when they eat one another

e.g. primary consumers eat producers etc to form a food chain

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8
Q

How can biomass be measured?

A

As dry mass or using a calorimeters

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9
Q

How can biomass be measured?

A

In terms of the mass of carbon in an organism

Or dry mass of its tissue per unit area

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10
Q

What is dry mass?

A

The mass of the organism with the water removed

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11
Q

How is dry mass measured?

A

A sample of the organism is dried, often in an oven set at a low temp

Sample is weighed at regular intervals (e.g. everyday)

Once mass becomes constant you know all the water has been removed

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12
Q

What is the typical unit for dry mass?

A

Kg/m^2

The result can be scaled up if needed to give the total population of the area

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13
Q

How is the mass of carbon be figured out from the dry mass?

A

The mass of carbon is generally taken to be 50% of the dry mass

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14
Q

What is a calorimeter used for?

A

Can be used to estimate the amount of chemical energy stored in biomass

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15
Q

What is chemical energy from biomass measured in?

A

Joules (J) or kilojoules (kJ)

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16
Q

How do you use a calorimeter?

A

1 - Sample of dry biomass is burnt & energy released is used to heat a known volume of water

2 - Change in temp of the water is used to calculate the chemical energy of the dry biomass

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17
Q

What are GPP and NPP types of?

A

Chemical energy stores

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18
Q

What is GPP?

A

The total amount of chemical energy converted from light energy by plants, in a given area

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19
Q

What does GPP stand for?

A

Gross Primary Production

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20
Q

What are respiratory losses (relating to GPP)?

A

Around 50% of the GPP is lost to the environment as heat when plants respire

This is called respiratory losses

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21
Q

What does NPP stand for?

A

Net Primary Production

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22
Q

What is NPP?

A

The available energy to a plant for growth and reproduction - the energy is stored in the plant’s biomass

It is also the energy available to organisms at the next stage of the food chain

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23
Q

What is the formula relating NPP and GPP?

A

NPP = GPP - R

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24
Q

What are the units for primary production?

A

kJ/ha/year can also be written: kJ ha^-1 year ^-1

Or

kJ/m^2/year can also be written: kJ m^-2 yr^-1

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25
Q

When primary production is expressed as a rate what is this called?

A

Primary productivity

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26
Q

Where do consumers store their biomass?

A

In their biomass

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27
Q

Where do consumers get energy from?

A

By ingesting plant material or animals that have eaten plant material

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28
Q

How much of the consumers’ food is transferred to the next trophic level?

A

Only about 10%

Around 90% of the total available energy is lost in various ways

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29
Q

How is chemical energy lost between trophic levels?

A
  • Not all of the food is eaten (e.g. bones)
  • Some are egested as faeces
  • Via respriration and urine
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30
Q

What happens to the energy (biomass) in a consumer that is not lost to the environment?

A

The energy that is left is stored in the consumers’ biomass & is availble at the next trophic level

This is called the consumers’ Net Production

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31
Q

What is the formula used to calculate net production?

A

N = I - (F + R)

N = net production
I = Chemical energy in ingested food
F = Chemical energy lost in faeces & urine
R = Energy lost through respiration
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32
Q

What is the formula used to calculate the efficiency of an energy transfer?

A

(Net productivity/chemical energy ingested) X 100

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33
Q

What do food webs show?

A

How energy us transferred between organisms

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34
Q

What is a food chain?

A

They show simple lines of energy transfer - each of the stages in a food chain is called a trophiv level

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35
Q

What is a food web?

A

They show lots of food chains in an ecosystem and how they overlap

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36
Q

What are decomposers?

A

They break down dead or undigested material, allowing nutrients to be recycled

Key part of food webs

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37
Q

Why are farming practices used?

A

Most of them aim to increase the amount of energy that is availble for human consumption

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38
Q

What are the two ways that farmers try to reduce energy losses?

A
  • The energy lost to other organisms (e.g. pests) can be reduced
  • The enrgy lost through respiration can be reduced
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39
Q

How can farmers reduce energy losses to other organisms?

A

By simplifying food webs

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40
Q

How do farmers simplify food webs?

A

Through pest control

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41
Q

What are two methods of pest control?

A
  • Chemical pesticieds

- Biological agents

42
Q

Give two examples of chemical pesticides

A
  • Insecticides

- Herbicides

43
Q

What do insecticides do?

A

Kill insect pests that eat & damage crops

Killing insect pests means less biomass is lost from crops, so they grow to be larger - this means NPP is greater

44
Q

What do herbicides do?

A

Kill weeds - this removes direct competition with the crop for energy from the sun

Can also remove preferred habitat or food source of the insect pests - helps to further reduce their no.s & simplify the food web

45
Q

What are biological agents?

A

These reduce the no. pests so crops lose less energy & biomass - increases the efficiency of the transfer to humans

46
Q

Give two examples of biological agents

A
  • Parasites

- Pathogenic

47
Q

What do parasites do (as biological agents)?

A

Live in or lay their egss on a pest insect - parasites either kill the insect or reduce its ability to function

e.g. some wasp species lay their eggs inside catepillars, the eggs hatch & kill the catepillar

48
Q

What do pathogens do (as biological agents)?

A

They are disease-causing bacteria and viruses that are used to kill pests

e.g. the bacterium Bacillus thuringiensis produces a toxin that kills a wide range of catepillars

49
Q

Do farmers use chemical pesticides or biological agents?

A

Both - the intergrated systems combine both biological & chemical methods

The combined effect reduces pesticides even more than either could alone meaning NPP is increased even more

50
Q

What is one method that farmers use to reduce respiratory losses?

A

Controlling their living conditions to increase net production - so more energy is used for growth & less is lost through respiration

e.g. keeping cows close together

51
Q

What are two ways in which farmers control the livestock living conditions to reduce respiratory losses?

A
  • Movement increases rate of respiration, animals are kept in pens - movement is restricted
  • Pens are often indoors & kept warm - less energy is wasted by generating body heat
52
Q

What are the benefits of farmers controlling livestock living conditions?

A

More food can be produced in a shorter space of time, often at a lower cost (as less biomass is lost as waste products)

This increases net production & the efficiency of energy transfers to humans

53
Q

What are some ethical issues that arise due to farmers controlling livestock living conditions?

A

Some people think that the conditions intensively reared animant are kept in cause the animals pain, distress or restricts thier natural behaviour

Therefore they shouldn’t be done

54
Q

What happens to nutrients when crops are harvested?

A

They can be lost

55
Q

Where and why do crops take in minerals from?

A

They take in minerals from the soil as they grow & use them to build their own tissues

56
Q

Why are nutrients lost when crops are harvested?

A

When crops are harvested they’re removed from the field where they’re grown rather than dying and decomposing there

Mineral ions that they contain are not returned to the soil by decomposers in the nitrogen or phosphorus cycle

57
Q

How can animals/animal products being taken from the land affect the environment?

A

Phosphates & nitrates are lost from the system when they’re removed

Animals eat grass & plants taking their nutrients

When they’re taken elsewhere the nutrients aren’t replaced through remains or waste products

58
Q

Why are fertilisers added to soils?

A

To replace lost nutrients

59
Q

Why are fertilisers used?

A

Adding fertiliser replaces the lost minerals - more energy from the ecosystem can be used for growth

Increases the efficiency of the energy transfer

60
Q

What are the two types of fertilisers?

A
  • Artificial fertiliser

- Natural fertiliser

61
Q

What are artificial fertilisers?

A

They are inorganic

They contain pure chemicals (e.g. ammonium nitrate) as powders of pellets

62
Q

What are natural fertilisers?

A

They are organic matter

They include manure, composted vegetables, crop residues and sewage sludge

63
Q

What happens when too much fertiliser is applied to plants?

A

The fertilisers can leach into waterways

64
Q

What is leaching?

A

When water-soluble compounds in the soil are washed away, often into nearby ponds and rivers

e.g. by rain or irrigation systems

65
Q

What can leaching lead to?

A

Eutrophication

66
Q

When is leaching more likely to occur?

A

If the fertiliser is applied just before heavy rainfall

67
Q

Why are chemical fertilisers more likely to be leached?

A

Chemical fertilisers are relatively soluble

This means excess minerals are not used immediately are more likely to leach into waterways

68
Q

Why are natural fertilisers less likely to be leached?

A

The nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants

This means that their release into the soil for uptake by plants is more controlled & leaching is less likely

69
Q

What is a natural ecosystem?

A

One that hasn’t been changed by human activity

70
Q

What are saprobionts?

A

Type of decomposer

71
Q

Is the leaching of phosphates or nitrates more likely?

A

The leaching of phosphates is less likely than the leaching of nitrates because phosphates are less soluble in water

72
Q

What happens if too much of a particular nutrient is used?

A

If this happens it can cause crops to die as it changes the balance of nutrients in the soil

73
Q

What is eutrophication caused by?

A

Excdess nutrients in the soil

74
Q

What is the process of eutrophication?

A

1 - mineral ions leached from fetilised fields stimulate the rapid growth of algae in ponds & rivers
2 - Large amounts of algae block light from reaching the plants below
3 - Eventually the plants die as they’re unable to photosynthesise enough
4 - Bacteria feed on the dead plant matter. Increased no. bacteria reduce the oxygen conc. in the water by carrying out aerobic respiration
5 - Fish and other aquatic organisms die because there isn’t enough dissolved oxygen

75
Q

How do saprobionts break down food?

A

Secrete enzymes & digest food externally (extracellular digestion)

76
Q

How do fungi form a mutualistic relationship with plants?

A

Fungi attach to plants, the fungi increases surface area so plants can absorb ions and the plant gives the fungi inorganic compounds

77
Q

What are the 4 main parts of the nutrient cycle?

A
  • Nitrogen fixation
  • Ammonification
  • Nitrification
  • Denitrification
78
Q

What is nitrogen fixation?

A

Nitrogen gas in atmosphere turned into nitrogen-containing compounds

79
Q

What is biological nitrogen fixation carried out by?

A

Bacteria such as Rhizobium

80
Q

What happens in biological nitrogen fixation?

A

Turn nitrogen into ammonia which then turns into ammonia ions

81
Q

Where is Rhizobium found?

A

Inside roots of nodules of leguminous plants

82
Q

What is ammonification?

A

Nitrogen compounds from dead organisms are turned into ammonia by saprobionts

83
Q

What are examples of nitrogen containing compounds?

A

Animal waste (urine and feces)

84
Q

What is nitrification?

A

Ammonia ions in soil converted into nitrogen compounds

85
Q

What is nitrification carried out by?

A

Nitrifying bacteria

86
Q

What are the stages of nitrification?

A

Ammonia ions - nitrites - nitrates

87
Q

What is denitrification?

A

Nitrates in soil converted into nitrogen gas

88
Q

What is denitrification carried out by?

A

Denitrifying bacteria

89
Q

What are the conditions for denitrification?

A

Anaerobic conditions in waterlogged soils

90
Q

What is the nitrifying bacteria that converts ammonia ions to nitrites?

A

Nitrosomonas

Extra knowledge so don’t worry too much about this

91
Q

What is the nitrifying bacteria that converts nitrites to nitrates?

A

Nitrobacter

92
Q

What do plants and animals need phosphorus?

A

Make biological molecules such as phospholipids, DNA and ATP

93
Q

Where is phosphorus found?

A

Rocks and dissolved in the oceans as phosphate ions

94
Q

How does phosphorus taken in by plants?

A

Assimilated

95
Q

How is phosphate in rocks released into the soil?

A

Weathering

96
Q

Where do plants take phosphorus from?

A

The soil through there roots

97
Q

How is phosphorus transferred from plants to animals?

A

Eaten, food chain

98
Q

How are phosphate ions lost by animals?

A

Waste, secretion

99
Q

What part do saprobionts play in the phosphorus cycle?

A

Break down organic compounds (dead animals, urine and feces), releasing phosphate ions into the soil

100
Q

Where does weathering of rocks release phosphate ions to?

A

Seas, lakes and rivers

101
Q

What happens to phosphate ions in the sea?

A

Taken up by aquatic producers (algae), then passed on to birds

102
Q

What is the waste of birds called?

A

Guano, contains high proportion of phosphate ions

Biology A-level (20 decks)

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